Understanding and using the H&K input buffer

I've posted this before on a number of threads but it still comes up with new owners.  I decided it may be better to have a dedicated thread with the info in so I could just link direct to it instead of writing it all out again.  It still should be reviewed and considered for a variety of issues as it may be relevant to your current situation.

It is important to understand how the GM36, and we assume the GM40 as they are the same family, have their input circuitry set up in order to get the best of any gain (boost/overdrive/distortion) pedal.  The design of that input buffer stage makes them respond to input signals in a more sensitive way than "normal" amps.

There is a clipping overdrive/distortion mechanism built into the input buffer stage and it is significant in its effect on tone.  You can't turn it off, there is absolutely no need to do so.  It is present in every setup you can dial into the amp and is only altered by the channel selection which increases its effect when either the Lead or Ultra channel is turned on.  People bleat at the fact that they can't remove it but you only need to understand it and have the confidence to work it as it should be worked then you may find your amp opens up to you even more.  It never interferes with your ability to get any tone the amp can produce and it does the job of buffering the guitar perfectly as well.  The buffer is a perfectly clean single opamp stage which gives the guitar a rock solid input impedance and amplifies the input signal by just over 3x to match the point where the valve stages can be heavily overdriven to help enable them to give the higher gain sounds most users want.  At low levels it has absolutely NO effect on the signal at all.  No crap about "tonesuck" please, it simply doesn't exist in this context.

The mechanism is an assymetric clipping circuit around that opamp, (assymetric = different on +ve and -ve sides of the signal which is the more musical type of distortion).  It comprises of four 3V9 zener diodes in the opamp's feedback loop, 3 in one direction with the fourth in reverse.  This means the diodes will turn on and clip at about 3x0.6V + 3.9V = 5.7V in one direction and 3x3.9V + 0.6V = 12.3V in the other.  It responds only to one thing, the level of your input signal from either the guitar or whichever pedal is the last in line before it.  This puts the onus on you to control that signal level to the point where you get the tone you are looking for and you must do that with the volume control of your guitar or the output level control of the last pedal.  It's a real adult's distortion mechanism right under your finger and I like to look on it as a free boost/overdrive/distortion pedal built into the amp!

At low levels of guitar/pedal signal it is completely transparent and, to all intents and purposes, is out of circuit.  You can increase the Gain/Volume of the amp to compensate, there is plenty of gain to spare after it.  That way you are getting only the effect of the amp's valve stages in terms of distortion.

If you increase the input level to a certain point the clipping on one side of the signal kicks in and you get sweetened classic valve overdrive type sounds.  At this level clipping is very gradual as there are the 4 diodes creating it which smooths out the rounding off of the signal.

At a slightly higher level the mechanism clips that lower side more but you then also get the other side of the signal beginning to be clipped too.

At your highest signal level both sides are clipping fairly hard so you effectively have a full on distortion pedal before your amp circuitry.  Remember, that is before you add any other pedals between guitar and amp.  

With the Lead or Ultra channel engaged the input signal is amplified more by this stage with a trimmed frequency response which drives this mechanism harder by a factor of about 2x so distortion becomes more extreme.

Try this experiment.  Plug your guitar into the amp directly with no pedals.  Turn the volume down very low on the guitar, maybe even as far as 1 or 2, and set up the amp on the Clean channel with whatever volume you like.  The input stage is now totally clean and tone is coming only from the later valve stages.  Play with the Gain, (remember that is only the Gain of the valve stages), and set it up for whatever overall level of amp distortion you like as things stand.  Once you are familiar with the sounds you can create with that level of signal, keep the amp on Clean, turn the Gain back down to remove valve distortion and turn your guitar up until you detect the input distortion kicking in.  Again play with the amp's Gain control to see what tones you can get.  I find this input type a good basis for Crunch tones.  Finally, still on the Clean channel, turn amp Gain down, the guitar up full and again trim the Gain control.  With low amp gain you have only the input stage producing distortion so testing in this way allows you to hear what it is contributing.  With the input in its basic three stages of distortion, (there is much more subtlety in real use), you have simply added in a degree of valve stage distortion to trim it.  Once I learned to use the amp in this way I found my use of any other distortion pedals really dropped away.

A large amount of complaints of harsh or confused distortion tones in the GMs are caused by too much of a "pedals + input stage + valve stages + output stages" full on approach.  You need to concentrate on one of those mechanisms and blend in the others sparingly if at all.  With too much from all of them you will just confuse the whole sound and make it very strident and harsh.  Of course you may like that but it doesn't sound as though that is often the case from many peoples' comments.  Understanding this is the approach you should take in finding your distortion tones.  It relies on you getting the level right at the input socket.  Too often I find myself unaware of the fact that I am playing full on from my guitar and unsuccessfully trying to dial what I want in on the amp.  Once I trim back the input signal it clears up and I can then get the amp settings right.  The same thing applies with your pedals and their signal level into the amp I suspect.  With active pedals in the mix it definitely needs the output level of the last pedal to be trimmed to control the GM input stage.

I really do find there is too much choice nowadays and it makes us suffer from that modern FOMO phenomenon, (Fear Of Missing Out - as in, I've paid a fortune for this pedal so I have to have it in use all the time.).  If we aren't careful it can make us "pedal collectors" in an unhealthy way as it can confuse the Hell out of us when we try to use them to get what we want.  I now strictly restrict my own pedal board to only a tuner, a Sliderig compressor used only for slide work, a classic Wah which is only used in a couple of funk numbers and a single overdrive distortion pedal chosen from either a Blackstar HT Dual (current choice) or a Marshall Bluesbreaker or my own corrected Okko Diablo type dual SRPP configuration circuit.  With both of the amps I use, GM36 at home or JVM205H for gigging, this gives me every tone I can want and more, and distortion ranges from none to dirtier than I would ever use for my music with no overcluttered effect at all.  And limiting the input stage distortion contribution really does help to remove some of that GM36 top end earache.



[EDIT:  After looking back at the circuitry I found I was wrong in what I originally wrote about this!  My apologies for my poor memory.  The increased gain/distortion in the input stage is automatically selected when you bring in the Lead or Ultra channels NOT by kicking in the Boost function as I first said.]

Thanks for the thorough info!

Although I haven't experimented as much as you suggest, I've noticed the input response on my GM40 in use with a TC Electronic Spark.  At this point, it's difficult for me to attribute any drive response to either the Spark or the front end four diodes, but ...

... when the TC is engaged, there's a noticeably more 'top-end earache'.  However, I mitigated some of that by switching to a Veteran 30 speaker (at least, it's mitigated somewhat to my ears).

