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Thread: High gain 12ax7 tubes?

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    Default High gain 12ax7 tubes?

    What do they mean when a certain 12ax7 tube is high gain? Is it that they break up more easily allowing you to get more gain/distortion?

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    LoveMachineologist jeremy's Avatar
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    Default Re: High gain 12ax7 tubes?

    not really.

    a low gain tube will typically break up earlier but not have as much output to drive the next stage. a high gain tube will typically have a cleaner sound but give more output which will drive the next stage harder possibly making it distort.

    guitarist think of gain as distortion, everyone else means output strength

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    Mojo's Minions misterwhizzy's Avatar
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    Default Re: High gain 12ax7 tubes?

    I don't think so. I'm pretty sure it's just a measure of the input voltage versus the maximum output voltage without clipping. A vacuum tube is capable of making an exact but multiplied copy of the input signal at the output terminal, up to a certain level. When it gets beyond that level, you get distortion.

    Basically, putting a higher gain-tube in an early amplification stage causes a higher-voltage input signal to later stages, meaning they are more likely to go into clipping.

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    Default Re: High gain 12ax7 tubes?

    yes. you get more dist with the high-gain 12ax7 tube(s). It is audible
    chinese 12ax7b is a high-gain tube

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    Default Re: High gain 12ax7 tubes?

    I thought that a high gain 12ax7 just amplified the signal more than a low gain 12ax7. Depending on the circuit and the location of the tube, you could get more distortion, but not necessarily.

    Of course, you should just wait until glassman comes into the thread and gives you the correct answer.

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    Default Re: High gain 12ax7 tubes?

    I guess it would help if I put this question into context...

    I got a JCM800 combo which needs a new set of preamp tubes (I'm keeping the matsu****a EL34s in there). I was looking at several brands that wouldn't cost me an arm and leg, and JJ ECC83s came to mind because they do get favorable reviews here. They say it's warm, middy - which can only be good as far as I'm concerned. Reading on some websites, they also say it's a high gain tube - more gain that similar tubes from different brands. Now, that I'm not sure if I will like. I do love more gain on the JCM800 since I play heavy metal, so if it means I get more distortion by turning the preamp gain knob to the right, then the JJs would be perfect for me.

    What do you folks think?

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    Alnico 6/8 gibson175's Avatar
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    Default Re: High gain 12ax7 tubes?

    Quote Originally Posted by firebirdV View Post
    I thought that a high gain 12ax7 just amplified the signal more than a low gain 12ax7. Depending on the circuit and the location of the tube, you could get more distortion, but not necessarily.

    Of course, you should just wait until glassman comes into the thread and gives you the correct answer.
    A high gain 12ax7 will amplify the signal more than a low gain 12ax7. It should also give you a better signal/noise ratio. In a cascading gain type amp, it will drive the tube after it harder - giving more distortion.
    If you want more dirt for your metal sound then go for EH12ax7 bcause they are middy and crunchy sounding - they are also a high gain tube like the jj. The JJs tend to be a bit smoother, rounder.

    A question....how do you know you only need new preamp tubes. Its generally the power tubes that need replacing as they wear out much quicker.
    If its because the power tubes are new and you want to change your sound a bit then i understand.
    Anyway, if you do go power tubes as well then i reckon EH in the preamp for crunch, and JJs in the power amp for big bottom end.

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    Default Re: High gain 12ax7 tubes?

    I've tried some Ruby hi gain 12ax7's and I wasn't really impressed with the tone, and they didn't really seem to add any distortion?

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    Default Re: High gain 12ax7 tubes?

    Quote Originally Posted by gibson175 View Post
    A high gain 12ax7 will amplify the signal more than a low gain 12ax7. It should also give you a better signal/noise ratio. In a cascading gain type amp, it will drive the tube after it harder - giving more distortion.
    If you want more dirt for your metal sound then go for EH12ax7 bcause they are middy and crunchy sounding - they are also a high gain tube like the jj. The JJs tend to be a bit smoother, rounder.

    A question....how do you know you only need new preamp tubes. Its generally the power tubes that need replacing as they wear out much quicker.
    If its because the power tubes are new and you want to change your sound a bit then i understand.
    Anyway, if you do go power tubes as well then i reckon EH in the preamp for crunch, and JJs in the power amp for big bottom end.
    +1 for EH's if you want some crunch and sizzle. They're solid, and cheap.

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    Default Re: High gain 12ax7 tubes?

    The whole high gain tube thing is kinda misleading. The spec for a 12AX7 in an amplification factor (mu) of 100; the output voltage (AC) under ideal conditions is 100 time larger than the input signal. The lowest gain 12AX7s out there have an actual mu of around 80 and the highest have a mu of near 100...these would be considered a high gain tube in modern terminology.

    A 20% difference seems like a lot and would be if it weren't for the circuits these tubes reside in. For instance, in a typical Fender input circuit with all the controls set on 5 (tone stack and volume), the output at the tube has a mu of 66 without considering the tone stack load. Introduce the tone stack load and the mu is reduced to 31. Now introduce the load of the volume control and the mu is reduced down to 1.5...this is with a high gain tube with a mu of 100. Substitute a low gain tube (mu of 80) and the mu is reduced to around 1.4...not much of a difference but it may be audible. Most likely what one hears is actually the differences in frequency response between different tubes.

    A typical Marshall (JCM800) first stage with the gain control on 5 has a mu of 3.7 in the midrange and treble frequencies with the bass frequencies sloping off to a mu of around 1 (unity) at the lowest frequencies. This is with a tube with a mu of 100; a tube with a mu of 80 would have a circuit gain factor around 3.

