The Tube Swapping Thread

Hi there

I finally got round to swapping out my valves but cannot get the valve out of V1
I have removed to push and twist metal cover but the valve won't come out.

Do I need to unscrew the metal baseplate too?

Any help appreciated!

Thank you

Nothing special needed Davus. It just pulls out exactly like the ohters do. You don't have as much "wiggle room" as the other two so it is harder. Just vibrate it slightly from side to side as you pull upwards. It'll come out with a slight plop. While you need to be careful and as gentle as you can be of course, valves are much stronger than say light bulbs. The glass envelopes are much thicker and tougher. You can grip them quite hard. It might help to put on something like a rubber glove while you are pulling up on it which will not slip off so easily. Make sure the valve is cool when you try.

Impatience got the better of me and I loosened the metal housing in the end for fear of breaking the glass. A rubber glove probably would have done the trick!

Anyway new tubes in. I only had time for a very quick test. Straight away I needed to up the treble from 2 (which was almost the most I ever had it with the stock tubes) to around 6 so in terms of my wish for a less trebly amp it was granted.

A little tweaking and I soon had a lusher lead tone going. Dropped to 5 watts and pushed the master to 12 and was in super creamy lead territory.

This was through my new Zilla cab with Celestion Greenback so possibly a combination of the two but either way I'm very happy.

Don't get me wrong I loved my GM before but having to have the treble so ridiculously low never seemed right to me.

Only gripe is that the TSC rating for the new tubes isn't the best - 12 flashes with all 4 Leds and then a further 2 flashes with one of the pairs but it sounds good and that's all that matters.

I went for the JJ revalve kit from Eurotubes.

Cheers for all the help

David

Don't even give the TSC setting a second thought, it's perfect as you have it.  The valve guys have done a good job in balancing as both pairs are matched valve to valve to the last flash.  There is no benefit in having the two pairs balanced with each other, only each valve with its partner in their pair.

The object is to balance up as accurately as possible the DC current through the transformer.  Txs don't like to have a DC standing current magnetising their core all the time.  It means that the core saturates in one direction earlier than the other.  And there is even an argument that says that is a good thing because it generates even harmonic distortion.  If each valve in a pair has the same current then they cancel each other out perfectly.  For you that means that at 1W/5W/18W with a single pair they are totally in balance, and then at 36W with both pairs adding together they would still be balanced.  Those additional 2 flashes are absolutely nothing as long as they represent each valve in the same pair.

Your description of your improvement doesn't shock me at all .  We have nearly all found exactly the same thing.  And it is very definitely down to the Greenback as well as the valves in my honest opinion.  It would be interesting for you to try it with your original speaker and see if some of the toppiness comes back.

Tube update!
Jj el84 for power amp,v1-jj 12ax7,v3-jj12ax7 and the best of the best.....jj-12at7 for v2!!!!!! The tone controls came alive!!! The distortion became creamier!!!the effects warmer!!!No hifi no fiziness at all!Still plenty of distortion but waaaayyyy better!give it a try!

bordonbert wrote:Be very selective with your speaker choice Luke. You really need to hear the match with a GM36 before you put any money in. There is a fair bit of discussion on the forum re speaker choice, most people find that their amp is very sensitive to it.  Look on the TM36 forum as well and the 112 and 212 forums (should that be fora? )

I totally agree with the speaker being huge factor that needs to be considered, in conjunction with swapping tubes. I have 2 notes torpedo that allows you to take a test trial up to 140 different types of cabs that they have on there store before you buy them. I'm sure this would be much more helpful to many musicians if they had a way of hooking up there current amp choice so they could audition different cabinets, while at the same time test out some of the various  preamp tubes they have collected over the years.

I played with it some, but in the end decided it be best to try, and solve the issues i had with my current cabinet, via swapping out some preamp tubes that i already had. I did find a combo of preamp tubes that worked pretty well, in conjunction with my Jensen blackbird/ tornado loaded Port City OS cab, that i liked.

