Help with Gain calculation

[ronjodu]

I'm looking for suggestions for a maximum setting (gain) for a PGA2320 volume control. I have a Pic Micro controlling the chip and want to set a maximum volume to help protect my speakers. The Amp is a Dual Mono BrianGT LM3886 chipamp with 2 Avel Limdberg 250 va 25/25 torroids feeding 2 BrianGT power supplies.
The input for now is an 80 gig Ipod and the speakers are 2-Wharfdale Diamond 9.1 bookshelf speakers at 6 ohms each. I am absolutely amazed at the sound this setup puts out. I couldn't be more pleased. I've read many threads on Gain calculations and can't seem to grasp what I need to do to come out with an acurate setting. Here is a picture of the Preamp done on perf board for now.

Any help will be welcome.

[BWRX]

Hi ron. What gain setting you choose is really entirely up to you. Generally, gains are set so that the maximum source input voltage results in the maximum amplifier output voltage. Take an iPod and a Gainclone with 30V power supply rails as an example. If the iPod is capable of 1V peak output (unclipped sine wave) then you would aim for a gain of about 30V/V so that a 1V peak input will make the amplifier try to produce 30V peak output. Don't forget to keep in mind that a gainclone with 30V supply rails will go into clipping when trying to reproduce a 30V peak output.

[Nordic]

A 30V supply can only produce a 21V output.... in an ideal world... so probably less... (V / sqrt 2)

In other words on an input of 1V signal a maximum gain of about 20.

Of course you have 25VAC torroids so you will be looking at about 35VDC supply which will give a max output somewhere south of 25V... which why you see gain for 8 ohm GC systems typicaly at about 22.

[AndrewT]

First you need to know the maximum output of the source component.

When you have measured that come back.