EL32 What were they used in or could used for?

[ctc15]

Hi All
EL32 What were they used in or could used for?
I have a lot of N.O.S. ones.
Keith

[Cobaltblue]

According to valve museum Car Radios and AC/DC sets

http://www.r-type.org/exhib/aaa1118.htm

Several designs on the Web using these.

Cheers

Mike T

[M0FYA Andy]

They were used in various military radios, and also used by the Post Office in undersea cable telephone repeater amplifiers.

Andy

[boxdoctor]

I seem to recall that these valves were originally designed as a r.f.power amplifier/driver in military equipment. The main features are that they are very economical on hearter current. also, with the anode being brought out to a top cap, the max. anode voltage is appreciably more than one might expect. Wayback in the '60s, I built an amp using a pair in puh-pull with moderate success.
A nice stable valve, somewhat similar in characteristics to the KT63.
AFAIK, The Audiophool fraternity do not appear to have got wind of them yet, so perhaps it would be a good idea to hang on to them for a while. Tony.

[Biggles]

I've used the EL32 in a home construction project as an single ended audio amp in a radio before and they have adequate output (2 or 3 Watts?) as well as having a relatively low heater current requirement. I used one in my design mainly because I had one lying around and the mains transformer I was using couldn't supply very much heater current. I have no idea how old it is but it has performed faultlessly for a few years now. Good audio valve I reckon, worth considering. The top cap might put a few people off, but it fitted well into my design. I would guess that a lot of EL32's are marked with a CV number instead. As has been said, I think it was probably aimed at military use.
Alan.

[Alistair D]

To add to what Andy said, The Eddystone 358 receiver originally used an EL32 as the audio output. Looking at my 358 (December 1941 vintage) it would seem that my set was rewired to take a different valve. I presume that the change was either an official mod or part of a refurbishment as the work looks professionally done.

Al

[Wellington]

The Ferguson 201C used two of these in push-pull.

[g4aaw pete]

Also appeared in the original P.C.R. receiver design as output valve.
Many (perhaps later) used the 6V6G though.

[kalee20]

Originally Posted by M0FYA Andy

They were used in various military radios, and also used by the Post Office in undersea cable telephone repeater amplifiers.

Interesting! That says they had a long and stable lifetime. Somehow I'd got the idea that perhaps the cathode material might have been something exotic that maximised emission at the expense of everything else, including life - clearly not!

So if it was possible to make the EL32 pentode with just 0.2A heater current, yet give over 3.5W audio output, why wasn't the same techniques used in the EL84 (far less than double the output for nearly 4x the heater current)?

[GrimJosef]

Originally Posted by boxdoctor

... also, with the anode being brought out to a top cap, the max. anode voltage is appreciably more than one might expect ...

Point of detail, the top cap is the control grid.

Cheers,

GJ

[GrimJosef]

Originally Posted by kalee20

... So if it was possible to make the EL32 pentode with just 0.2A heater current, yet give over 3.5W audio output, why wasn't the same techniques used in the EL84 (far less than double the output for nearly 4x the heater current)?

The datasheet figures for maximum Ik are 45mA for the EL32 but only 65mA for the EL84. Could physical size, perhaps cathode emitting area, be a limiting factor ? The EL84 is squeezed into a pretty small bottle.

Cheers,

GJ

[Skywave]

Could the reason be that the EL32 - with its envelope larger than the EL84 - has a greater emitting surface area of the cathode? In which case, to get the same electron current flow from the cathode of the smaller EL84, the temperature of the cathode of the EL84 has to be much higher - hence the increased heater current. I don't know the relative anode power efficiencies of the two valves, but the above reasoning suggests that the EL32 is more efficient. I do know that the EL84 does get very hot when it's been delivering a few watts of audio for some time - too hot to grasp with the fingers and remove it from its socket without waiting for it to cool down first.

Just a quick thought.

N.B. This post crossed with GJ's above.

Al.

[kalee20]

Several things there! A (postulated) greater surface area of cathode in the EL32 does lead to a lower milliamps per square centimetre of emission, so a lower temperature could perhaps be accepted.

But, greater surface area in EL32 implies greater heat loss, which means more power to maintain the temperature! Which effect 'wins' I don't know.

Having said that, the EL84 cathode does not look a brighter red than the EL32 when running (if memory isn't playing tricks, it's a long time since I saw an EL32). Which would indicate that temperatures are actually similar.

[Leon Crampin]

My admittedly limited experience with the EL2/32 is that they have short lives when run as output valves with appreciable anode current. As they were used, presumably reliably by the PO for repeater applications, I can only assume they were underrun.

As restorers, and with the benefit of hind sight, valves with a high heater power in relation to their anode current seem to last the longest. Many Mazda 4V valves still meet their full spec for gm, despite hundreds of hours' use.

The EL32 was never popular as an output device - and with a top cap grid, I wonder if it was actually an RF pentode "adapted" for car radio use. Philips certainty continued the 200mA heater output valves with the EL42 and the EL85 and EL95, until Ge power devices took over in car radios. They, of course, had an appreciable interest in car radio, probably more than any other maker.

Leon.

[G6Tanuki]

Originally Posted by g4aaw pete

Also appeared in the original P.C.R. receiver design as output valve.
Many (perhaps later) used the 6V6G though.

Yes, my two PCRs have 6V6 output-stages which look original, but adjacent to the output-valve socket on both of them is a hole about 8mm diameter fitted with a smooth-bore metal bush - my belief is that these are a production-legacy from when a screened lead would have needed to come from beneath the chassis to connect to the top-cap of the original-design's EL32.