TM36 Upgrade

Hi,
Just finished the upgrade to my Tubemeister 36 Combo, When I first got it I found the amp to be too bright and needed warming up.
So I took out the Chinese 12ax7bs and fitted in the pre amp V1-Mullard I61 - V2 Mullard I63 - V3 TAd 12ax7a-c. And 4x Philips 6BQ5s -EL84s
on output. I also treated the amp to a celestion alnico gold speaker, Although the speaker still requires breaking in, Its first time I have had EQ controls to half
way and still get a good warm tone which cuts through drums bass and keyboards evenly, I am really pleased with the results.
Before I had bass on 3/4 Treble on 1/4 and my Strat with tone controls backed off. Now its improved sustain on clean channel.
Just thought I would share my upgrade with guys and gals that's got the same Fantastic amplifier.
Best Regards.
Stringer7

Hi,
Its been two weeks now and the speaker has been broke in . I have tube rolled once again,
And finally found the warmer tone I am after for Jazz and Blues with this amp.
The difference is amazing from the very bright tone I was getting at the beginning.
My latest tube set is -- V1=Tad 7025 WA RT080
V2=TAD 12AX7A-c
V3=Harma ECC83 Retro
And 4x=Harma E84L --EL84s.

The gain has reduced a bit but my Les Paul Traditional can cope leaving my Stratocaster
with my Q20 Echo unit a very clean tone.
Its worth working on the tone as its a good amp with very good features.
Regards
Stringer7

I went to the tubestore dot com and bought all Matched tubes. All Mullards and it sounds great.
I have a 4x12 Hughes and Kettner cab with Celestion Rock Crushers that sounds good.
My main speaker cab is a little Marshall Slant cab with 2x12 Gt-75 Celestions.
I run this amp with another amp, its a little secret of mine.
A fender SuperChamp XD, with a 22 Watt Supersonic Transformer stuffed into it, with a Mullard pre-amp tube.
Turned it into a head. So I have a Marshall 4x12 GT-65 Celestion Rolla's made in England wired stereo.
I run the XD on one side with two speakers and the Gradmeister on the other with two speakers with a Morely AB and I can use the two four 12 cabs putting one by my bass player and one by me and OMG it sounds huge.

On this score, does anyone have experience of using it with two different matched pairs? If say Chinese cheapies give you a rougher sound, rather than just replacing them all, can a pair of the originals be blended with a smoother pair like the Harmas to give a hybrid with benefits?

There is no technical reason why they shouldn't work together, they are still in matched pairs after all and the valves on each side simply add their current through the output Tx. You would have to use the amp on the 36W setting for a blend of course, but that gives you the expanded option of one of the pairs working alone in 18W mode with the FSM-432. Could be an interesting idea.

bordonbert wrote:On this score, does anyone have experience of using it with two different matched pairs?  If say Chinese cheapies give you a rougher sound, rather than just replacing them all, can a pair of the originals be blended with a smoother pair like the Harmas to give a hybrid with benefits?

There is no technical reason why they shouldn't work together, they are still in matched pairs after all and the valves on each side simply add their current through the output Tx.  You would have to use the amp on the 36W setting for a blend of course, but that gives you the expanded option of one of the pairs working alone in 18W mode with the FSM-432.  Could be an interesting idea.

Bordonbert, did you try this?  I've considered this also...

Haven't tried this yet I'm afraid.  I've been engaged with speakers.

I originally bought the TM36 head as a standalone unit without speakers of any sort.  I have a classic 1960s Marshall 4x12 cab which I could use but wanted to source something a bit less valuable, more portable in my Peugeot 206 ( ) and more robust with today's more powerful drivers.  I looked at a lot of "boxes with speakers in them and a premium name" and was unimpressed.  I settled on a stopgap of 2 of Thomann's Harley Benton G112 1x12 8ohm cabs based on their drivers.  They are unbelievable value for money.  They use a standard Celestion G12 Vintage 30 in a decent quality 18mm ply open back cabinet for the price of the driver!  No brainer.  Sure it was taking a punt but it worked out, I love them.

However, the sound they produced was a little lacking in bottom end when matched with the H&K.  It is fine with my Vox so this is obviously an issue of careful pairing with certain amps.  The bass controls didn't really do as much as I expected them to and the sound was too shrill 90s for my tastes, I prefer the more classic pre-punk rock sound.  So the last little while has been spent sorting out the match.  The best result is adding an 18mm 42cm square back to each of the cabs from scrap pieces and voila, more bottom end, tight not at all flabby, more useful use of the H&K bass control, more rock, more joy!  I can recommend this approach for anyone who is looking for a cab setup with an H&K TM series at least.

I really do plan to get to grips with this approach of swapping out a single pair of valves when I have the cash.  I am a HUGE sceptic of most of the hearsay knowledge that gets trotted around guitar circles as "proven truth".  The vast majority of it doesn't stand up to any proper testing, and almost all of the rest is down to poor engineering.  For example, how many different ways are there of clipping a signal with two back to back diodes?  Basically about 3 or 4 meaningful ways.  So why so many "boutique" overdrive/distortion units at £100+ all employing this method?  Magic diodes, transistors, opamps, capacitors just don't exist, there is only good robust design and shit design.  And most distortion pedals which claim to rely on specific components fall squarely on the latter side of that list.  Mojo is mostly a myth, if it exists at all it lives in your fingers!