While I am glad you have found the sound you are looking for DIB, I can't agree that the valves are anywhere near as important as the speaker. The effect of changing out of valves is real but subtle. You can't make a H&K into a Marshall of Fender just by rolling valves, (not that I would want to), but you can trim its top end and the top/middle balance a little. The effect of swapping out speakers is massive though and should be the way you set your foundation sound character with the GM. A change from a pair of 1x12 V30s to a Marshall 4x12 loaded with G12M Greenbacks is to produce a totally different character to the sound. It has to be speakers first to establish base sound, then valves second to trim it for me. Valve rolling is useful but highly hyped and overrated in the music industry.

I don't think you got the jist of what i was saying. I basically said hey i have speakers hear already in my cab, and i wasn't getting a good enough sound, so instead of going out, wasting more money on new speakers, i instead said "hey why don't i see if i can tweak my speakers a bit with some preamp tubes (that i already had on hand), to see if i could get the amp to a more desirable tone, before going out, and buying new speakers.

This was just a process of elimination, that i did before i decided to go get some new speakers, which i was about to do, if my attempt at vetting out my preamps tubes didn't work. If this occurred, I was going to try to locate speakers/ cab using the 140, or so cab sims on the 2notes store for testing purposes to see what would most likely work with the amp i currently have.

The speakers were not bad, it was just they only work with certain tubes/ amp combo in my opinion.

I see what you mean. I had missed the 2 Notes Torpedo reference, that's not a unit I had come across before.  If you're sure you're absolutely happy with the speakers you already have despite saying you have issues then yes, of course, the valves are the next step.  But it is still my belief they are the "next" step, their influence is subtle not massive.

Oh don't get me wrong i did come a crossed some cab IR's in the 2notes webstore that i that i thought worked well, and sounded pretty good, but I spent like a grand on the Jensen Port city cab combination so yeah i definitely want to make sure it is not usable before moving on. I took a gamble on the Jensen speakers, and i think i probably could of found something better, at a lower price, but I think i didn't have the 2 notes torpedo at the time that i was trying to figure out speakers for my amp.

This site is awesome. I bought a new set of JJ tubes... 4x EL84, 2x ECC83S, 1 balanced ECC83S, 1x 12at7, 1x 12ay7. Here are my thoughts

1) Stock: too much gain and fizz

2) ECC83S V1 and V2 and Balanced ECC83S V3: smoother but still too much gain and fizz

3) 12AY7 V1, ECC83S V2, 12AT7 V3: Clean had more headroom, other channels still too much gain and fizz ; slight overall volume drop

4) 12AY7 V1, 12AT7 V2, Balanced ECC83S V3: lots of headroom on clean, all of the gain channels opened up and loss a lot of the grit. Sounds much better for rock and blues but enough to still do metal.

I think I'm going to keep the 12AY7 and 12AT7 in V1 and V2 get another 12AY7 for V3 to keep the overall volume down.

I'd recommend you to go back to Page2 of this thread and start reading a bit from Post43.  The idea of just swapping out a "low gain" 12A*7 (TUY) for a 12AX7 is not a good idea, despite the advice every "tech savvy" guitar shop worker "knows".  There is more to it that you should be at least aware of.  It's not rocket science, just keep an open mind and read from the people who actually know what is going on in the circuits.  (And by that I don't mean me, my info needs to be crosschecked against what others more experienced in valves say to be seen as reliable, but it will be I promise you.)

Of course you could just take the view that it works so I'm running with it as most people do.  That's why H&K don't sanction valve rolling and in fact it goes against the warranty even though they have told us it could be done if you must.  That's fine but it's like shoehorning a V8 into a Honda Civic and expecting it to be a fast safe car just because the engine is more powerful.  Brakes?  Suspension?  Steering?  Chassis integrity?  Naaaah!  It wouldn't compromise those would it?  That guy in the lockup behind the butchers did it and his goes like a rocket.  (What, he's in hospital and his car's wrecked.  Must have been a pensioner did something stupid. )  Does that maybe make a point?