Which makes me wonder if the TC is value-added or whether it's time to experiment with the 3 stages of distortion.  Any input from you would be appreciated.

Steve

Hi Steve.  Let's face it, you can leave the TC in there and just kick it out of use while you try out the relevant H&K settings I suggested.  You can also make sure you use only the TC for its own contribution just by keeping its output level down so it doesn't kick in the H&K input stage.  There is plenty of gain following that input stage to generate the valve distortion you might want.  Remember, that input stage is completely transparent below a reasonable input level and you will find out at what level it kicks in as you play and increase your signal on the guitar or the TC.  It costs you nothing to try this out to see if it suits your playing.

This will be very fun and useful experimentation, thanks. I think that the practice of characterizing the breakover of the output stage and then input stage valuable advice. You should make this a sticky.

Hi,
I registered just now to ask this question:
Is there a possibility to bypass the input distortion stage for the use of higher output pickups and/or boost pedals?
I plan to pick up a Grandmaster 36 used and I have no hold backs to mod it.
I‘d love to use it with my Fortin 33 pedal wich is a clean boost with 22dB of gain. Sounds like it will introduce distortion that might be unwanted.
Also the passive pickups I use are extremely hot: OTT from Kent Armstrong...
Thanks for your input.

I would really advise against modding the input stage in any way.  It is really unnecessary even for high output pickups.  It isn't a distortion stage per se, it just has the ability to distort at its two levels if you whack it really hard.  There is ample gain in the later stages to give you even extreme levels of distortion with an input signal which is well below the level needed to trigger that.  Are you telling me that you can't get enough distortion out of the amp with lower level inputs as it is?

There are other benefits from having it there.  It offers a solid unvarying resistive/capacitive load on your guitar pickups if you fire straight into it which is an absolute requirement for a consistent tone from your guitars.  I realise we are in an age where everyone uses a collection of pedals, each with their own loading, and switches between them at random but doing so means no consistent loading so a potentially variable guitar sound.  I always use a buffer first thing at the end of my lead to get round that problem.  I have one which is a tiny preamp built into the lead at the guitar which feeds a preamp on the board.  Yes, it's solid state and ultra clean, there is no such thing as "tone suck" or "solid state sound" in properly designed modern SS electronics.  The sterile sound it is said to produce is only possible when it is solid state all the way and, once again, badly designed for guitar work.  With valves producing the tone as in the H&K amps, well designed SS support circuitry adds nothing to that nor can it take anything away which in electronic terms is the same thing.  Added or taken away, electrically it is ALL added distortion and there is none of that that can be heard.  Something which adds only 0.05% distortion amongst valve circuitry producing around 2% when it is clean is not altering the tone in any way.  True Bypass is a nono nowadays!  It's a really bad thing if you use a pedal board.

I'm not sure what you are trying to achieve with massive amounts of input signal.  If your Fortin is producing clean boost then there can be no difference between it and the input buffer which also produces clean boost to hit the valves following it.  There will only be a discernible difference when either the input stage or the Fortin distorts.  A boost is only relevant when you are getting some benefit from hitting your first stages harder in some way.  As I said, there is enough gain in the amp itself to hit the valve stages as hard as you want.  But, hey, what do I know, there may be some point to it which I miss?

If you must mod the amp you would need to deal with two series 2.7V zener diodes across the amp input.  These restrict the input level to around 3V or a tad higher, (they are in series).  These are actually there to protect and prevent damage to the following stage not to shape tone in any way and they are H&K's way of saying you don't need anything bigger than that.  Assuming you removed them you would then need to change the zeners in the feedback network around the first stage.  It currently has 4x 3.9V zener diodes in series, three in one direction and one in the other.  This gives you the gradual development of distortion through assymetric even harmonic into symmetrical odd harmonic.  These diodes have another job.  They prevent the opamp for that stage from clipping internally under any circumstances.  This prevents it from producing the harsh type of overload that badly designed stages create and which give opamp stages a bad name too.  You need to keep that network so it becomes symmetrical in both directions, allows the largest signal swing possible and does not allow opamp clipping in either direction.  You could add two more 3.9V zeners to the single leg but you run the risk of getting too close to allowing the clipping level to pass from the diodes and onto the opamp.  It would be better to swap the whole network for 4 zeners around 5.6V or 6.8V, two in each direction.

It's all getting a bit "work for the sake of work" when the amp is made to not need that any way.  It's kind of becoming "I have high output pickups and a Boost pedal and by God I'm not afraid to use them.  In fact, by God I AM going to use them!"

Thanks for the reply!
Sorry if I don‘t get the point in every respect, I‘m far from knowledgeable when it comes to complex electronic devices.
I do not want to use the pedal for the sake of using it, but because it gives me a certain character I am looking for.
If the GM36 has an input design, that prevents me from getting the effect of a boost tightening loose characteristics of an amp, I would like to have the option to bypass that. With a switch at best.
I do not have the amp yet and I honestly loved the lead channel on a TM40 without any pedal.
So I will first look into achieving the tone I’m looking for with an unmodified unboosted GM36. In case I fail, I would like to have the option to make it work for me.

In respect of pickups: a pickup swap is not an option.
I build these guitars myself (krachgarten.com) and I chose the pickup for its tonal qualities, not for the high output.

When I got you right, the circuit you mentioned is only engaged, when selecting lead or the ultra channel?
Why not making it an option to make this selecteable?

"When I got you right, the circuit you mentioned is only engaged, when selecting lead or the ultra channel?  Why not making it an option to make this selecteable?"

If you mean the input buffer for that then no, it is engaged all the time on all channels.  It is switched to a higher gain mode with a slightly trimmed frequency response when the Boost function is selected but it is present in all channels when normal too.  That is one of the reasons why it would be difficult to modify.

I did do a LOT of work on looking into the circuitry of the GM36 and modelling each stage in Spice, (the electronics industry standard simulation environment), because just like you I wanted to be able to modify my own GM36 to sound more classic and less modern high gain.  I gave up!  I found that the way the H&K amps are voiced is far too complicated and intertwined to modify in any way.  What you would gain with a change in one sense would absolutely destroy things in other areas.  It is possible to change individual components or single values but the effects are so different for each channel that by improving the Lead sound you will be spoiling the Clean sound and so on.  You can find details here:  Spice Modelling of GM36

I can certainly advise you with details of how the circuitry works but I have to say that improving things will not be at all easy in any way.  The GM36 is just about optimised as it is.  And I must stress that the input buffer is absolutely not having any effect on tone itself if you can just turn down your input to normal levels.  I'm not saying that your high output pickups need changed, only that you don't need to use all of that output just because you have it.  Their high output is only useful in hitting inputs which do not have enough gain in them harder than normal to achieve full drive.  You can easily turn them down a touch at the guitar and allow the input buffer to cleanly increase them for an input where the amount of gain present gets full drive out of the gain stages already as it does in the H&K amps.  The Tubemeisters also have this same circuit in them so if you liked the sound of the TM40 without pedals then the input buffer would be a part of that sound already.

