GM40 High End and Treble

Hi people,

New to the forum, and new to Hughes and Kettner amps.

Received my GM40 yesterday and enjoying it very much. Loving the clean tones and just the pure versatility of this thing.

The one issue I seem to be having is taming the high-end/treble on the Crunch and Lead channel. Whether I boost the Resonance, or dime the Presence I can't seem to dial it out.
I noticed also, that even if I turn the treble to 0, there's still a fair bit of high-end, particularly on the crunch channel.

I'm using my Les Paul Trad, into the GM40, then into a Orange 2x12 with V30s.
The other amp I use is a Egnater Renegade.

Any help would be much appreciated,

Thanks.

Hi BigA.

This is an ongoing problem with the entire range of H&K amps of this class. Look not only in the GM40 forum but in the GM36 forum too as there is a huge backlog of useful discussion and advice in there which applies to the GM40 just as well. The truth is that there is little you can do at the amp itself. The design is so complex you can't simply mod a couple of caps to remove it. The tonal interactions are such that you will improve one channel and ruin two others.

Some relief can be found by swapping out the Chinese valves, (but not much IMHO). You also havwe to be aware that the 36/40 have a Direct Coupled Cathode Follower stage in there and with H&Ks Standby setup the 12AX7 triode is pretty much pushed past its safe limits at every switch on. Chinese valves are much better at taking that sort of abuse but if you leave the Chinese DCCF in there you then have a Chinese triode as your final gain stage. You p;ays your money and takes your choice. The best way to approach it is through your speaker choice as all these amps are very pernicketty about what is hung off their rear end.

Personally I can't live with my GM36 and V30s. For the record, H&K use V30s in their own cabs and these sound pretty decent (if expensive) but they are specially voiced for them by Celestion so they aren't really representative. Linking to V30s turns the amp into a bacon slicer with my ears on the block. The best solution for me came with G12M Greenbacks in a 4x12 though everyone will have their own favourite model and configuration. Now the GM36 and GM40 are reputed to be different beasts with the GM40 being much more refined, (generally by GM40 owners, "...well he would say that wouldn't he". You know who you are ). I feel I can still hear the H&K family tonal characteristics. The sharp top end, very forward upper mids and lack of bottom end sound very similar to me. I really think you should look for something mellow and less modern. If you already have that on the back end then it's welcome to the club I'm afraid!

(Incidentally it was this very problem that drove me back into the arms of Marshall for most of my live playing. )

Hi bordonbert,

Thank you for your reply.

Yes, I read about the "fizzy" nature of the GM36 on this forum, and had seen your very informative replies. But I hadn't seen as many complain about the GM40 in the same way.
I couldn't agree more with you regarding the V30s. I even find them spiky and harsh with my Orange Rockerverb, so using the GM40, which is bright in nature is indeed asking for trouble.

I'm getting a new cab for my Egnater Renegade, and will be loading it with different speakers. So may try the GM40 through that before I make any rash decisions. Also got a rehearsal next week, so will give it a run in a full band
context.

But really appreciate you clearing things up for me, was thinking I was going a bit crazy, or I had dodgy amp.

Thanks again.

Hi BigA--

Yes, those V30's really accentuate the upper mids and are a little harsh to my taste.

I own the GM40 and the 1x12 cab with the V30. I've been trying to shape my tones to tame that sharper top-end.  But I'm not accomplishing the tone I want.

I just ordered a Veteran 30 from Warehouse Guitar Speakers. They offer this speaker in direct response to the famous V30 harshness. They reportedly tame the upper mids and mellow out the upper end.

I'm getting it in a few days, and I'll let you know how it sounds in comparison.

What will be interesting is whether or not the speaker will be 'creamy' enough to tame the high-end nature of the HK, or whether it's necessary to go more extreme in the 'creamy' department.  You know, go a bit overboard on the speaker selection as far as the dark sound in order to somewhat tame the sharper top-end and forward mids.

We'll see. I do like experimenting, so I'll start with the Veteran 30 and assess. If I don't like, I'll make a second choice and let you know that as well.  I play out a couple times a month, which is the real truth-teller.

Have a great day,
Steve

I put a WGS Retro 30 and ET65 in my 2x12 with my GM40 and I the tone is pretty nice.  

I have also since swapped out the tubes:

• Ruby EL84CZ (JJ)
  
• Ruby 12AX7AC5 HG+ in V1 (Chinese)
  
• Ruby 12AX7ACZ HG med gain in V2 (JJ)
  
• Ruby 12AX7AC7 HG balanced in V3 (Chinese)
  

The tone was originally very warm and fuzzy (not fuzzy fuzzy, but hopefully you know what I mean). The tube complement above made the tone WAY clearer, more transparent. I'm debating putting a higher gain tube back into V2 to see what that will do.

Hi BigA--

I went with the Veteran 30 to replace the V30. I really like the choice!! It tames the high end nicely. The Veteran 30 still has a very nice and crisp crunch, it's just not annoying like the V30. I think you'll like it. I've gigged with it 4 times so far and am falling in love all over again with the GM40.

Steve

I'm using a 2x12"open cab with Alnico Gold or a 1x12" with Alnico cream. For my taste a bteer sound then with a 1x12" V30 or closed 1x12" with the big EV speaker.

I have been having a similar issue especially when using my les paul, never could really tame the fizz as much as i would like. I borrowed a tube screamer mini this weekend and put it in front. i set the tone about 11 o'clock, gain about 9 o'clock and level to a tiny increase. This really toned things down for me and also tightened up the low E ( D standard tuning ) which was a bit floppy sounding.

