Single-Ended 13E1 amplifier

[Steve Cresswell]

I've been at this for a good few months now and it has been through several revisions but I now feel it is a good amplifier.

I've seen one or two of these amps, the main one being Pat Turner's 13E1 SEUL on Turner Audio, there are not that many about though.

I suppose the most well known 13E1 amp would be Morgan Jones Crystal Palace pp amp

This one is a three stager SE using a 6EW7 as the voltage amp/driver stage.
It is cap-coupled throughout and has cathode feedback applied at the output stage, by including the output transformer secondary in the 13E1's cathode circuit.

It puts out around 10Wpc and sounds very nice indeed.



The PSU is dead simple as the whole thing runs on AC heaters. All the heater runs are carefully routed away from signal wiring and are screened inside earthed aluminum tubing.

Hum is virtually non-existent.



I built it as an antidote to my other amp which used 801As driven by Mazda AC/Ps coupled to AC/P1s. This amp weighs a ton and is full of separate DC heater supplies, solid state regulators and oodles of iron.

Although the 801A amp sounds lovely, I did feel that with it, I had gone too far down the road of complexity. I wanted to get back to basics with the 13E1.



Output transformers are gapped for 200mA and are by Majestic Transformers of Poole Dorset. Great sounding and good value for money
What I like about this amp is that it kicks butt without needing KV of HT.

I like it anyway

Has anyone else had a go with this valve?
If so, what did you think of it?

Steve

[Matt.B.H.]

Very nice amp Steve

Just out of interest, how much were the Majestic output trannys? I have thought about getting them to wind a pair for me.

Cheers Matt.

[mashaffer]

Very nice.

[Steve Cresswell]

Originally Posted by Matt.B.H.

Very nice amp Steve

Just out of interest, how much were the Majestic output trannys? I have thought about getting them to wind a pair for me.

Cheers Matt.

Hi Matt,

The transformers were 113GBP each plus VAT.
They are a nice company to deal with, which is always a bonus.

Steve

[EC8010]

That looks like a nice amplifier (and pretty, too). 6EW7 was a very good choice as the medium mu (20) triode section is one of the best out of the 6SN7 family.

[Matt.B.H.]

The transformers were 113GBP each plus VAT.
They are a nice company to deal with, which is always a bonus

That is very reasonable, I will drop them a line tomorrow

Thanks.

[jamj]

Nice. I like the looks of the tube but they are rather rare now.

If I'm not mistaken, the tubes are of English origin, is this correct ?

[Steve Cresswell]

Originally Posted by jamj

Nice. I like the looks of the tube but they are rather rare now.

If I'm not mistaken, the tubes are of English origin, is this correct ?

With these valves it's a case of, you have to know where to look.
I got mine from a friend, who has a large collection of British valves.
He was not going to do anything with them so learning that I wanted to design and build a 13E1 amp he simply gave them to me; a generous guy

The 13E1 is of English origin. The two main manufacturers were Ediswan and STC, later to become ITT. The most common these days (if you can find them) are the 70s produced ITT ones. The older type Ediswan and STC types seem to be rare tubes indeed.

Steve

[vega65]

Steve
I am working on a 13e1 se.I made a simple chassis for test purpose.I arrived at the following schematic during this year.I have chosen to run 13e1 as tetrode with plate to grid feedback. pentode with unbypassed cathoderesistor as one stage driver.I have tried several driver tubes: z759, d3a,E180F, E280F,e810F,E282F.I don't know why but E282F seems to be the best performer.G2 is from a vr tube.The emitterfollower is g2 for 13e1.
The amplifier is clipping at 30 something watt and attached is distortion figures at full output, and frequency response at full output.The red line is distortion at 1 w out. 0,5% at 16W/1khz.
opt is ll1693 (the off shelf nearest to my needs)

[Steve Cresswell]

Looks great!
The responses and the distortion look good.
Presumably you had the chassis top plate laser cut by a contractor?
That is something I am thinking of doing with mine during the Summer, when I build it into a proper chassis.

The only thing I regret with my own amp is that I did dot ask for 66% ultralinear taps on the output transformers.
I could have got a lot more power with SEUL and a negligible increase in distortion (that's according to Pat Turner)

I have never tried pentode drivers myself
I have heard that they can sound very good if done right

Steve