Tube change question.

[boxcarmonument]

Well I finally had to buy some new tubes. And I wanted to get some TAD'S for my power section. I just purchased the premium kit from the Tubestore and it came with6l6GC- STR TAD's and Electro-Harmonix 12ax7-EH. Buy the way this is in a 3 Channel DR.

I guess my question is has anyone tried the 12ax7-EH? Are these decent tubes? I was going to order a power kit from one site and a pre kit from another. But I figured I would just order the whole package. I can only assume that even if these aren't the greatest tubes it's still has to be better than my current setup.(Mesa 6l6GC str440 and 5 Groove tube 12ax7c's)
I know this question might be kind of vauge but what tonal differances might I expect from EH tubes in the pre section?

So in other words did I make a mistake?

Thanks for any replies.
Dave B.

 

[domct203]

The EH 12AX7 is the tube used for the MESA Russian-2 12AX7, which is what came in my Rodaster. They are a decent tube, but I found the EH branded tubes to be short lived, going either microphonic or producing clicks and whooshes. I still have my MESA Russian-2's for backup and troubleshooting. I don't think you've made a mistake, but there other better options IMO.

Depending on which MESA you have, watch out with those EH's in the cathode follower position. When I was comparing MESA branded vs EH branded I lost an EH in one of the cathode follower slots, and another went noisy in V1.

Dom

Here's the info from the Mesa Memo...

SOUND “DROP-OUTS” / INTERMITTENT SIGNAL

One Possible Cause

Most (but not all) Mesa/Boogie amplifiers have one or two “cathode follower” tube
stages in their preamps. Tube selection is CRITICAL in these stages.

Specifically, in a 12AX7 tube used as a “cathode follower”, the voltage difference
between that present at the cathode, as compared with the heater voltage, can be
withstood or tolerated by certain types of tubes, whereas other tubes will fail. The
failure of a “cathode follower“ tube will cause sound dropouts or signal loss.

For the past few years, Mesa has been using two types of 12AX7 tubes: ones
originating in Russia (Sovtek EH), and ones originating in China. The Russian (Sovtek)
tube is NOT reliable as a cathode follower. Of the tubes we are using today (March
2008), ONLY THE CHINESE 12AX7 IS RELIABLE AS A CATHODE FOLLOWER.

In conclusion, if you are troubleshooting for signal dropout in a Mesa/Boogie amp,
suspect a cathode follower tube, and try replacing it with a Mesa 12AX7 that is marked
as “CHINESE” (silk-screened on the tube itself).

Below is a partial list of Mesa amps and cathode follower tube locations:

GUITAR AMPS BASS AMPS

Lone Star & LS Special: V3
M-Pulse: V2
Stiletto: V3 & V4
Venture: V2
Road King I: V3 & V4
Big Block 750: V4
Road King II: V3 & V5
Titan: V4
Roadster: V3 & V5
M2000: V2
Dual & Triple (2ch or 3ch): V3 & V4
Bass 400+: V2
Tremoverb: V3 & V4

ANOTHER POSSIBLE SCENARIO may occur in the “SPONGY” (or on some models,
“TWEED”) power setting: the reduced filament voltage may cause very low output from
a RUSSIAN preamp tube. Again, the recommended fix is to replace the “sagging” tube
with the CHINESE type of Mesa 12AX7 - which are more immune to this type of failure.

 

[boxcarmonument]

Thanks Dom!
I was wondering about this. It had crossed my mind, but it was after the I'd ordered them.

Is this something that would happen right away or over the course of a few hours? This is in a 3 ch DR by the way. I put them in today and so far everything seems ok. And FWIW it's sounds a million times better with the TAD's instead of the Stocks mesa's. But I won't count out the cathode follower cooking the tube.

As far as new preamp tubes go does anybody have any good suggestions for my amp? I have looked at the combo packs from dougstubes and eurotubes. And dougstubes recommends the same combo for just about every amp. Or could it just be that simple?

Thanks,
Dave

 

[domct203]

If you notice volume drops or strange noises change V3 and or V4 to see if that fixes it. It's hard to tell how long a certian tube will handle the stresses. I ran my MESA Russian-2 for almost a year in a cathode follower spot with no issues, but had an EH fail within 8-10 hours of band volume playing.

For me, what I found nice about the Doug's combo is that it involves a mix of different tubes to try in the V1 spot first to hear their differences. They are a good start in the recommended positions as well. Some here really like the Tung-Sol RI in V1. The 9th generation Shuguang IMO is a good current production tube that will have no problems in the cathode follower slots ( V3 & V4 in your amp). The Sovtek LPS is one of my favorite PI tubes (V5 for you), right after the Matsushita 12AX7. The JJ is a rugged all around tube, nothing too special but not too bad either in the right application, and not so bad when used in V2. Some really like the JJ in the PI as well. IMO a full setup of JJ's will mud up the preamp and add to the fizz. The JJ803S is a decent current production longplate tube, which is what I have as a backup for the Vintage GE longplate I use in the tone stack (V3).

What kind of tone are you looking for? What guitar do you use? What is it about your current tone that you want to tweak/change? Have you tried different p'ups/guitars? How about speakers? Ever try a clean boost? How long/what kind of cables do you use? etc., etc., etc. There are many complex interactions that make up 'tone'.

If you like what you hear now but want to experiment with different tubes the Doug's set is a good start, with a couple more JJ's (ECC83S High Gain & ECC803S longplate), and maybe a 12AT7 or 5751 as well. Swapping these through V1 can let YOU experience how they differ. Then research your amp to understand the functions of each tube in the circuit and experiment.

All the best,
Dom