    I always suggest that you select tubes based on tone and ignore the gain claims. Every amp reacts a little different to different tubes based on the topography of the amp they are used in and one tube may sound terrible in one amp while it sounds wonderful in another. The tube selection possibilities we have today versus 10 or 15 years ago is really inspiring. We have SO many opportunities to tone shape now that wasn't available then.
    Now operating part time: Glassman Tube Amps...repairs, rebuilds, restorations & modifications of tube equipment.

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    Default Re: High gain 12ax7 tubes?

    Higher gain preamp tubes break up earlier in my experience. Jeremy said low gain tubes break up earlier but I've found that to be the opposite. I use lower gain tubes in my JVM to open up the sound more and to lower the gain. I have to turn my gain knob around 12 or 1 o'clock to get the same gain I'd achieve with 12AX7s in V2 and the knob at 9 o'clock. I use a 12AT7 in the main gain stage to lower things down. Most people would agree a 12AT7 isn't a very good sounding tube and is more of a worker than a tone generator but using it in the gain stage works for me. It alters tone some but nothing like using in the V1 slot of an amp. It works for me and shows that a lower gain tube does cut distortion.

    Having said all of that I don't think paying the extra few dollars to get a "high gain" rated tube is worth it. Just get a regular one. Any alteration in gain is going to be small and maybe not even noticeable. It's not going to make a JCM sound like KK JCM 800.

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    Default Re: High gain 12ax7 tubes?

    Quote Originally Posted by gibson175 View Post

    A question....how do you know you only need new preamp tubes. Its generally the power tubes that need replacing as they wear out much quicker.
    If its because the power tubes are new and you want to change your sound a bit then i understand.
    Anyway, if you do go power tubes as well then i reckon EH in the preamp for crunch, and JJs in the power amp for big bottom end.
    Both preamp and poweramp tubes are still working well. It may sound silly, but unlike the poweramp tubes (Matsu****a EL34s), I don't know what kind of preamp tubes are in there. They certainly are NOT EH or JJs, and so if I can get more gain from those 2 brands, then I figured I'm better off replacing them for now. The powertubes, I recon will be replaced at a later time.

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    Default Re: High gain 12ax7 tubes?

    Quote Originally Posted by ACH91332 View Post
    Having said all of that I don't think paying the extra few dollars to get a "high gain" rated tube is worth it. Just get a regular one. Any alteration in gain is going to be small and maybe not even noticeable. It's not going to make a JCM sound like KK JCM 800.
    The JJs are a benchmark price-wise. I'm not gonna go crazy and spend so much money on preamp tubes. And yes, I do recognize I won't get to KK levels of gain, but I would want to get as much distortion as I can from the amp itself, and not rely on my ZW OD or TS9 so much. Although, with the my genre, I don't think I can escape using an OD. Which I don't really mind. If it's good enough for ZW, it's good enough for me. His rhythm tone is best for me.

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    Default Re: High gain 12ax7 tubes?

    Quote Originally Posted by glassman View Post
    I always suggest that you select tubes based on tone and ignore the gain claims. Every amp reacts a little different to different tubes based on the topography of the amp they are used in and one tube may sound terrible in one amp while it sounds wonderful in another. The tube selection possibilities we have today versus 10 or 15 years ago is really inspiring. We have SO many opportunities to tone shape now that wasn't available then.
    I like my amps to be middy. My JCM800 already is. I don't like scooped sounds and overly bright amps (my treble knob rarely goes beyond 12 o'clock). It has to have good lows as well.

    Are JJs or EHs good for this?

    They're relatively cheap, gets good reviews, seems to be reliable, and not hard to find.

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    Default Re: High gain 12ax7 tubes?

    Quote Originally Posted by ACH91332 View Post
    Higher gain preamp tubes break up earlier in my experience. Jeremy said low gain tubes break up earlier but I've found that to be the opposite. I use lower gain tubes in my JVM to open up the sound more and to lower the gain. I have to turn my gain knob around 12 or 1 o'clock to get the same gain I'd achieve with 12AX7s in V2 and the knob at 9 o'clock. I use a 12AT7 in the main gain stage to lower things down. Most people would agree a 12AT7 isn't a very good sounding tube and is more of a worker than a tone generator but using it in the gain stage works for me. It alters tone some but nothing like using in the V1 slot of an amp. It works for me and shows that a lower gain tube does cut distortion.

    Having said all of that I don't think paying the extra few dollars to get a "high gain" rated tube is worth it. Just get a regular one. Any alteration in gain is going to be small and maybe not even noticeable. It's not going to make a JCM sound like KK JCM 800.
    you and i are talking about slightly different things. im comparing a low gain 12ax7 to a high gain 12ax7, you are comparing different tube types.

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    Default Re: High gain 12ax7 tubes?

    I notice a bit of a difference between my ERA (not sure what they are but thats the label) vintage tubes and any new production tubes. The ERA's are loud (most noticable in v1) and have more punch. It may drive the other tubes harder which may mean more distortion in a technical sense but it sounds cleaner as it isn't as fizzy.
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    Default Re: High gain 12ax7 tubes?

    Quote Originally Posted by jeremy View Post
    you and i are talking about slightly different things. im comparing a low gain 12ax7 to a high gain 12ax7, you are comparing different tube types.
    Well touche sir haha. But yeah I tend to not notice the difference. It could just be my ears though. I only have noticed tone and compression differences between tube types and different brands.

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    Default Re: High gain 12ax7 tubes?

    The 12AX7 is, by definition, a high gain pre-amp valve (tube). Manufacturers feel the need to make a distinction because the 12AX7/ECC83 employs a pin base format that is common to numerous other, lower gain, valves and one higher gain design - the 7025.

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    Default Re: High gain 12ax7 tubes?

    I guess everyone would agree I not not likely notice an increase in gain levels by getting "high gain" 12AX7 tubes, and that JJs is a good choice for the price range?

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