Look into the 5751 valve, it's talked about at length earlier in the thread, it's the right one to choose to do the job your trying to do, reduce gain without disturbing the other setup of the stage too much.  Designers are pretty clever blokes and they always have to work towards more in their designs than the non-technical person can even imagine.  It pays to stick with as much of the original design critieria as you can.

Just thought I'd quickly check on this.

thetubestore.com wrote:Before you discover the new possibilities in your amp, let us give a disclaimer. Your amp was originally designed for a certain type, and although tube amps are often forgiving, it may not have a tone that you like with a different tube type. For instance, changing the tube type doesn't only change the gain factor; there are other variables as well and your amp may have a circuit that is more particular than others. As a general rule, the substitutions we describe here should work well but there are exceptions and we don't warranty any problems that result from trying mismatched tube types. For the best results, find other people on the net who have experience swapping tubes with the amp you use.

Now let's see, why would they bother to put that bland not too upsetting (EDIT: Got it! INSIPID was the term I was looking for.) disclaimer at the bottom of their page?    I'll go further as you can't sue me for it like you could them, you change the valve you risk damage too in many amps.

I'd like to slightly deviate to the "other" tubes, the EL84s.  Two questions:
1)  Anyone have ideas/opinions/bs on the difference of tone/response/<other subjective phrases here> of using two 84s VS using four 84s?
2)  Anyone have ideas about longevity of the 84s in the GM?


I'll start
1)  it seems that using four gives the tone a little rounder sound, while using two maybe breaks up a little earlier (meaning at the same gain knob settings, not spl).
2)  H&K points out they use 300V as plate V, which is what the 84 is designed for.  This yields 8 watts per tube.  Other companies use 400+V per tube (12 watts per tube), and the user needs to replace once per year.  Also, I read a quote on a site (the quote supposedly came from Eurotubes, but it isn't on their site now) that states if you drive 84s into saturation, they don't last as long.  The idea is they are dissipating relatively significant power compared to a voltage gain stage driven by a 12AX7.  I currently am contracting at an RF h/w company, and one of their h/w guys is a ham radio stud.  He believes the power tube saturation wear-out is true.


And on a side note, anyone notice when you record the GM how the waveform distorts when you drive the 84s into saturation? Some part of "saturation" looks suspiciously like the dreaded op-amp-tube-screamer distortion. Is there another one of these stages at the output??? That question might be subtly directed at bordonbert, to whom I already owe a dark frothy beverage.

Has anyone tried using the JJ EL844 made special for Eurotubes in any of their GM tube swaps? Interested in hearing how they would be in these amps as some of us are seeking to adjust the gain levels. Even though they are claimed to distort sooner than el84's. Eurotubes says they offer other benefits too. I plan to experiment with them as earlier pwr tube break up is desirable for my lower home/ bedroom volume levels I play at. With one customer review saying he experienced less top end cut and enhanced low end they sound like they might help achieve what some GM owners are chasing. Also curious if they have any negative impact on the TSC system?

I was planning to do some more reading on this area before replying to Namklak's post re 2xEL84s v 4xEL84s.  It's an interesting one which I have considered myself in the past.  Living in a terraced house in an older neighbourhood doesn't make it easy to try things out at 36W for honest comparison!  With discussion starting around the output valves I'll wade in now with a few preliminary ideas for consideration.  Jump over the info portion if you are bored by that sort of thing or know it already, (genuinely understand it, not just "have a mate who's postman's grandmother's dog groomer says that..."  

Info:

What is the job that the output valves actually do?  Most of us will know that the signal from the preamp is split into two by the Phase Splitter/Inverter stage with one version as normal and the other inverted.  When each of these signal versions is fed to one of the output valves, (or one pair), they then each amplify one half of the signal, (being turned off by the other half of their own signal).  Oddly, each valve then produces a CURRENT (not a voltage) version of its half of the signal and they are both positive even though one comes from the negative half of the input.  It is then the job of the Output Transformer to take these two currents and to make sense of them so they return to a combined accurate version of the original signal.  To do this one valve feeds its current into the transformer input primary winding in one direction and the other feeds its current from the other end in the opposite direction, with the supply voltage being applied at the midpoint.  So each valve (pair) controls half of the primary winding for half of the time in opposite directions.  That transformer is an integral part of the output stage which could not function without it, (at least in valve circuits), and it will have a considerable contribution to the sound.  Leo Fender says so!

