What is Gain?

mickeydg5

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I agree about the gain and distortion scenario. People confuse gain with distortion. They call it gain. The voltage gain is driven high enough to cause overdrive/distortion.
Then they call an amplifier with higher distortion/harmonics a high gain amplifier. There is no more gain in that amplifier as in another of the same power level but rather more overdriven stages which produce the distortion/harmonics.
They should call it an overdriven multi-stage amplifier or maybe optional stage amplifier since most have a cleaner channel along with varying other overdrive channels.

Yes we do agree. It is splitting hairs.

What is funny or interesting though is that gains curves are very much almost opposite of the audio taper curves found in our GAIN and VOLUME controls.
 
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spacerocker

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I agree about the gain and distortion scenario. People confuse gain with distortion. They call it gain. The voltage gain is driven high enough to cause overdrive/distortion.
Then they call an amplifier with higher distortion/harmonics a high gain amplifier. There is no more gain in that amplifier as in another of the same power level but rather more overdriven stages which produce the distortion/harmonics.
They should call it an overdriven multi-stage amplifier or maybe optional stage amplifier since most have a cleaner channel along with varying other overdrive channels.

Yes we do agree. It is splitting hairs.

What is funny or interesting though is that gains curves are very much almost opposite of the audio taper curves found in our GAIN and VOLUME controls.

That's interesting....

Also some amps (like the JVM) Increase overdrive by lowering the plate voltage by using a higher value plate resistor, thus effectively lowering the threshold for clipping - and this is seen by some as "increasing gain"!
 

mickeydg5

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That's interesting....

Also some amps (like the JVM) Increase overdrive by lowering the plate voltage by using a higher value plate resistor, thus effectively lowering the threshold for clipping - and this is seen by some as "increasing gain"!
Wait, whaaaaat?
That does increase the overall gain of the tube circuit. In that instance the load of the tube circuit would be lessened therefore increasing amplification factor and gain.
It is also shown in the tube data and verified in tube manuals.

Are you screwing with me?
 

South Park

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The jcm 800 has three stages . the first stage is the gain stage . The first Half is for gain ramped up signal.the second halve normal head room.so it clipped the signal. The second stage inverts the signal both sides are clipped no gain for second stage. The third is the phase splitter normal head room. Feeds the drivers grids.distortion is clipping.it is a balance of tone and crunch
 

mickeydg5

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The jcm 800 has three stages . the first stage is the gain stage . The first Half is for gain ramped up signal.the second halve normal head room.so it clipped the signal. The second stage inverts the signal both sides are clipped no gain for second stage. The third is the phase splitter normal head room. Feeds the drivers grids.distortion is clipping.it is a balance of tone and crunch
You should really specify which JC800 model if you want to make a case.
 

South Park

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The original jcm 800 . It’s just not all about gain. It how the rest of the amp works the signal.
 

spacerocker

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That's interesting....

Also some amps (like the JVM) Increase overdrive by lowering the plate voltage by using a higher value plate resistor, thus effectively lowering the threshold for clipping - and this is seen by some as "increasing gain"!

Wait, whaaaaat?
That does increase the overall gain of the tube circuit. In that instance the load of the tube circuit would be lessened therefore increasing amplification factor and gain.
It is also shown in the tube data and verified in tube manuals.

Are you screwing with me?

Yes - I've been back to check the equations - and you are, of course correct! - Increasing the value of the plate resistor does increase the gain!

But it also reduces the plate voltage (causing more clipping) - which was the explanation I had previously read.

So I think the summary is that increasing the plate resistor from the "traditional" value of 100K to 220K increases the gain AND clipping in that stage....
 

mickeydg5

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Yes - I've been back to check the equations - and you are, of course correct! - Increasing the value of the plate resistor does increase the gain!

But it also reduces the plate voltage (causing more clipping) - which was the explanation I had previously read.

So I think the summary is that increasing the plate resistor from the "traditional" value of 100K to 220K increases the gain AND clipping in that stage....
When explaining or giving details to these things I look at the big picture, usually everything included.
I have mentioned both AC and DC.
In the above statement mostly regards to DC operation is involved. However, the plate resistor affects not only DC but AC as well. The other resistors beyond the coupling capacitor also affect AC loading. All of these things work together in regards to exponentially raising and lowering the amplification factor and gain.

We are back to splitting hairs. :) At higher signal levels there is much less difference in amplification factor and gain. At low signal levels the differences are greater and have a more drastic/exponential curve.

This is why I like an amplifier that provides a wider control range from clean levels to overdrive levels to higher distortion levels. I do not like an amplifier that is clean on 1 or 2, by 3 overdriven and four maxed out.
 

Vinsanitizer

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Gain is like where you had $2, you invested it, and now you have $20.
But that's low gain. I'm not sure I can accurately define high gain.
 

kinleyd

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No!

... ok, yes. :D How've you been bro?
Been good Vin, thank you. Been focusing on the family (kids school/college, etc.) and practicing guitar more than providing my unqualified comments on MF and TGP. In a couple of weeks I hit my sixth anniversary since picking up the guitar! In short, it's been wonderful : )

Do hope all is well with you too.
 

Vinsanitizer

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Been good Vin, thank you. Been focusing on the family (kids school/college, etc.) and practicing guitar more than providing my unqualified comments on MF and TGP. In a couple of weeks I hit my sixth anniversary since picking up the guitar! In short, it's been wonderful : )

Do hope all is well with you too.
Yup. Been hanging out on the forum a bit more lately and setting aside some time to play guitar. Sometimes I just get tired of working all the time.
 


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