If a Boost pedal is a true Boost pedal then it does just as it says, it boosts the level without altering the character in any way.  In that respect it will have exactly the same effect as the input buffer already does.  In that sense we are not talking about things which alter the tone, only the volume.

Thanks for referring in depth about that topic.

The time I was checking out the Tubemeister was not with my guitar but with a fishman active pickup wich should be high output as well.

The Fortin 33 is not a linear boost though, it has a low shelve going and boosts some high mids a little.
I should be able to reduce the output level though.

I did not want to make premature decisions, I just got used to the fact, that the pickups I’m using are quite hot, wich is very welcome in every application I used them with, yet. If the GM36 behaves differently to anything else and it does not play well with my existing gear, it might not be the amp I want to go with.

If there was a simple mod to switch the input to work like other amps, I’d not hesitate to apply it.
If not, or if it ruins the rest of the amp, I’d move on and see what else works for me.

I first have to get one though

I’m not comfortable dialing down the volume control of the guitar though.

"A boost is only relevant when you are getting some benefit from hitting your first stages harder in some way.  As I said, there is enough gain in the amp itself to hit the valve stages as hard as you want.  But, hey, what do I know, there may be some point to it which I miss?"

Actually, I may have a use case that you may have overlooked, Bordonbert (or maybe I just misunderstood the impetus of your post). For some players, "Front-Ending" or "Front-Loading" a tube amp with an OD is not necessarily meant to add gain, per se - though, I have seen it used that way - but more as a way to give a bit of mid boost and to clean up low-end flub, thereby tightening up attack and punching through the mix in a band setting. I have also heard of guitarists who use the phasing of a distortion pedal to smooth out the 'hair' of the onboard gain stage of an amp that is too shrill. I have heard of many guitarist, especially metal rhythm players, like myself, who use a Tubescreamer type pedal in front of their amps and never shut it off; the idea being to shape the EQ of the guitar, not necessarily to boost the signal in the strictest sense. As you said, my GM D 40 has more than enough gain; more than I will ever use. So, upping the gain, in my case, would miss the point. In light of your explanation, above, it would seem that using such a pedal as a boost would have little effect - and this is definitely useful information, going forward - but as a way to shape the guitar's tone, such a practice might still be useful. Just my $0.02.

I agree with some of what you say Jereth, but with a simple reservation.  Shaping EQ with a pedal before the amp is fine and I wholeheartedly agree with the idea.  If you want say that lift in the mids then some form of specific EQ pedal is one simple way to do it.  Likewise using something like a TS can achieve it if it gives the characteristics you are looking for.  I have a Blackstar HT Dual valve preamp pedal I can use in this way which gives a whole preampworth of tone adjustment and in the past I have used an old Marshall Bluesbreaker 2 in that way myself.

My only point would be that that is not "boosting".  By definition anything correctly defined as a boost pedal must be totally transparent in other terms, all it must do is boost the entire signal equally.  The signal coming out of it must only differ from the one going in by the fact that it is an absolute replica on a bigger scale.  If it has EQ shaping built into it or any form of distortion added it is plain not a boost pedal.  You can of course argue that that is just semantics but I know from lots of past experience that it is important to get points like that correct so discussion can follow which is clear on both sides.  For me (and a lot of industry) there is "boost" and there is tone shaping and the two are separate processes. This actually points us to the argument that two true boost pedals must sound exactly alike as neither is adding or removing anything to the original signal. If they do sound different then at least one is shaping the signal in some way and can't be called a Boost pedal in the first place.

And if I am honest the H&K input stage actually has a tad of EQ built into it so even that is not an absolute true Boost circuit.  I've attached the two Spice plots of the GM36 frequency response for Clean/Crunch and Lead/Ultra. Sorry, I don't have access to the details for the GM40D but it should be very similar.  You can see that the Clean/Crunch side is completely flat up to way above anything we would ever need with a slight tail off at the lower end, (3dB point at 98Hz).  The Lead/Ultra channels are much higher gain by about 10x as we could expect, in order to hit the two valve gain stages harder. They also have some EQ applied to them just as you suggest with a few dB dip applied somewhere just above 100Hz.  The H&K designers are Germans and Germans love their high gain so that lower end is a feature of their designing even if can be a tad "controversial"!  The Clean/Crunch selection with signal levels up to about 1.5V is completely clean and after that the single sided clipping starts. The Lead/Ultra channels are clean up to about 200mV and then show the same behaviour with sharper single sided clipping for even harmonics up to just over 500mV when clipping on the other side kicks in and adds more odd harmonic.

bordonbert wrote:My only point would be that that is not "boosting".  By definition anything correctly defined as a boost pedal must be totally transparent in other terms, all it must do is boost the entire signal equally.  The signal coming out of it must only differ from the one going in by the fact that it is an absolute replica on a bigger scale.  If it has EQ shaping built into it or any form of distortion added it is plain not a boost pedal.

You'll get no arguments from me on this. I absolutely agree that an OD in my proposed use-case, above, is not a boost in the strictest sense. I just had the odd feeling that you and derbstens might be talking past each other. He said the following:

derbstens wrote:I do not want to use the pedal for the sake of using it, but because it gives me a certain character I am looking for.
If the GM36 has an input design, that prevents me from getting the effect of a boost tightening loose characteristics of an amp, I would like to have the option to bypass that.

Using an OD to tighten aspects of a guitar's tone - which is what it's actually doing, not tightening the amp's tone - sounds like what the OP might have been trying to get at, e.g. using the OD pedal to roll off some bottom end flub and 'boost' the mids slightly. It sound to me like this was what he was trying to get at and I basically wanted to get your take on it in that light.

This is going to sound odd Jereth but... It's great to be on the same page even when we're not on the same page. I love intelligently structured argument with someone who actually thinks about what you are saying.

You're right of course, I maybe need to take in more what Derbstens was getting at originally. (I'm not famous for staying bang on the point, nor for answering in 4 word textspeak.) Thanks for the tactful heads up.

