2-ACA Output Trafo Conundrum

[living sounds]

I'm currently testing my console and am trying to make sense of what I found regarding the trafo output of the 2-ACA summing and buffering board. With no load I get a nice representation of the 8k square wave (looks pretty much exactly as the "signal generator" [Moog Modular] puts it out). This is measuring pin 2 to ground.

But with the converter input connected the signal changes to a higher amplitude but more triangle/sawtooth like pattern.  The converter shouldn't put a lot of load on the signal, and the discrete op amp / output trafo combination should handle a modern converter input easily.

Any idea what's going on here and what to do about it? Thanks!

 

[living sounds]

This is what the output looks like with the converter connected.

 

[shabtek]

What about sin wave? I'd be inclined to see what happens when loaded with 600...assuming a/d is 10k input.

 

[scott2000]

Looks kinda like the  High Frequency Loss/phase shift here on this chart????

 

[living sounds]

What about sin wave? I'd be inclined to see what happens when loaded with 600...assuming a/d is 10k input.

Sine wave looks all right, but it also increases in amplitude.

Do you think adding 600 accross the secondaries might cure it?

 

[shabtek]

Not clear what you mean with pin2 to ground--are both ends of secondary connected or is one floating?

 

[living sounds]

Not clear what you mean with pin2 to ground--are both ends of secondary connected or is one floating?

Oscillator tip touches pin 2, Oscillator ground touches ground. Pin 3 measures similar to pin 2 (it's the other side of the transformer secondary after all).