Quote:
Originally Posted by gramofiend
From my reading of what you say in post 1. a QUAD 405-2 power amplifier should produce no hiss or any noise even if placing your ear next to the speaker! You say you get hiss when the pre-amp is increased which indicates a volume control which a 405-2 does not possess so which preamplifier is in front of the power module and which type of audio cable conects the two, 4pin Din or Phono! Therfore any noise is comming from the unit before the 405 as the 405 is a fixed gain block working at full binge into the speakers!
The fact that you get a crack from the amp when switching on seems to me to indicate a DC offset. What sort of noise does it make when you switch off?
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Hi Mike, thanks for your input.
I may have misled you slightly with my original description of the faults. The hiss and hum described are there with or without any signal source connected. As the volume is raised the hiss on the left channel is masked by the programme material and doesn’t actually increase. The right channel with hum has low output level compared to the left and gets very distorted with any increase in input level
The large splat I described is on power down rather than power up. There is the usual power up thump, which seems standard on these amps, and I know from experience and my research that a small power down splat is also very common on these, but the one I’m getting is quite a lot larger than I have had before.
I may well send it to Quad if I can’t sort it out but, for the moment at least, I’m reasonably keen to see if I can do it myself, learning as I go. I do like the idea of sending just the boards rather than the whole amp though, I hadn’t thought of that.
Ray