The Tube Swapping Thread

I recently swapped my TM212 cab for a 1x12 with a vintage Greenback, which has improved the sound. Hopefully the new valves will be the icing on tne cake.

Haha! Another Greenback convert. I love it when a plan works out.

Don't think you can lose with the valves Davus, I can't remember anyone ever having anything bad to say about JJs in the GM36. Keep us up to date.

Sorry if this has been covered already but...
I have bought a set of JJ EL84s, a 5751 and 2x ECC83S's.
Is it OK to put just 1 5751 in V1 and then have V2 and V3 as ECC83's?
Thanks.

That's absolutely fine Nick. V1 = 5751, V2 = ECC83S, V3 = ECC83S is sound.

You may like to experiment with the idea of putting the 5751 in V2 with an ECC83S in V1 instead. I'm not sure if it will sound significantly different, someone else may have experience of that, but I would be surprised if there wasn't some difference even if small.

The V3 position is a difficult one to assess when dropping the gain. That valve has a totally different job to do to the other two. I'm not sure if the idea of a lower gain phase inverter is a good idea or not. Usually a PI swap entails just using a balanced valve where the two triodes in it have been checked for equal gain. I don't know how much you understand of what goes on in an amp so apologies if you know more than I seem to credit you for here. The other two preamp valves basically raise the voltage of the signal at different stages in the chain either to create the sound we want by overloading themselves and their mates and distorting the signal, or to make up for something else which has taken away some of the signal, tone controls for example. The PI takes the signal after that process and makes two mirrored versions of it, each an "upside down opposite" of the other so they can be fed to the pairs of output valves which create the high current we need. I can't see a benefit in having a lower gain PI really but that's just a gut thing, I have absolutely no experience of having tested and listened to that setup. Again maybe other members can shed some light on this?

For my part :

V1: 12ax7 JJ

V2: 12ax7 EHX

V3: 12at7 TAD

El84 JJ

The 12at7 in v3 decreases the gain of the amp is more progressive I think.

I'm afraid not Kurowan, it's a very bad move from an engineering standpoint. Have a read of post 46 and 47 in this thread. If you can get your head around that and are still interested in why it is a bad thing then I can explain more deeply but it does get a tad technical with the valve datasheet graphs and such, (and it seems to rock the "mojo" driven way a lot of people approach their amp relationships which upsets some).

Ok thank you bordonbert, i'll replace the TAD 12at7 by Sovtek 12ax7lps

You can really get all of the benefits of lower gain by using a 5751 without the drawbacks of a 12AT7.  The 12AT7 may work in 12AX7 stages in most cases, but it will really change the designed conditions of the stage and lead to unpredictable problems.  I think in your V3 phase inverter slot you may well be better just sticking to the original 12AX7 type.  I'm not sure if there is any benefit in sound to drop the gain of that stage.  Others with more experience than me in that side may be able to fill us in with what they have found on that one.  There is always Jeff's magical ECC803 with its one side 12AX7 and the other 5751!  (How does he come up with it? )

Cheers for the info. One thing, do I need a balanced 12AX7 for V3? I just have a standard JJ ECC83S - no idea if its balanced. Cheers

There are arguments for and against a balanced valve in V3. We don't really know how H&K have gone about designing their phase inverter stage. There are some configurations where it can be done with a single triode, the TM seems to be designed like that, and some where it is based around a pair. Without the schematic we can't tell which applies in the GM36. If it is a single triode stage then there is no point in having a balanced valve. If it is a pair then it would affect things.

The idea is theoretically to make the top half of the signal match the bottom half as exactly as possible. In a long tailed pair approach with one triode for the top half and another for the bottom half of the signal, both in the same valve, if they are unbalanced that would make the top and bottom amplify slightly different to each other. But that is only a problem if we are wanting to get as low distortion as we can, say in a hifi amp. If the two triodes are unbalanced that adds in even harmonic distortion and that is the sweet type which we are trying to introduce, so having an unbalanced valve in V3 could also be seen as an additional way of adding tone.

The best way would be to try it but that means buying an additional balanced valve, and it may make no difference at all! However there is something which always creeps into this sort of issue and should be considered. Would you be going to the expense of paying for a balanced valve because you had been led to believe it would sound better or because you are actually unhappy with your sound now? It is too easy to be led into obsessively chasing something which you believe may be out there and miss enjoying something which is extremely good and satisfying in the meantime. I know too many people who are always changing their gear, modding it or swapping it out for new, and who never settle down to just play. I will mess around with my gear but it isn't driving me to always be unhappy and look for something which is going to lead me to the Shangri La of tone. Things don't work that way.

