The Tube Swapping Thread

No problem Fatjac, it's a JJ ECC83S.  You probably know already but that's a custom balanced ECC83 which is nowadays considered to be the same as an American 12AX7.  Technically there are diffeerences, or rather were, but they are the same thing and not just a "common knowledge" substitute.

Still sounding absolutely great with this lineup.  With the gain spread the way I have it I can dial in very "boutique" tones now, not just the common or garden screaming Marshalls and clean Fenders that we tend to measure by.  I have finally laid to bed that top end "fizz" which you can get with a GM.  Mind you I don't think it would suit a metal merchant.  My lack of fizz is their dull as ditch water, and the extreme Ultra/Boost/Gain tones are only to be found at the very top of the settings where I would never go.  I actually have a pedal for that, same as they always do!

Thanks. Following my experimentation some months ago I ended up with a matched set of JJ EL84's, V1 a 5751, V2 & V3 JJ ECC83s's.

I didn't like it so I went back to the original 12AX7's. I might try V1 & V2 again but with 5751's & put an ECC83s into V3 as it could have been the V2...

Gary

It's difficult to say with some of this stuff.  It's all too easy to convince yourself there is a change when there isn't.  Implementing that change can take a minute or so with cool down and warm up and the memory doesn't hold a reliably accurate impression of sound for that length of time unless it is a staggering difference.  It really takes lengthy evaluation with frequent swapping to be sure.

The JJ EL84s will be my stock for the future, I can find nothing wrong with the way the power amp comes alive when driven and the ECC83S is the right tool for the job for a well balanced output stage.  This assumes that the phase splitter is a two triode paraphase type and not a single triode concertina type but you have to expect that in an amp of the quality of the GM.  That said, there is an argument that says that if the phase splitter is not made symmetrical, i.e. the two triodes in our ECC83S are not balanced for gain, you get more even harmonic distortion generated and this can lead to a sweeter distorted sound.  Logical to me but I'm happy with it as it stands.

For my needs, Blues and 70s/80s classic rock with no interest in metal or big hair and spandex and makeup, the 5751 pair in V1 and V2 sets the gain distortion characteristics perfectly.  The JJs are smooth enough to my ears and remove all of the fizz we all complain about regularly, (well me at least!).  The only thing that would make me change them out now is if I could find a valve make which kept the top end and middle and gave me more in the low end, but my own view is that the differences between valve makes is sometimes detectable but is minimal in the scheme of things.  I think it makes only subtle differences to the overall tonal balance.  The way to address that is first speakers then actual tone shaping circuitry changes.  But we don't have the schematics to be able to fiddle with that in a reliable way.  (Modder should not be synonymous with Bodger. That way lies pedal fiddling!)  Your ECC83S in V2 is not a problem as it is exactly the same as a 12AX7 which happens by chance to have the same characteristics in its two triodes, but is really overkill.  Unlike the phase splitter V3 where they are acting as two sides of the same coin, the two triodes in the valve more than likely act as separate stages with no reliance on the two having the same characteristics.  To balance them offers you no real improvement to either, (unless there is something quite unique going on in the schematic).

The last thing I would say once again is, from an engineering perspective 5751s - big yes, 12AT7s - huge no!

Hi all GM 36 lovers,

at first thanks a lot BB to provide me the opportunity to discover the Mitchell foam rings tips. I applied it in my 2*12 TT Cab, on the G12M speaker (the other Eminence CRex is dark enought).
I did it with a piece of fitness mat (!), 12 mm thickness, and it provide me that tame sound on the high I  was loocking for.

For tube I end up with V1=NOS 12AU7, V2=JJ 5751, V3=JJ EC83S, and I can have the creamier tones I was after for blues rock, classic & hard rock.

Personally I would never do that 12AX7 -> 12AU7 swap, for the same reason that I wouldn't make a 12AT7 swap. It's spelled out elsewhere. You got it best with your 5751 in V2, that's the valve which is closest in all its parameters to a 12AX7 and will keep the DC conditions and bandwidth closest to the original design. You have to give credit to the H&K designers, they are not idiots and came up with a great unit as stock. We should want to tweak it to our own taste but keep close to the underlying setup for reliability and safety.

