APS audio transformers

Our NEW method of DC offset correction.

To adjust the DC offset to below 2 mV, we connect our test fixture to two transformer pins: 1, 3, and one to ground. With a MV meter connected to pins 1 and 3 of the transformer, red (+) is on pin 1 and black (-) is on pin 3 for measurements during the test. If the DC offset is negative, we configure our test fixture switch to the negative position. If it is positive, we adjust the switch to the positive position. We turn the test fixture potentiometer until we approach near zero. We then measure the value of the test fixture and add that resistor value to either pin 1 or pin 3 of the transformer to ground based on whether it is positive or negative. This sinks the offending DC offset voltage. This test process helps us determine the correct resistor value to correct the offset.

Our R2 transformers experience less impact from DC offset compared to the factory transformers; however, for the best sound quality, we feel this is necessary to maintain low distortion in the bass region.

Please note: With our new type of Vocm buffer mod, this method of DC offset correction has been updated. The old way of changing the common mode resistor values will simply change the total common mode voltage. We changed this DC offset method altogether.

We want to highlight that there is a current sandwich of X7R capacitors in parallel with the additional Vocm capacitor added for the Vocm modification. This was the old way of doing the Vocm mod. Our new method is far superior.