So ask yourself, are you looking for something that others have made you believe is there if you just follow "the rules", or are you looking for something because you are really unhappy with what you have now? If you aren't really unhappy then enjoy!

Thanks BB. I will see how I go.

If a bit superfluous and redundant, I`ll offer this: I`ve got two GM36`s, each with radically different tube brands. Side by side, simultaneously I can`t tell the difference. If I isolate the two and run them with the exact same settings, then I can tell them apart.

A while back when JJ`s were really getting popular there was some hubbub about how the 803`s were noisy and microphonic. Well, I have an amp loaded with them, a high gain amp at that, and they`re not any more noisy than the audiophile grade tubes in the other amp. These are my go-to tubes now.

I have never personally noticed any difference whatsoever in balanced or matched preamp tubes. It`s related to why there is absolutely no sense in biasing them.

So my revalve set fTom Eurotubes arrived. I've watched the video of how to replace them. Almost good to go, but....

Which valve is v3?

According to Eurotubes it's the one farthest from the input Jack and they've given me a balanced ECC83S for it. Thev fact it's different makes me think it should go in the one nearest the input Jack which has a metal cover over it?

Also how do I get that off?

Any help appreciated.

Cheers

David

It's this set by the way:
http://www.eurotubes.com/store/pc/viewPrd.asp?idproduct=2001&idcategory=606

The balanced tube goes in the V3 position which is furthest from the input jack.

V1 is the position closest to the input jack, with the metal cover. To remove the cover, just push it down a bit and turn counter-clockwise.

Good luck and let us know what you think of the JJ's!

Thank you!

Will do

Well an update for me.
Firstly i replaced the power amp tubes with jj's el84.Good improvement in the overall sound .The fizziness dicreased and the sound became warmer.Then i changed the two preamp tubes with jj's 12ax7.I tested them in all the positions with the following results:V1-2 not so good results the sound was a bit muffled. Then positions v2-3 with a stock Chinese in v1, better option the fizziness dicreased even more it almost disappeared .And finally i bought a tung sol 12ax7 and replaced the Chinese in v1.Have to say this:the amp is perfect now.Great improvement.I will buy another tung sol to see the impact in v2-3 and see if it gets even better,if not i 'll stick with the previous configuration!


P.s: I wonder why did the amp come with those stock tubes?Have they really heard what this amp is capable of with some better tubes.It would have sell like a butter with better tubes.Too bad!

ignantios wrote:

P.s: I wonder why did the amp come with those stock tubes?Have they really heard what this amp is capable for with some better tubes.It would have sell like a butter with better tubes.Too bad!

I spoke at length with the H&K folks about it. They know exactly what a shortcoming the chinese tubes are. The issue is cost. With name brand tubes in there, their cost goes up X dollars. Because they don`t sell direct, that cost get multiplied at LEAST 4 times by the time it hits retail, so it would effectively hit us for another $150-200 on the retail end. At that much of a price jump we can put whatever tubes we want in it, and they know it.

Wow, these guys really are pretty sensible and open in their attitudes and that's laudable in today's market. Now there are some who will jump down their necks for admitting that Jeff, but I prefer to praise them for it. I really think it's an almost unique stance to take.

Firstly, there are plenty of people out their playing metal type stuff who will actually like the sound of those stock valves, (have I mentioned the amp is made in Germany in the last few days? ) Secondly, why put in a set of more expensive valves when you know so many people will just swap them out anyway for their own particular favourites. Thirdly, the cost issue is a very real one for a manufacturer and keeping it down while allowing future expansion if it is wished at the customer's expense is a fair approach. Mind you, I wonder why they didn't come up with their own upgrade mechanism built into the ordering process. I wonder how many outlets are quietly offering a recommended valve upgrade service of their own built in to their sales system!

