10W SET

[pre65]

If I wanted an SET amp to give a genuine 10W output what valves are there to choose from ?

Ideally

1) Not too rare or expensive
2) HT of around 400v or less
3) Not ultralinear

[Nick]

At what distortion level do you want the 10W?

If you are in A1, for 10W you will need a plate dissapation of at least 40W. If its less that 400v, assuming fixed bias, that gives you a minimum current of 100ma.

If A2 is open, then that will reduce the dissapation to 30W which lets in more candidates, and needs 75ma.

You don't say if it needs to be done with one output valve, or if PSE is acceptable.

PSE EL34 would be my first thought, after that, maybe 6C33P comes to mind.

[Cressy Snr]

I've got some 13E1s ....arf arf

[pre65]

Ah, PSE ?

I did 829b PSE a while ago, I wonder what that was putting out ?

So, KT66 PSE would be about the same as EL34 PSE ?

[colin.hepburn]

A Ha and I think Philip has asked the same question I have be wondering about as well except I would add between 8/10 watt not much in it suppose but single valve 5k output TX and same HT voltages

[Cressy Snr]

If I wanted an SET amp to give a genuine 10W output what valves are there to choose from ?

Ideally

1) Not too rare or expensive
2) HT of around 400v or less
3) Not ultralinear

OK seriously.

I now am pretty sure what went wrong with the 13E1 amplifier.
It was simply a grid resistor of too high a value that caused the valve to run away. After having dismantled the 13E1 last week
to scavenge a few parts for the 2A3 amplifiers, I found that the grid resistors I had fitted were 470K
Jeez that value would have ensured the 13E1a could almost run away when the amp was off.

How it happened I'm not sure. I must have accidentally fitted the wrong value when I was playing around with it as a SEP.
It was one of those things that I reckon to have checked again and again when Paul was trying to help me out online.

Anyway, enough incriminating talk.

Here is the thing. I need to clear out some stuff, so...

I can give you the chassis all punched out with the septar sockets still in place, three 13E1 tubes and the 1.25K 200mA gapped Majestic OPTs
free gratis and for nothing, plus a 26V toroidal transformer for the 13E1 heaters.
I got the 13E1s free from Steve S, so it would be churlish to sell them on.

At the voltages and currents you'd be using them at they will last forever.
400V HT and 150mA is a nice OP for them. At that power they will put out 12W per channel with no trouble.

All you need to provide is a suitable mains transformer and a big choke for the PSU.

In triode mode it made a bloody good amplifier, able to drive anything.

If you are interested Phil, drop me a PM.

[pre65]

Hi Steve, a very interesting proposition.

PM sent.

[pre65]

Thanks to a VERY generous offer from Steve I'm sorted on this project now.

I'm now off for a 5 mile walk in the north Essex (very nearly Suffolk ) countryside. Just packing a few things in the rucksack. Got to make the most of these last few sunny days.

[Paul Barker]

The obvious and standard way is with triode connected KT88.

[andrew Ivimey]

Too easy I spose, Paul!

[Paul Barker]

well I think you all know I wouldn't use the 13e1 for the job. I don't think the 12E1 is powerful enough, nor the 807. You are talking KT88 for 10 watts high voltage low current 3.5k to 5k.

Or if you can get hold of any Svetlana SV811-10 in A2 gives the sweetest 10 watts I ever heard, makes a 300b sound like it's stuffed inside a feather pillow trying to get out.

Of course you can get an easy 10 watts out of the GE vt4c and it's still cheap compared to 300b's and may not cost much more than a quality KT88.

[Paul Barker]

Obviously the 211 is a specific sound some love some loath.

The SV811-10 is not as unique sounding it has a more open exciting sound, but totally different from 300b. Different in the better sense of the word to some people. But 300b's have their advocates.

The kt88 is quite nice triode connected but not as niice as say a Mullard EL34, though that is lower powered. But any dht mentioned above would trance it for quality of sound, including the 300b.

Then for cheapness there would be a pair of 6b4G's in parallel. Must be about the biggest bargain NOS valve even today. I can't believe how cheap they are, when you consider they sound exactly the same as a 2a3, have the exact same plate and grid with a filament wound for a different voltage and an octal base. Similarly the 6a3 far too cheap but retains the 4 pin base. You can't distinguish between the three types for sound.

I even find the 6a5g sounds the same as the dht versions. But for reason's I don't understand it commands a much higher price, so I suggest let someone else buy it. I have always had a pair, I can tell you it is nothing special not worth a penny more.

[Nick]

Yep, but not at the less than 400v original requiirement.

[colin.hepburn]

Yep parallel 6b4G was is a option I was looking at trouble is whenever I suggest PSE it always seems to get talked down the main story
I have read on pse was the one about WAD 2a3 sounding better when pulling one off the 2a3s from each channel also some say that pse smears the sound so is putting me of the idea of pse but I suppose the only way to find out is to try it what are your views on pse

[pre65]

Colin, I was looking for 10W for a specific application, so PSE may have been an option.

Do you actually NEED any more power than the single EL34 gives ?

I did try 829b as PSE, because "normal" SE won't work with that valve.

That amp did not last long before it was converted to a single KT66 SET and that was better IMHO.