But that said, if the sound comes out as you want then it works for you.

I've have a balanced Mullard 12AT7 in v3 for some time as the phase inverter and I think the sound is warmer and fatter. 12AX7 in v1 and v2

What was it about the 12AT7 that made you choose it as your substitute Stapletongas?

I can't find it now but I read somewhere about sending a cleaner signal to the power amp and having more clarity. Sounded worth trying, even if I didn't really understand the technicalities!

Warmer to my ears than a 12AX7 in there

Definitely doesn't do what they have told you! Sorry if this is too technical but if you think about what I say a little you should get the point.

In theory the 12AT7 will only "send a cleaner signal to the power amp and offer more clarity" when the signal level is higher. It's obvious that the higher gain 12AX7 would clip earlier. So you would think you are getting more headroom with a valve that acts like a lower gain 12AX7, that's what we are trying to achieve. In reality it won't work that way. In the design stage the engineers will have set the valve's anode DC level to be midway between the HT and the valve's bottoming out voltage. That way you get the biggest clean swing in your signal before it clips at either the top or the bottom end. That DC condition was set up for a 12AX7! A 12AT7 has a completely different set of characteristics and dropping it into the same circuit which was optimised for a 12AX7 will shift that DC point quite a bit. The stage will now clip on one side of the signal earlier than it would before. So you have reduced your gain to get more headroom and at the same time shifted your DC point to give less headroom!

As well as that, 12AT7s have a different loading effect on their anode. This affects the lower cutoff frequency of the filter which sits on the stage's output caused by its output capacitor. This will be set for a 12AX7 to not too far below 82Hz, the lowest frequency of a guitar. Extended bass does not sound good in a guitar amp so they don't do it! Putting in a 12AT7 shifts this cutoff upwards by as much as a factor of 3 or more taking it above the frequency of the E string. This means you lose a lot of bottom end and it can give 12AT7 substituted stages a thin weedy sound.

I have tried this myself with a recommended NOS Mullard CV4024. This is a classic military designated high quality 12AT7WA which was said to reduce bass much less than other 12AT7s. It lasted a run in period and one rehearsal as guess what, it thinned out the bottom end more than I could stand.

I can only guess that your perceived warmer sound could be due to the bass/lower mid balance being then slanted away from the bass and more into the mid. If you have a system which is not overwhelmingly strong at the top end it may not sound bad. And yes, it certainly is a personal thing, but the physics can never be sidestepped. The 5751 is a much much better match for 12AX7 circuitry than a 12AT7 in any properly designed case and should offer the same type of audible results as a 12AT7 but with a much better match in the other areas I rambled about.

Hi All
at the moment my combination, even if not in the right scheme from H&K, what I perfectly understand, fit what I expect: a warm sound, with not too much distortion (blues rock to hard rock), and very controlable at home studio level. And it tames the harshness in the highs as mentionned (along with the donnut in the cab!)

I can play with the 36w position, master at 9 oclock, and its remains manageable in my room: a bit loud, depending on my mood ! And great for 18, 5, 1 W.

Nevertheless, I have to try with a second 5751 in V1 in addition to my 5751 in V2: must order one at Banzai tubes...Will certainly do that and keep you in the loop. What i don't want, is to have the harshness in highs, back .

After swapping in 5751s and different 12ax7s (JJ, Sovtek, etc) and a 12at7 for giggles (sometimes non-symmetrical clipping can be tasty), and getting a nice warm sound in my bedroom - the sound guys then whined my sound was too dark.  So, I swapped EH 12ax7s into all positions - I lost a little of the bedroom warmth but I do cut thru the large band on stage better.  Still JJ EL84s of course...

Bordonbert must be old, he has a Steve Marriott quote in his signature...

namklak wrote:Bordonbert must be old, he has a Steve Marriott quote in his signature...

I have another line from that song in my signature! Marriott was one of the greats!

