How to find the peak decibel gain of the highest gain channel of a high gain amp?

[teemuk]

So would that be 36.1 dB max gain if the input amplitude is one microvolt? And is it still the same 36.1 dB max gain if the input amplitude is 10 volts?

Other than appealing to that HotBluePlates says so, why do you think something limits the total gain of multiple cascaded Metal Zones?

[wpaulvogel]

If you attempt to use a practical example vs a theoretical model, you’ll find that achieving 115dB gain is not possible. The input voltage from the instrument is going to place the amplifier in a situation where the input voltage can rise and the output voltage stops rising peak or rms. Inputting micro volts isn’t something that occurs with electric guitar.

[thinkingchicken]

So would that be 36.1 dB max gain if the input amplitude is one microvolt? And is it still the same 36.1 dB max gain if the input amplitude is 10 volts?

Other than appealing to that HotBluePlates says so, why do you think something limits the total gain of multiple cascaded Metal Zones?

If the power supply is 9 V, no. The peak dB gain keep changing depending on the input amplitude. Oh, so because the input amplitude is dynamic, so does the peak dB gain. Thanks for pointing out the error, teemuk. This is very confusing because different people tell different things, but here what you're saying make sense.

[thinkingchicken]

If you attempt to use a practical example vs a theoretical model, you’ll find that achieving 115dB gain is not possible. The input voltage from the instrument is going to place the amplifier in a situation where the input voltage can rise and the output voltage stops rising peak or rms. Inputting micro volts isn’t something that occurs with electric guitar.

I believe your previous point is when we're starting to play the guitar with the amp gain knob at max, the resulting soundwaves will immediately hit the headroom ceiling and the soundwaves become clipped thus we will never get the 115 dB gain figure. And power supply is the headroom where the soundwaves will clipped after they hit the ceiling. Correct?

That's why I feel weird after seeing the input amplitude being only 0.00044457 V, with the power supply at 250 V, in order to generate a peak dB gain of 115 dB. I'm not sure if an electric guitar can generate an input amplitude that low. Thus, are those high dB figures somehow suppositious?

[wpaulvogel]

If you attempt to use a practical example vs a theoretical model, you’ll find that achieving 115dB gain is not possible. The input voltage from the instrument is going to place the amplifier in a situation where the input voltage can rise and the output voltage stops rising peak or rms. Inputting micro volts isn’t something that occurs with electric guitar.

I believe your previous point is when we're starting to play the guitar with the amp gain knob at max, the resulting soundwaves will immediately hit the headroom ceiling and the soundwaves become clipped thus we will never get the 115 dB gain figure. And power supply is the headroom where the soundwaves will clipped after they hit the ceiling. Correct?

That's why I feel weird after seeing the input amplitude being only 0.00044457 V, with the power supply at 250 V, in order to generate a peak dB gain of 115 dB. I'm not sure if an electric guitar can generate an input amplitude that low. Thus, are those high dB figures somehow suppositious?

It’s not possible to produce the gain in a practical application. In theory, if you input such a small signal, it’s possible to achieve the theoretical gain but with the instrument intended to be used to apply the input voltage, it’s basically impossible for that instrument to (under normal operating conditions) produce such a small voltage output.

[wpaulvogel]

I think you have a sound in your head and maybe you even have a device that gets you close to that sound. You need to take the sound and look at it with a scope. At that point you then have the ability to make a device that can produce that waveform with adjustment and you can tweak the waveform to produce your sound. Just saying you need this much gain is ridiculous because there’s easier ways to get to pure square waves and then you sculpt them to suit your taste. A Plexi can do it with help from pedals and EQ.

[thinkingchicken]

If you attempt to use a practical example vs a theoretical model, you’ll find that achieving 115dB gain is not possible. The input voltage from the instrument is going to place the amplifier in a situation where the input voltage can rise and the output voltage stops rising peak or rms. Inputting micro volts isn’t something that occurs with electric guitar.

I believe your previous point is when we're starting to play the guitar with the amp gain knob at max, the resulting soundwaves will immediately hit the headroom ceiling and the soundwaves become clipped thus we will never get the 115 dB gain figure. And power supply is the headroom where the soundwaves will clipped after they hit the ceiling. Correct?

That's why I feel weird after seeing the input amplitude being only 0.00044457 V, with the power supply at 250 V, in order to generate a peak dB gain of 115 dB. I'm not sure if an electric guitar can generate an input amplitude that low. Thus, are those high dB figures somehow suppositious?

It’s not possible to produce the gain in a practical application. In theory, if you input such a small signal, it’s possible to achieve the theoretical gain but with the instrument intended to be used to apply the input voltage, it’s basically impossible for that instrument to (under normal operating conditions) produce such a small voltage output.

