jamesltaylor
- Jul 25, 2010
- 3
- Joined
- Jul 25, 2010
- Messages
- 3
I have a repair question and yours is the first site I have approached. If you cannot or will not respond to my question please direct me, if you can, to a site where I can field this question.
Background: I thought I heard distortion in one of the channels of my final amp. I got documentation for the amp and started to check it out. I checked the performance and then I replaced all of the capacitors in the amp since it is old. Then I fired it back up and checked the offset and bias. The bias was just a little off on one channel offset was fine. From the start I noticed that when I input a sine wave when the output went over 1 volt p-p noise started to appear on the peaks of the sine wave. At 1.5 volts the noise was a significant part of the output waveform but as volume was increased the noise amplitude remains the same and becomes a small part of the output waveform.
The noise is present on the ground bus of the preamp, which also shows up in the output waveform, and appears to be generated by reverse EMF from the speakers getting into the ground plane. By all outward signs the amp sounds normal.
Question: Is this normal behavior for a Phase Linear 400 type 2 final amplifier? If not what may be wrong
Background: I thought I heard distortion in one of the channels of my final amp. I got documentation for the amp and started to check it out. I checked the performance and then I replaced all of the capacitors in the amp since it is old. Then I fired it back up and checked the offset and bias. The bias was just a little off on one channel offset was fine. From the start I noticed that when I input a sine wave when the output went over 1 volt p-p noise started to appear on the peaks of the sine wave. At 1.5 volts the noise was a significant part of the output waveform but as volume was increased the noise amplitude remains the same and becomes a small part of the output waveform.
The noise is present on the ground bus of the preamp, which also shows up in the output waveform, and appears to be generated by reverse EMF from the speakers getting into the ground plane. By all outward signs the amp sounds normal.
Question: Is this normal behavior for a Phase Linear 400 type 2 final amplifier? If not what may be wrong