Hi,
I am new to the forum. I have been using a Tubemeister 40 for some time and recently added a Grandmeister 40 to my collection to have a hassle-free clean set up for rehearsals and gigs.
I am rarely use pedals and if I am generally very conservative especially when it comes to levels, this may be due to the fact that for most of my time as a guitarist I am used to digital equipment and clipping is something that has to be prevented by any cost.
So, I guess this is where my dilemma starts.
I really have no idea what levels are expected from my guitar pickups, but I would suspect that these could easily exceed 3V in transients when we are talking EMG (707), Seymor Duncan Hot Rails or Fishman Fluence. However, this really bugs me, as from my understanding I am not supposed to use such "hot" pickups with my amps, as the input buffer would clip, which more or less prevents to have a defined distortion.
Turn down the volume of the guitar is not really an option, as on passive pickups you alter your RC and, hence, your frequency response. In the case of active pickups this should not be an issue at all, but to be true to myself I would not be able to dial in the same volume over and over again, as I just forget it sometimes.

However, when I am able to dial in a clean sound in the clean channel, that should be a sign, that the input buffer does not clip, am I correct?

For tighten my Rythm Sound (I am playing mostly metal, using extended range such as 7- and 8-string) my idea was to use an equalizer before the amp and essentially cut bass and treble and, hence, focus the mids, but leaving the maximum of the mid band at 0 dB. In this case from my understanding, I should be save, as I do not introduce additional level, just a cut at some frequencies.

However, trying this approach with the grandmeister, I had the feeling that I get in the same direction if I turn down the bass control almost to 0. My question here: Is the tonestack before oder after the distortion? I would have guessed after, but after this observation I am not so sure anymore. The thing is, that the additional eq for me is yet again the starting point towards a very complex system, which a I already have enough of.

Additionally, how should I deal with the relatively wide spread of pickup output? Is there a way to really recognize an overload of the preamp section?

Sorry, most probably I am overthinking this topic, but it bothers me, nevertheless.

I am looking forward to your reply.
Best wishes
Jo

Don't overestimate the audibility of this.  It isn't like a switch, On and clean or Off and fuzz.  It's a very gradual process and under your own control.  The only way to get to grips with it is to practice and listen for signs of what is happening.  Your ears are your own best friend as long as you don't use them to hear something you already know is going to be there.  Too may people do that in the guitar world!  Hence we have myths and exaggerations like "dead solid state sound", "tone capacitors", "digital roughness" and the long standing "differences in valve makes".  It's the same as guitarists saying they use a Tubescreamer to "thicken up" their tone.  They don't want its out and out distortion, they just want the difference in the feel of the sound which is much more subtle.

There is no reason to think your pickups will change massively in tone when you turn them down, you are only altering the loading on the pickup very lightly.  And, a word to the wise from an engineer, the resistance of a pickup is a totally useless parameter to specify it by despite what all techs and pickup salesmen seem to want you to believe!  You need the pickup's inductance and possibly interwinding capacitances to predict its frequency responses.  Resistance is only at all relevant if you know the material and diameter of the winding wire to be able to work out how many turns that resistance relates to and then the characteristics of the core material to see how that translates into inductance.  Did you ever see a pickup specified with its inductance?  Resistance does not play any part in determining your pickup/amp frequency response, it only affects the height of the changes which inductance and capacitance make, (the resonant peak).  Have a look here, if you haven't seen this it is a good simple read, especially lower down the article:  Guitar Pickup Secrets

As to turning them down to prevent clipping at the input, you shouldn't even need to.  Guitar pickup signal level is a difficult subject to tie down.  In my own experience which I use for my own designs, I always work to 1V peak.  Most designers work to much lower levels than that.  If I feed my own Gibson LP Traditional with standard humbuckers direct into my oscilloscope without any other loading, (that will give an artificially high signal level), I am hard pressed to whack the strings hard enough to get more than that.  I am not saying that there are no pickups out there which give higher outputs but they are not going to give you 3x as much without boost and single coils would be significantly lower than that too.  I will also say that the Seymour Duncan site is a mass of misinformation on this subject.  Guitarists are the most easily led buyers on the planet!  Just hint that something "sounds more open" or is "more delicate in the upper mids" and sure enough, they will hear it and insist on handing over money to do something about it.  I went on there to look for your Hot Rails spec and fell about laughing at the "marketing speak" which clearly gets in the way of the "engineering truth" in so many ways.  Don't be led by anything other than your own ears, and use them without influence from preloading of your expectations by someone who is trying to convince you of something, (me included, just as for everyone else nothing I say should be assumed without testing it which is what I welcome and others steer clear of).

Remember, you have an analogue signal path.  The only thing digital which touches the signal in the GM40 is the effects and that is a very secondary issue as it is behind a lot of circuitry which is designed to feed it so as to not be able to overload it in any way.  The basic signal path is analogue throughout and has a number of points where soft clipping can be introduced.  Every section of the solid state circuitry is protected against the really bad things which most guitar opamp circuitry is not.  Allowing clipping an opamp internally can really play havoc with the sound, as can allowing it to operate outside of its working frequency range.  Both have measures put in to prevent them from happening in the H&K amps.  I know the inside of the GM36 very well for example and the GM40 is based on the same design family.  These are extremely thoroughly developed circuits unlike most amps around which give the good ones a bad name at the hands of people who don't understand circuit design in any way.  You are used to worrying quite rightly about digital artifacts being introduced by clipping which are a real no-no.  This is different and slight occasional clipping would be absolutely unnoticeable in the final sound, especially if you are playing metal!

Your worry about tone controls may perhaps be oversensitivity too.  The 4 channels in the GM40 have different frequency responses built in to compensate for the desire to drop the bass levels under increased gain settings.  The Germans love metal.  The GM family is at heart a metal amp.  Its design reflects that with "bass lightening" built in as gain increases across the channels.  The tone stack sits after the valve components just as in most amps so the Gain control is there to use for internal signal levels - just as in any other amp.  The GM36 usually gets criticised because it can sound bass light if anything.  Most of us in the past have found the Bass control is a bit lacking in the amount of bass it can add giving a nasal quality to the sound sometimes.

If you are not experiencing any bad effects in the sound then you are not having any problem with your input buffer.  It is there.  It will clip with high signal levels.  Those levels are usually achieved with uninformed use of boost and overdrive pedals.  These should be set to give the tone that is required but the output level should be kept down to suit what is being achieved with the following equipment.  This means that the last pedal in a chain which feeds the GM40 is crucial and just needs to be kept at a reasonable output level and all is right with the world.  Playing with this aspect without any pedals, on the Clean channel, with Gain turned down low to eliminate any other sources of clipping to see what you can hear is crucial.  That will be the very best way you will convince yourself of what that input buffer is actually doing in your own case.  If you set the amp up like that, direct into the amp, Clean channel, Boost Off, Gain and Volumes low, Guitar full up, can you hear any signs of clipping distortion?  If not, why are you worrying?