'spose I must be old too...

Getting on for as old as Shaky Jake!  Don't have skin as tough as hickory though.  But I am just as curmudgeonly to boot.

Marriott is my all time rock favourite, the best rock/soul voice Britain has ever produced.  If you want to see his influence give this a listen:  



Make sure to hear around 3:30!  Ignoring the backing which is their more pop oriented style, whose vocal style is that?    That was 1966 and LZ were formed in... now wasn't it '68?  Time travel apparently exists.

LZ fans should look into the relationship between Marriott and Plant, it makes for interesting reading. You may find the word "gopher" used a few times.  Also, Marriott was first up for the vocalist role in LZ.  I'll use someone else's words here, "The legend goes that Marriott's crime-connected manager threatened Page with broken fingers if he tried to steal Marriott away, leading to one of the great "what-ifs" of rock."

And Humble Pie really were the "best little rock and roll band in the world" just as their introduction tells us.  As I keep telling all of you Phillistines but you take no notice!

Good post!

As you know, I agree 100%!

Thanks so much for this Thread. As a new owner of a GM 36 I am doing two things: playing the amp in order to get a feel for the tone and watching this thread so that if i decide to upgrade tubes/valves I'll know what to choose.

So, I found 3 ecc83, Groove Tube, that I used to have in a mark iii Boogie15-20 years ago. Nice articulate and smooth tone, gain well under control and less gain than the JJ ecc83s tubes I tried.

So, what is the difference between an ecc83 and an ecc83s?

I have finally changed the power -amp tubes with jj's and i have to confess that i was pretty amazed from the results.The fizziness disappeared from the lead and crunch channels,more organic sound with more harmonics!.I am about to change the pre -amp tubes and i want your help.I am leaning towards the svetlanna pre- amp 12ax7, since there is a retubing kit which uses them with the jj's el84.What do you mates recommend as an alternative solution?I want the less grainy and gritty sound from the amp and i want to stick with the 12ax7 's.Any suggestions?

http://www.thetubestore.com/Shop-by-Amp/Hughes-Kettner-GrandMeister-36-Amp/Hughes-Kettner-GrandMeister-36-Value-Package

Thanks for your post...it is very helpful to me.
I too have seen these "Packages" at The tube Store. They have 3 different ones for the GM 36. But, in my opinion, they do not do a good job telling the consumer WHY they are including the various tubes in the package. I would want to read more of what makes the value package different/better/worse than the two higher packages. I don't sense that they have done much homework on this. How can the consumer tell if no substantial info is given?

I think you guys have hit on a common problem here.  The sellers of valves (and many other things guitar related) are caught in the age old cleft stick, can I afford to be truthful if it would reduce sales?  They have to think up ways of describing differences between their products even when there aren't any significant ones.  They need to convince you of something which will in turn convince you of your need to buy, and a perceived difference from their descriptions will do the trick.  It's a case of the Emperor's new clothes!  If they tell us there is a difference the vast majority of us will hear one.  It always amazes me how they make out that one make is night and day different to another when usually there is only the most subtle of changes in specific situations.  If you look at the descriptions on any of the sites offering a range of valves of the same type, you will see how the same phrases crop up in different makes and models.  They have to put something in there to make each one sound special and there are only so many hyperbole they can use.

In truth, VoodooJeff described it best when he said that he had always found that any differences between valve makes are best described as subtle.  And he speaks as a professional who is confronted with issues like this every day so has really good practical experience.  I was originally of the mind that there were very few differences of any kind at all that could be heard as I know there are none in so many other areas which are held out to be anything but subtle by too many who don't actually listen critically!  That was until I tried a swap out and then had to admit that, with valves, there is a case for his description, subtle.  But I would add significant!  I openly climbed down on this one and now say yes, there are differences but I urge caution in the way you approach dealing with them.

