• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

U Series valves

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#2
You can easily go through the data sheets and find them. As you probably know they have varying heater voltages as they are designed for a 0.1A supply.
Other than heater voltage, most of the "u" series have similar characteristics to the "e" series but one or two are different, so beware.
Originally each valve's heater would be connected in series and often connected vie a dropper resistor directly from the mains. This is not a safe system for a DIY amp!
However there is nothing to stop you from supplying a pair of UCL82 heaters from 50v connected in parallel. Or for that matter any identical u valves.

If you want to mix types, the complications of supplying bespoke heater supplies will outweigh any advantage - availability or cost.
 
#3
most of the "u" series have similar characteristics to the "e" series but one or two are different, so beware
Click to expand...

One of my favorites is the 45B5 / UL84.....And NO, it's not a 45 volt EL84 it's a 45 volt 6CW5 / EL86. This is one of those tubes that ARE different from the E version.

The UL84 can crank out 24 watts per pair according to the data sheet. Two of them can be driven with one or two 26AQ8 / UCC85's, which are 26 volt 100 mA ECC85's. All of the heaters can be wired in series and fed by the output of a 120 to 120 volt isolation transformer in the US, or a 240 to 120 volt transformer in the UK. A voltage doubler on the 120 VAC makes the B+ while a simple rectifier makes the screen voltage for the UL84's. I made a guitar amp this way, but the same lineup can be used for HiFi.
 
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