Another trip down tube-swap lane.
The EL84s are always JJ.
I initially tried JJs 12AX7, 5751, and even had some ECC81 (12AY7) laying around.  Really nice brown blues tones in the bedroom.  In the AllBros tribute band I'm in (7 piece including 2 guitars and 2 drummers), I wasn't cutting thru.  Sound guy bitched, even the other guitarist bitched.
So over the last 6 months I was using V1 EH 12ax7, V2 Sovtek 12ax7, V3 EH 12ax7.  Fairly good.  I find the EH to be sparkly, even HiFi maybe.
I was reading recently the Tung-Sol relative specs in a chart someone made - seemed like the Tung-Sol would be a cross between JJ and EH.  Supposedly very reliable and low noise.  So Doug sold me 2 Tung-Sol (herein known as TS), one gain of 90, the other gain of 110.  My plan was to use the 110 in V1 for more grit/hair on the Clean channel, and the 90 in V2 to tame the high gain Lead and Ultra channels.
Note: anecdotal evidence it appears to me that V1 is mainly for Clean and Crunch, and V2 is mainly for Lead and Ultra.  Maybe V2 adds gain stages for the Lead and Ultra - see Mesa Boogies for reference to kind of the inventor of extra stages.  Or maybe Tom Scholz.
Result:
V1: although I liked the slightly extra gain of the TS 110 in the Clean channel, I went back to the EH, as it give me a real sparkly clean Clean channel.  And I really like the way it sounds if I hit the front of the gm with an overdrive or tube screamer.
V2:  The TS with a gain of 90 did give me more range on the Gain adjustment for the Lead and Ultra.  I use low Gain values for those channels, and the 90 definitely lowered the gain.  I also re-tried a JJ (nice and brown but I've been there) and an EH (too HiFi for the Lead and Ultra).  Stuck with the TS 90.  Btw, the TS is really low noise, and really lowered the noise of the Lead and Ultra channels - lowest of any tube I tried.
V3: I swapped many tubes in for this, and ended up with the TS gain of 110 in this position.  Notes seemed to sustain a little better and every channel seemed to have a little more "balls" I guess.

I'm pretty "happier" with all of the channels now - the Clean is sparkly with a hint of hair at a gain of 255 (aka 10) and overdrives nicely.  Crunch is good.  And I like the extra range of adjustment of the Gain on the low end on the Lead and Ultra with the TS with a gain of 90. This combo really brought out the natural low-mid range "snap" of my SG.  Gig in 2 weeks, that'll really shake it out.

On a side note, I dropped my GM in it's case while loading out from a gig last Friday.  The GM was on a stack of crap on a cart - I pulled out my large cab and the GM rolled and then dropped a little over a foot.  Landed on the top - so the soft case handle maybe added a little extra padding.  Result - no functional nor cosmetic damage.  YAY!  German engineering eh?

So here is kind of a subjective-term description of how each of these tubes behaved in this amp:
EH - sparkly clean almost HiFi with great hi freq response.  IMO great for V1 if you like a sparkly clean Clean channel.  My choice for V1
JJ - warm and brown with melodic overtones on breakup.  Good for blues and classic rock, but may not cut thru mix in large band.  JJ's known to be very reliable.
Sovtek - middle of the road on almost every parameter.  Hi freq response in between EH and JJ, okay sound on breakup with decent headroom.  I found it good in V2 for metal and hard rock on the Lead and Ultra channels.
Tung-Sol - almost as good freq response as EH and very good breakup tones, very low noise. Good pick response, something of a gentle low-mid freq boost or ??? that gives better transient dynamics.  My current choice for V2,3.

Hi all

for a few months now I have V1, V2, V3=5751, 5751, 83s, all in JJ, as for the EL84. Was hesitating with a TungSOl Gold in V3, quite good too, but the tone appears to be warmer with the 83s.

Very pleased with. My 2*12 cab at home is the TT REX with G12m and C.Rex, or a Palmer 1*12 with a Wizard.
I'm tempted to take a Palmer 2*12 to put the Wizard + Governor. I did that previously with that Palmer and I was very pleased too, but with a more compressed sound than my TT Rex, as the Palmer is closed back.

And in order to tame a bit more the highs, I put on the grill clothe of the TTREX a centered foam disc with a CDROM size. Excellent results. I have to mention that I play only at home with that 2*12 TTREX.

If you mean you are using a foam circle fitted into the centre of your grille trying to emulate the Beam Blocker add on then you're making your cabinet dispersion worse. The foam may well adjust the frequency response to sound nicer to you but elsewhere it will be very unpredictable and very, if not wildly, different to the on axis response. For dispersion it will be definitely worse than not having it at all. You can't buck the Physics! This means that some people in your audience may hear a very well balanced response but others in a different place will hear a very different one.

No Pb with the physics for me, coz in my case I just do that with my 2*12 in my studio, at 2 meters. So That's ok in that specific use case. Would be very different in a band context=> std cab configuration.

Spot on Trb, I get your point!