Single supply 6922 buffer with 2SK CCS

[Will]

Hi,
I'm a bit poor on this tube topic so please help me out.

The circuit on the right (dual supply buffer) has been done before so I guess it's a working model.

My question is, can the diagram on the left using single supply be used with the same CCS?

The reason being I have the trafo and choke to provide a good 80V supply and if possible I would like to use high voltage PIO as ouput caps.

Many thanks.

[WT]

I don't think you have enough voltage to make the ccs work for the single supply.

[Will]

How much more voltage do I need to make it work?

[Eli Duttman]

Will,

Aside from the lack of Volts, the single supply circuit will NOT work, as drawn. Where's the negative bias on the triode's grid? A DC coupled I/P is possible, only when a bipolar PSU is employed.

What are the ratings of the power trafo's rectifier winding? Depending on the rectifier winding's wiring, it may be possible to get the Volts you need, either by bridge rectification or Greinacher voltage doubling.

[WT]

You can use -6V on the tail of CCS by using the V from heater supply. Also take out the 6.8K resistor as well, or change it to 10 ohm or 1 ohm so you can use it to measure current.

Another way is to replace all of the ccs with choke which I think will make this circuit more elegance.

[Will]

Originally posted by Eli Duttman
Will,

Aside from the lack of Volts, the single supply circuit will NOT work, as drawn. Where's the negative bias on the triode's grid? A DC coupled I/P is possible, only when a bipolar PSU is employed.

What are the ratings of the power trafo's rectifier winding? Depending on the rectifier winding's wiring, it may be possible to get the Volts you need, either by bridge rectification or Greinacher voltage doubling.

Thanks for the info, do excuse my lack of knowledge.
I have a 120v trafo (secondary) and when after full wave rectification will produce 120x1.4 = 168v. Hence plenty of headroom to bring voltage down. I have a 50H choke. Any suggestion?

[Will]

Originally posted by WT

Another way is to replace all of the ccs with choke which I think will make this circuit more elegance.

How would you calculate the choke value? Assuming I want to bias the tube at 15mA.

[revintage]

The 6922 is totally unusable if you want to make single supply CF.

If you use a pair of 12B4A with I=10mA you will get 7Vrms with Zout=150ohm.

If you use a 6N30P you will get 3Vrms with Zout=120ohm.

[leadbelly]

Originally posted by revintage
The 6922 is totally unusable if you want to make single supply CF.

Why? The ECC88/6DJ8/6922... family are great for CF's.

[revintage]

Hey Leadbelly,
Read the whole sentence ! It says "single supply" as in the Wills left picture. Otherwise you are right, it is really good as CF (if you happen to like CFs).

If one decide to use a input cap and lift the triodes grid from ground potential it will not be a problem to use 6DJ8.