Amp from Stella ST240U - UK Vintage Radio Repair and Restoration Discussion Forum

Jack Spark · 20th Jul 2009, 10:02 am

Hi all,

I have been given a Stella ST240U by a friend and they asked if its possible to make a small valve amp from its components.
It uses the fairly common (as I understand it) arrangement of UY85 and UL84 valves as the output, but I can't find any clear schematics.

Can anyone point me in the right direction?

TIA

Jack

Steve_P · 20th Jul 2009, 12:39 pm

Yes, but it won't be all that good. And this is an AC/DC amp, so it could be dangerous unless it is sealed in a non-matallic box, tied the right way round to the mains and the sockets have a capacitors in them to isolate them from the mains.

For me, it wouldn't be worth it as there are plenty safe designs on the web for such things.

http://cool386.tripod.com/amps/amps.html

Cheers,

Steve P.

Herald1360 · 20th Jul 2009, 12:46 pm

Not really without considerable additional components. Also, unless great care is taken it would be potentially dangerous- there would be no isolation from the mains, the original application would have relied on the case construction and the fixed out of reach input and output connections for safety.

You COULD use the valves and bases, but at the least you'll need another valve for a preamp and a custom PSU (possibly using back to back transformers for cheapness

).

It really would be easier (as they say) to start from something else....

Chris

Too slow again!

20th Jul 2009, 10:02 am	#1
Jack Spark Retired Dormant Member Join Date: Aug 2008 Location: London, UK. Posts: 47	Amp from Stella ST240U Hi all, I have been given a Stella ST240U by a friend and they asked if its possible to make a small valve amp from its components. It uses the fairly common (as I understand it) arrangement of UY85 and UL84 valves as the output, but I can't find any clear schematics. Can anyone point me in the right direction? TIA Jack

20th Jul 2009, 12:39 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Amp from Stella ST240U Yes, but it won't be all that good. And this is an AC/DC amp, so it could be dangerous unless it is sealed in a non-matallic box, tied the right way round to the mains and the sockets have a capacitors in them to isolate them from the mains. For me, it wouldn't be worth it as there are plenty safe designs on the web for such things. http://cool386.tripod.com/amps/amps.html Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

20th Jul 2009, 12:46 pm	#3
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Amp from Stella ST240U Not really without considerable additional components. Also, unless great care is taken it would be potentially dangerous- there would be no isolation from the mains, the original application would have relied on the case construction and the fixed out of reach input and output connections for safety. You COULD use the valves and bases, but at the least you'll need another valve for a preamp and a custom PSU (possibly using back to back transformers for cheapness ). It really would be easier (as they say) to start from something else.... Chris Too slow again! Last edited by Herald1360; 20th Jul 2009 at 12:47 pm. Reason: Beaten to the draw by Steve!