PSE EL84 Amplifier

[Paul Barker]

These arrived, dont seem used at all.

[Paul Barker]

I’ve found a cheaper EL12 alternative, EL36 with a top cap anode.

Good looking triode curves, class A se into 4k 4.5 watts 375v 50mA

[Paul Barker]

OK Ive ordered two of the EL36’s from Langex for £25 delivered . So those are going into the EL34 SE amplifier.

The EL821’s and EL822’s are going in a new push pull amp. (The 1’s are shorter stature but mostly close)

So I’ll have two amps at home with Mullard bottles in a SE and a push pull.

Its going to get interesting.

[Cressy Snr]

I have 4 x NOS, PL36 if you want them Paul. They are Thorn or Mazda (can't be sure until I dig them out) never been used. They have 25V heaters. Might be useful?

[Paul Barker]

Yes please Steve.

[Cressy Snr]

Hi Paul,
PM your address and I’ll get them off to you.

[Paul Barker]

Ive sent address in text to number ending 752

[Cressy Snr]

Not got the text Paul.

[Paul Barker]

Sent pm instead maybe you changed phone?

[Cressy Snr]

Nope,
Still the same as it was.

[Mike H]

Why 4 watts? because on the speakers 2 watts would be a waste of project.

Sorry misundestood, I thought you were saying the driver had to be 4 Watts.

[Paul Barker]

YES mike single ended triode connected EL84 is lucky to make 2 watts of music is what I was sayicng, but I’m now taking the push pull output because there is less distortion at the output. So I get my 4 watts Class A push pull with less overall distortion. But I’m driving the output stage with a Sukuma style same driver as the output valves. (Except its an 821 shorter than a 822 but basic same characteristic. I only bouht those two because they look attractive and I’m enjoying the exploration. So there ought to be a nice tonal character before the push pull output, but without overdoing the 2nd. The EL821 has mu of 23 so it may provide enough drive. So I’d then expect 4 watts from class A push pull output stage.

Listening to the single ended EL34 which due to lower Anode voltage and higher current to compensate, that is now only 3 watts. All because my variac is sick. Its still lush with 2nd because its al SE. But its cleaner and has much better controlled 2nd. I gues thats a good approach with second and single ended. Dont go at power max like a bull in a china shop, stop when the distortion makes it sound much lowder only because of the greater distortion. Hence why the 45 2a3 et all sound real nice on efficient speakers. But too strong and they arent in a sweet spot but a loud spot too distorted.

Im saying the antidote is do something about the distortion. One way is use an se output valve that is very low distortion. Hence the GM70 its distortion is remarkable at 30 watts. But its a mamoth task making that 30 watt amp. I just dont see the point for home anymore.

Sat here now listening to 3 watts into q57’s I like.

Maybe instead of gm70 I’ll frther explore this indirect path but with dht’s. So maybe 10Y driving push pull 45’s. Or if thats not loud enough push pull px25 if I have 4, thats a big ask. I may not have four. So I’ll carry on exploring this topology or rather these topologies. A pure se triode amp idht or dht, and a push pull in the output. Mirroring what Im experimenting with on what will be two amps.

I dont feel pressured to ever build the GM70. Jonothan at eggborough said about my 212 “its not worth it”.

I mostly agree. I am not in the camp of I can do it so I must. Im having more fun than that. Im not ina competition to make the best 30 watt amp. The winner of that competition might not be the builder of an se valve amp, if its an anything goes competition, which it ought to be. I wouldnt even bother turning up with my valve amp these days.

[Paul Barker]

Beyond that, there are a few things going on in my se amp right now, the EL34. I really dont know what effect certain measures are having, very little I think. So one is a triode driving a triode, two stage. Its as clear as day that does not cancel 2nd, it may slightly mitigate it, but there is no cancelation, unlike push pull on the same level. That cancels even distortion near enough. So Im building both topologies to tweak with this phenomenon.

Then there is the power supply noise thing. Copied off the Darlingfest. Both levels get the same power supply noise. That I think I heard to a small degree. But when I split the cathode bypass from cathode to ground and a fraction of it to inverted mu+1 to B+. Man that was night and day. That really cleaned up the power supple which I didnt even know needed cleaning up. So the Jeremy Epstein effect was so slight its bear,y noticeable, in the same way the mythology of distortion at one level fixing the distortion at the next level. Barely dioes anything.

Then theres the chasing over natural timbre. These are the guys who use a pentode voltage amp. Whether a ef87 or a 4P1L so if you have an se output triode give it nice timbre with a pentode first.

Ive yet to donit, but Im doing it backwoods in the pp amp. Maybe in the SE amp, I need a pentode volt amp. I’ll get there, but after I’ve tried sukuma.

[Paul Barker]

Right now the el34 chinese though it is, is sounding considerably less distoted by reducing the power to less power. 2nd rises with power so half power, less distortion is palpable. Not maybe as night and day as the ultrapath, no actually it is that same night and day. So the next step for the el34 is when the Mullard valves meaning valve type change occurs. Lets get that change done next. Will it be night and day through tube rolling? Youd hope so. We’ll find out.I’ll take the winner maybe to Steve if I’m allowed. Either Steve will do, Im not fussy, there are three Steves.