Odd Dyna ST-35 behavior with no input connected

[DerekVa]

When I was setting up my new ST35 build, I realized I had reversed the left and right channels (thanks to the line 'A push from the left and a shove from the right' in the song Coup d'Etat by The Circle Jerks), so I swapped my inputs. When I disconnected the right channel, there was no problem, however, when I disconnected the left, there was a warbling / motorboating sound (not just motorboating, more of a feedback warble). From what I understand, if I have a bad cathode resistor or swapped OPT connections, I could get this sort of behavior, but it would be all the time. This only occurs when there is no signal on the left channel. Any ideas? Bad input cap? Imps in my power supply? Bad karma?

Thanks!


-Derek

[TomMcNally]

Hi Derek ...

You shouldn't turn on a power amplifier with no volume control with no input (or output) connected. If you are doing noise tests, you want to connect shorted RCA plugs to the inputs. With nothing connected, the amp is sitting there wide open, and the inputs act like antennas and pick up power line hum, RF, or whatever is in the air. It's normal.

... tom

[DerekVa]

Hi Derek ...

You shouldn't turn on a power amplifier with no volume control with no input (or output) connected. If you are doing noise tests, you want to connect shorted RCA plugs to the inputs. With nothing connected, the amp is sitting there wide open, and the inputs act like antennas and pick up power line hum, RF, or whatever is in the air. It's normal.

... tom

Hmmm...OK. I new about output so you don't fry the OPTs, but didn't realize that no input was a bad thing. Now I know. Ironically, this isn't a problem on my P2P ST35 (not that I habitually run my amps without an input, of course). Given the noise, I'm not sure what I was picking up...Sasquatch?

-D