So to produce a peak decibel gain of 115 dB, the headroom must be too large and the input amplitude from the guitar must be at a very low voltage, for example 0.00044457 V. Isn't it?

[thinkingchicken]

I think you have a sound in your head and maybe you even have a device that gets you close to that sound. You need to take the sound and look at it with a scope. At that point you then have the ability to make a device that can produce that waveform with adjustment and you can tweak the waveform to produce your sound. Just saying you need this much gain is ridiculous because there’s easier ways to get to pure square waves and then you sculpt them to suit your taste. A Plexi can do it with help from pedals and EQ.

I just listened to demos of comparator fuzz pedals. The output waveforms are totally square, but it is very noisy and there are lots of gated sounds.

[teemuk]

If you attempt to use a practical example vs a theoretical model, you’ll find that achieving 115dB gain is not possible. The input voltage from the instrument is going to place the amplifier in a situation where the input voltage can rise and the output voltage stops rising peak or rms.

Well duh, we are discussing distorting pedals and amps. Isn't this obvious?

So, if we want to get really practical we should realize we can't even express "gain" by a single figure. It's a function related to input amplitude and you have to express it as a graph that is non-linear at least in one end.

But for all purposes simply referring to gain as a single nominal figure of amplification factor or amplification ratio we can exclude practicality of circuit limitations, which typically just obfuscate discussion. If we say e.g. that non-inverting opamp gain stage in a 9V pedal circuit has voltage gain ratio of 40x we don't have to state the obvious that the linear math works only for a limited range of input.

[thinkingchicken]

If you attempt to use a practical example vs a theoretical model, you’ll find that achieving 115dB gain is not possible. The input voltage from the instrument is going to place the amplifier in a situation where the input voltage can rise and the output voltage stops rising peak or rms.

Well duh, we are discussing distorting pedals and amps. Isn't this obvious?

So, if we want to get really practical we should realize we can't even express "gain" by a single figure. It's a function related to input amplitude and you have to express it as a graph that is non-linear at least in one end.

But for all purposes simply referring to gain as a single nominal figure of amplification factor or amplification ratio we can exclude practicality of circuit limitations, which typically just obfuscate discussion. If we say e.g. that non-inverting opamp gain stage in a 9V pedal circuit has voltage gain ratio of 40x we don't have to state the obvious that the linear math works only for a limited range of input.

Is amplification factor the ability of a sinewave to remain undistorted until it finally hit the headroom? Because it seems like the lower the input amplitude, the higher the output amplitude as long as there are still lots of space in the headroom.

[thinkingchicken]

Below is the frequency response of LT1012 opamp showing open loop (black) and closed loop (red) gain in db vs frequency.

fig3LT1012 Op Amp Open Loop & Closed Loop Gain vs. Frequency.png

Is it possible to increase the gain around the 3khz-10khz frequency to beyond 110 db?

[teemuk]

Is amplification factor the ability of a sinewave to remain undistorted until it finally hit the headroom?

Could amplification factor be the ratio by which the circuit/amp amplifies the input signal?

Because it seems like the lower the input amplitude, the higher the output amplitude as long as there are still lots of space in the headroom.

Can you describe me how this "reverse" amplifier of yours works?

[thinkingchicken]

Is amplification factor the ability of a sinewave to remain undistorted until it finally hit the headroom?

Could amplification factor be the ratio by which the circuit/amp amplifies the input signal?

Because it seems like the lower the input amplitude, the higher the output amplitude as long as there are still lots of space in the headroom.

Can you describe me how this "reverse" amplifier of yours works?

Ok, I'm curious to see about your descriptions and explanations of what is gain and how gain works.

[thinkingchicken]

Sorry if this question had been answered, but what makes the peak dB gain of high gain tube amps much higher? Is it because of the 200-400 V power supply while the power supply for typical distortion pedals are only at 9 V?

[teemuk]

What makes you think that peak gain of tube amplifiers is much higher? Please, don't answer that HotBluesPlate said so. Do you have a statistical on this? Isn't a solid-state Ampeg VH-140C much gainier than a tube Magnatone 260 or do I just have clot ears?

And do you think there is a difference if one amp has gain of 20 dB (10x) and clipping threshold of 10 V and one amp that has gain of 26 dB (20x) and a clipping threshold of 20V, assuming both receive input signal of same amplitude? Why might a tube amp with higher clipping threshold aim to higher gain than an effect pedal with lower threshold? It just doesn't make sense...

And continuing on your previous question, how would you make the amplifier know that it must amplify lower input with higher ratio than higher input? Would this imply some sort of dynamically variable, envelope controlled gain adjustment scheme with feedforward or feedback input? And if an amp amplifies lower amplitude input signals with higher gain than higher amplitude input signals will it mean that the output waveform can not be just an amplified replication of the input signal but has "compressed" the peak portions of waveforms, which means the waveform is actually distorted?