High Gain 12AX7?

8len8

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Is there one brand of 12AX7 that tends to have more gain than others?
 

Adamclayton

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1,180
Chinese 12AX7B's are high gain, u just gotta sort through the crappy ones to find the ones that aren't flawed or microphonic. The new TungSol and Mullard Reissue 12ax7's are high gain. I like the Tungsols and Ruby 12ax7AC5 HG's (best of the best Chinese).
 

DaveKS

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16,704
JJ ecc803 (not ecc83), Sovtek LPS.

But a high testing NOS Raytheon black plate makes either of those seem timid in comparison.
1250gm is nominal gain spec for 12ax7, follow one of these with 1-2 JJ ecc803 and you will have more articulate, harmonically dense, tight bottomed gain than you know what to do with. These are the Godzilla of high gain tubes.



Also RCA long grey plate and Telefunken ribbed plates.
 

Blue Strat

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30,194
None of the tubes listed above are high gain. I've tested 100s-1000s of each.

Now, if you mean easily overdriven, which has nothing to do with gain, then some of those MIGHT be.

Gain is the amount of amplification you get from a device. It has nothing to do with overdrive/distortion.

Every brand of 12AX7 ever has had a +/- 10 % variation from the center point...20% span overall...so there are none that consistently rate higher for gain than others.

JJ ECC803S and ECC83 have some of the lowest gain readings I've ever seen.

The gain of the amplifier circuit completely overwhelms the gain of the tube most of the time. Variations in the gain of the tube will have little to no effect.

So, the question is, "what is your goal, what have you already tried, and what amp are you thinking about?".
 

8len8

Silver Supporting Member
Messages
13,971
None of the tubes listed above are high gain. I've tested 100s-1000s of each.

Now, if you mean easily overdriven, which has nothing to do with gain, then some of those MIGHT be.

Gain is the amount of amplification you get from a device. It has nothing to do with overdrive/distortion.

Every brand of 12AX7 ever has had a +/- 10 % variation from the center point...20% span overall...so there are none that consistently rate higher for gain than others.

JJ ECC803S and ECC83 have some of the lowest gain readings I've ever seen.

The gain of the amplifier circuit completely overwhelms the gain of the tube most of the time. Variations in the gain of the tube will have little to no effect.

So, the question is, "what is your goal, what have you already tried, and what amp are you thinking about?".
It's a Phaez SIBLY that I'm looking to get more "distortion" out of, so I'm guessing that means more sensitivity? I'm assuming more gain would be good in the preamp too in order to overdrive the PI?
 

gulliver

Silver Supporting Member
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11,131
I used to feel one high output JJ in a cascade was the most explosive combination, but the last re-tube I did consisted of various medium output 12AX7s. I bought a bunch of slightly used ones from the emporium and just kept swapping until I liked what I heard. That's the best way to do it.
 

DaveKS

Member
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16,704
It's a Phaez SIBLY that I'm looking to get more "distortion" out of, so I'm guessing that means more sensitivity? I'm assuming more gain would be good in the preamp too in order to overdrive the PI?
Think what Blue Strat was alluding to is most peoples misuse of the term gain. Gain in the true "electrical engineer" sense of word is a volume increase. What most guitarist mean when they say gain, they talking about the clipping that occurs when a preamp tube is overdriven by the amps circuit.

In a perfect world all amps would have the gain knob relabeled as overdrive, and volume knob technically should be relabeled Gain. Gain= increase in volume not distortion caused by clipping.
 

Timbre Wolf

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10,284
For true high gain, try a 12BZ7. It'll give a couple more dB clean boost.

I don't think that's what the OP means, however.

Try Raytheon black-plate for early-breakup & bright clarity. For a darker & more murky early-breakup, RFT ECC83. '50s short-plate Sylvania (gray- or brighter and more clear black-plate) are rare, but worth pursuing as well.

- Thim
 

8len8

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13,971
I should have reworded my question. I'm looking for a brand of 12AX7 that will result in the most distortion from a distorted amp.
 

phonix

Member
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35
Shuguang 12XA7A's are good, Tung Sol RI's are good but can't handle cathode follower positions well. I run a Sovtek 12AX7WB in V2 (first gain stage) and it sounds great clean, although not as high gain as the other 2 I mentioned. That's all I have personal experience with, interested to see what everyone else says.
 
Messages
180
You can't go wrong with the JJs 12Ax7 hand selected (maybe labeled Ruby 12ax7 ACZ)
I have these in almost all my amps in V1-V2-V3 => concrete wall gain!
 

Blue Strat

Member
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30,194
I should have reworded my question. I'm looking for a brand of 12AX7 that will result in the most distortion from a distorted amp.

NOS RFT 12AX7. Don't expect a radical change with any tube. The circuit is really what dictates how much overdrive you'll get.
 

Mike9

Silver Supporting Member
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10,964
I was going to mention the RFT - great high gain tube. There were some Chinese 12ax7s some years back that had square getters that just rocked.

Be careful with 12BZ7s they are two 12ax7s in one bottle hence double the current draw. Make sure your PT can handle it.
 

Timbre Wolf

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10,284
Be careful with 12BZ7s they are two 12ax7s in one bottle hence double the current draw. Make sure your PT can handle it.
True!

I've never encountered a problem subbing 12BZ7 for 12AX7 in any modern amp, but I recommend only using one at a time in an amp. Also note that the glass envelope is 3/8" taller than 12AX7.

It's not what the OP wants anyway.

- T
 

8len8

Silver Supporting Member
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13,971
It's sounding like there's no simple preamp tube swap that'll get me close to what a boost pedal does to get more gain out of my amp.
 

Timbre Wolf

Hyperspatial Gravity Surfer
Platinum Supporting Member
Messages
10,284
It's sounding like there's no simple preamp tube swap that'll get me close to what a boost pedal does to get more gain out of my amp.
No tube swap will satisfactorily emulate the addition of a gain stage. You'd have to modify the circuit for that. Or stick with your boost pedal.

- T
 
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