[sdiy] M-Audio Delta-44 schematics ?

[Richard Wentk]

At 10:33 08/05/2006, Andre Majorel wrote:

>I've already looked at the breakout box. Nothing in there. The
>sub-D 15 carries 8 signals and 4 x ground. All there is in the
>breakout box is a 22 µF cap and a 10 k resistor in series between
>each ring and tip (pseudo-balanced I/O).

You don't need the schematics. You just need a scope.

First use something like Reaktor or Audition to create a square wave at 
around 20Hz. Check what this looks like before the cap. If it's distorted 
there's DC blocking earlier in the chain. If it's not distorted and there's 
a DC offset, there's no DC blockingc and if you get rid of the cap you'll 
have DC coupling.

I modded a Maya USB interface to DC couple it. Removing the cap was easy - 
all I had to do was short the traces around it. Working out which traces to 
short should be obvious enough. The output cap is the last one in the chain 
before the connector.

After that there was a 2V (approx) DC offset to deal with. That was trimmed 
out with an op-amp fed by a trimmer voltage divider. Since this wasn't an 
audiophile project I used TL072s. For anything more serious I'd use 
something better.

Richard