O3s tube HP amp

[rex_johnston]

Anyone seen one of these? Tube compliment is 2 x 2p3. Also includes a 2xIRF610, 7812 and 2xLM317. It's taken quite a bit of work to quieten it, but the tubes are still hugely microphonic, emitting a high freq. whine whenever there is the slightest disturbance.

Just these Chinese tubes?

Cheers, Rex

 

[Kay Pirinha]

These are battery operated, directly heated tubes? These are prone of being microphonic, due to their thin, long, and thus vibrating cathodes. Not even those snake oiled silicone rings around them can prevent the cathodes from vibrating.
/
A huge design flaw, if you'd ask me.

Best regards!

 

[316a]

Anyone seen one of these? Tube compliment is 2 x 2p3. Also includes a 2xIRF610, 7812 and 2xLM317. It's taken quite a bit of work to quieten it, but the tubes are still hugely microphonic, emitting a high freq. whine whenever there is the slightest disturbance.

Just these Chinese tubes?

Cheers, Rex

Not knowing the 2P3 , it may be to do with the horizontal mounting , but I'm not able to locate a manufacturer's datasheet . Obvious things to check are the filament voltage , you could always try backing off the volts a little to see if that helps

316a

 

[rex_johnston]

These are battery operated, directly heated tubes? These are prone of being microphonic, due to their thin, long, and thus vibrating cathodes. Not even those snake oiled silicone rings around them can prevent the cathodes from vibrating.
/
A huge design flaw, if you'd ask me.

Best regards!

Yup, direct heated pentode. Low voltage (6.5v on the plate here).

I was wondering if a philips DL93 might be better, but i guess not.

Cheers, Rex