As a final thought.  We are all subject to manipulation of our expectations of everything in life nowadays.  This is down to sales, (they want your money), or population control, (they want you to shut up and do as you are told).  Fear is the latest tactic and this issue is just the same.  Unprincipled people around the guitar scene with an agenda and the weak minded who buy in and champion them are turning it into a morass.  They have created the phenomenon of the "tone junkie" who has to be constantly unhappy with his sound as he looks for something better to aspire to, more and more finer and finer hairs to split. Well, the key is in the word "junkie". They are not known for their level headed discriminating qualities are they?. It is now a field where there is a "guru" only as far away as every website and everyone seeks praise from the guru and others around him for doing as he tells them.  Engineering which is what really drives this area is forgotten as it doesn't have that "boutique cachet" as "the secret knowledge" does.  And, of course, everyone in the field seems to want to be viewed as a guru by their inferiors as they have access to the "Holy Gospel of the Common Knowledge".  There is one secret and one secret only, listen with your own ears and no preconceptions.  "Common knowledge" is generally an oxymoron, those two terms do not go together in any way.  How can a thing be proven truthful knowledge just because many people believe it?  Remember when everyone knew that the Sun went around the Earth which was flat? Even engineering, which is an independent way of accurately authenticating factual claims, is not the ultimate answer to questions of taste.  If it sounds good to you it is good and the disciples are at best disagreeing with your tastes which is fine, at worst talking utter horse apples which you strongly need to shrug off, (and it's most probably the latter).

Hi bordonbert,

thank you very much for your quick and comprehensive answer.
You are absolutely right when referencing to "how the sound feels", for me an amp which is fed by a bass cut guitar feels a lot better, whereas the sonic representation only changes slightly.

It does not really matter, but anyhow, back when I bought the Hot-Rails it was not due to any marketing fuzz, bluntly they were the only single coil sized humbuckers which were available at my local store at this time, so I have not done any research, I just wanted humbuckers in my Strat, that's all.
Anyhow, I am not a person which is susceptible to marketing at all.

Concerning the clipping, thank you for your information, I really have to measure the output of my guitars at some point, but first I have to find my scope in the pile of moving packages :-)
However, I would have suspect what you measure with a scope would be more or less what the Grandmeister input buffer sees, as a scope to my memory has an input impedance of about 1 M Ohm which is the same as the Grandmeister. How is the Grandmeister coupled? I would guess it is AC coupled with a cut-off frequency of several Hz.

It is really funny to read that the GM is a Metal amp by heart. If you read in the more metal orientated forums you will get the impression that the GM sucks for anything beyond classic rock :-) If you look at the more vintage orientated forums you get the impression that the GM sucks as it is a metal amp, so in the end no one likes it :-)
This is clearly not my opinion and I do not care what others say. I bought the GM after having a TM for some years.
However, with the TM it was easier for me to dial in a tone, as you can leave the tone stock more or less at noon. The GM is a completely different beast which I have honestly underestimated, which is not the fault of the GM, its mine as I have to learn to work with it properly and I think your advises and insights could help me big time.
Additionally, due to the options of the GM it is very easy to fall into the preset- or options trap, were I regularly have to climb out of.

I have to confess I am not at the point at which I would say I get the tone stack. Working with it leaves me often confused after some time. Maybe, by any chance you could tell me how you approach dialling in the eq?

Thanks again for your reply and
best wishes.
Jo

Good questions Jo.  Let's deal with the tech ones first.  You sound like you might be interested in this which I posted some years ago:  Thread GM36 Spice Analysis.  There is a link in there to plots I made from within LTspice for the various stages of the GM36.  Here it is again:  GM36 Analysis Plots.  The circuitry modeled is exactly to the GM36 schematic.  Spice is never perfect but the simulation will be very close to what is actually going on.

The input of the GM36 is just as you say, set to 1Meg across an opamp stage.  It has two back to back series zener diodes in parallel with the resistor to offer protection from input transients and stupidity with high voltage levels.  The input cap is 10nF which, if you use 1Meg as the guitar impedance, (a very very rough and not terribly accurate picture but you have to start somewhere), you get around 8Hz cutoff.  Pretty much spot on in your thinking there.  (By the way, my scope is 10Meg and can be slugged down to 1Meg so loading is lighter than into the amp giving the higher voltage I quoted.  It's pretty much all rule of thumb in the real world anyway as you know.)

I've been a member of this forum for a good few years and the chat here has always been by satisfied metal players and dissatisfied classic rock players.  It's odd to me to hear that elsewhere the amp is thought of as not good for metal because it certainly isn't at its best playing my own 60s/70s classic rock material, at least to my ears.  Its rendition of tones from classic Marshalls and Fenders is pretty - well - rough and ragged!  While it has a good "edge" to its tones it certainly doesn't balance that with the right degree of smoothness for me, and for most of the other old time players who used to be members here.  That edge can easily slip off into harshness and too often does.  It is notable that those early Blues/Southern Rock/British Rock posters have moved on now one at a time, presumably because they found other amps which they find better than the H&Ks for their genres.  I am still here simply because, as an electronics design engineer myself, I believe in the whole ethos of the amp even though it is not my choice for a gigging rig nowadays.  I'm currently torn between my '68 JMP SL100 with a Fryette Power Station PS-100 and my Vox Valvetronix AD120VT, (that's one of the original research project Blueface models NOT the utterly appalling metal face models they morphed into).  The GM often goes along as a backup amp, though nowadays the simple little Marshall SC20H is creeping up on it for that role.

From the point of view of its circuit design you can clearly see that this amp really IS intended to play metal.  Talking to the H&K design team over the years on behalf of the forum confirms that.  It has a great Clean channel, a so-so halfway house Crunch channel which is way too restricted in the bottom end to sound good with light crunch, an over the top Lead channel with way too much gain, and an Ultra channel which I don't think I've ever used as it just sounds like an overworked fuzzbox in a wasp's nest to me.  Many people have reported finding that the Gain control is way too enthusiastic and needs to be turned right down to get to lighter tones, but that seems to thin the sound out and make it weak.  The reviews that H&K host introducing well known players on YT and elsewhere seem to be exclusively "chug chug chugga chugga chug on to screaming max-gain solo then a bit of quiet ultra clean noodling to show taste before back to chug chugga chug chugga chug" types, where classic rock tones are not even considered to exist.  The metal players know their field though and, if they think the amps don't fulfill that role well, I certainly can't argue.  (I have to be honest and admit I can't summon up any enthusiasm for metal in any form beyond LedZep and Sabbath.  Humble Pie is my absolute sweet spot.)

