PSE schematic

croccodillo · 25th October 2005, 01:37 PM

I have 4 KT88 tubes and some new SED Svetlana 12AX7 laying around, and I'd like to use them...
So I drawn a schematic, a KT88 PSE (I have 4 KT88, and why not to use them?)
Questions:

1. Can the paralleled 12AX7 tubes drive the KT88 in the right way? THe LTP current (sum) is of about 2mA.

2. Does it worth the try to use two paralleled KT88 as output tubes?

3. I already have a -15V for the long LTP, so why do not use it as the bias voltage? It should works better than bias the tubes via the cathode resistors, isn't it?

3.pdf

I've used a LTP as a differential amplifier for the global feedback (as usually done in SS amplifiers), and added some sort of LF from the plate of the output tubes...

Your opinion?

Ciao,
Giovanni

croccodillo · 25th October 2005, 01:39 PM

Just in case the circuit can work (I'm not sure, I'm still too inexpert), how should the output trafo impedance be?
I suppose it should be the half than the nominal one for a single tube (2K3, as far as I remember).
Is this right?

Ciao,
Giovanni

croccodillo · 25th October 2005, 02:32 PM

I have to self-correct my schematic: the bias voltage is too low (too high?), I need at least -35V; with -15V I have 200mA for each tube, too high!

25th October 2005, 01:37 PM	#1
croccodillo diyAudio Member Join Date: Mar 2005 Location: Bergamo	PSE schematic I have 4 KT88 tubes and some new SED Svetlana 12AX7 laying around, and I'd like to use them... So I drawn a schematic, a KT88 PSE (I have 4 KT88, and why not to use them?) Questions: 1. Can the paralleled 12AX7 tubes drive the KT88 in the right way? THe LTP current (sum) is of about 2mA. 2. Does it worth the try to use two paralleled KT88 as output tubes? 3. I already have a -15V for the long LTP, so why do not use it as the bias voltage? It should works better than bias the tubes via the cathode resistors, isn't it? 3.pdf I've used a LTP as a differential amplifier for the global feedback (as usually done in SS amplifiers), and added some sort of LF from the plate of the output tubes... Your opinion? Ciao, Giovanni

25th October 2005, 01:39 PM	#2
croccodillo diyAudio Member Join Date: Mar 2005 Location: Bergamo	Output trafo Just in case the circuit can work (I'm not sure, I'm still too inexpert), how should the output trafo impedance be? I suppose it should be the half than the nominal one for a single tube (2K3, as far as I remember). Is this right? Ciao, Giovanni

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25th October 2005, 02:32 PM	#3
croccodillo diyAudio Member Join Date: Mar 2005 Location: Bergamo	I have to self-correct my schematic: the bias voltage is too low (too high?), I need at least -35V; with -15V I have 200mA for each tube, too high!

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