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i really haveta try a mark iii. i dont think itd be different enough from my iib to clinch it- but im curious about crunch mode and pull deep switches..
 
More tube experiments with the Mark V 90.

It's clearly quite sensitive to both power and preamp tubes.
  • V4 with Philips 12AT7 gives you more usable gain range on ch3, and seems to make it overall clearer
  • V6 with 12AT7 reduces volume and has a similar effect on all channels. Didn't care for this.
  • V6 with a long plate JJ ECC803S sounded really nice. But I think either the tube is a bit busted or it was poorly in its slot because it started making a BRRR sound on ch3. Other channels still worked fine.
  • V6 with TAD 12AX7-C was brighter, but with the V4 12AT7 became harsh.
  • V6 with TAD 12AX7WA that I had been using there before was better.
I would advice Mark V owners to experiment with the tubes if you have a decent stash. Find a set of power tubes you love first, then preamp tubes can be tweaked. I can imagine depending on what cab you use you might end up with totally different ones than what I have. With the 1x12 combo it's often about reducing max treble because it can easily get rather bright compared to e.g my 4x10 with Greenbacks.

Changing tubes even on the combo is a pain in the ass when you have to take out the power tubes that are on the way. Makes it hard to compare too when you have to wait for them to cool down.
 
laxu said:
More tube experiments with the Mark V 90.

It's clearly quite sensitive to both power and preamp tubes.
  • V4 with Philips 12AT7 gives you more usable gain range on ch3, and seems to make it overall clearer
  • V6 with 12AT7 reduces volume and has a similar effect on all channels. Didn't care for this.
  • V6 with a long plate JJ ECC803S sounded really nice. But I think either the tube is a bit busted or it was poorly in its slot because it started making a BRRR sound on ch3. Other channels still worked fine.
  • V6 with TAD 12AX7-C was brighter, but with the V4 12AT7 became harsh.
  • V6 with TAD 12AX7WA that I had been using there before was better.
I would advice Mark V owners to experiment with the tubes if you have a decent stash. Find a set of power tubes you love first, then preamp tubes can be tweaked. I can imagine depending on what cab you use you might end up with totally different ones than what I have. With the 1x12 combo it's often about reducing max treble because it can easily get rather bright compared to e.g my 4x10 with Greenbacks.

Changing tubes even on the combo is a pain in the ass when you have to take out the power tubes that are on the way. Makes it hard to compare too when you have to wait for them to cool down.
Click to expand...
IIRC the JJ 803s can be microphonic. I used one in my Mark III and honestly can’t remember if it’s still in there. It sounded great so it’s probably still there. I haven’t had issues but have read of others. I know for sure they are not recommended for combo amps.

Also, you owe it to yourself to try 5751 in place of those 12at7 swaps. I’ve always found the 5751 to work better in my Mesas.
 
laxu said:
I would advice Mark V owners to experiment with the tubes if you have a decent stash.
Click to expand...
Good advice. Tube rolling is a lot of fun, regardless of the make/model of the amplifier. I have collected about 20 various preamp tube spares that I will roll through any amp I acquire.

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id honestly never ever use a 12at in a mesa save as a phase inverter. theyre just too dry in any tone generating context. if you wanna dump gain try an ay or an au or a 5751!
 
EOengineer said:
IIRC the JJ 803s can be microphonic. I used one in my Mark III and honestly can’t remember if it’s still in there. It sounded great so it’s probably still there. I haven’t had issues but have read of others. I know for sure they are not recommended for combo amps.

Also, you owe it to yourself to try 5751 in place of those 12at7 swaps. I’ve always found the 5751 to work better in my Mesas.
Click to expand...
Yeah the ECC803S can be microphonic but this will depend on the individual tube and where it's used. I liked it to brighten a Bogner a bit and there it didn't have any issue.

I do have a JAN GE 5751 I could try. I gave it a try in V6 when I got the amp but didn't notice much difference to whatever tube I had.
 
Tried V4 5751. Not as good as the 12AT7. There's something that it does that I like. With the 12AT7 there's not that much less gain, but there seems to be a difference in clarity and saturation. I can turn the gain up more, and it seems to stay clearer still. Could not get the same result fiddling with the controls.

So worth a try. I got a fairly affordable NOS 12AT7, seems it might've been too cheap because the vendor has raised its price a lot now...
 
Last edited:
After a heavy dose of cork-sniffing, this is where I ended up:

Preamp:
  1. TAD 7025 WA "Highgrade/Premium Selected". It should be similar to Mesa SPAX7 low noise tubes.
  2. Groove Tubes 12AX7M. This was their Mullard copy. It was known for high failure rate but the two I own have worked for years.
  3. GT 12AX7M.
  4. NOS Philips ECC81/12AT7. This opens up CH3 nicely.
  5. SED =C= 12AX7. It's a bit darker sounding tube.
  6. TAD ECC83WA. I had a brighter TAD 12AX7-C here but I think the WA works better.
  7. TAD 12AX7-C. Tried the WA and it was fine with the combo MC90 speaker but sounded a bit congested with MC90 + 4x10 GB. 12AX7-C seems to add just the right brightness to the PI that it helps with my cabs and doesn't become harsh even with just the combo speaker.
Poweramp:
  1. Outer pair: TAD Redbase 6L6GCM-STR. These complement the SED a bit better than the TAD 6L6GC-STR.
  2. Inner pair: SED =C= 6L6GC. I will be sad when these stop working.
Don't take this as some "buy these for great tone" chart. What cabs/speakers you use, how loud, what guitar etc will matter a lot.

I've had amps where only the first few tubes had any effect, as well as amps where none of the preamp tube changes did anything. This can be both a plus or minus as then you can use whatever tube, but the Mesa seems to really give different flavors with tube selection.
 
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