Velleman K4000 stereo valve amp

Dec 18, 2006 2 Replies
N

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.


-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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M

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

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D

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.

*Upon the advice of my attorney, my shirt bears no message at this time Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound.
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