I dont know enough technical stuff to understand why but its really been great so far. Great in crunch and lead channels with and without boost. I found that higher gain on the pedal colored the tone a bit more making it sound like the pedal more than the amp, but at lower gain im loving it.

At last I have put this info into its own thread. For those who aren't aware of the way H&K have designed the GM input stage this may well be a helpful read.

GM Input Buffer Stage Use

Wow that buffer stage thread is a great one!! I've tended to push all the amp stages on full, and the results have not been good at higher volumes. Had come to the same conclusion about distortion and had stopped using anything else, but was still unhappy with that aspect. Now I have a good road map to really improve things!! Thanks...

So here is the first part of my review still not completed review of Grandmeister deluxe 40 . I post this here because it deals with the fizziness problem.

First of all I bought it because of all the features. No more cable mess as in the past and I thought okay the sound can't be bad even though I've read mixed reviews and that H&K amps in general are very bright and somewhat sterile. 
I wasn't very satisfied with the sound at first but I was expecting this as I read beforehand that the EQ section and especially Presence are very sensitive.
So the Clean and Crunch channels sound pretty good stock.
At first the lead and ultra lead channels were always thin, brittle and fizzy. I did change the stock chinese tubes with JJ pre amp and power amp tubes. The difference was very subtle and didn't get rid of the biggest problem, the fizziness. 
I didn't have much time to experiment to dial the sounds in but lately after about a year, I've finally made it.
I have to say that the boost knob makes every channel sound better but I wanted to get all 4 channels to sound great without boost engaged.
So here is the big culprit for lead channels. It is the presence knob... usually I like my amps to sound good with treble and middle Eq at noon, flat. Than I adjust for what I need with regards to live situation.
This wasn't the case with lead channels on GM40. So after not being able to dial good sounds with EQ only, I set the presence to zero. Almost no fizz. Than I ended up with middle on 80 to 100%. This took away fizz completely but was also very dark sounding because of low presence. Than I experimented with treble and ended up with a bit over noon around 3 o'clock. The amp was clearer with still no fizziness. Than i started dialing the presence in very slowly until I just heard a bit of fizz again and dialed a bit back. So it is set to around 10 to 20% now (around 8 O'Clock). The sound was very good, more organic and sustained better (i think mostly because of mid eq set high) .
Also note that ultra gain channel is very bassy and boomy. So I set Bass and Resonance to zero on that channel.
On Lead channel I set Resonance and Bass to around 9 O' Clock.
Now this should work for all who find these channels too bright and shrill.  It is different from what most of us are used to in other amps.
One thing is sure, they can sound very good you just need much more time to dial it in, in comparison to other amps. This is very different from some Marshalls and Peaveys I own. So spend some time with it first before judging.

On the other hand, clean and crunch channels respond to presence differently. So it is set to around 10 or 12 O'Clock. 
On crunch channel I still had middle set to 100% and Treble around 3 O'Clock with Bass at 12 O'Clock. 

The clean channel at 12 O'Clock for middle and 3 to 4 O'Clock for treble. Bass to taste. 

Hope some try this and share their experience with the settings I posted.

Cheers!!!

Hey everyone,
I just wanted to dig this thread out because I was facing similar issues with my GM40.

Yesterday I sat down in front of the speakers and played while adjusting the eq and I also noticed that the presence control is very sensitive. I ended up with following settings on the lead channel :
Presence 9 o clock
Resonance 12 o clock
Treble around 13 o clock
Mids 3 o clock
Bass 13 o clock

The presence knob feels like below around 9 o clock suddenly cuts all the trebly frequencies and when you move it just a tiny bit, the fizz is there.

I love that presence and resonance is independant for each channel, but I like to have both working as a global eq for gigs to adjust the amp based on the venue without changing each channel separately. The problem is that these two knobs work differently on each channel.

At least when you don't use presets but rather just the 4 channels of the amp, it's no problem dialing the resonance out or some presence in if needed without using global presence and resonance rather than the programmable presence and resonance...

Nevertheless, killer amp. With presence down and mids and bass turned slightly up, it reminds me on a budda superdrive. Actually my Marshall JVM 410h has a serious competitor tone wise now...

I've been using the WGS ET90 with my Coreblade and lately been using it with my fatter less tight Switchblade. It is a good speaker for tightening things up.

I have stayed out of this discussion for a while though it has some really good advice and info in it, as the GM40 is outside my experience and I have no access to its schematic, (unlike the GM36).  However, we can assume that the general approach in broad terms is the same between the 36 and 40.  It is VERY unlikely that they would design a complete new amplifier from scratch to fit as the flagship in an existing range.

Here is a set of plots from a LTspice simulation of just the Resonance/Presence control section.  I have previously simulated most of the GM36, the plots and info are on this site in the GM36 section, but I had never tried the Res/Pres part.  It isn't all a pretty picture to my eyes!

The Resonance control looks good.  It does what it says on the tin and creates a peak or trough around 90-95Hz.

Presence isn't so straight forward.  Notice how the highest setting of the control produces the lowest level of output initially, odd but fine.  However that becomes a steeply rising signal as frequency increases not just a peak.  That is a confused response in terms of the high region of the top end.  I would really expect that rise to have been topped off and cut at some frequency.  

I could have made a mistake in my simulating but I've checked and rechecked.  I've also attached an extended picture which shows that it peaks at 7kHz and dies away but it is still at the same signal level as at low frequencies when it is at 33kHz.  That means there will be significant output at frequencies of up to the limits of hearing.  Maybe that is at least part of the answer as to the hard high end of these amps with the Presence turned up after about half way.