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help needed with grounded grid CCS upgrade
help needed with grounded grid CCS upgrade
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Old 23rd March 2010, 06:03 PM   #11
Merlinb is offline Merlinb  United Kingdom
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Quote:
Originally Posted by ultrachrome View Post
Merlinb:
In your example you have HT+ and V+. What range of voltage would V+ typically be? The 1.8V label suggests 12V or lower?
HT+ will be the usual, say 250V to 400V. V+ can also be anything; either a convenient low voltage supply, or R1 could even be connected to the HT, although that does mean more wasted power of course. When I built this circuit I used the DC heater supply for V+.

I built the circuit with 12AX7, but it should work even better with 12AU7, with suitable adjustment of the emitter resistor / base voltage.
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Old 23rd March 2010, 06:34 PM   #12
revintage is offline revintage
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Hey Svein,
Did a quickie at Google and found them at 20-30EURs a piece. Could thankfully not find them at the price you indicate.
But 5687 or E182CC might be something to use.
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Old 23rd March 2010, 07:44 PM   #13
ultrachrome is offline ultrachrome  United States
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Quote:
Originally Posted by DougL View Post
FWIW, Figure 2.48 (b) or (e) on page 134 of "Valve Amplifiers" Third addition has the circuit you are looking for. The emitter of the PNP would be attached to the cathodes of the Long tail Pair. (Grounded grid is a misnaming of the circuit by the designer).
I agree with Svein that the circuit shown in post 4 by Merlinb is not what I would recommend because it does not use a negitive supply.
Page 128 Figure 2.46 has a FET CSS between stages. Looking again Page 136 figure 2.49 has a great example of what you are trying to accomplish.

HTH

Doug
Thanks. That's very helpful. I'll look at it tonight.

Revintage, thanks for that comment. Your mention of "SRPP" was an interesting clue.


Merlinb, that's what I was hoping you'd say. Looking at some of schematics in the salas thread and other CCS's, it was not yet obvious to me how they were connected.
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Old 23rd March 2010, 08:59 PM   #14
revintage is offline revintage
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Hey Ultra,

This is to show how it could be done, avoiding unnecessary "sounddegrading" stages. Zout below 1kohm. Negative supply could be as low as 9-12V

An option isa to use a gyrator or CCS on top of the second tube instead of anoderesistor.
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Old 23rd March 2010, 09:42 PM   #15
jerluwoo is offline jerluwoo  United States
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Here's some good reading about cathode coupled stages. PCB Update & Cathode-Coupled Amplifiers The links at the top that says background blogs also cover cathode coupled circuits.
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