Mullard EL38 Triode connected.

[Paul Barker]

Just had to try it same pinout as EL34.







I took a look at has a lovely bright cathode, beautiful to behold.

Looked at the EL37 data. I dont think its the same.

My b+ is 275v its dissipating 7 watts the 620 ohm rk is biasing it at 16v drawing 25mA.

So it clearly needs utracing to see whats going on.

Mu is clearly greater than el34.

But the ever so good news is that it is beyond words better than the Chinese EL34. I am so glad I tried it.

Id better order a new Utracer get the data and figure out how to bias it for best.

Too busy listeningto what sounds like live music.

Id better get back on ebay pdq, see if the seller has any more of these.

[Paul Barker]

Ive two more nos both sellers only had one. One is Langrex the other isnt a person known. Going rate it 35 plus carriage. Worth every penny. You can get used tested for 20 +.

[Paul Barker]

Ok, I had to get more b+ so I got the blue bariac.

Tuned up anode and g2 voltage to 400v which is max for both. With both at 400v the bias is 25v 35mA so dissipation is 15 watts which is conservative as max combined is 25watts. Estimate power between 1/4 3.7 W to 1/3rd 4.9 watts.
Cant hear distortion. A strong sound from this large bright kathode.

[Max N]

Billington are showing NOS. Mullards in their wholesale list Paul

[Paul Barker]

Good spot Max. Thank you.

[Paul Barker]

I’ve sent the email to order the uTracer 6 (1,000v) and the extra board for +100v grid bias and associated current measurement.

[Paul Barker]

I did some assessment looking at the el37 triode cathode bias compared to its pentode bias. Studied the el38 pentode bias resistor, made me judge 300 oms. Found that a good idea. Had 29 watts so throttled down to 25 w dissipation . All good. Its the right way up at last. Very happy. Not putting the EL34’s back.

[Paul Barker]

[Paul Barker]

Strong looking fat bottles with big Kathode. Loving the sound.

[Paul Barker]

Ok now I’m in sefenth heaven. This amp is a keeper. Well thats my R core 5K6 into 8 ohm output transformers bagged for good.

So now I’ll definately have to use the Sowter push pull transformers for the next project. Maybe I should do push pull 45? I was planning to use a lesser PP transformer for a centre tapped grid choke. But now Im not sure. Kel84 always sounds good. Maybe that phase splitter is up to standard? Any views?

The sound of the el38 if you gave me a 300b amp I’d “ohh thank you ever so much but I couldn’t possibly take it from you. Give it to Herb Ricot hes looking for a good 300b amp!”

[Nick]

Well, the best PP valve amp I can remember hearing was Marks build of Lynns Aurora. But not sure I could justify the cost of the iron and valves.

[Paul Barker]

Definately not.

I dont need my utracer anyway as Ive discovered the late great Patrick Turner had trod the path before me. Ive put my operating point at the top 5k6 loadline. Patrick had put some stuff down at the bottom left. I measured 3.7 watts.

Im thinking change from E88 Cc to EL38 driver, either IT or LCL coupled. Myabe enough, but if not, mesh plate 27’s before hand. Try without first. My other two valves arrived. Seems a shame to have bunged them in a drawer. They might never come out. Life is short. Cant carry on puting valves bought for projects in drawers instead of making things.

[Paul Barker]

[Paul Barker]

Forget Sukuma.

[Paul Barker]

Back to Sukuma.

At moment this is the only amp. So it stays as it is. But after Ive built the EL36 that will take over while I build this EL38 as Sukuma style. Im building it with a grid choke input so volume is set by the gain of the VA. Ill listen to that in my manshed on the top floor where the Q57’s belong. Depending on the volume I shall put the sowter transformer volume controls. But I want to hear only the grid choke first. It may be about right.