I'm not sure what you meant about "the options trap".  When I first bought my TM36 it had restricted MIDI capability so I didn't give it a thought.  When I moved up to a GM36 the idea became more interesting.  I got a FSM432 MkII and whaddya know, I was hooked.  Now, the way I approach it, I use a single bank of goto tones based on the Clean and Crunch channel for 90% of numbers, and a couple of banks of other tones for specialist numbers.  That's it.  You certainly can dial in a tone or two for every number in a set, we have had many people here who did just that, but it certainly isn't necessary.  We have a lot of members who just flip from channel to channel in Stompbox Mode in their playing very happily.  It's something you either get to grips with and it works for you or it just irritates the heck out of you.  I absolutely agree that it can become another one of those "gizmo junkie" creating things.  I just can't see the criticism that there aren't enough preset slots that you hear occasionally.  That many?  Your cruising down the wrong narrow canal in a very long punt!

Aha, the Tone Stack.  Yea-a-a-a-aahh!  I get that.  It's not the most flexible and expressive I find.  In the Spice work I did I simulated it too.  The pics were absolutely as you would think.  They looked very like any other standard tone stack would with the same range.  Yet the bass control always feels too light and lacking range to me.  I put that down to the limitations on low frequency placed elsewhere, in the name of clarity at high gain, and also on teh speakers you use.  The GM36 is VERY sensitive to speakers and can sound dog rough with the wrong ones.  My fiddling with speaker types showed me that Celestion V12s, for example, are not suited to at least classic tones from the amp.  A sharp sounding modern design of speaker is not going to give any sense of refinement from the GM36.

Anyway, I'm rambling again.  If you're interested, take a look at that link and have a peek at a few of the curves there.  You may see something which gives you a degree of backing to what you are thinking.

Hi bordonbert,

thanks again for your valuable reply.
I surely will take at the look at your LTspice analysis thank you very much. Very cool you have taken the effort to build models in LTspice.

Yes, I could imagine that there are a lot of satisfied metal players, I am also a very satisfied H&K player. But, how should I say, the forums and the people in this genre become more and more equipment snobish and as H&K is not really a boutique manufacturer it often gets not the credit it may should. But as I said, I do not care.
I am a very technic affin and I always had the impression that the stuff of H&K ist through and through engineered with a tad of forward thinking.
I am not an expert in classic Rock and crunch stuff, but I am a big fan of the stuff Blackmore has done, especially with Rainbow. I have to say that playing my single coil equipped Strat through the crunch and lead channel with low gain is a real happy place, I love that. Also, Funk stuff works very well and that even without a compressor. But again, this is just my opinion, and I am not someone who searches for a copy of a sound, I really dig the idea of H&K that it does not sound like and marshall, or a mesa, they have their own voice and I like that.

What I meant with the options trap is that due to 128 possible presets and the possibility to save every aspect you could get lost in tweaking as it is so easy to start over. And I am very susceptible to the thought it could sound a little better, so I start tweaking. It would be better to just play, but tweaking is a lot of fun, so I get trapped in tweaking. For me personally it would be better if the Amp would have a lot fewer storage, but again, my problem, nothing wrong with the amp.

Concerning speakers, I like 2x12 a lot. My TM has its H&K 2x12, but to be honest I dislike its weight. The sound is good, by it is plain to heavy. The GM worked OK with a 2x12 with Celestion V30, but for my taste better with a Hesu equipped 2x12.
I am thinking of building a box with Jensen Tornados as an alternative, as they seem to make a good match concerning their frequency response and they are also very lightweight.

But for now, I think I will use at is and just try to cut a little more bass in front of the amp because my EMG and Fishman equipped guitars sound very good, whereas my other passive guitars tend to sound more muddy. Comparing them on the clean channel one directly hears that the active ones feature a lot less bass and hence the result is a tighter tone using high gain.
Just, a maybe fun fact, my rhythm sound uses the lead channel with gain at a little bit over 9 o'clock, with just the guitar at the amp.
So, we are not all playing at full throttle as often suspected :-)

Best wishes,
Jo

(Duuurrrhhh! I meant V30s of course. V12s? Where did that come from? My own personal speaker setup is a 2x12 with either Celestion Greenback G12Ms or 1968 original G12Hs out of my '60s Marshall 4x12 slant cab. That puts a bit of smoothness and bottom end back in but it's still a little lacking in some rooms.)

Hi,

I really want to try the GM with greenbacks or creambacks, but I was not able to find a box with it yet and I do not want to just buy a pair, because I have no idea if I would like the combination.

just for the sake of completeness:
This weekend, I took some time to focus on the tone stack, as I have done before, but this time using an equalizer connected in front of the amp and another one in the effect loop. As the equalizer I have used was a graphic equalizer it was more straight forward to use in comparison to a three band control with interacting behaviour.
I will not tell the boring story of tedious fiddling, but I was able to get some nice tones out of this setup. Knowing what I want I was able to dial in the sound I want with the controls of the amp and get rid of the eq-setup.
What I was able to achieve with the amp alone is about 98% of what I was achieving using two equalizers and to be honest this 2% vanish more or less by day to day listening to your setup.

The conclusion is: The amp can do it all, but it is really hard to dial in if you have no reference point you can quickly refer to. I am quite amazed what is possible.
In contrary to other amps I am used to the GM can sound really bad, due to its wide range, and also, but that may be me, has its sweetspot not at all controls at noon. For finding my sound I had to be a little more adventurous.

Bordonbert, I believe I may have read in one of your posts that you advised someone to use a clean boost to drive the more TS like overdrive of the input buffer.
Is that something which still stands? Is that something you would consider as feasible or to avoid? Is there any possibility of breaking something? I have a guitar with passive EMG HZ (I would not consider them as high output, more as low to medium output humbukers) and a 20 dB boost, do I risk damage? Sorry, but I better ask before breaking.

Best wishes,
Jo

Well done Sabaism for some really thorough investigation there.  It is rare to find a guitarist who bothers with things at the depth to which you obviously do.  And, also unusually, I think there is nothing there which is getting into the "cork sniffing" area which is so common, it's all practical and useful.  It's interesting to hear you say you have tried a graphic equaliser with the GM40.  I have never done that with my GM36 but just a few weeks ago I picked up a cheap Behringer Ultragraph Pro 2x15 graphic equalizer which is pretty much unused.  I bought it in order to compensate for my 2x12" speaker cabinet which I think is a little bit honky with the SL100 and Fryette.  I haven't had it long enough to do much with it yet but now you have got me thinking it might work well with the GM36.  And of course, it has the stereo setup to use it both in front and in the loop.  For my needs I may not need to do both.  Good ideas there, thanks for that!

