I have a pro class A/B amp that's outputting odd noise for small signals, like very quiet orchestral passagse. The noise is low in volume but noticeable. Increasing the input level causes the noise to also increase in volume, but eventually with a high enough input the noise go away. Decreasing the input level back keeps the noise away for a few seconds, but then it comes back. The noise isn't quite uniform; it sounds like it has more HF energy.
I suspect that the bias of the transistors might be wrong, causing them to slip out of the linear region, does this seem plausible?
Opening the amplifier, I see 2SA1302/2SC3281 transistors in the output stage; each channel has a pot which I assume is used to adjust the bias.
Does anyone have tips or advice as to how I can figure out what's wrong and fix it? I can get to an oscilloscope, but it's a lot easier for me to find a multimeter.
I suspect that the bias of the transistors might be wrong, causing them to slip out of the linear region, does this seem plausible?
Opening the amplifier, I see 2SA1302/2SC3281 transistors in the output stage; each channel has a pot which I assume is used to adjust the bias.
Does anyone have tips or advice as to how I can figure out what's wrong and fix it? I can get to an oscilloscope, but it's a lot easier for me to find a multimeter.
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