Represent Max Output Voltage on Volume Dial Scale

[Robbie010]

I'm just trying to get my head around gain structures and can't seem to find a calculator or chart that gives me a numerical or visual representation of the correlation between my known max output voltage and the volume dial on my pre-amp.

I have connected my streamer / pre-amp via XLR cable, the stated output voltage of the XLR connection is 5.2v, which I assume is with the volume knob turned to maximum.

The volume dial runs on a scale of -100db - 0db.

My understanding is that the volume dial will be logarithmic, so -50db does not represent 2.6v i.e. half of the max output voltage, so I'm looking for a scale / chart showing the incremental correlation between the 2.

The reason for this is that my power amp has an input sensitivity of 2.6v in to 4 ohms and I'm trying to work out how to set the output volume/gain/voltage for my 8 ohm speaker drivers while setting up an active system.

My initial thinking is that I should set the pre-amp volume to achieve around half the required voltage needed to drive the power amp to full output, giving me plenty of headroom either way.

Thanks

 

[pjug]

Half is -6dB. Here is a calculator including the equations: https://sengpielaudio.com/calculator-gainloss.htm

 

[Robbie010]

Half is -6dB. Here is a calculator including the equations: https://sengpielaudio.com/calculator-gainloss.htm

Wow! Really…..

Sorry, I got the numbers wrong. The input sensitivity of the power amp is 2.3v, not 2.6.

So, if -6.0db in the volume dial equates to 2.6v and I want to half that again (plus a bit more) I need to set my volume dial to around -14/-13db, giving me around 1.1v - 1.2v?

 

[pjug]

For 1.2V your voltage ratio is 1.2/5.2=0.23. So plug that into the calculator or use the equation in the link:
dB = 20 * log(V2/V1) = 20 * log(0.23) = -12.8dB
You can use this equation in a spreadsheet to make the chart you wanted.

 

[raindance]

But that voltage "calibration" would only be accurate for a steady state test signal. For music it would vary wildly depending on the mastering.

This is why I'm constantly saying that the position of the volume knob tells you very little. If you can't hear distortion when you turn it up too high, then you have another problem. But that is the warning sign.

 

[Robbie010]

But that voltage "calibration" would only be accurate for a steady state test signal. For music it would vary wildly depending on the mastering.

This is why I'm constantly saying that the position of the volume knob tells you very little. If you can't hear distortion when you turn it up too high, then you have another problem. But that is the warning sign.

All I’m looking for here is a middle of the road starting point that allows me safe volume control.

Up to this point I have started with the pre-amp volume dial to -50db (half way point), which according to the calculator is somewhere around 0.02v output, no where near enough to drive the power amp and subsequently, I’m running out of room in the dsp to suitable set the output gain of the drivers.

 

[pjug]

All I’m looking for here is a middle of the road starting point that allows me safe volume control.

Up to this point I have started with the pre-amp volume dial to -50db (half way point), which according to the calculator is somewhere around 0.02v output, no where near enough to drive the power amp and subsequently, I’m running out of room in the dsp to suitable set the output gain of the drivers.

You are just using the dial for a safety measure and doing regular volume control with software? I wouldn't worry too much, just dial it back a little if it gives you peace of mind but now you see you don't need to turn the dial back very much.

 

[AnalogSteph]

-50 dB is awfully low indeed. You generally want to achieve normal, all-day playback volume at around -30 dB, maybe high -20s on the main volume control. (That assumes playback volume has been made reasonably constant across sources, obviously. Somewhere around -16 to-26 LUFS average depending on your range of material.)