We all think of those valves "reaching breakup", but no one ever really considers the effects of the transformer on the distortion.  The metal core of the transformer is magnetised by the valve currents in the primary winding which in turn produces the current in the output secondary winding.  No material can just keep on carrying stronger and stronger magnetic fields so if these currents are large enough then the core "saturates", i.e. the magnetic field becomes too great for the metal of the core to handle and no increased magnetisation can occur.  This means that the input current from the valves may still be increasing but the output current will go static.  Effectively the Tx is kind of clipping the output in its own right.  It doesn't happen at an absolute level but begins to reduce and gradually gets worse over a fair voltage range.  Now, getting into this effect is a great thing for the output as it is a major part of producing the characteristic output stage compression, but going fully into it is a bad thing as it gets really harsh and can even damage the output stage!  The valve effectively sees a short circuit for the portion of the signal where the Tx is fully saturated.  You would think that the answer is to have a larger transformer, and some designers go down that route particularly in hifi amps where distortion is the enemy!  That leads to other effects/problems.  The frequency response will change as the size affects not only the bottom end but the top end capability too.  It may sound better or it may sound worse.  There are problems due to minimum magnetisation levels too.  So a larger transformer will stay cleaner louder but can perform less well at the lower levels and frequency response may actually be wider than we want.  A balance must be found or a compromise accepted.

Finally, any transformer is only partially efficient, they cannot ever transfer all of the energy fed into them by the valves into energy sent out to the speaker.  The difference is wasted as heat in the Tx.  That should be considered too.  Too small or of inferior build and material quality and it can simply burn out.

The End


Ok, theory over!!!  Namklak has pounced on an interesting issue in the GM36.  When we are running it full out at 36W we have a pair of valves driving the transformer on each side of the signal.  When we drop the power to 18W we reduce that to a single valve on each side, but the transformer has stayed the same.  We now have a lot more "transformer headroom" and will not drive the core so near to saturation, but we have to accept that those "lower levels" are making up a larger proportion of the signal which will also have a sonic impact.  If the bandwidth has opened up to a higher level then that may also be a factor.  I have always considered that part of the brightness of the GM36 may be down to its bandwidth being too great at lower power levels.  You pays your money and you takes your choice!

For the record, we have had posts here where people have rubbished the quality of the Txs in the H&K amps.  I totally disagree with that, I think they are a good choice.  Anyone who can offer an amp with 8-16ohm matching capability has confidence in the quality of their hardware, in particular the output Tx which soaks up all of the extra energy wasted when the matching is not perfect.  This has to be dissipated as heat in the Tx.  The guys at H&K have done their homework as we all know that there are a minimum of Tx problems reported on H&K amps.  Anyone know of one that has given up the ghost?

H&K are right when they say that the Power Soak is a great tonal tool.  It may be even better if it were fitted after the output stage and constantly worked on the 36W 4x valve output configuration.  There is a lot to be said for the idea that we should fit an external power soak of our own.  To make one is easy and costs a few pounds only.  If anyone is interested I can offer help with that.

Regarding the problem of valves wearing out, it's another dodgy area.  Valves have maximum voltage and current capabilities which are a factor of their mechanical internal construction.  The bigger they are the more electron emission or bombardment they can cope with due to heating and physical damage, and the gaps between parts are plain bigger so there are lower field conventrations.  We should not take them over that level without expecting wear issues, those maximum values are measured and quoted for good reasons.  Inside those constraints there is very little that they suffer in normal use, they certainly don't wear in any way when just idling.  As I have pointed out before, the use of Standby switches is the real killer!  I never use mine now, I always just turn down the master volume.

