Suggestion on tube for CCS

[dsavitsk]

I am looking for a pentode to use as a CCS, or part of a hybrid Pimm style CCS. I'd like about 30 to 35mA, an octal or loctal base, and to drop the least amount of volts possible. Oh, and cheap is good. Suggestions?

 

[billr]

hello

If you can get your hands on Valve Amplifiers, 3rd Edition, by Morgan Jones, he has such a list available.

This list has valve type, current draw, and I think volts drop too.

I'm sorry I don't have my copy to hand.

Others may be able to assist.

Kind regards

Bill.

 

[Wavebourn]

Again, 12L6

 

[Ipanema]

Wonder why transistor base CCS is not very popular in tube amp? What's your experience on this?

Regards.

 

[Wavebourn]

Wonder why transistor base CCS is not very popular in tube amp? What's your experience on this?

Very popular. Rich experience. The question was, "Which tube". 12L6 is one good option for such current and voltage. It is good as well on such currents/voltages when triode strapped.

 

[Bandersnatch]

hey-Hey!!!,
Build one with two tubes. One triode and a pentode. Cascode connection like Gary Pimm designed MOSFET CCS. Pick high gm/high plate Z pentode for the top, and high gain( within plate Z limits as set out by design parametes ) for the bottom triode. This will burn significant amounts of B+, but it can work *VERY* well.
cheers,
Douglas

 

[ray_moth]

I'd like about 30 to 35mA, an octal or loctal base, and to drop the least amount of volts possible.

Sounds like you're looking for the type of pentode that would be suitable as the pass-element in a voltage regulator. In Steve Bench's multi-part article on voltage regulation, he uses the EL509 throughout. I'd guess there are others that might be suitable.

 

[Bandersnatch]

to drop the least amount of volts possible.

On this, getting a large current-set/cathode R can burn up significant voltage. Unbypassed cathode resistance has a predictable, and useful effect on the circuit as a whole( increased plate Z ), so consider spending B+ on useful performance trades, yes?
cheers,
Douglas

 

[Ipanema]

i got a piece of EH ECC88 only. Most of the design I saw are either using resistor/tube load. I'm a tube virgin and a cheapskate too Do you have any design using transistor CCS for this tube?

If you don't mind, can you help to explain what are the pro and con of using transistor CCS compared to tube? Any link would be appreciated as well.

Thank you.

 

[dsavitsk]

Thanks for the suggestions. Application is I have a chassis with space for 2 octals and 2 novals, and I was thinking of putting something like this on it. I figured the tube ccs would fill the octal spots. As drawn, it would need a sand ccs as otherwise the voltage is too low.

An externally hosted image should be here but it was not working when we last tested it.

 

[Wavebourn]

...one more CCS and you have a bridged output SE for better bass response with smaller tranny.

 

[korneluk]

Re: Re: Suggestion on tube for CCS

hey-Hey!!!,
Build one with two tubes. One triode and a pentode. Cascode connection like Gary Pimm designed MOSFET CCS. Pick high gm/high plate Z pentode for the top, and high gain( within plate Z limits as set out by design parametes ) for the bottom triode. This will burn significant amounts of B+, but it can work *VERY* well.

Do you have any specific tube suggestions?

-- josé k.

 

[Bandersnatch]

Re: Re: Re: Suggestion on tube for CCS

Do you have any specific tube suggestions?

-- josé k.

12BY7 on top, triode-strapped 12HL7 on the bottom. Create a large voltage ref. so a cathode R of a few kOhm can be used at +20 mA. From 12HL7 cathode-plate set the voltage ref. to deliver at least 1.5V grid-cathode( or the pentode cathode to the triode cathode ) . I suppose a 7788 would also make a nice subject for the lower triode valve. Bypass the pentode g2 to its cathode with a good cap, and select a dropping R to get ~30V below B+.

It winds up looking very much like a Pimm MOSFET cascode.
cheers,
Douglas

 

[korneluk]

Link to a 1965 UCLA/NASA paper on current sources for vacuum tube circuits. Skip to figures 5 and 6 for a working circuit.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650077554_1965077554.pdf

Enjoy,

-- josé k.

 

[billr]

Link to a 1965 UCLA/NASA paper on current sources for vacuum tube circuits. Skip to figures 5 and 6 for a working circuit.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650077554_1965077554.pdf

Enjoy,

-- josé k.

surely that figure 6 is incorrect? the rectifiers are a hard short over the secondaries.

need to get rid of the little blob from the bottom rectifier as the link crosses the centre tap.

bill