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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

U**** series triode valve on noval base?

There are some US spec 7 pin series heater tubes that fit the U series 100 mA string. The single triode is an 18FY6, It has the same characteristics as a 12AX7, just ignore the two diodes. There are plenty of them in stock for about $1 each.

the US 20EZ7 IS a 12AX7 with a 20 volt 100 mA heater and an odd pinout. It's rather hard to find though.

The Western Electric / Sylvania 407A is a 2C51 / 5670 with a 20 volt 100 mA heater. Not too hard to find or expensive.

The previously mentioned UCC85 is a twin triode with a 26 volt 100 mA heater.

There are some 100 mA series string pentodes that work well when triode wired. The 18FW6 is like a 6BA6. The 18GD6 is like a 6AU6, and there are the UF80 and UBF89.

I have used all of these in series string heater guitar amps. Use 32ET5's for output tubes in small 2 to 4 watt amps, and UL84's for up to 25 watts.
 
I've never seen or heard of UCL84 and UCL86 so I don't think they exist !? I'm not 100% sure about that, but I have a ~ 52 year old electronics practice! ;)
Fidelity, in the UK, produced a record player with a UY85 rectifier and UCL84 pre-amp/output stage circa 1960. Equivalent to ECL84 with 100mA heaters.
 

Pauld35

Member
2014-09-27 11:16 am
There are some US spec 7 pin series heater tubes that fit the U series 100 mA string. The single triode is an 18FY6, It has the same characteristics as a 12AX7, just ignore the two diodes. There are plenty of them in stock for about $1 each.

the US 20EZ7 IS a 12AX7 with a 20 volt 100 mA heater and an odd pinout. It's rather hard to find though.

The Western Electric / Sylvania 407A is a 2C51 / 5670 with a 20 volt 100 mA heater. Not too hard to find or expensive.

The previously mentioned UCC85 is a twin triode with a 26 volt 100 mA heater.

There are some 100 mA series string pentodes that work well when triode wired. The 18FW6 is like a 6BA6. The 18GD6 is like a 6AU6, and there are the UF80 and UBF89.

I have used all of these in series string heater guitar amps. Use 32ET5's for output tubes in small 2 to 4 watt amps, and UL84's for up to 25 watts.
ah thats intresting to know, i had just come some info on pentodes used as triodes. here is the link for anyone reading



http://www.audiodesignguide.com/New2A3/ETF06TS.pdf
 
Hi, i saw these valves are for RF, do you know if it is possible or worthwhile using RF valves for AF?

the UCC84 is the same as the ECC84 and has nice curves, should be nice for audio, even with the non standard pinout. The 6N14P russian is supposedly a close equivalent, and is reported to be a great little tube. Good for cascode applications, will run decent at lower plate voltage. I think it would make a lovely tube for direct coupled voltage amplifier to concertina types of applications, like the front of a williamson.
 
I've never seen or heard of UCL84 and UCL86 so I don't think they exist !? I'm not 100% sure about that, but I have a ~ 52 year old electronics practice! ;)
Neither did I, Davorin ;)! ECL86 and PCL86 came into the market after the time for AC/DC radios had expired. And ECL84/PCL84 was a dedicated TV tube to drive the CRT's cathode where there was no need for a 100 mA string version.
Fidelity, in the UK, produced a record player with a UY85 rectifier and UCL84 pre-amp/output stage circa 1960. Equivalent to ECL84 with 100mA heaters.
That makes me curious. Are you sure about that, as the ECL84/PCL84 weren't exactly designed as AF power output tubes?
Best regards!
 
...That makes me curious. Are you sure about that, as the ECL84/PCL84 weren't exactly designed as AF power output tubes?
Best regards!
ECL84 is the same tube as ECL84!
 

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That makes me curious. Are you sure about that, as the ECL84/PCL84 weren't exactly designed as AF power output tubes?
Best regards!

The pentode section of the ECL84 looks to have nice curves, every bit as clean as most of the popular sweep tubes, even if dissipation is limited. I can't find curves for the triode section, other than the single trace on some of the sheets for 200 volts plate.

As in all things audio, original intent is not nearly as important as the actual measurements and performance, there are plenty of tubes that were not meant for audio that have fantastic curves and linearity. Take the 6SN7 for instance, it was a multi-purpose type that even saw use in vertical deflection or computer circuitry, but just so happened to be common enough and suitable for audio :)