The Valve Wizard wrote:You may have heard of 'cathode stripping', which is a specious argument wheeled out by standby-switch obsessives. In its purest form, cathode stripping occurs when particles of the oxide coating are physically torn from the surface of the cathode when it is exposed to a powerful electrostatic field from the anode. This would happen if the valve is operated at saturation, without a usual space-charge of electrons to protect it. Fortunately, this effect does not exist in receiving valves, even when operated at saturation, because it requires an electric field strength of at least 4MV/m (yes, 4 million volts per metre!). No guitar amp ever comes close to this.

Another type of cathode stripping occurs when stray gas molecules in the valve become ionised by the electron stream. The positive ions will then be accelerated towards the more negative grid and cathode. If these manage to miss the grid then they may crash into the cathode, physically damaging its surface. The proper name for this process is cathode sputtering. Sputtering is a known problem in gas tubes and transmitting valves operating at kilovolt levels, near saturation. It doesn't occur to any significant degree in ordinary audio circuits. Note that even the RCA Transmitting Tubes Technical Manual No. 4, p65, states: “Voltage should not be applied to the plates or anodes of vacuum, mercury-vapor, or inert-gas rectifier tubes (except receiving types) until the filaments or cathodes have reached normal operating temperature” [My emphasis].

Receiving valves are the small kind used in radio receivers, i.e audio valves like those in guitar amps, in case you were wondering.

This guy knows his stuff!

Thanks again bordonbert, you pointed out a part of the equation i forgot - the txs.  I probably choose to forget those as that's my weakest area of audio electronics.

Yes, using 4 tubes vs 2 tubes definitely changes the operation/performance of the Tx.
1) headroom change.  My very weak knowledge was a Tx should never dissipate heat?  But it makes sense in a guitar amp you design the Tx to reach headroom-loss level just a little, for extra tasty munge at peak level.  So using only 2 tubes would mean never reaching that potentially designed-for peak.
2) as you stated, 4 tubes vs 2 tubes changes the output current.  As Mr. Ohm would posit, you could say the tube stage's output impedance has just changed by a factor of 2.  H&K must be doing some circuit magic to deal with this eh?  Just like the circuit magic that allows a tube amp to drive a load impedance change of a factor of 2 with no user intervention.
3) freq response.   Most on this forum (myself included) think the amp is a little too bright.  An easy plug-n-play change is JJ EL84s.  Also can change the preamp tubes cheap and easy.  Another change (albeit more costly and time consuming) is speaker swap.  Plus there a million speakers and only a small handful of tube manufacturers.  

So saturating the Tx might be advantageous in this case.  So that supports driving all 4 tubes hard and using an external power soak.  Hey, that's what I've been doing!

But back to 4 vs 2.  There are two pairs of tubes, with each pair doing sort of a push-pull thing.  Having two pairs is redundant in reference to the signal chain functionality, but offers twice the fun uh I mean current.  So you have two tubes doing each job instead of one - does that maybe smooth out some of the early saturation?

My whole point of being in this hobby is performance, I love it!  So I built an active power soak into a bigger 1x12 cab - this is easy and quick to setup at a gig.  I have a power cable for the GM, one for the power soak cab (it has a Crate Powerblock, fan on the 100W 8 ohm resistor, sanity light), and a cable from the gm to the power soak cab.  easy peasy.  Crank Master on GM and have fun.

BUT (there is always one of those), sometimes we play festivals with small stages, so there I'd like to use my super small 1x12 cab on a stand - and maybe passive power soak.  And that's where I  wondered about only 2 tubes to reduce the size/cost of the passive power soak.  And then I have to have a second set of presets that just uses 18W mode...  Sounds like running 4 tubes hard is where are all the fame and glory is...


Off subject on your off subject - you state you never use the Standby.  But then there is this quote from the RCA Tube Manual (of which I have an old copy buried in the basement):
"Voltage should not be applied to the plates or anodes of vacuum, mercury-vapor, or inert-gas rectifier tubes (except receiving types) until the filaments or cathodes have reached normal operating temperature" - isn't that specifically a reason to use the Standby?   By the way, receiving tubes are small signal tubes like 12AX7.  A couple of guys I know in the ham hobby (one of which is in fact the husband of the groomer of my wife's poodles) don't consider power tubes receiving tubes.

