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EL37 Tubes

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Kris Rocka

Member
Joined 2018
#1
Greetings Fellow tube heads,

I just found a pair of Mullard branded EL 37 tubes and wondered if they could be substituted in place of EL34s. I have a Boyuu A9 SE UL amplifier which I built from a kit. Has anyone tried this? Why not try them and see for yourself I hear you ask? Because I want to check they are ok on a tube tester first.

I would very much appreciate any opinions about these tubes. I've just noticed there are some threads about this tube so please excuse my repeating the query

Kind regards
 
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#4
Agreed, I found a pair of 70s Mullard EL37, and sold then on to someone looking to use them in their amplifier.

They *were* a matched pair, that still worked, but I had no emission or gm measurement kit, so I set them in auction for a low starting bid of £10 for the pair.

I ended up getting over £280 for them, and a thank you email from the Japanese buyer, which was very happy with them.

So they must have been in almost new nick.

I also have a random KT61 if anyone would like that? 🙂
 
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#7
On a related issue, I believe the EL37 has a mu of 9 in triode - similar to an EL34 which is 10.5 I believe.

Does anyone know which of the EL series had a larger mu? Like around 15 for an EL38, or around 18-20 for EL33 and EL12?

Any others in the EL or KT or other series that had a mu of over 10 in triode, like KT61? Wondering about 4654 for instance.
 
#13
KT61 is an interesting valve in itself. I have a early ish Mullard one, If I recall with Marconi M-OV label, brown bakelite base.

It's a pity they're so rare, I only have a single valve.

Since it's worth nothing as a single valve, I might as well throw it in my 6P6S amp, it likes a similar OPT similar supply voltage, and maybe will give me another 0.5 W for the lab mono sound system!
 
#14
andyjevans said:
From what I read of the EL36, it's unsuitable for audio. Apart from ingenious stuff like screen drive etc. I was thinking of the usual topologies.
Click to expand...
As with almost any other sweep tube, limited to not suitable at all in pentode SE, but suitable in triode or screen drive SE and all PP modes.
Take care: There has been another EL36, made by Mullard, without top cap, which is completely another tube!
Best regards!
 
#17
I see this is an old thread but in case anyone is still interested I’ve been using EL37 tubes in my Marantz 8 for a couple years. The sound is great. The amp is wired for triode. Since the EL37 max power is less than the EL34 I backed the bias back some. I don’t hear a lot of difference in between the two except the EL37s seem to open up after about 15 minutes running. The 37s look really nice on the amp and I get a nice blue glow. The cage won’t fit over the 37s but I don’t use it anyway.
 
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