Hi-end 845 with only two stage

[gaborbela]

Hello Thomas

I have more than 20 years DIY experience, also I work as a assistant in TV repair shop and with electrician mostly residential but sometimes in factory with 360V to.
I have some soldering skills that is not a problem.
I have more than half of the parts for these amp, I go slowly how I get some money..
If there is a working schematic I can build anything.
I do not own oscilloscope etc but probably I can get some help from my friend. Some DD Multimeter etc I have of course.

Greetings gabor

 

[Vinylsavor]

Hi Gabor,

ok that's good. Just wanted to make sure since there are dangerously high voltages involved in such a project

Best regards

Thomas

 

[gaborbela]

Thank you Thomas
I know,I thought about before I started to collect the parts!
Safety first.
I think these 2 stage will be better than the schematic I posted. Even do I'll purchased some 6SN7 & 6J5 tubes also octal sockets..
I see Andrea and many other (guru) DIY-ers go with two stage.
Someone told me avoid the instage transformer, use just tubes but I think the transformer still better than many coupling capacitors.
I attache some picture from the parts I already have..
12PC Epcos
3PC amplifier enclosure, two the same as on the picture, one larger for PS
4PC GM70, 2 socket
high voltage choke - about 3.5Kg, 12PC electrolytic etc.

Greetings gabor

 

[gaborbela]

Fiat OPT

Hello Andrea

How much it cost a pair Fiat OP transformer for GM70. I think 25-30W would be enough.
Please let me know
Thank you very much

Greetings gaborbela

gaborbela,
look this dc solution

GM70 amplifier with Fiat transformers

 

[Bigun]

There is actually one triode out there with descent Gm and mu over 100. The triode section of the 6F12P can deliver over 90V rms at Ua 200V and Ia 10ma. But a high inductance will be needed as Ri is in the ballpark of 6k at 10mA.

I have measured the ten I bought from Russia in my AVO and linearity seems to be quite good. Have not tried them in circuit yet, though.

The pentode section has a Pa of 5W and could maybe be used as a DC-coupled CF if driving into A2 range if called for.

Did anybody try this, 6f12p driving an 845 ?