As I said, the differences are not night and day to me, and some of the descriptions are flowery sales talk.  I think it's safer to view it as a ladder of simple quality with them all sitting somewhere on it.  I feel it's a very short ladder, not too great a range of difference at all, and it depends on how high your degree of fussiness wants to go as to which you should choose.  As you have shown, you can pay massive amounts for valves which are only marginally different, (not necessarily better), than a much cheaper model, if at all.  So my tips would have to be:

* In our case, virtually any move to a sensible valve will yield improvements.  The top end fizz reported was sorted out completely in my case by simple JJs and a suitable speaker choice.  I don't know of anyone here who insists that incredibly expensive "NOS Mullards from between the wars made in the Cleethorpes plant on a Wednesday" are the only choice to make.

* Changing makes of the same type is a different issue to changing types.  Do not confuse the two.  I love using 5751s for their lower gain and speak out against 12AT7s on technical grounds.  12AX7s should be stuck to unless you feel the need to take out some of the potential overdrive.

* Don't talk yourself into spending money you don't need to, it's incredibly easy to do that.  If your instinct tells you that a choice will be good enough it probably will, don't go above that just to "be sure".

* Only use your ears to make choices where you can, and only when valves are swapped in the same amp with exactly the same settings hooked up to exactly the same external kit.  Anything else is totally meaningless.  How can you compare the valves from a Fender with Groove Tubes in it against a Marshall with JJs?  The concept is ludicrous yet people do take that sort of advice and make a choice based on it.  "He tells me they sound great in his Peavey so they will be the ones to have for my H&K".

* Most important of all, and this will sound odd but, make yourself start from a position where you are trying to convince yourself that there is no difference!!!  That is better than listening with the aim of hearing a difference.  If you can convince yourself you are not hearing a difference then it means just that - there is no difference.  If your mindset is that you are trying to hear a difference then you most probably will, even when there is none to hear.  Remember that you are swapping out valves before you can hear the comparison.  That takes time, too much time for your memory to be reliable.  It takes many swaps and comparisons before you can be sure you are hearing something for real.  That is why you see people make decisions based on a couple of swaps then a month later they are back asking the same question.  We have all done it at some time or other.  Other than blind listening tests there is no other way I know of to make a fairly sensible dispassionate decision.

As to the packages you list there from The Tube Store, I would like a little more info than "our expensive one is of course better" based on phrases like "prized vintage tube" on which to make a decision.  Frankly $90 for a 12AX7 is highway robbery, nothing is worth that.  My own view would be that I would start with a sensibly improved type, JJs or EH say, and be prepared to use them until they give up the ghost or until I have gained a better understanding, maybe by borrowing a set from somewhere to try out for a while.  They will offer an improvement I'm sure.  Any other fine tuning can take place over an extended time ready for the next valve service change.  That way you aren't constantly paying over the top prices for something you will swap out again a month later.

bordonbert wrote:I think you guys have hit on a common problem here.  The sellers of valves (and many other things guitar related) are caught in the age old cleft stick, can I afford to be truthful if it would reduce sales?  They have to think up ways of describing differences between their products even when there aren't any significant ones.  They need to convince you of something which will in turn convince you of your need to buy, and a perceived difference from their descriptions will do the trick.  It's a case of the Emperor's new clothes!  If they tell us there is a difference the vast majority of us will hear one.  It always amazes me how they make out that one make is night and day different to another when usually there is only the most subtle of changes in specific situations.  If you look at the descriptions on any of the sites offering a range of valves of the same type, you will see how the same phrases crop up in different makes and models.  They have to put something in there to make each one sound special and there are only so many hyperbole they can use.

In truth, VoodooJeff described it best when he said that he had always found that any differences between valve makes are best described as subtle.  And he speaks as a professional who is confronted with issues like this every day so has really good practical experience.  I was originally of the mind that there were very few differences of any kind at all that could be heard as I know there are none in so many other areas which are held out to be anything but subtle by too many who don't actually listen critically!  That was until I tried a swap out and then had to admit that, with valves, there is a case for his description, subtle.  But I would add significant!  I openly climbed down on this one and now say yes, there are differences but I urge caution in the way you approach dealing with them.

