When I measure the voltage on the base of Q501 on the power amp boards, I can hear the amp buzz/oscillating through the channel I'm measuring. The test leads aren't touching anything they shouldn't be and I'm using the small clip on leads that have a small hook that is spring loaded. I turn the amp off before disconnecting/connecting the test leads.
Measurements are what the schematic shows for each pin on the transistor, second photo.
DC Offset and bias adjust and hold, the amp sounds fine, waveforms on the o-scope look good.
Am I showing symptoms of having OCD? Should I change the diff pair to matched BC550C's? Or, should I button it up and use it, get drunk?
Measurements are what the schematic shows for each pin on the transistor, second photo.
DC Offset and bias adjust and hold, the amp sounds fine, waveforms on the o-scope look good.
Am I showing symptoms of having OCD? Should I change the diff pair to matched BC550C's? Or, should I button it up and use it, get drunk?
Attachments
OCD "over complicated design" ?
I can design an amp with 7 transistors that does the same job.
Lots of gain in your circuit so probably explains why test lead is causing noise.
I can design an amp with 7 transistors that does the same job.
Lots of gain in your circuit so probably explains why test lead is causing noise.
Your test lead is acting as an antenna, and any RF crap in the air is being picked up and rectified by the transistor. Nothing to worry about in normal use
You're measuring with a high impedance probe with long leads ('antenna') within the high gain open loop. The circuit act as a radio without the tuning parts. At least short the input to ground. Cheerio.