Nathan Short wrote on Wed, 24 February 2010 13:44 |
I am a firm believer that the pots on my amps should always be at full. This makes sure that the only fiddling that can go on is in a reduction direction.
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always good to eliminate variables.
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The amp when driven by a 15kHz or 30Hz sine wave at full gain on the amp, driven into slightly flashing limit, regardless of switching the inputs back and forth,
Channel 1 81v unwaivering
Channel 2 60v + or minus 3v very stable
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OK, this is still unclear (to me).
Are you saying that with the exact same input signal, one channel makes 60V and the other 80V? Or are you saying one channel flashes the clip light at 60V (output) and the other flashes the clip light at 80V (output), but with different input voltages too?
One situation suggests a seriously flawed amplifier (3 dB gain mismatch), the other a less than precise clip indication. If both outputs actually make 80V clean for same input voltage, this is a premature clip light.
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Going further in input level will cause a solid clip indication on the amp leading me to believe I am doing nothing positive.
Going on what I measured many many amps on in similar conditions
The 3602 should be putting out about 60v per channel for the test I was doing. 60v would be in the expected range of the rest of my results. 81v is the anomalous reading.
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A simple trick to confirm how long the outputs track each other, is to connect a speaker across the two hots. With both amps set for same gain, with the same input voltage there should be only a tiny signal (null of gain error) in that speaker. If one output actually clips 20V before the other, you will get a lot of sound from that speaker between when the first channel stops and the second one keeps going. If they both clip about the same time, not so much noise.
Of course a scope would be easier yet.
JR
PS: My apologies to Bob who is on the case.. but it's always the last thing you check.