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Questions about CCS load on anode of valve .

222.166.2.28
Posted on June 25, 2015 at 07:03:09
akltam
Audiophile

Posts: 1057
Location: Hong Kong
Joined: September 29, 2002



I am thinking about trying a CCS as load on the anode of a valve instead of resistor.

I am thinking of using IXCP10M45S. See attached.

I have thinking about 120V on the anode of the 12AU7 and running the valve at 5-6mA.

What voltage should I supply at the anode of the IXCP10M45S ?

Thanks in advance.
Alan



 

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RE: Questions about CCS load on anode of valve . , posted on June 25, 2015 at 08:16:24
danlaudionut
Audiophile

Posts: 5480
Location: Schenectady
Joined: June 6, 2002
 Minimally 20V plus peak voltage swing
Optimally 100V plus peak voltage swing

DanL



 

RE: Questions about CCS load on anode of valve . , posted on June 25, 2015 at 14:09:47
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 What Dan said and two additional things;

You will be better off with two 10m45s in cascode.

You will need 1k ohm gate stop resistors to keep those things from oscillating.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Questions about CCS load on anode of valve . , posted on June 25, 2015 at 14:41:20
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 5.5mA through 330 Ohms is 1.8V of bias.

1.8V of bias and 5.5mA on the 12AU7 curves shows just under 100V on the plate.

Your current schematic does not show the Ixys chip setup for this current.

If we assume that you will have 100V on the plate, and 1.8V of bias, 150V of B+ is a reasonable decision. This will keep device dissipation at 1/4W, and you shouldn't run out of compliance with some tube-to-tube variation.

 

RE: Questions about CCS load on anode of valve . , posted on June 25, 2015 at 17:10:10
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 BTW once the CCS is in place and set, the cathode resistor just supplies bias and determines the plate voltage.

He can set it anywhere he wants.

An adjustable cathode resistor is great for direct coupling to the next stage (output).

The driver tube's cathode resistor adjustment becomes the output tube's bias adjustment.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Questions about CCS load on anode of valve . , posted on June 25, 2015 at 19:48:39
akltam
Audiophile

Posts: 1057
Location: Hong Kong
Joined: September 29, 2002
 Appreciate if you can draw out how to have two 10m45s in cascode and the additional 1K gate stop resistors.

Alan

 

RE: Questions about CCS load on anode of valve . , posted on June 25, 2015 at 23:24:49
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002

Basic idea.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Thanks. , posted on June 27, 2015 at 20:30:08
akltam
Audiophile

Posts: 1057
Location: Hong Kong
Joined: September 29, 2002
 I just tried this out with K&K Audio's CCS kit. The kit has exactly the same circuit on what is on your drawing but with different MOSFET.

I replaced the cathode resistor of a 'long tail' differential pair of the driving tube with the kit.

It provide quite an improvement. I really like it.

Thanks for sharing the circuit.

Alan

 

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