APS audio transformers

A note on DC offset and power supply regulators running too hot on Directstream MK1 DACs.

Using the Bridge II card will cause these MK1 DACs to overheat two of the 5v regulators. If you're using a Bridge II card, we suggest either obtaining the Bridge ready upgrade or just switching off the back power button when the DAC is not in use. See Photos of burned heat sinks and residue from burnt transformer wires.

Testing for DC offset. Pay close attention.

To measure DC offset, use a high-quality MV meter and connect one probe to pin 1 and another to pin 2 of the transformer while the DAC is powered and in MUTE mode. Exercise caution to avoid shorting anything with the probes.

One member of the PS Audio Forum "Anton_ss" believed he didn't have a DC offset problem, but it turns out he did because he measured it incorrectly.

We assess and record each transformer installation at this location before we desolder and take out the old ones and once the new transformers have been set up. Everyone here burst into laughter upon viewing the measurements that "Anton_ss" from PS Audio Forums shared, as we were certain they were inaccurate; we'd never encountered an MK1 DAC with both channels this low... NEVER, I returned and reviewed our records regarding the accurate measurements.

Indeed, it was 3mv and 12mv... not the .03 and .14mv he believed he had.

The truth is it's clear Anton_ss did not adhere closely to our instructions on how to accurately measure the DC offset.

He inquired about this after going through our guidelines.
"Are these the right pins? And the other probe goes to the ground doesn't it?"

Anton_ss was measuring from ground to each pin... This is Wrong! Don't do this!