I agree with you fully that the GM amps are so versatile they can be a devil to tune into.  People buy them and simply switch them on and whack things up way too high in the way they do with more mainstream designs and then shoot them out of the water when they sound poor.  You have spotlighted that you need to spend some time playing and testing to see what works for you.  I find the same thing.  And it's easy to slip off that edge even when you know what you are doing.  I wish I had a penny for each time I find myself thinking it sounds rough and then I find I have simply ended up with my guitar volume too high and the MV too low by a gradual process of poor tweaking.

Yes, I always advise investigating using a genuine "clean" boost, I warn you they are pretty rare, rather than another overdrive pedal even when set at low gain.  As a true clean boost will alter nothing about the incoming signal itself it will simply hit the input buffer of the GM harder to make it add in its own overdrive capability.  No overdrive pedal that I have ever found is absolutely clean, they all have a degree of frequency response shaping to their mix.  The overdrive mechanisms are all the same, even from cheap to expensive models!  There are only a handful of ways of performing clipping or response bending and every one of the units using the same method will have the same general characteristics.  That can be shown by the maths involved, (no one believes in the Schockley diode equation for example), or on the bench with accurate test equipment.  Ears?  Schmeers!  They are the least accurate way to assess something, but necessarily the final way of assessing something.  The bits in between should be left to engineering.  The real differences in pedals come in the simple passive frequency corrections they incorporate and that is a few days work and a few pence worth of components.  So £150+ for a "boutique" distortion pedal?  Not recommended by me.

Anyway, there is absolutely no way you can damage your amp with anything like a Boost pedal.  The input socket of the amp has two protection zeners across it limiting what can be passed inside to about 3-3.5V pk to pk.  It also has a series 1k resistor which makes no difference to what the signal sees but would limit input current to a milliamp per volt even if fed from a very low impedance source which was capable of supplying damaging currents.  If you try to feed more than that from your pedal it will simply clip it down to protect the first opamp input buffer stage.  The zeners are rated at 250mA continuous current which translates to around 250V continuous protection.

On Clean and Crunch channels the buffer has a mid-frequency gain of about 4X with the first stage of assymetric clipping coming in at around 1.5V input level.  You can see that is above the level of just a guitar so clean and "just buffering" is the norm for the input though it does mean making sure you keep your signal level down at the last pedal.  For the Lead and Ultra channels the buffer gain is increased to around 9X so input clipping starts at about 660mV.  I will also point out that the clipping under these correctly controlled conditions is purely performed by the components in the feedback around the first stage not by the zeners across the input.  If you are a little below those levels of signal there is no clipping performed by this stage at all and no discernible distortion is introduced of any form.  The idea that opamp stages with <0.05% distortion are introducing a "deadness" to the sound is totally hysterically laughable to an engineer.  Introducing to all intents and purposes NO distortion at all is the only way of NOT changing the sound in any way!  You can't introduce a flatness to the sound by not introducing any change.  In essence, there is no benefit whatsoever to feeding the amp with anything over about 2.5-3V and you choose the degree of "pre-valve stiffness" you want to introduce to your chosen channel within that range.

That's a bit more info to digest, but you are doing a great job in getting to grips with your GM40.  Make sure to keep posting where you go!

Hi bordonbert,

to me a graphic eq is a great tool for coarse adjustments beyond what you could achieve with a tonestack of an amp alone. If your bands are narrow enough, you could use the ultragraph as intended. For the case where you want to get rid of a frequency which corresponds with "honkyness" I personally would rather go with a parametric eq where you can get rid of the annoying frequency very precise. However, at first, I would most probably also use a graphic one, as they tend to be more intuitive.
Further, I do not think you will find any cork-sniffing on my side, at least I hope so. I tend to be a perfectionist and, hence, may have the tendency to technical data overkill, but in the end, everything based on data and evidence not emotions.

Yesterday at rehearsal, together with my co-guitarist, the trend was ongoing for more extreme settings, but that was expected as the amp for itself and at low volumes is not really comparable to itself when cranked.
It has nothing to do with the topic, but however what kind of leaves me pondering is, that 40 watts seem to be not enough, or at least does not leave me with a lot of headroom. My bandmate uses a modelling top with 150 Watts into 2x12 V30 which have an efficiency of 100 dB/W/m if I remember correctly. He sets is master at about 10 o'clock. I have the GM set to 40 Watt into 2x12 cabinet using Hesu Speaker, which have 103 dB/W/m. I have to set my master to about 14 o'clock to 15 o'clock and sometimes also struggle to be heard. I have checked multiple times if the TSC are all of, they are. Switching the power modes also works as expected. At some point I will measure the SPL, because I expected that 40 Watts from a tubeamp should be more than enough, especially if you would only get an increase of about roughly 4.5 dB going to 100 Watts which is not that much.
Using a tube amp with a 16 Ohm cabinet instead of an 8 Ohm cabinet should not decrease its output power significantly (as with low impedance transistor power amps), because as I remeber correctly a tube amp should be a current source, not a voltage source. So taken mismatches and so into account (I think there is an impedance missmatch, as the GM does not seem to have a tapped output transformer) I would suspect an output power in the range of 90% of the case of impedance matching, which should not be audible. Do you may know more, or do I have an error in my train of thought?

Good to hear about the clean boost, I indeed have multiple ones, some of them homemade, mainly for compensation of longer lines and gain adjustments. Be sure I believe in the Shockley equation. In fact, I used to build my own overdrive and distortion pedals, often combining asymmetric clipping in the first stage and symmetric in the second stage.
I also experimented with different diodes in the feedback loop of the op amps. Especially I have done some experiments usings LED's of different  color, as the doping determines the band gap and, hence, the characteristic curve and therefore the level of clipping. By using different combinations, you can steer the clipping of the positive and the negative halfwave separately.
However, funny thing about the Schockley equation: A friend of mine is a fuzz enthusiastic. He has built himself a germanium fuzz. The band gap in Ge is narrow compared to silicon and, hence, temperature drift is higher. So, in the end he encountered that is fuzz was behaving a little bit different when the temperature changes.

Good to hear, that H&K has done its job protection wise, it was expected, but better ask. When it comes to protection of delicate circuits you often see bad design, if protection is implemented at all. Even at very expensive equipment.
I personally think that such protection circuits are really important, but that comes from experience, I once designed an integral amplifier capable measuring currents down to pico amperes. On the other hand, if one would have forgotten to connect these properly a voltage of easily in the kV region could build up and you can imagine what happens when you connect the system without protection. So, my amplifiers got their input protection designed and we never had issues with them.

The more info, the better, it is awesome that you have this real in-depth knowledge and experience of these amps and share it with us.