As I said, the differences are not night and day to me, and some of the descriptions are flowery sales talk.  I think it's safer to view it as a ladder of simple quality with them all sitting somewhere on it.  I feel it's a very short ladder, not too great a range of difference at all, and it depends on how high your degree of fussiness wants to go as to which you should choose.  As you have shown, you can pay massive amounts for valves which are only marginally different, (not necessarily better), than a much cheaper model, if at all.  So my tips would have to be:

* In our case, virtually any move to a sensible valve will yield improvements.  The top end fizz reported was sorted out completely in my case by simple JJs and a suitable speaker choice.  I don't know of anyone here who insists that incredibly expensive "NOS Mullards from between the wars made in the Cleethorpes plant on a Wednesday" are the only choice to make.

* Changing makes of the same type is a different issue to changing types.  Do not confuse the two.  I love using 5751s for their lower gain and speak out against 12AT7s on technical grounds.  12AX7s should be stuck to unless you feel the need to take out some of the potential overdrive.

* Don't talk yourself into spending money you don't need to, it's incredibly easy to do that.  If your instinct tells you that a choice will be good enough it probably will, don't go above that just to "be sure".

* Only use your ears to make choices where you can, and only when valves are swapped in the same amp with exactly the same settings hooked up to exactly the same external kit.  Anything else is totally meaningless.  How can you compare the valves from a Fender with Groove Tubes in it against a Marshall with JJs?  The concept is ludicrous yet people do take that sort of advice and make a choice based on it.  "He tells me they sound great in his Peavey so they will be the ones to have for my H&K".

* Most important of all, and this will sound odd but, make yourself start from a position where you are trying to convince yourself that there is no difference!!!  That is better than listening with the aim of hearing a difference.  If you can convince yourself you are not hearing a difference then it means just that - there is no difference.  If your mindset is that you are trying to hear a difference then you most probably will, even when there is none to hear.  Remember that you are swapping out valves before you can hear the comparison.  That takes time, too much time for your memory to be reliable.  It takes many swaps and comparisons before you can be sure you are hearing something for real.  That is why you see people make decisions based on a couple of swaps then a month later they are back asking the same question.  We have all done it at some time or other.  Other than blind listening tests there is no other way I know of to make a fairly sensible dispassionate decision.

As to the packages you list there from The Tube Store, I would like a little more info than "our expensive one is of course better" based on phrases like "prized vintage tube" on which to make a decision.  Frankly $90 for a 12AX7 is highway robbery, nothing is worth that.  My own view would be that I would start with a sensibly improved type, JJs or EH say, and be prepared to use them until they give up the ghost or until I have gained a better understanding, maybe by borrowing a set from somewhere to try out for a while.  They will offer an improvement I'm sure.  Any other fine tuning can take place over an extended time ready for the next valve service change.  That way you aren't constantly paying over the top prices for something you will swap out again a month later.

Excellent points! The flowery prose heaped upon tubes reminds me of descriptions of food and libation products.
I appreciate your posts throughout this thread, Bordonbert!

bordonbert wrote:I think you guys have hit on a common problem here.  The sellers of valves (and many other things guitar related) are caught in the age old cleft stick, can I afford to be truthful if it would reduce sales?  They have to think up ways of describing differences between their products even when there aren't any significant ones.  They need to convince you of something which will in turn convince you of your need to buy, and a perceived difference from their descriptions will do the trick.  It's a case of the Emperor's new clothes!  If they tell us there is a difference the vast majority of us will hear one.  It always amazes me how they make out that one make is night and day different to another when usually there is only the most subtle of changes in specific situations.  If you look at the descriptions on any of the sites offering a range of valves of the same type, you will see how the same phrases crop up in different makes and models.  They have to put something in there to make each one sound special and there are only so many hyperbole they can use.

In truth, VoodooJeff described it best when he said that he had always found that any differences between valve makes are best described as subtle.  And he speaks as a professional who is confronted with issues like this every day so has really good practical experience.  I was originally of the mind that there were very few differences of any kind at all that could be heard as I know there are none in so many other areas which are held out to be anything but subtle by too many who don't actually listen critically!  That was until I tried a swap out and then had to admit that, with valves, there is a case for his description, subtle.  But I would add significant!  I openly climbed down on this one and now say yes, there are differences but I urge caution in the way you approach dealing with them.

