U Series valves

[trickie_dickie]

Has anyone got a list of the U series valves, UCL82, UY85, for example?
Also, are these any good for an unusual Hi Fi amplifier?

[Herald1360]

Scan through Iliffe Radio Valve Data 8th ed suggests:


UCL83
UL41
UL46
UBL21
UL84
UCL82


UCH42
UCH21
UCF80
UCH81


UAF42
UF41
UBF80
UF80
UF85
UF42
UF86
UF89
UBF89


UCC84
UC92
UBC41
UBC81
UCC85
UABC80


UY21
UY31
UY41
UY1N
UY85


Any of the U*L series can be used as output valves, the UCL ones have audio triodes as well. Of the pentodes, probably only UF86 much use, though UF89 has been used in some record players. UBC and UABC contain audio triodes but the UCC double triodes are all RF types.


Quoted output powers tend to be lowish due to the expectation of fairly low half wave mains derived HT voltages, but if the characteristics are compared with E series valves there may be some leeway for creativity with higher HT and non standard loading.


Food for thought, anyway.....

[Michael Maurice]

There is also UM84

[Wellington]

The National Valve Museum provides a good list. (Note to self: must start supporting this excellent site again).

The AVO valve tester manuals listed valves alphabetically — there are some useful links here.

Are they any good for using in unusual amps? I have a suspicion that they're considered to be somewhat inferior for Hi-Fi use, probably for the reason that Herald gives above.

[Herald1360]

There are also some other more unusual U prefix valves like UL11, UL12, UL21, UL71, ULL80 to be found in Radiomuseum. They're mostly just old continental based forerunners of more common rimlock or noval types, though.

[Synchrodyne]

The various published Mullard audio amplifier designs included a 7-watt AC/DC mode using the UF86, UCL82 and UY85 valves. See for example: http://www.sowter.co.uk/pdf/Mullard-...Amplifiers.pdf.

Cheers,

[RobRusbridge]

The output valves have high heater voltages (UBL21 runs at 55V) so you need to think about how to string them all together. No point in putting a triode used in a sensitive input stage well up any heater chain. Hum hum. Neutral end for that one. It's a bit of an art-form in itself. Or you could run the sensitive valves from a heater transformer to keep all those heaters in parallel and grounded at one end. The output valves will be better at "making the best" of what you can give them.

Unless you run the whole thing from a proper isolating transformer you'll end up with the negative end of the power supply being mains neutral, not earth, which can set up interesting challenges trying to get rid of hum pick-up. Safety issues here too.

If you end up trying to squeeze the utmost from a pair of UL84s, you need to know they're actually not really EL84s with a different heater, they seem to be EL86s with a different heater; lower impedance loads needed. Been there, done that.

Most of the regular AC/DC rectifiers will run enough current for a push-pull pair of suitable output valves. UY21 will power PP UBL21s, UY41 will power PP UL41s, etc. If you can find a push-pull pair of UBL21s or afford a push-pull pair of UL41s you'l be doing well, however.

PCL82, PCL83, ECL80, 12A6, 20P3 all good output valves from the junk-box and cheaper than the U(niversal) valve series. Heater voltages lower and easier to accommodate as well.

[trickie_dickie]

That lot is great. Just what I wanted. I had forgotten the Mullard 7Watt amp. This is what I was thinking of but with a special mains transformer giving the correct heater voltage with the Varistor and the correct HT volts. Two monoblocks or one stereo ? Now there's the rub.
Many thanks to all of you.

[Stylo N M]

Originally Posted by Michael Maurice

There is also UM84

There is also a UM80

Paul.