Quoted by Namklak wrote:"Voltage should not be applied to the plates or anodes of vacuum, mercury-vapor, or inert-gas rectifier tubes (except receiving types) until the filaments or cathodes have reached normal operating temperature" - isn't that specifically a reason to use the Standby?   By the way, receiving tubes are small signal tubes like 12AX7.  A couple of guys I know in the ham hobby (one of which is in fact the husband of the groomer of my wife's poodles) don't consider power tubes receiving tubes.

You hit the nail on the head with that quote concerning receiving types, and that's just what they are!  All of the valves we use in audio electronics are of the receiving type.  They were designed for lower voltage lower current work as would be found in radio receivers, (including our output valves), rather than higher voltage and power types for say transmitting radio, tv or radar, or mercury rectifiers.

The two things which are often quoted as the valve killers requiring a standby are Cathode Stripping and Cathode Sputtering.  The first can occur when the valve is left with its HT on and particles of the cathode coating are torn away by the electric field.  In reality this only happens near saturation so when in use, not at idle, (and when do you use a standby switch). For cathode stripping to occur you need field strengths in excess of 4MV/m, (that's megavolts per metre, and it's the equivalent of >4kV/mm. Imagine that in a 12AX7!)  We get nowhere near that in guitar amps in either the preamp or the power amp valves, it just doesn't happen in our class of valve.  The second occurs when there are gas molecules in the valve envelope.  These can be positively ionised by the electroin stream then pulled to the grid and cathode.  Some miss the grid and bombard the cathode, damaging its surface if they have enough energy.  And there's the rub, once again it is only effective at high voltages, (>1kV), and near saturation.

The real killer which does happen to our valves and under everyday working conditions is cathode poisoning, most commonly interface resistance build up.  This is where a layer of high resistance material grows in the cathode between its metallic base and the coating.  This gradually interferes with current flow until the valve is useless.  And that problem happens guess when, when the cathode is left heated with no anode current flowing for a length of time, in other words when it is in standby.  And no anode voltage, no anode current!  It is rather like having a slowly increasing unbiased cathode resistor introduced into the circuit cutting down gain.  It is slow to build up but once it happens it can't be reversed and the valve is junk.

There are a few other reasons why standby switches are bad news, switching effects and stresses for example.  I think originally the only one who got it right were Vox who never bothered with a standby switch on their early amps, and with no problems caused by that.  They then bowed to "peer pressure" and introduced one, I believe disastrously at first.  Leo didn't really know what he was doing to start with, and Jim just copied him blindly.  And everyone else has seemed to go down the same route because their competitors do.  Look for "The Valve Wizard".  He has a very informative page on his site devoted to the evils of Standby.

On a happier note, is your external power soak purely resistive or have you set up one with inductance included as a design feature?

Just a snippet.  Have a look here:  Mullard Receiving Valves Naming Convention.  Note the title given by Mullard and that Mullard states:

Mullard wrote:The type nomemclature for Mullard receiving and amplifying valves and small thyratrons generally consists of...

 They then give the lettering/numbering convention for all of the valves we use, including the EL34/84 and KTxx types.  All under the banner of Receiving Types.

A receiving tube by any other name is still a receiving tube.  uh whatever that means.  Okay...

Active power soak is resistive only.   Ya have a design handy that includes a reactive component I'm all ears.

Kind of an unexpected recommendation - try putting a stock Chinese tube back in to V2.  One of the triodes in V2 is configured in a Cathode Follower topology.  If you google "russian tubes fail in cathode follower" you'll get plenty of hits. As it turns out, some of the Chinese tubes have some construction differences that help them survive a Cathode Follower circuit better than many Russian tubes and more to the point to this thread sound better.  I put the original Chinese 12AX7s back in my GM, with the JJ EL84s installed.  It sounded uh interesting - I liked it.  I play classic rock.  I would tube roll my fav EH12AX7 back into V1 but I'm sort-of retiring the GM.

