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In Reply to: RE: New PPP... tolerances? posted by harrypt on May 07, 2009 at 10:59:57
That's really strange. The metering system is not perfect by any means and you will see some variance normally. Usually one volt or so and this is due to temperature. However, the THD bit has me stumped as I am sure the load remains the same? The fact that the input THD is the same and the output is varying like that doesn't sound right. Are you sure nothing in the system is changing at night? You're not adding any equipment?
I have a tube pre, cd player and 70 watt stereo tube amp plugged into the PPP. Prior I had a P-300 running the amp and a P-300 running the front end with no problems so I thought a PPP should work.
Came home tonight and checked readings before turning anything on. It read ~118-119 input adding 3 volts to output 122. THD input ~2.5%, output ~0.4%. Turned everything on to warmup and nothing changed. Came back about 20 minutes later, unmuted the preamp and turned volume up to listening level (with nothing playing) and saw the THD output jump to ~1.2%. Turning the amp off reduces it back to .4 THD. Turning amp back on it immediately jumps back to low to mid 1%.
Is 1.2-1.5% too high and is that abnormal?
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