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Velleman K4000 stereo valve amp

I've only checked over unpowered so far, this amp, as its a kit thing. One horror and 2 inappropriates found so far. Was working well apparently but the hum that was always there, but acceptable level, has now increased. Is it acceptable to have a large toroidal mains transformer sandwiched immediately (1 mm clearance) between 2 similar size large toroidal output matching transformers, no mu-metal anywhere ? Stage amps I'm more familiar with always seem to have the mains one at one end and the output one at the other end.

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Reply to
N Cook
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Certainly not good practice, but it should work like that. Toroids are a lot less affected by external fields than EI cores, but still 1mm is a bit silly. Perhaps the builder was hoping a bit of nfb would keep the resulting hum down?

I take it you've piggy backed the reservoirs to see if thats where some of the hum problem lies - keeping within the rec valve's capacitance ratings of course, if it has a valve rect.

NT

Reply to
meow2222

Assuming it's been built to spec, Vellerman kits usually do what they say on the box. Not that I've any experience of this amp. However, toroidals have pretty low external magnetic fields.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Dave Plowman (News)

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