As I said, the differences are not night and day to me, and some of the descriptions are flowery sales talk.  I think it's safer to view it as a ladder of simple quality with them all sitting somewhere on it.  I feel it's a very short ladder, not too great a range of difference at all, and it depends on how high your degree of fussiness wants to go as to which you should choose.  As you have shown, you can pay massive amounts for valves which are only marginally different, (not necessarily better), than a much cheaper model, if at all.  So my tips would have to be:

* In our case, virtually any move to a sensible valve will yield improvements.  The top end fizz reported was sorted out completely in my case by simple JJs and a suitable speaker choice.  I don't know of anyone here who insists that incredibly expensive "NOS Mullards from between the wars made in the Cleethorpes plant on a Wednesday" are the only choice to make.

* Changing makes of the same type is a different issue to changing types.  Do not confuse the two.  I love using 5751s for their lower gain and speak out against 12AT7s on technical grounds.  12AX7s should be stuck to unless you feel the need to take out some of the potential overdrive.

* Don't talk yourself into spending money you don't need to, it's incredibly easy to do that.  If your instinct tells you that a choice will be good enough it probably will, don't go above that just to "be sure".

* Only use your ears to make choices where you can, and only when valves are swapped in the same amp with exactly the same settings hooked up to exactly the same external kit.  Anything else is totally meaningless.  How can you compare the valves from a Fender with Groove Tubes in it against a Marshall with JJs?  The concept is ludicrous yet people do take that sort of advice and make a choice based on it.  "He tells me they sound great in his Peavey so they will be the ones to have for my H&K".

* Most important of all, and this will sound odd but, make yourself start from a position where you are trying to convince yourself that there is no difference!!!  That is better than listening with the aim of hearing a difference.  If you can convince yourself you are not hearing a difference then it means just that - there is no difference.  If your mindset is that you are trying to hear a difference then you most probably will, even when there is none to hear.  Remember that you are swapping out valves before you can hear the comparison.  That takes time, too much time for your memory to be reliable.  It takes many swaps and comparisons before you can be sure you are hearing something for real.  That is why you see people make decisions based on a couple of swaps then a month later they are back asking the same question.  We have all done it at some time or other.  Other than blind listening tests there is no other way I know of to make a fairly sensible dispassionate decision.

As to the packages you list there from The Tube Store, I would like a little more info than "our expensive one is of course better" based on phrases like "prized vintage tube" on which to make a decision.  Frankly $90 for a 12AX7 is highway robbery, nothing is worth that.  My own view would be that I would start with a sensibly improved type, JJs or EH say, and be prepared to use them until they give up the ghost or until I have gained a better understanding, maybe by borrowing a set from somewhere to try out for a while.  They will offer an improvement I'm sure.  Any other fine tuning can take place over an extended time ready for the next valve service change.  That way you aren't constantly paying over the top prices for something you will swap out again a month later.

mate i wasn't reffering to the expensive package,only to the basic.I put here this link to show that this company thinks that the jj's power tubes(,which i have already installed)pair well with the svetlana pre amp tubes. So i was wondering ....if i won't be able to find svetlana 12ax7 tubes,which brand from the inexpensive has the less gritty grainy sound!That's all.Nothing more

Tubedepot.com has the JJ`s (both preamp and poweramp) for $10 a piece. That`s $70 for a full set of JJ`s. It`s a no brainer.

Yeah, I have a deal with Wathen Audiophile tubes as an artist, but even with artist considerations I`m in for WAY more than that for a set. And with a second GM36 about to show up, I suspect I`ll have one loaded with Wathen and one with JJ`s (just don`t tell anyone!).

Do the Walthen's really make a difference Jeff?  If so, how would you describe it?



EDIT: Gulp! Just had a look at their prices. Guess I won't be going for a set of them in the near future.

bordonbert wrote:Do the Walthen's really make a difference Jeff?  If so, how would you describe it?