Anyway, if you like it, do not use the stock H&K tubes.  My buddy at GC told me they fail - a lot.  Maybe buy one of the Marshall Shuguangs or GC has a GT12AX7-C with the C meaning Chinese.

Later.

HI Guys not GM36 related, but I have a GM40D on order from Thomann..

I am in the UK and was going to buy JJ's via eurotubes, but unfortunately the costs including shipping/ and no doubt import tax start to make the shipping and costs more than the valves themselves.

Watford Valves offer the following, has anyone else used this exact specification?

2 Specially Selected Harma ECC83 STR
1 Specially Selected & Balanced Harma ECC83 STR
4 Specially Selected EL84-6P14P-EP-Reflector Super 10K in a matched Quad.

Any thoughts? its the package they advise.. but given the trial and error in this thread I am sure there are some better alternatives.

Sorry George but I'm the cynic in the group, best get me out of the way early on!  

You say, "its the package they advise..".  Well I would point out, "they wouldn't they, seeing as they are selling the overfussy kit which they recommend as a replacement".  I'm always suspicious of the words "specially selected".  Think, what the heck does that actually mean?  Have they told you what criteria they used to select them?  If not it could be they picked the ones with shinier bottles or straighter pins!

I won't suggest that you read it all but do go back a good few pages into this thread, there is more relevant info in there than you can imagine.  I will always quote the best advice that any of us have given on this subject as being the final word.  Go to Page 5 Post 122 of this thread and pick up the next few posts Voodoo Jeff makes concerning his Wathen valves.  Their valves for the GM36 are individually priced at about £700 and discounted for a full set at about £500 per amp.  He tells you his thoughts on using that "quality" of valve.  Look for the phrase "at best subtle".

My own view is that I will stick with the plain old JJs.  They improve the amp, subtly which is all any valve change will achieve, they can be bought anywhere though there are some low priced sources around, and they have proved in my case to be long lasting.  I don't expect more and I would claim that anyone else who describes themselves as a "tone junkie" to the extent of raving about esoteric valve types and checking out hundreds of combinations to find the one Holy Grail "right" setup is kind of into the image rather than the reality of guitaring.

For the record I've had good prices and good service from Karltone for valves because I know what I want and they just supply it.  Others have suggested other good suppliers too.  So as a tip, make your mind up which makes and models of valve you want before you go onto any supply site based on real info you source elsewhere, as you are doing here.  The supplier's hyped up descriptions of "silky top ends" and "slightly withdrawn lower middles" are marketing bullspit written to suggest there is much more to this issue of choosing valve types than there really is.  In the real world of playing with other musicians you can't hear any of it even if it existed in the first place.

Ha! yes, I knew I was at risk of showing myself up as a philistine and looking for a quick fix. I am aware of the guff they all talk and one wonders in reality (however reputable Watford valves actually are) has anyone even swapped those valves into the amp at all....

Of course they might have but perhaps that person may not have the same long term familiarity with the GM40/ 36 as anyone on here.

I know I will retube at one stage but I wont rush into it, I will consider the points raised by all in the above thread. Thanks for your help :-)

From what I can glean from the above thread then this seems like a popular way to go...

2 off JJ ECC83s (12AX7) - Valve Testing Options: Premium tested. for V2 and V3
1 off JJ 5751 - Valve Testing Options: Premium tested. for V1
4 off JJ EL84 - Matching Options: Matched Quad for power tubes but you don't need matched quads only matched pairs as such.

Edit *** DONE!

Delighted I did, before I did I actually struggled to get anything much out of my SG, cleans and clear, and any hi-fi sounding tones are no more.

That said the changes are not hugely dramatic but I still believe it worthwhile. I have many different guitars and I am doing way too much tone tinkering... think I am confusing myself tonally, time to get rocking. Band plays this weekend so she will get a proper work out then.

Hi all,

Tube noobie here. Can I ask, why are people putting a different tube in the V1 slot? If am switching my tubes out for JJs, and I don't want to change gain levels, is there any reason I shouldn't just put a standard 12AX7 in the V1 slot?