What makes high gain amps to have higher voltage gain thus higher peak dB gain?

[teemuk]

It's good for selling stuff. if i pull up a decibel chart 110-120db is listed as rock concert/siren. so not knowing what they're actually saying, it tells your average joe "this thing is loud!"

Decibel is basically just a shorthand for expressing figures with a lot of zeroes in them in a more simple manner using logarithmic math.

Problem is, being only such a shorthand dB has no "unit" so it can refer to, say, voltage, power, pressure or whatever.

First we must know the unit it refers to; like 120 dB in the context of a rock concert probably refers to sound pressure, or 50 dB in the context of a preamp probably refers to its voltage gain ratio. Then we must acknowledge that we use two principal scaling types: power and amplitude. Now it gets even more confusing because these mean different ratios.

So, 10 dB change means 10x change in power or 3.16x change in amplitude; 20 dB means 100x and 10x respectively; 30 dB means 1000x and 36.2x, 40 dB 10000x and 100x; and so on.

Then we have to know the reference and my God do these vary... there's dBV, dBv, dBu, dB SPL, dBm, dBZ, dB(Hz) and a huge pile more depending on intented application.

[martin manning]

All specifications are for selling stuff. "More is better" doesn't do it for me. Does anyone know how the "overall system gain" is calculated? It's a meaningless number unless its basis is understood.

[teemuk]

I'm quite sure they calculate potential voltage gain at 1 kHz. They might have even had a test input signal to scope against the output signal instead of relying on calculation. No, they don't consider non-linear operation. Pretty much the concept I have - in vain - tried to ardeously explain in several threads OP has started about the topic.

SLM service notes often have those handy notes of signal amplitudes at various signal points and little figures portraying waveforms that one should expect to see in various test points at stated input. They are pretty nice tutorial for inner workings of a high gain amp such as SS140C. Little bit of consultation on those should show pretty obviously where "gain" comes from, how much gain there is, where distortion comes from, what it looks like, what are the clipping thresholds etc.

Decibels are not a marketing ploy but an universally accepted standard to state unit measures in audio applications (and various others).

[John_P_WI]

The irony of all of this is that "high gain or distortion amps" in regard to the pre amps have less actual gain than a clean amp. Compare a diode clipped "Jose" mod clamped down to 12v to a SVT. Never thought of the SVT as high gain, but looking at the dB thru the amp it is greater than the "high gain" distortion amps one thinks of with the signal clipped.

[thinkingchicken]

I'm quite sure they calculate potential voltage gain at 1 kHz. They might have even had a test input signal to scope against the output signal instead of relying on calculation. No, they don't consider non-linear operation. Pretty much the concept I have - in vain - tried to ardeously explain in several threads OP has started about the topic.

SLM service notes often have those handy notes of signal amplitudes at various signal points and little figures portraying waveforms that one should expect to see in various test points at stated input. They are pretty nice tutorial for inner workings of a high gain amp such as SS140C. Little bit of consultation on those should show pretty obviously where "gain" comes from, how much gain there is, where distortion comes from, what it looks like, what are the clipping thresholds etc.

Decibels are not a marketing ploy but an universally accepted standard to state unit measures in audio applications (and various others).

Yes, it is 115dB at 1khz. Looks like you have seen the technical specifications of SC140C yourself. I agree when you said we should make a manual test on amps in order to see the gain measurements, freq response, clipping thresholds, etc. among other things because how an amp distorted, etc. don't involved dB/amplification factor only. Something that I got after "meditating" on what you, HotBluePlates, RG, and others said

[thinkingchicken]

The irony of all of this is that "high gain or distortion amps" in regard to the pre amps have less actual gain than a clean amp. Compare a diode clipped "Jose" mod clamped down to 12v to a SVT. Never thought of the SVT as high gain, but looking at the dB thru the amp it is greater than the "high gain" distortion amps one thinks of with the signal clipped.

I just come to understand, that actually an amp that generate a clean sinewave at say, 115 dB or more, actually have higher gain than a distorted amp with clipped waveforms that is supposed to produce a clean soundwave at 115 dB but it was limited by its own power supply.

[martin manning]

I'm quite sure they calculate potential voltage gain at 1 kHz.

How can you get a number over 100dB doing that? Even if the input signal is quite small, say 10mV rms, and the "overall system" can deliver 100W into an 8 ohm load, you have 69 dB based on voltage gain. The only way I can see to get a figure like the ones being tossed around here is to calculate system power gain, which for the case above, assuming a 1M input impedance, would be 120 dB. However, I fail to see how that means anything wrt the OP's desire to experiment with extremely distorted sounds approaching random noise. Those could be produced at virtually any overall gain. It appears that there is still a lack of understanding (and conflation) of gain and distortion.

[sluckey]

I think that db number is simply the sum of the theoretical gain of each stage minus the loss of each voltage divider, tone stack etc. For example, four cascade gain stages each having a gain of 32db would have a theoretical gain of 128db. But you have two -6db voltage dividers between stages and a -6db loss in the tone stack. So that's -18db and will be combined with the 128db theoretical gain for an overall theoretical gain of 110db. Of course, in practice this theoretical gain will be limited by the power supply voltages, and you put in a sine wave, you will get out a square wave. Fuzz!

