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Best 12ax7 for Ampeg SVT? The ultimate v1!?

Ballin'bass

Ballin'bass

Jun 16, 2014
2,398
1,950
Madison, WI
#1
I am trying to start experimenting with a new v1 tube (and probably the v2 and driver ax7) in my Ampeg svt-cl to try to really make it push my tone through richly, clearly and powerfully!:bassist: I don't currently get the quality of gain that I'm looking for. I really want my hot rod of a bass to sing through (for reference I have a very modern tone from my custom modulus vj4 and avatar 410 neo cabs).

I have some fresh, matched sovtek power tubes so that part is all good for now.

I have no first hand experience with anything besides the tubes that came with my amp (I imagine they're sovteks but I haven't checked) I wanna know what 12ax7's YOU guys think are best for me to get deep, punchy, clean, gainy headroom as well as the in-your-face bitey overdrive if I want to kick up my gain stage! Also open to ideas for the v2 and the phase inverter of the driver. I'm also looking for reliability and long-life!

Price isn't really an issue if they will provide sweet tone and last a good long time, I don't throttle my amp really. Current production might be preferable but NOS suggestions are totally welcome!

Also notice the poll! Please cast a vote!:thumbsup:
 
#6
Swap the two 12AX7s in the preamp chassis with JJs. Swap the 12AX7 in driver section with a JJ and the 12AU7s with NOS JAN Philips (military grade). JJs seem to make Ampegs sound *just* right. Also I don't suggest using the long plate ECC803. They tend to be microphonic anywhere but in phase-inverter postions, so just go with the regular JJ ECC83. As for Sovtek, Tung-Sol and EHX, they're all made in the same factory on the same machines with the same parts. The price points just reflect levels of QC.
 
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#8
If you get a good couple of tubes they'll last for years, however even with testing and burning in I'd say new production tubes have a 25-50% failure rate. NOS is more like 10-15% That being said reputable vendors have extremely lenient return policies with genuinely defective tubes.
 
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#9
Ballin'bass said:
Does anybody know what kind of life-span the JJ's are known for having? It'd be nice to just buy a couple really nice preamp tubes that i won't have to change if i take care of them.
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Some will last years, some will last months, some will break tomorrow. It's kind of unpredictable. The ones that came in my Ampegs are lasting a good while so far (a year and a half in the HSVT, over a year in the V4B), though ones I've bought at stores have not done as well.

I've not done a lot of tube rolling, but I've done a little...a no-name NOS that I think is GE, a couple Japanese Raytheons, a Ruby, a new Tung Sol...the GE and Raytheons made them a little too bright for me, the Tung Sol made it way too bright for me, and the Ruby and JJ just seemed right. What makes a tube good for me is how much it makes my amps sound like my 69 SVT with all NOS tubes, and with the Ruby and JJ, the Heritage and V4B sounded right, and with the others, too trebly.
 
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#10
Don't waste your money on the Northern Electric. No matter how good they claim that they are it's not worth paying $55 for a Chinese tube.

It's been a while since I had an SVT with a 12AX7 in V1, I think I tried one of the higher end EHX made ones and some JJs in my CL and they were both fine. Ended up sticking with the EHX, but this was 7-8 years ago. In my V4 I have some old stock RCAs and I enjoy those. For new production I've enjoyed the JJ and new sensor Tung-sol reissues. I found the mullard reissue and gold-lion reissues a bit bright (or microphonic) and better in guitar amps than bass amps. I think I'd get either the JJ or TS over the standard EHX/Sovtek offerings. I second Walt's recommendation to keep it to something with shorter plates to avoid noise issues down the road.
 
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#11
JimmyM said:
Some will last years, some will last months, some will break tomorrow. It's kind of unpredictable. The ones that came in my Ampegs are lasting a good while so far (a year and a half in the HSVT, over a year in the V4B), though ones I've bought at stores have not done as well.

I've not done a lot of tube rolling, but I've done a little...a no-name NOS that I think is GE, a couple Japanese Raytheons, a Ruby, a new Tung Sol...the GE and Raytheons made them a little too bright for me, the Tung Sol made it was too bright for me, and the Ruby and JJ just seemed right. What makes a tube good for me is how much it makes my amps sound like my 69 SVT with all NOS tubes, and with the Ruby and JJ, the Heritage and V4B sounded right, and with the others, too trebly.
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There is a big difference between various NOS 12ax7 types.

I have at least 60+ types in my 12ax7 collection....unfortunately I have no experience with 12ax7 in bass amps but I can tell you there is a vast difference in tone & response with guitar amps.

I test my 12ax7 with a small single ended amp like my 1968 Vibro Champ or in V1 of my other amps...some are brighter, some more compressed, some more mid range push (or gainier) and some have more top and and bass (like longplate Telefunken).

You wont find nearly the variety with modern production 12ax7 as there are only a handful of 12ax7 designs these days.
 
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#12
I do recall the current production Tung-Sol 12AX7 that is its own design and not a relabled New Sensor sounds really good for bass or guitar in Ampegs. There's one in my buddy's V-4 and his tones are awesome through his V-4B cab, yes the folded horn 2x15. I have an RCA 7025 and I had a Philips Holland 12AX7 in the V1 of my V-4 before it went bad, I liked the Philips Holland more than the RCA but in general I think European tubes have smoother distortion than American. Also it should be noted that "upgraded" tubes are probably a waste of money. Tone might be marginally better but it's still a new production tube and subject to all the shortcomings associated with current productions.
 
#13
Despite the claims of the various manufacturers that you listed, the very best way to find a low noise 12AX7 by testing them before they are sold. Manufacturers will screen tubes for low noise and classify them as such. But within that group, performance can be fine tunes by the reseller to select the best ones..

Find a reputable tube seller that can test the actual tube that you are buying. SO you are buying a low noise tube not by brand but based on tests performed. Below is an example of one way to test these tubes.



​
 
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#15
beans-on-toast said:
Despite the claims of the various manufacturers that you listed, the very best way to find a low noise 12AX7 by testing them before they are sold. Manufacturers will screen tubes for low noise and classify them as such. But within that group, performance can be fine tunes by the reseller to select the best ones..

Find a reputable tube seller that can test the actual tube that you are buying. SO you are buying a low noise tube not by brand but based on tests performed. Below is an example of one way to test these tubes.



​
Click to expand...

This is where the single ended amp like a Fender Champ comes in....any noisy 12ax7 will be very apparent when tested in a Champ or similar amp
 
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#17
beans-on-toast said:
Plugging the tube into an SVT is the ultimate test. Not everyone has a big bag of tubes to do this with though. That's why it helps if the re-seller can do it for you. :)
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Very true....keep in mind some of the very best sounding 12ax7 tubes can be a bit microphonic too........this can come from them being very high gain examples not necessarily faulty tubes.

Also, keep in mind the players particular bass will have an effect, according to the type of pickup....what 12ax7 sounds best with a vintage P bass may not be the same as say a T-Bird or J bass.
 
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