ecc99 - 6C19n PP, (6S19P)

[Wavebourn]

thanks guys, for the hints and pointers

diff.pair
I take it you are suggesting ccs feed to each output anode/plate

Yes. Either a CCS, or 10W 820 Ohm resistor. 300V B+, grids grounded through grid leak resistors. Driver powered from the same 300V source. Simple and robust. For driver I would use something like 6J52P or 6P15P.

 

[piano3]

Sinks, not sources. My driver is 6E6P.

 

[tinitus]

thinking about coupling the IT like CFB(cathode feedback)

 

[tinitus]

SE driver with CFB

taken from Williamson and Walker output stage(Quad)

 

[tinitus]

maybe something like this

 

[tinitus]

would like to try this
I can get relativeky cheap IT's
probably fore instrument amps
but I don't care so much about the sound right now
more interested to see if it works

 

[tinitus]

and yet another crazy idea for the IT 😱

but right now interstage is too costly
so why bother, I do not know

 

[tinitus]

ah, found this phase splitter(Jeremy Epstein)
looks similar to mine from post 224

 

[tinitus]

ok, new direction...maybe

thought about circlotron, and whether maybe EL34, KT66 or 6L6 would be ok with my 1.6Kom OT

mind you, I'm not expecting high output

 

[Bigun]

My gosh, you're drawing pen is on fire - you could be the new Broskie 😀

 

[tinitus]

If they dont work out in this project 1K6 is perfect for a 6AS7 amp.

Shoog

... 😉 ... it only took me 2 years to realise it ... 5watt will have to do 😀

 

[tinitus]

or just use those 6S19P I have, and quit worrying about mismatched non linear tubes

guess it will be either that or nothing

 

[tinitus]

searching for valve bases, and guess what ... it's just a common Noval B9A 🙂
(and also, found a couple more amp schematics now)

 

[tinitus]

Yes. Either a CCS, or 10W 820 Ohm resistor. 300V B+, grids grounded through grid leak resistors. Driver powered from the same 300V source. Simple and robust. For driver I would use something like 6J52P or 6P15P.

if I understand this correctly, a higher B+ with CCS biased cathode, would be almost similar to lower B+ voltage with fixed bias

 

[Wavebourn]

Let's resurrect the thread...

if I understand this correctly, a higher B+ with CCS biased cathode, would be almost similar to lower B+ voltage with fixed bias

Actually, fixed bias current instead of fixed bias voltage.

However, today I would do differently, 6 years later...

The same 300V B+, but something like 36 Ohm in cathodes, and a fixed bias like -70V; also, I would bootstrap drivers from cathodes of 6S19P, getting such a way also a positive feedback by current. However, grid leak resistors should have pretty low values (relative to other tubes), since people reported run-aways?

Let's check this idea, I am going to experiment...

For the driver I want to try ГУ-17 tube (QQE03/12), with 1K in common cathode and 10K+1K load.


What do you think?

 

[Wavebourn]

Here is my result. No bootstrap yet. 180 Ohm in cathodes, about -90V bias through 130K resistors.
280V B+, 4K5 output transformers.
GU-19 driver, 6F12P phase splitter.
With Edcor "15W" cheap transformers I got 9W of class A triode push-pull power.

I believe with lower load impedance and B+ I may get better results

 

[Wavebourn]

Too rude, I am going to drop B+ down to 240V...

 

[Wavebourn]

Decreased cathode resistors to 36 Ohm, decreased B+ to 240V, got 10W.

 

[piano3]

Is there any particular reason why you are using GU-17 other than convenience?

 

[Wavebourn]

Is there any particular reason why you are using GU-17 other than convenience?

It fits. 🙂

As you may see, 200V swing from each half, 10k load resistors.