6CB5 in triode PP?

[Tubelab_com]

double the B+ via doubler to ~650V......I'm firing into 1.9K here

4 tubes, 650 volts, 1.9K ohms should result in about 250 watts or more. Do you have the ability to run the OPT at 3.8K? (8 ohm load on the 4 ohm tap)

 

[deicide67]

Good morning George

Here is the chassis layout so you can see what I am working with. I'm going to use the pots on the front of the chassis to overcome the 6GFA variance in gain if it is experienced.

I can keep the B+ around 340V or so if I do not use a doubler.


The outputs transformers are Hammond 1650T that are capable of 120W. They will handle a little over 400mA per side on the primary. I cannot shift them up or down because my speakers are 4ohm almost through the entire bandwidth.

I added the 6DJ8 up front in case I need more gain to swing the output stage.

Regarding the regulation, I was thinking about using something like the OB2 for neg bias, and trying one of the SS regulator circuits for my screens. When using a regulator tube for neg bias, do you install it , "backwards" since it's a negative supply?

Thanks!

Blair

 

[Tubelab_com]

do you install it , "backwards" since it's a negative supply?

Yes it has a polarity just like a zener diode. In this case the plate goes to ground.

 

[TheGimp]

Post filter the negative bias supply with an RC network to eliminate noise from the OB2. Don't put a cap across the OB2 larger than 0.1uF or it can form a relaxation oscillator.

 

[deicide67]

Like this?

That's enough for a clean bias supply, or does it need to be filtered before the regulator?

 

[multi]

Seems to me you would be better off getting rid of the first tube and using a push pull driver {12Bh7, 6N6T Ecc99}. Maybe even a cathode follower direct coupled to the 6cb5 such as a 6BL7 or two.
That is how I intend to do my 6CB5 amp. 6N6T voltage amp Phase splitter;6N6T PPull driver, two cathode follower 6BL7's.
Phil

 

[deicide67]

OK,

After what may be the worst Holiday season ever, $30K insurance claim from water damage on my home, loss of a car, the list goes on..., I'm back to looking at this project. Is a single OA2 sufficient to deliver enough screen current for two tubes? An OA2 can deliver a regulated 30mA at 150V.

I was thinking about a single OA2 per PP pair.

Thanks!

Blair