Best wishes,
Jo

That is odd about the lack of output power.  These amps are not known as lacking in volume.  I've used my GM36 against a full band with the other guitarist using a Marshall SL100 and 4x12" and I had no problem fitting in equally with him.  Of course you may play at a lot higher level than we do, we are a classic rock outfit, but we aren't a quiet band by any means.  With 2x V30s at 60W each the "Nominal" power may be 120W but I wouldn't like to run those speakers with a 150W output amp for long.  I suspect in real life he may be playing a fair bit lower than his 150W.  As you know the audible impression of power levels is very skewed and 40W is not a lot lower in sound levels that 150W.  Your GM40 should really keep up with that.

The GM series has an output impedance of 8-16ohms.  You are right, there are no output taps to match exactly but, in truth, there is no such thing as a perfect match with valves and speakers.  The impedance of any speaker varies so wildly over the frequency range that there are only a couple of specific frequencies where it would match.  And valve technology, like most "Victorian Engineering", is very forgiving of abuse such as mismatches.  A decent amp will cope with around a 2x mismatch either way, (that's with 4ohm or 16ohm load when set to 8ohm output), you will lose efficiency just as you say but it is unlikely to cause any expensive damage.  I suspect the GM amps are matched to about 12ohm, in the middle of that 8-16ohm range.  When they are set to half power and below, one pair of the output valves is removed from circuit which creates an even greater mismatch.  To keep the matching close when "pulling" a pair of valves the load impedance should really be doubled.  All of these effects will have been investigated and tested by the H&K design team.  They are extremely thorough and I have only ever heard of one or two cases of output stage damage to any H&K amp, I actually can't even remember a single one clearly.  The mismatch at either impedance is not really significant as it is not leading to a long list of repairs.

As a point to watch out for which may be counterintuitive, running a valve amp with no load is more stressful to it than running it into a short circuit.  It means an infinite load on the valves and makes the output produce massive flyback spikes on the primary side which can exceed the rating of the insulation and puncture it and that can mean shorts inside the coils.  I don't mean try it, I just mean that the amp can cope with a short for longer than an open output.  Designs should always be set to fail with some load on there where that is possible.  Putting a 220R-470R (ish) 5W resistor permanently soldered in place across the output is a good means of protection.  It makes no difference to the amp when it is working as it should, 8R load//220R resistor=7.72R and the speaker itself will be way off that at times, but it means some load is there in the event of the amp losing its speaker load.  You have this built into the GM40 of course as the output constantly monitors the situation and switches to the internal power soak load in the event of a disconnection to the external speaker load.

My thoughts on diode clipped pedal circuits is simply that, with the exception of using different diode types such as LEDs or zeners or combinations, they all basically come down to the same character of distortion.  You can trim other circuit parameters to make them all distort the same so why bother specifying a particular model?  If you want to do the job properly and very simply try a multiple diode ladder with resistor values trimmed to produce the actual curve you want.  I have used these very successfully to produce very sweet mild to medium distortion.  Here is a link to this circuit in action:  Look at Output Limiter.  This can easily be adapted to a pedal, not so easy if you stick to 9V supply but you can produce step up voltage supplies easily nowadays.  It gets even better if you split it into two separate ladders, one for each side of the signal, and introduce some asymmetric distortion.  Spice is great for modelling things like that before you build and I do have some transfer curves that I produced when I played around with it.  It is so much more flexible, (tunable), than a simple two diode back to back approach.

And here is an even more interesting idea where a valve stage is modeled accurately with a multiple transistor design.  Simulating Valves with BJTs.  I have built an amp incorporating both these designs for each of its stages, the valve simulating for the preamp stages which overall then modeled a standard valve amp configuration, with the diode ladder shaping the signal into the mixed mode feedback power amp to introduce the same transfer curve as a valve power amp would show.  It actually sounds great and plays well with great feel also.  It really isn't like any other solid state amp I have played, (barring modelling types of course).  I swapped info with the guy doing this work.  He was a really nice chap and shared his ideas very openly.

There's a lifetime of spending your time productively in all of this.  You just have to be able to give up your attachment to what you already know to be true first, just the same as for any worthwhile area of learning new stuff.

Just a little update on the original topic of this thread.  I recently got my hands on a Fender amp.  Fender is not usually my own first choice.  It's not that they are not good, just that I usually prefer the British Marshall sound to the US Fender so my amp choices and needs are based around that.  I chose to look one of these out because I fixed a friend's for him which had a simple fault and was absolutely bowled over by its sound once I had time to play with it in its fixed form.  The amp I got was almost brand new and was very cheap.  It's a Hotrod DeVille 410.  Now there are guitarists out there throwing up at that admission, (yes, I know who you are!   )  These amps are known to have a decent Clean channel but, by reputation, they have a loathesome Drive channel.  It's - guess what - , "common knowledge".

I first tried out the amp as you normally would and found that, under some settings that is just the case.  The Drive channel certainly could sound sharp and rough.  But then my H&K brain kicked in.  I swapped to the lower signal input which would affect both channels and turned the guitar volume on my trusty LP Traditional down to 5 and hey presto.  I now have a wonderful Fender Clean sound which still breaks up when its Volume is turned up, and a Drive channel which goes from Crunch beautifully with its Gain set at about 4-5 up to singing with the Gain only on about 6-7.  With the third "More Drive" option in place the amp lets me do rip-roaring soaring solos in real classic style.

The point isn't that the Fender Hotrod DeVille is a good or bad amp, it is that it seems to be a much better amp than is known and acknowledged if you only stop blasting its input with massive signal levels.  Of course there will be people who love its sound when driven that way but there seem to be many more who think it is a dog because of the way they are setup when they test it.  If only we had the confidence to turn down, turn down a bit more, then finish off by turning down just that tad more!  There is a lot to be discovered with this approach.

Hi bordonbert,

you are absolutely right, it is awesome what your gear can do if you are willing to ignore the saying of corksniffers and just go for it.
I have to confess I was mainly influenced by the saying of my fellow guitarist in the band who could not stand my sound (I do not like his sound either ;-)).
However, we have played a good amount of gigs the recent weeks and I just didn't want to carry around a pedalboard, I wanted to use the amp as it is.
I applied what I think I have learned from your expertise and I was getting compliments for my sound at every gig from random people.
The bass player of the other band (he is a guitar player by profession) also said he especially likes my lead sound, as it has a tonal quality which reminds him of a cello.
All in all I also can confirm that the Grandmeister works great with 8-String guitars (tuned down a whole step) without the use of any external devices, I am very, very happy with this amp.
I am not shure if I would say so without the help of bordonbert, his insights and tips were very valuable and important.

Best wishes,
Jo