Tweakers' Asylum

Hmm....

24.17.167.105

In Reply to: RE: OPA-2604 voltage posted by 1973shovel on June 09, 2008 at 20:44:44

Without seeing a schematic I am making a couple guesses here.

If the opamp is indeed getting a split supply voltage (+/- VDC and Ground) from a single 12VDC power supply. Then they are doing some fancy foot work to get the negative rail.

BTW: (there's a 4007 at the DC in jack to reverse bias for the negative voltage). Is incorrect, most likely just a polarity protection diode.

They would either have to use a charge pump IC, basically a very low current negative voltage switching power supply. But charge pumps are notoriously noisy, so not often used in audio.

That would leave a simple voltage divider network with the center grounded. That could explain the poor regulation of the +/- rails.

Or they are using the classic input offset method to run the opamp single ended, but then you would see 0 volts on the V- pin.

Either way you can not do what I think you are wanting to do.

Now you could (make that should) build a split power supply.
You already have half of it done.

Follow Ups:

Some more information - 1973shovel 22:35:22 06/09/08 (4)
- Yes, but... - Tweekeng 23:40:21 06/09/08 (3)
  - RE: "you can run just about any (non-inverting) opamp single ended mode" - 1973shovel 09:23:20 06/10/08 (2)
    - Shouldn't hurt but may not help either... - Tweekeng 19:41:49 06/10/08 (1)
      - RE: Shouldn't hurt but may not help either... - 1973shovel 20:19:58 06/10/08 (0)

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