Mark III preamp tube suggestions

[VinylJunkie]

Hello all.

I’ve been doing a lot of preamp tube swapping in my Mark III the past few days. I found a couple combinations that I like parts of, but nothing that I like overall. I tried a RFT in V1, which drastically improved the R1 and R2. It made the clean channel very open and three dimensional, and R2 much more usable without an o.d. in front (this is an early model with low gain R2). Unfortunately the lead channel had lackluster bottom end with the RFT in place. With a EH in V1 the lead channel is gainy with a nice chunky bottom end, but R1 is a bit thin and narrow sounding, and R2 is virtually a clone of R1 with just a tiny bit of extra gain on tap. I generally play with a lot of low end on the lead channel, so the EH is back in, but it would be nice to find a compromise between good R1 & R2, and a chunky lead channel. Has anyone found a preamp combination that gives good tone on all three channels? I haven’t tried the Tung-Sol reissues yet, and I’m not opposed to spending the money on NOS if it will yield the results I’m after.

The amp is a black dot DRG with 105PT, 3+, R2 vol, and adjustable bias. Current preamp tube layout is:
V1-EH, V2-early Chinese “perfect tubes branded”, V3 =C= Svetlana, V5-Sovtek LPS

Thanks!

 

[MrMarkIII]

V1 does indeed affect all channels, but V3 is dedicated to the Lead Channel only. Maybe try the EH in V3, with the RFT in V1.

Or a NOS Mullard. Works for me.

Generally, you don't want a ton of low end in the Lead sound, as it causes the dreaded "flub", but you can dial it back in with the Graphic (if available). The Graphic comes after the V3 gain, so it retains a tight bottom, which, of course, is most desirable.

 

[Markedman]

Here's what I know about tubes and Mark lll amps. You should try different tubes at the sound level you plan to use the amp at. A tube might sound awesome at bedroom levels only to be harmonic or screechy at stage volume. Also, what sounds great in one amp or in V1 might sound, to your ears anyway, darker or paler in another Mark lll. These amps have so much gain, dialing them back with lower gain tubes such as 12at7's is an option some guitarist use. Take an hour or so with your amp set up for easy access to the tubes and switch the tubes around. A nice set of gloves helps when handling hot tubes. Everyone has a favorite tube, mine for my black/no dot is an 60's Amperex Bugle Boy ax7 in V1, and I have 1 in V3 but it sounded weak in my blue stripe which took off when I put an old GE in V1. My black is 60/100 and the blue is simul-class with 6l6's and EL34's. I have Mullard reissues that a lot of posters on the Board love but I found them fizzy, so to that, each their own. The Mullards do sound awesome in my 1972 Marshall Super Lead and my other old low gain amps though. The guitar and style of music dictate what tube I use in my Mark lll's, blue stripe/Jackson guitars with humbuckers for Metal, Black stripe with stratocasters with single coil pick-ups for blues and rock. If you play metal and want that Mark lll to blow you away, finding the right tubes is essential. If it doesn't totally rip your face off, it might need to see Mike at Mesa because any good Mark lll is unrivaled for metal tone and gain. More useable gain than any amp period!

 

[VinylJunkie]

Thanks for the suggestions. I play everything from jazz to metal, so getting all three channels to do what I want is just going to take a lot of trial and error. I haven't had this amp very long, and I'm just starting to experiment with tubes. I'm shooting for good bedroom level tones. I haven't played out in years, and don't plan to, so stage level microphonics aren't really an issue.

MrMarkIII - I never run the bass control above 2 on the lead channel. I put it all back in with the graphic. I guess “a lot of low end” wasn’t really a correct description. I just like the lead channel to chug nicely. The RFT tube didn’t chug like the EH in V1. I’ve since replaced the Sovtek in the phase inverter with the RFT, which I like.

I found a couple vintage RCA gray plates that test near new, so I’m going to try them in V1 and V5. I may try to hunt down a Mullard and/or a Tungsram as well.

 

[Markedman]

Someone is selling some real nice tubes in the classified section.

 

[kippiejr]

I think I have tried every tube and combination out there!. The real factor for me is the gain output of the tube.. A 12ax7 is suppose to be 100. Rarely do I test a tube and it reads 100. Also 12ax7 is a dual triode tube. Two tubes in one. So one side could be 100 and the other 85. Very common you would be shocked. Get a Mesa SPA for V1. 9 out 10 times I test those they have a high gain factor above 95 good for V1 start the input hot. . RFT mostly come high. Once in while I have seen a lower 85/90. Drop the RFT in V3. I have had great success finishing of V5 with something again near 100/100. EH, Tungsol, JJ, Mullard re-issue are always reading on my Valley Tube Tester 90 at the highest if I am lucky. Most NOS 80-90. Great for some styles but if you want Metal drop in some 100's or better.. Without a tester you will never know. Always start V1 with the best you got. When need more high gain I go to RFT or I will order JJ's from the high gain section. Last batch of 5 only 2 made it over 100 on the tester. They went straight to V1 and V3. IN Mark III try to get V1,V3,V5 cookin' and bask in its glory. Now maybe my tester is off a bit but every tube I get from doug's tubes, the amp doctor or euro tubes and the say and write like 110/115 on their tube as high gain never read anywhere close on my tester. But I get a SPA from Mesa and pow 95/100 or 100/105 etc... If you dont' have a tester. Mesa SPA is the best gamble. The one with the shrink wrap!!!!