However, while the engineer in me hates to admit it, valves are a different kettle of fish.  They fall into an area where there is a blend of electronics, material and mechanical engineering.  This does make them susceptible to differences between manufacturing processes and hence manufacturers.  So the idea which we are tossing around would seem to me to have some validity.  Whether it is another "can be measured but can't be heard" issue, as so many others, is open to discussion.

Consider this.  The genuine hifi amp is a refined beast, the guitar amp is a lowly beast.  They offer '<0.01% reliably' and '>0.1% distortion on a very good day' respectively.  We hold the levels of our hifi amps down to below serious distortion generation while we ramp up our guitar amps to deliberately generate overdrive and the distortion soars.  Then we put a pedal in front to generate more distortion and it rockets.  And in amongst this we claim to hear the difference between a good quality poly cap and a magic orange drop, or a correctly driven TL072 and a OPA2134?  In the hifi amp where there are incredibly subtle aspects like 3D soundstage to generate yes, but in the screaming guitar amp, not in anyone's universe!  The valve issue may be the same, though I strongly suspect that, if the claims of those swapping out their valves and reporting on the results are to be believed, the smooth/rough top end area which is commonly claimed to be most affected may well still show through, being as it is after most of these distortions and adding additional components based on them in the most sensitive areas.

Report back here if you try it before I do, it really is an issue we should give a run out.  (In the best interests of mojo of course.   )

A TL072 has an unsymmetrical slew rate, and sounds a little funny with high level high freq signals.  
Tubes are definitely a cross between mech and electrical - and add even harmonics, which as you know straight semiconductor clipping is mostly odd harmonics.  Anyway, it is very possible that two different mechanical designs produce different clipping spectrum.   After I make a couple of payments to the CFO on my GM36 (I switched), I will be playing with EL84s.
My initial thought was to have clean bright high headroom 84s in the inner positions (18W), and lower gain "browner" 84s in the outside, which are added when going to 36W mode. I could really try this with the original Chinese tubes on the inner positions...
I use the 36W mode for leads, to give a boost. I do use 18W for a more compressed lead on one patch. I have an external active power soak, so I never use the internal power soak. H&K will never be able to convince me that the high heat has no effect on the semiconductors in this (well the GM36) amp. I work in data storage, and people make careers out of removing heat to ensure the life of semiconductors. But that is off the subject...

Thanks for the reply, interesting thoughts here Namklak.  Teehee, I love a good "discussion"!  

Now, you said it yourself,

A TL072 has an unsymmetrical slew rate, and sounds a little funny with high level high freq signals.

High level high frequency?  For a TL072?  Haha, I did unfortunately use the phrase "shit design" didn't I? (There's a smiley, I'm really only teasing.)

Rule 1: Don't design a circuit which operates any of the components outside of their abilities.

That way you can do predictable reliable design and not have to plan on finding the right one out of 500 NOS germaniums from a long defunct manufacturer of the 50s, then find a use for the other 499!  How many overdrive/distortion/fuzz pedals operate by driving a variety of components into clipping?  And how many use a variable unpredictable "mojo" component in that role?  Why don't they do it by using a more elegant controllable way of clipping based on a predictable component and trim the method not search for the Holy Grail item?  There's nothing magic about older pieces of kit, they were just badly designed according to the limitations of the components available in their day, so why try to copy them now?

And the same works in reverse. TL072s are absolutely perfectly adequate for what we would (should) use them for.  If slew rate is an issue, don't operate them close to their slew rate limit.  Are you aware of how many older much loved tracks have passed through dozens of 741s in their studio stages and sound perfectly clean and dynamic?  (If I'm honest I even remember 709s!   )  You'd never really know it as long as the boards and their components were driven within their specs.

I work in data storage, and people make careers out of removing heat to ensure the life of semiconductors. But that is off the subject...

Off track maybe but an interesting observation.  The issue here is not always absolute temperature but thermal cycling.  As you will no doubt be aware in your work, leaving electronic equipment on permanently, even at high temperatures, is generally better than constantly turning it off and on and submitting it to constant expansion and contraction.  It's surprising how reliable semiconductors have become in this aspect over the years.  I would have thought that, with the valves up top and sufficient airflow from beneath upwards and out of the top back, the bottom void of the casing would not be overly hot.  That would be an interesting bit of diagnostic work wouldn't it? (CAREFULLY OF COURSE, VALVE VOLTAGES BITE!)  You would hope that H&K have already done it but, like you, I'd like to know myself what level that rises to.

"709s"?  Dude, you're old!!!  
Yes, thermal cycling and the resultant physical expansion/contraction is bad.  I practice anywhere from 15 minutes to an hour per day - I guess that is only one temp cycle per day.  At gigs I hit the standby switch at breaks - a thermal cycle right there.   But I guess looking at "orders of magnitude", that really isn't a "lot" of power cycles.  So maybe H&K is right (imagine that), thermals aren't a huge deal in this amp.  BUT, I'm not removing the low noise/cfm 80mm fans mounted in my gig and practice cabs pointing up under the GM...