Gain vs. Volume

In my experience, there is no clear understanding of the difference between the two out there. I've been getting advice that equated the two and then been told that it's all about matching the different components in the playback system without explaining what varying gain does to the sound .

To put this in context, both my phono preamp and line preamp have variable gain which allows experimentation with different settings. However, even before I bought my current phono pre, I noticed that there was a difference between a higher gain, lower volume setting vs. a lower gain, higher volume setting on my line pre. No matter how high the volume was, the sound was not the same with the lower gain setting. That told me that varying gain does something different to the sound curve than adjusting volume/attenuation does. The sound was more dynamic and "filling," as if the soundstage widened, and the sound was "thicker."

Now that both my phono pre and line pre allow gain adjustment, I have been experimenting with different settings. I'm still in the early stages of experimentation, the purpose of which is to find the setting at which the sound is satisfyingly rich and loud, but not too harsh, which I found a gain too high for the cartridge can result in, even if the noise level is very low.

So to sum up, it is very clear to me that gain and volume do different things to the sound even if the sound level is the same. I believe gain must be changing the sound curve so that certain frequencies are accentuated and ultimately affect the character of the sound.

If my hypothesis is obvious to anyone, please feel free to educate me, but so far I have seen no information on this forum or outside of it that draws a clear and sensible distinction between gain and volume.
Hi Marek,

By adjusting gain, you are changing the signal level/voltage being processed by the circuitry that is at points in the signal path between the gain adjustment provision and the volume control. That can affect various kinds of distortion that may be introduced by that circuitry, and the ratio of signal to noise that is generated by or coupled into that circuitry. You are also changing the effects that the volume control mechanism and the gain adjustment provisions themselves may have on the signal.

As long as the settings you are comparing are within reasonable limits, so that the volume control is being used in a reasonable part of its range and noise levels are not objectionable, the optimal combination of settings figures to not have much predictability, and most likely has to be found experimentally, as you are doing.

Best regards,
-- Al
There is a principle used when optimizing signal paths in recording studios referred to as gain-staging. Gain is a ratio of amplification. Oversimplified: Output voltage/input voltage or output current/input current is expressed as a numerical amplification factor. Too much or not enough gain may result in operating the amplifying device (tube, transistor, whatever) in a non-linear portion of it's response curve where its supply voltage or bias may be insufficient
for full range frequency response leading to a colored sound (the color being distortion).
As per above, gain is the amplification provided by a circuit. The circuit gain is changed by altering the circuit itself eg changing resistor values, feedback, removing/adding an entire amplification stage etc. So you are right, different gain settings are likely to sound different because of this.

The 'volume' control is generally positioned at the input of the preamp stage and attenuates the input signal applied to preamp's gain stage/s (from phono or line sources). There are various methods of building 'volume' controls and these will sound different. The setting of the volume control can also load the circuit differently causing changes in high frequency rolloff etc. So different 'volume' positions can change the sound.

So IMO you're right, both volume position and gain setting will change the sound. Which gain setting and which position of the 'volume' control is preferable will depend on the design, the system and likely the listener.
All the above are correct but may be confusing. A simple way to look at it is to use the least amount of gain that you can to get the job done, as the more gain, the more can go wrong.
Arthur Salvatore has a very nice and understandable article on this theme.