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kstagger 12th May 2008 12:19 PM

for fans of the EL38 - the E3375
GEC made a version of the EL38 called the 'E3375' - looks to be based on the KT77 output tube. They bias up exactly like the EL38 and also require a 6mm plate cap. I accidentally came across one that was labelled 'Heinz Kauffman' and started googling around.

I always though the GEC 'E' prefix was for experimental, so I'm not sure how these ever got released for general sale. Perhaps GEC made a small run to replace the EL38 for military use or ??? Your guess is as good as mine.

mark6699331 14th November 2012 07:05 AM

I was told the EL38 tube was for a television sweep purpose.
Is it feasable to make a good audio diy amp out of a mullard EL38?

Parafeed813 14th November 2012 03:30 PM


Originally Posted by mark6699331 (
I was told the EL38 tube was for a television sweep purpose.
Is it feasable to make a good audio diy amp out of a mullard EL38?

Quite some years ago I build an experimental amp using 3 EL36's per channel: the first in traditional triode, screendriving the others through a transformer. After a while I came across some EL38's that found their place in the power section. They never left :p
I remember the sound was extremely transparent. Dark ambient music got, ehm, scary. I couldn't put my finger on it, but it seemed as emotions got enhanced somehow.
Speaker damping was non-existent 'though.
Perhaps someday I will continu the experiment, trying cathode feedback windings on the output transformers, MOSFet follower drive vs transformer coupling...
My advise: try those EL38's! The insides of mine look a lot like that of a smoked glass CV1075 that got crushed :mad:.

kstagger 15th November 2012 12:45 PM

The EL38 can be used as an audio tube - spec much like a EL34 (filament, 8W screen) but with a plate cap. A few years ago, on an updated Dynaco 70, I installed plate cap leads and Mullard EL38s worked just fine.

mark6699331 18th November 2012 07:37 AM

Thanks, I happen to come across two quads of NOS Mullards in Box Nos for farily cheap, and a few military versions. Then I read it was a sweep tube and was disappointed. Seems I remember an aduiophile friend of mine awhile back told me the high plate rating 625 maxB+ would allow it to run virtutally forever on a 450v type amp.
They are very seductive looking tubes. I got into them as the 37 prices went to the moon-almost more than kt66's. Finally found a fairly cheap source of NOS/NIB's of those from a private party in London.
I also read alot on French sites about the supposed "professional" audio tube the EL39, which is almost impossible to find unless your French or want to risk being overcharged and then being sent the old tube and not the pro audio gold versoin.
The ST70 idea is nice as they are readily available and you could yank the board and point to point it with good caps too. I guess I just don't understand why there would be that much difference in construction and usage between the 37 and 38. Seems from the 33 to 39 it just changes in voltage, grid screen ratings etc going up as time goes by. Maybe I misunderstand.
Lately, speaking of unusual anode cap tubes, I've been having great success with 5933wa sylvanias with the two holes in the black plates, and even much better 350A type sound with the GEC/Cossor NOS NIB ATS-25 tube. Only problem is the 300V screen rating even though the plates can gobble up 650volts like a electric pacman. I got a pair of Ampex 6516's recently for a good price already refurbed and will throw those in there very soon. Wondering if with some mods if I might use the El38's or if it's a completely different beast. BTW, those Ampex amps are amazing-Peerless Iron on the input tranny and OPT and the OPT is only slightly smaller than the input. I'm dying to hook them up! Thanks for the tips and pointers.l I thought I wasted 150 bucks on on all those el38s and was about to resell them!

kstagger 18th November 2012 12:52 PM

the nice thing about the EL38 is the high screen voltage (and wattage), so it can be run in ultralinear. I'm sure something better than the 'ol Dynaco 70 could be knocked up, but it was an easy modification to make for an amplifier on hand.

I'm building a SE 1625 12V version of the 807) amplifier right now, but have opted for pentode operation with regulated screens. I'm curious to hear how it sounds.

SY 18th November 2012 12:55 PM

Mullard and Philips datasheets show 400V max for screens.

kstagger 19th November 2012 12:22 PM


Originally Posted by SY (
Mullard and Philips datasheets show 400V max for screens.

true that - but better than many other sweeps.

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