6V6 line preamp

[merlin el mago]

Salas do you use RC to separate rails for each channel?

 

[Salas]

In my shunt NFB common cathode & B+ Mosfet Filter modified example build no.

 

[merlin el mago]

I use your SSSHV2, I put 1R 47uF per separation channel

 

[Salas]

This scheme should also probably work. Remember, that last capacitor's impedance dominates Zo now.

 

[merlin el mago]

It's lytic, tomorrow I can change for film or I get off the RC?

The preamp is finished just need a power on/off switch to delay 1 or 2 minutes the B+

 

[Salas]

That RC branching is a detail... you will replace caps to see, also test with and without branches and you will decide. Not a problem for initial test.

 

[merlin el mago]

Ok thanks.

What a pity I can't hear just for the switch for B+

 

[Lingwendil]

Work in progress.

Huge chassis!

 

[merlin el mago]

Yes very big, I like to have enough space t work.

 

[merlin el mago]

Salas is enough 315Vin for 6V6, SSHV2 set to 60mA (20mA each tube + 20mA SSHV2)?

 

[merlin el mago]

Could I set B+ for 300-310V? Mains tx are 250VAC so a little bit weak to reach de 330VAC.

 

[Lingwendil]

I've been doing my testing at 300 volts B+ and it has worked well.

 

[merlin el mago]

Thank you

 

[merlin el mago]

Measured 2 mV AC ripple at each current regulator, not bad for a simple design.

 

[Lingwendil]

You can reduce further with a couple RC stages at the feed to the LM317s, but 2mV is likely to be inaudible with the indirect heated cathode. Should work well.

 

[merlin el mago]

Yes I know but at the moment I left as is. Thanks.

 

[Salas]

You can reduce further with a couple RC stages at the feed to the LM317s, but 2mV is likely to be inaudible with the indirect heated cathode. Should work well.

Also able to burn some heat on RC filters before LM317 in situations where DCin is high and sink is small.

 

[merlin el mago]

What's the input impedance?

 

[Salas]

Volume potentiometer's nominal value is the input impedance.

 

[merlin el mago]

I use 100K so 100K input impedance great.