This theoretical gain number has little meaning to tech people but can serve as an indication of just how fuzzy sounding an amp is. The higher the number, the fuzzier the sound. (Not necessarily related to louder, more power.) And that's something that non-tech people can relate to and compare amps and brag that I have more gain than you do.

[thinkingchicken]

I think that db number is simply the sum of the theoretical gain of each stage minus the loss of each voltage divider, tone stack etc. For example, four cascade gain stages each having a gain of 32db would have a theoretical gain of 128db. But you have two -6db voltage dividers between stages and a -6db loss in the tone stack. So that's -18db and will be combined with the 128db theoretical gain for an overall theoretical gain of 110db. Of course, in practice this theoretical gain will be limited by the power supply voltages, and you put in a sine wave, you will get out a square wave. Fuzz!

This theoretical gain number has little meaning to tech people but can serve as an indication of just how fuzzy sounding an amp is. The higher the number, the fuzzier the sound. (Not necessarily related to louder, more power.) And that's something that non-tech people can relate to and compare amps and brag that I have more gain than you do.

Bragging jokingly among friends is just fine usually it is those heavy metal musicians and listeners who like to brag about "who got the most gain is the most metal thing", something like that.

But what you're saying is pretty much spot on. I think the true indicator of the perceived "brootal"-ness of high gain amps especially those that are meant for heavy metal or even noise "music" is the amplification factor (not whether this preamp can generate 115 peak dB gain, 135 peak dB gain, 200 peak dB gain and so on without knowing the power supply like what I thought previously) of the amplifying components such as ICs, opamps and tubes. The higher the amplification factor and the lower the power supply, the more aggressive and more brutal the distortion.

Like what teemuk said, a dB figure alone doesn't explain anything if I remember correctly.

[romberg]

IThis theoretical gain number has little meaning to tech people but can serve as an indication of just how fuzzy sounding an amp is. The higher the number, the fuzzier the sound. (Not necessarily related to louder, more power.) And that's something that non-tech people can relate to and compare amps and brag that I have more gain than you do.

I agree with this assessment. I'd also like to point out that gain can be a strong contributing factor in another aspect of "high gain" amps. That being how much an amp compresses or sustains a note.

Of course any note that is gained up beyond a clipping point will turn into a square wave and be compressed down to a single amplitude. The more the signal is amplified beyond the clipping point then the longer the note will appear to sustain. More gain will tend to make this sustain for longer periods of time. Thus to a non-technical guitarist (which may be most), more gain can also help advertise an amp which may sustain notes longer.

The technical folks know that gain alone does not do this compression/sustain. And similar results can be achieved with a lower clipping point (say 0.7v diodes) and less overall gain. But the end result is still called a "high gain" amp/pedal.

Mike

[thinkingchicken]

IThis theoretical gain number has little meaning to tech people but can serve as an indication of just how fuzzy sounding an amp is. The higher the number, the fuzzier the sound. (Not necessarily related to louder, more power.) And that's something that non-tech people can relate to and compare amps and brag that I have more gain than you do.

I agree with this assessment. I'd also like to point out that gain can be a strong contributing factor in another aspect of "high gain" amps. That being how much an amp compresses or sustains a note.

Of course any note that is gained up beyond a clipping point will turn into a square wave and be compressed down to a single amplitude. The more the signal is amplified beyond the clipping point then the longer the note will appear to sustain. More gain will tend to make this sustain for longer periods of time. Thus to a non-technical guitarist (which may be most), more gain can also help advertise an amp which may sustain notes longer.

The technical folks know that gain alone does not do this compression/sustain. And similar results can be achieved with a lower clipping point (say 0.7v diodes) and less overall gain. But the end result is still called a "high gain" amp/pedal.

Mike

Is the sustain mechanism through a pedal the same as achieving a controlled feedback sustain by standing in front of a loud amp?

[wpaulvogel]

No!!!
Enough Already!!!
What’s it going to take to get this through your thick skull?
You’re just like some people that won’t do their own homework. I’m finished
Please everyone, stop feeding this codependent relationship. Wean him from the tit! Make him sleep in the crib! Everything he needs is available for him to explore and learn independently. Because his financial situation limits him from experiment, there’s no reason to continue.

[thinkingchicken]

No!!!
Enough Already!!!
What’s it going to take to get this through your thick skull?
You’re just like some people that won’t do their own homework. I’m finished
Please everyone, stop feeding this codependent relationship. Wean him from the tit! Make him sleep in the crib! Everything he needs is available for him to explore and learn independently. Because his financial situation limits him from experiment, there’s no reason to continue.

The fusses about the whole gain thing are already finished if you read the whole convos...

[wpaulvogel]

I’ve read and interacted with all the conversations on every forum you’ve posted on. It’s clear that you don’t have the capacity to understand. Case in point is the lack of realizing that sustain through a pedal is different than the feedback generated from the interaction of vibration between the speaker and guitar.

[thinkingchicken]

I’ve read and interacted with all the conversations on every forum you’ve posted on. It’s clear that you don’t have the capacity to understand. Case in point is the lack of realizing that sustain through a pedal is different than the feedback generated from the interaction of vibration between the speaker and guitar.

How did an infinite sustain which sounds like when someone get a feedback sustain from a loud amp, generated through a pedal like below?


Its a shame that it was discontinued.