Preamp valve replacement advice needed
Hi guys
Im not a novice when it comes to valves but im seeking a bit of knowledge before pulling the trigger on some new 12ax7's for my rig.
I have a JMP-1 and a Peavey Classic 60/60 Stereo Valve Power Amp that I've been gigging the rig pretty constantly for the last couple of years and its starting to get noisy.
I put a new set of 6l6's in the peavey when i got it but never touched the 12ax7's in there coz they were fine at the time.
As Im not sure wether its the valves in the marshall or the peavey that are starting to show their age, should i bite the bullet and replace the lot ?
What valves should i go for JJ, TAD, Genalex or Tung Sol?
Wotcha fink?
Cheers
I would certainly not replace The Lot!
Ten years is by no means uncommon for pre amp valves (how many peeps come on here and say they have just got this dusty, 40 year old amp from uncle Frank's loft and the Mullards work fine?).
Yes, they can go noisy, hissy, crackly, hummy and microphonic but even a valve that has gone a bit "miccy" can often be put in a less demanding part of the amp's signal chain and go on working fine for years.
I would just buy two valves. A TAD 7025 high grade which I have found to be very good at the price and maybe one of the expensive esoterica? This way you will see if they are worth the money but not be ££££'s down the tubes !!!! (sorry, could not resist).
Dave.
I often find replacing old, worn out pre-amp valves with any new valve gives an improvement.
I've not tried the Genelux 12AX7s (mainly due to cost), nor the TAD; however I have tried "premium tested" Chinese valves (which weren't cheap) from another source which look identical and wasn't overwhelmed.
Of the new 12AX7s my favourite (does this forum have an American spell checker??), is the JJ-ECC803s.
I normally say ECC83 but didnt coz ive been researching which valves to go for on an american site..Originally Posted by jpfamps
I dont know what valves are compatible with what and used the generic 12ax7 yank term, knowing theyre the same as ECC83.
Whats the difference between the ECC803s and the ECC83?
My next thought is should i just change the two valves in the JMP-1 first and see if the hum go's away?
There's a valve for the clean and dirty channel.
would it be wasteful to put a ECC803 in the dirty position given that there's a warning about microphony in high gain amps ( i wouldnt describe the jmp-1 as high gain but it does get pretty dirty with the gain turned up) or should i just stick to the bog standard JJ ECC83s?
I bought a few preamp valves to replace the generic Chinese ones that had been in my AC15 since it left the factory (in 1996!) - JJ ECC803s, Tung-Sol & Sovtek. I swapped them round the V1, Top Boost and PI positions (no bothering with reverb driver & tremolo positions), also trying the Electro-Harmonix ECC83/12AX7 I had in my Vox Tonelab. My observations were:
1) I couldn't really tell the difference between them in the AC15;
2) In the Tonelab, the Tung-Sol produced an output a whopping 12 dB lower than the others (as measured on the VU meters on my mixer).
The Tung-Sol in the AC15 had no audible difference to the others. Very strange, as the Tonelab runs the valve at very low plate voltage afaik.
I was a bit disappointed, I was expecting a little bit more sparkle and chime (or something) by replacing 15-year old unbranded Chinese valves with something "better".
Anyway, due to some quirk of construction the JJ ECC803s is apparently more prone to microphony than other modern production ECC83 valves, so you'll read a lot about them not being ideal in combos and high gain amps. I left mine in V1 and don't have a problem, although I don't play that amp very loud at all.
I don't actually run my set up that loud, as its mic'd up through the pa
So I don't think it would be that much of a problem but I'm not sure which to go for
what the pro's and cons are between JJ ECC83s and the JJ ECC803?
I think the warning applies to combos & mechanical vibrations, so that doesn't apply to rack-mounted preamps (although it may do for high gain sounds).
From the place I bought my valves from (Karltone):
As I said, I couldn't really discern any of the supposed characteristics that various makes/brands are supposed to have! At about £12 a pop, I'd buy 3-4 different types to try.The JJ ECC803 has a classic long plate design with a special grid to reduce microphonics noise. This is another offering from JJ and once again it's a beautiful sounding valve. It has a deep, tight low end that the ECC83S has but the mids in the ECC803S are even thicker and more harmonically complex than the ECC83S. The ECC803S is also a touch hotter in the high end than the ECC83S.
This is a great tube for V1 positions or for use in all positions in vintage amps. I do not recommend them for use in the gain stages of high gain amps if you like to run your gain full on. All preamp tubes are microphonic it's just a matter of where the threshold is and longer plate tubes will squeal before a short plate tube will, so for real high gain amps I would stick with the ECC83S. I wouldn't recommend these in small combos where the tubes are in close proximity to the speaker.
The JJ-ECC803s has a longer plate structure than the JJ-ECC83 which is why it is more prone to microphony.
I've used the ECC803s in (lowish gain) combos and in some higher gain heads without any issues so far.
You would be using it in a rack mounted pre-amp, so I would not anticipate any problems.
Sonically I find the ECC803s has more "presence" than the ECC83s.
I've also experimented with EH, Sovetek, and Tungsol 12AX7s. Out of these I prefer the EH.
I stopped using EH-12AX7s a few years ago when they had problems with the cathode/ heater insulation, a problem that seems now to have been sorted out.
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