what about pt15?

[IslandPink]

James,

Are the A1 curves available on paper anywhere, or have the values and the performance just been worked out by people like yourselves ?

Mark

[James D]

Pete Millet has the PT15 triode curves that he has measured and they agree with what I have found and what the Japanese have measured.

[Corne]

In triode you can run them A2 or AB2 for a part of the cycle this only slightly increases the total power dissipation by the amount of power dissipated by g1. In this case g1 dissipates power in peaks, up to several Watts, but due to the low duty cycle the average power dissipation is small.

I've built triode strapped PT15 AB2 amplifiers this way but it wasn't easy because of the complex driver circuit.


Corne

[dsdn.]

OK It would be difficult to run it in AB, so let's go for a pp in class A. Another difficulties is the socket, does someone know where I can find it? Or sall I have to make it by myself?

DAvid

[Corne]

It's only difficult if you want to run it AB2 not AB1.

Corne

[dsdn.]

And so in AB1 wich would be the main technical characteristics of the final stage?
I mean B+, transformer's impedance and Rk.

DAvid

[James D]

Hello Corne,

I found your amp on the VT52 site. Corne PT15

Is it still running and how is its performance? It looks very nice!

Have you compared it to running in Class A? Have you tried pentode mode?

best regards

James

[Corne]

In my AB2 amplifier I'm running :
Ua=650V
Ia=45-50mA
g2 to anode via 100ohm
g3 to ground
fixed bias at about -85V
Rk one 47ohm to ground on each filament connection
no anti hum potmeter because I use DC on the filaments
plate-plate load 10K

This will give you 20-25W AB1.

I know 650*0.05=32.5W which is more than 30W but total power dissipation is below Pa+Pg2=40W.

Corne

[Corne]

James,

Yes, those are my PT15 amplifiers and they are still running.
I'm quite happy with the performance, no hum, good clean sound with sufficient bass. I've never tried pure class A or pentode mode. Maybe I should try but at the moment I'm looking into SE PT15 designs. Looking for info on SE PT15 designs on the Web I found this forum.


Corne

[dsdn.]

Where did you find avalaibable sockets for this tube?

DAvid