Volume control by adjusting Voltage

[pinobot]

Hi.
I'm new to this diy amplifier stuff and i'm looking into buying my first T-amp. Now it seems you can change the gain by adjusting the voltage, but why isn't that done, are there sonic disadvantages and what are they?

 

[jan.didden]

Which voltage do you mean?
The supply voltage?

jan didden

 

[pinobot]

Yes

 

[wwenze]

If gain changes with supply voltage, any noise on the supply rails will show up on the output.

 

[DcibeL]

To clarify the above, no, the supply voltage does not affect the gain. Feedback defines gain. Look up basic op-amp calculations to get an idea of how that works.

 

[Capt Grogg]

Open loop class d amps change gain with power supply voltage change, power supply sag causes compression, noise also goes down with voltage. Lots of oportunities and yes instead of power supply rejection you get power supply injection. Used in many commercial products, including top of the line Sony multi-channel receivers