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Post subject: Please help clarify something about pre amp tubes
Posted: Sat Mar 07, 2015 9:05 am
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I have an old Deluxe. I'm curious about something, and someone who really knows something about tubes, please clarify.

One think I've read about are other options for pre amp tubes other than 12AX7s. Stevie used a 5751 in some amps, AT7s work better in the inverter position depending on what your'e looking for, blah, blah, blah.

So, I'm getting that the general idea is that if you use weaker/cleaner pre-amp tubes, you are cleaning up your signal, and lowering your volume. Then you need to raise the volume to achieve the same volume as before. However, you are driving the output tubes harder.

So as a result, you get a warmer power amp distortion as opposed to a crispier pre-amp distortion.

OK, then. But is there a point of diminishing returns on this concept. If I replace all of my AX7s with 5751s, or AY7s, and lower the output of the pre-amp section significantly, and I getting even MORE output tube overdrive goodness?

Or is it just a matter of when you get to a point where when you're amp is on 10 it's just not loud enough for you, then you need to go back and start putting in stronger pre-amp tubes until you get it right?

Thanks,

Lincoln


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Post subject: Re: Please help clarify something about pre amp tubes
Posted: Sat Mar 07, 2015 9:52 am
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First you need to understand the difference between volume and gain.
A organ has volume. An unchanging level that is adjusted by the expression pedel.
A guitar has a percussive envelope that is dependent on finger pressure and an amps internal gain structure.
A high gain amp will exaggerate the percussive envelope to cut through the rhythm. A low gain amp will reduce the envelope to stay dynamically in the background.
It also affects your playing style. If you like to jump up and down on the strings, a low gain amp is the ticket. If you have a light touch, higher gain will give you the right feel to your playing.
So the internal gain structure of the amp is as important as where the volume is actually set.
You adjust the internal gain by selecting the right amp in the first place and fine tuning the internal gain by selecting different tubes to get the dynamics your fingers expect


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Post subject: Re: Please help clarify something about pre amp tubes
Posted: Sat Mar 07, 2015 9:12 pm
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lincland wrote:
...So, I'm getting that the general idea is that if you use weaker/cleaner pre-amp tubes, you are cleaning up your signal, and lowering your volume. Then you need to raise the volume to achieve the same volume as before. However, you are driving the output tubes harder...


Using lower gain preamp/PI tubes does "clean up" the sound, less gain, but you are certainly not driving the tubes harder, quite the opposite. Generally speaking, less gain equals a cleaner sound and not driving the tubes as hard, even at higher volume. Basically, you get more clean headroom with lower gain preamp/PI tubes.

I have read this nonsense before about lower gain preamp/PI tubes driving the output tubes harder and it's ridiculous, it makes no sense at all.

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Post subject: Re: Please help clarify something about pre amp tubes
Posted: Thu Mar 12, 2015 7:54 pm
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Yes, I know it cleans it up. It also lowers the overall volume. Then as you turn your amps volume knob up to the previous level, it causes the output tubes to work harder to reach the same overall volume level that you had before with higher gain pre amp tubes.

I'm not talking about "gain". I'm talking about natural distortion, not the kind that comes form a hotter pre amp, or a gain and master volume setup.

So start with a 12AX7 on V1, then your amps volume on 6. Listen, play, listen, play, etc. Now switch out for a 5751. Immediately your sound is somewhat quieter and cleaner. So you raise your volume knob to 8 and get it to the same level as before. But the tone is different. It's a different kind of distortion because you're putting more of the work on the output tubes. It's warmer, and richer than the kind of thinner distortion you get with pre-amp drive.

I was just wondering if anyone had done any experimenting with this, or had any knowledge about this.


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Post subject: Re: Please help clarify something about pre amp tubes
Posted: Thu Mar 12, 2015 9:18 pm
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No, you have it wrong. What you are saying makes no sense at all, and if you think about it, maybe it will become clear.

If you have less gain by using lower gain preamp tubes, then you are driving the output tubes less, and they are not working as hard as with higher gain preamp tubes, even if you raise the volume to compensate. The output tubes only amplify the signal from the preamp, and if that preamp signal is lower (with lower gain preamp tubes) then the amplification of the output tubes will be lower, and raising the volume to get back to the same level as before can not push the output tubes harder, only equally at best. Using lower gain preamp tubes is basically about headroom, later onset of distortion fed into the output tubes, and later onset of distortion means that the output tubes are not driven as hard as with high gain preamp tubes.

Yes, there is a difference in sound when using lower gain preamp tubes and raising the volume to compensate, but the difference in sound that you are talking about is because the output tubes are NOT driven as hard with lower gain preamp tubes (more headroom).

Higher gain = earlier onset of distortion, the terms are not mutually exclusive. :wink:

Yes, many of us have done experiments like this, and the results are as I've explained above. An amp with a "Gain" and a "Master" is to push the preamp tubes, and the only way to push the output tubes is either use high gain preamp tubes, or crank the volume of the amp.

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Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Please help clarify something about pre amp tubes
Posted: Fri Mar 13, 2015 2:48 pm
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So as a result, you get a warmer power amp distortion as opposed to a crispier pre-amp distortion.


Perhaps, I have misread your issue and question. Most Deluxe players that I've met avoid power tube distortion. They use them for clean blues or harp.
OK? So you're looking for power tube distortion? Well that's a little different than what shimmilou and I were talking about.
Power tube distortion does sound better if the preamp is not distorting too..Warm is not the term I would use.
It's unlikely that an old Deluxe preamp will distort unless its driven very hard. Lowering preamp gain with low gain tubes will help keep the preamp clean, but the few pickers I've seen that use the old 5E3 Deluxe for distortion just dime the volume knob and control volume with the guitar This keeps the preamp clean and overdrives the power stage easily.
More distortion is not necessarily better. I like to hear distorted peaks, decaying into clean. right on the ragged edge of distortion. But everyone has their own taste.


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