EDIT:  Gulp!  Just had a look at their prices.  Guess I won't be going for a set of them in the near future.

Hahahaha.....that was my exact response when I looked them up for the first time. I was like "there is NO WAY a $100 tube sounds 10X better than a $10 tube". I told it straight to the president of the company`s face when I first was introduced to him. Do I have the budget to spring for a set of tubes at that price? *&^%% no. No way. He very politely asked me to just try the demo amp on hand (H&K`s own GM36, loaded with their tubes). I resisted, and told him it would be very hard to persuade me away from JJ`s at 1/10 the price when I already knew they sounded good. The next few minutes would change my opinion of boutique tubes. I will never in a million years say that they are the be all, end all, nothing else matters tube choice. ANY aftermarket tube sounds better than cheap chinese stockers, and anyone would be hard pressed to EVER tell the difference between brands (and yes, I will call BS to anyone claiming otherwise). Do they sound good? Of course. Do they sound "better"? Can`t say that`s the quality that makes them magic. It`s more of an earthiness I can only feel. Would I be brokenhearted if I had to put JJ`s in my amp again? Not one bit. I`m not a big enough deal to get all my gear for free and I`m perfectly happy with the JJ`s. But the Wathen tubes have a quality you just can`t put your finger on. Something you can`t duplicate with EQ changes or any mumbo jumbo magic capacitor swaps.

And for that, I am glad I have them B-)

It's good to see once again that I'm not the only one poohpoohing some of the stock "unquestionable truths" in this game.

I can relate to what you say about that magic quality you can't define.  It's the same with a great hifi system, (and I'm talking the top 0.01% of what is out there).  The tonal balance should be sorted out in any semi-decent setup nowadays, time considerations get addressed in the better quality ones and timing and rhythm feel right, but then there is the aspect of imaging which becomes almost breathing.  Very very few people ever set up a stereo system for imaging correctly, even if they have good equipment.  It requires making the entire room a part of the system.  But when you have the right system and you do take care with its set up it's a joy you never forget.  The soundtage drops into focus and everything is where it should be, especially with vinyl as a source.  With your eyes closed or even better, in the dark, it's as though the instruments are physically in space in front of you.  The sound becomes 3D and solid.  Everything has position side to side, forward and back, and somehow up and down.  It's astonishing and takes listening to music to another dimension totally.

So your magic bottles have that certain "je ne sais quoi".  At that price they should have something special mind you!  But are they not intended primarily for hifi amps rather than guitar gear?  I can't see them generating much capital from the likes of most musicians.  And there is another aspect to consider.  What is their longevity like.  The power valves in particular have to be considered as virtually consumables.  Preamp valves are a different kettle of fish and will more or less last the life of most amps if care is taken with them, despite what people think.  I'd hate to find they are more tempremental because of their quality and superior characteristics and die more quickly than stock ones.  Does their quality of design and production lead to a longer life or a shorter one?

I can't remember if I've posted this here before but it makes for a sobering read and it's relevant to this topic.  It's on the effect of standby switches on valves particularly in guitar amps.  Standby Switches Damage Your Valves! They are a bad thing!!!  You should think twice about putting your amp into standby and removing the anode voltage while leaving the valve heaters powered up.  The guy knows his stuff and explains it well.  There is circuitry there but if you aren't interested in that aspect just make sure to read the second section on Standby Switches And Folklore.  Cathode Stripping and Cathode Poisoning are real effects, and their relationship to standby switches is never understood correctly.  In truth, I only really know a little way beyond the basics but that at least tells me that the standard wisdom about standby switches prolonging the life of your valves is wrong.  My level of knowledge of this may be limited but that means I do know enough to get the best out of my valves.  With those prices you could do with reading it too.  It would be useful to have some idea of how the GM36 is set up with respect to these things.  I really wish I could get my hands on a schematic for private viewing, it would tell us so much about the amp and how to get the best out of it.  But hey ho, that's not going to happen.