Metropoulos Forum

Hello guys. Hoping someone can chirp in. I am in the process of parts coming from Robert for a 2203 metro amp I'm going to build... I can't wait for this amp.

I just finished another 1959 and had a question. It's in regard to noise. I realize the metro switches (1959) are stiffer than the carling ones on 50 watts.... (mechanically stiffer) when I turn on the 1959 I get a mechanical noise in the amp. Best way to describe it... I chopsticked the amp with my signal generator and my oscilloscope, and the amp plugged into
My hotplate on load and all the lead dress is good. I am in Canada and I use the tube store as my supplier (I use their EL34 preferred series) and I personally love their preferred series tubes hands down. I tap on the chassis and I have a lar/mar (PEC POT) in it. I get a amplified mechanical sound from the amp. Never happens on 50 watts. Only 100's.

Call me crazy. I realize tubes are mechanical devices and they are prone to microphonics. Anyway I thought the springs could be the culprit absorbing rattle and vibrations and carrying them into the power tubes. I undid the retainers and tried again and it was dead quiet

What's the consensus on spring retainers in a 100 watt amp?

Please
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Thank
You. Dan

Removed tube retainers, Noise gone

I believe the issue is because the 100 watt steel chassis is so big, its like a giant microphone for vibrations and noise

I have a 2203 going together next week, I'll omit these again

On a head, seems useless for the retainers anyway the tubes won't fall out plus there is new sockets there anyway so the chance of them falling out would be very low

Thanks again

Dan

I haven't ran into trouble with retainers on EL34's. But had terrible issues with them on 6550's in newer SVT's.

If you eliminated the issue by removing them, then the results speak for themselves. Nice sockets are very secure anyway, so no worries of tubes falling out.

george