Changing up tubes

CheapSuitG

CheapSuitG

The TubeSchemer
I’ve got an Egnater Tweaker 15 combo that I’ve been using for a while and I really like the three voicing options and overall tweakability. That said I can’t help wanting to tweak the Tweaker a bit more.

I’m think about doing some tube swaps. Would putting a 12AY7 in the V1 position be a good move? I’m also thinking about possibly trying 6V6s.

Assuming lower the overall gain a bit would hopefully widen the sweet spot. Right now it feels like the gain range where I really like the tone is pretty narrow and a bit touchy to dial in.

Thoughts?
 
That’s absolutely worth a try, it should give you a longer sweep in the lower gain range. I’ve done that with a number of amps over the years. A 5751 is just a hair lower gain than that, and my also have some noise benefits.

Oh, wait! Is your V1 normally a 12AT7, or AX7? I was thinking AT7 when I started. If you’re going from an AX7, I’d try an AT7 first, and then, if you want even less gain, an AY7. The Y has 40% of the X gain, and the T is at 70%.
 
Alan W said:
Oh, wait! Is your V1 normally a 12AT7, or AX7? I was thinking AT7 when I started. If you’re going from an AX7, I’d try an AT7 first, and then, if you want even less gain, an AY7. The Y has 40% of the X gain, and the T is at 70%.
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To me, that looks like algebra with all the letters correlating with numbers!

V1 I believe is a 12AX7 with EL84 in the power
 
If you’ve got them around, I’d try a 12AT7 or 5751 first, and see how that feels/ sounds. The 12AY7 will have about half that amoun5 of gain, and then there’s the 12AU7 that’s only got half of what the AT has—so plenty of room to experiment. And yeah, it’s a bit like algebra…. Sorry. ;~)
 
Post a schematic. You may just be able to use one of the hybrid tubes with dissimilar triodes to get the benefits you want without changing things massively
 
Few alternate
1, replace the gain pot with a linear pot
2. Replace R10 with a 500k and switch another 500k in parallel. A "MORE" switch. It may be worth upping the wattage rating to the next class of the non-swo5ched resistor.
3. Mess with the jfet input buffer?
 
9 Pin preamp tube mu (gain or amplification factor) From JJ Datasheets. You can also reframe the numbers to think of them as a % of gain compared to the 12AX7.

IME, I like the change from 12AX7to 12AY7 for headroom as the 12AY7 has a more pleasant tone quality for me than the 12AT7. However, the tone might be magic tone fairies and not everyone hears it the same YMMV.

12AX7 100
5751 70
12AT7 60
12AY7 40
12AU7 17
 
My advice with tube swaps is to record a loop into a looper, swap a tube, keep the same amp settings, and record the loop.

Then go back and A/B/X each tube, so you can actually hear what each tube does. I use a blind A/B program so I'm not subconsciously swayed by Mullard_12AX7_V1.wav vs JJ_12AX7_V1.wav as well :)
 
iamjackslackof said:
My advice with tube swaps is to record a loop into a looper, swap a tube, keep the same amp settings, and record the loop.

Then go back and A/B/X each tube, so you can actually hear what each tube does. I use a blind A/B program so I'm not subconsciously swayed by Mullard_12AX7_V1.wav vs JJ_12AX7_V1.wav as well :)
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That’s a clever idea. I might experiment with different amp settings though. Keeping everything identical might not always translate the same way kind of like swapping transistors in a pedal. Different ones can change the sound so a slight tweak might help each tube perform at its best.
 
CheapSuitG said:
That’s a clever idea. I might experiment with different amp settings though. Keeping everything identical might not always translate the same way kind of like swapping transistors in a pedal. Different ones can change the sound so a slight tweak might help each tube perform at its best.
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For sure. The important part is to A/B them later instead of relying on your memory and the knowledge of how much each tube cost and the maker, because it will influence you.
 
I’ve never cared for a 12AT7 in a main driver stage such a V1. They’re better suited for phase inverters or maybe a buffer. You could certainly try a 5751 or 12AY7. They’ll both be lower gain and quieter as well as add a slightly wider sweep on you volume or gain control. Personally I would try some 6V6GTs if you’re currently running EL84s. Massively different sounding tubes. I would also experiment with long plate 12ax7s vs short plates as well as black plate vs gray plates. You can score some anos GE 12ax7s for the price of a current production tube. I love the 50s and early 60s long gray plate GE. You can score some good made in Japan tubes as well. They’re very good tubes. Matsushitas were produced under Philips using the same tooling as Mullard, Amperex, etc. Some of my favorite new production tubes all 12AX7s are the JJ ECC803S, Sovtek 12ax7lps, Svetlana and Tung-Sol. For higher gain your JJ ECC83S, E83CC, EHX and for a neutral tone I like the Psvane. They’re neutral and quiet. I’m not a fan of the short plate Sovteks. Last, don’t forget about the speaker. It’s THE most tone contributing factor in an amp.
 
Honestly I've always been underwhelmed with anything in the main stage(s) by anything other than a 12AX7. It always sounds like it's a bit winded and struggling, if that makes any sonic sense. Kinda sterile. Now obviously ymmv.
 
Gordo said:
Honestly I've always been underwhelmed with anything in the main stage(s) by anything other than a 12AX7. It always sounds like it's a bit winded and struggling, if that makes any sonic sense. Kinda sterile. Now obviously ymmv.
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I agree for the most part. Of course it’s all amp dependent.

As for some pedal preamps that’s a whole different story. In several instances I’ve actually preferred a 12au7 instead of 12ax7 or other low gainers. Sounds pretty silly with such a low gain factor, but if I were to give you a 12AU7 with the label faded and not tell you what it was, and told you to try it in a particle accelerator or elementary, you’d never guess it was a 12AU7. Youd still have plenty of gain but with a much wider sweep. A 12at7 would be similar but with more high end content and possibly slightly less bass. More hi-fi sounding if you will.

I wouldn’t expect these results in an amp but you’d be suprised what a 12au7 can do. Fun experiment for sure.
 
HamishR said:
Are you referring to the Egnator Tweaker or all amps in general?
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Have you tried 6V6’s in your Tweaker? May be just the change you’re looking for. Moving away from the EL84 chime into a more Deluxe Reverb with a little more bass and less chime. I wish I still had my old Tweaker.
 
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