Small Signal Hen Scratches

Posted by Eli Duttman (A) on April 28, 2013 at 20:11:16

In Reply to: RE: Would any of these triodes also work? posted by Eli Duttman on April 26, 2013 at 18:08:07:

Please do some "lifting", Jeff. ;> ) Provide all interested parties with a nice, neat, "professional", graphic.

Add a protective Zener diode between the FET's gate and source electrodes. A 100 Ω CF "stopper" on the 6922's anode is a good idea too. The "hard" sound some people ascribe to the 6922 can be due to parasitic oscillation. If nothing else, the 6DJ8 family is HIGH gm and, therefore, parasitic oscillation prone. The CF plate "stopper" is very low cost "Boogeyman Insurance".

The topology of a voltage amplifier DC coupled to a "concertina" phase splitter is "as old as the hills". Fisher, Scott, Dyna ... used it frequently. We're adding "bells and whistles" to a proven setup. FETs can swing closer to the voltage rail than triodes can and volts are at a premium, in this situation. Not having to deal with heater power and a heater/cathode potential limit is also advantageous.

Eli D.

IRFBC20 Data Sheet. (Open in New Window)

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Follow Ups Full Thread

Topic - Driving 6Y6GTs with El Cheapo 12AT7 front end? - jyourison 10:47:34 04/25/13 (24)

RE: Driving 6Y6GTs with El Cheapo 12AT7 front end? - Paul Joppa 20:48:01 04/25/13 (2)

Grid current - Triode_Kingdom 22:42:04 04/26/13 (0)

RE: Driving 6Y6GTs with El Cheapo 12AT7 front end? - jyourison 21:11:03 04/25/13 (0)

RE: Driving 6Y6GTs with El Cheapo 12AT7 front end? - Eli Duttman 17:20:21 04/25/13 (18)

RE: Driving 6Y6GTs with El Cheapo 12AT7 front end? - jyourison 19:03:17 04/25/13 (17)

RE: Driving 6Y6GTs with El Cheapo 12AT7 front end? - Eli Duttman 22:06:45 04/25/13 (16)

Would any of these triodes also work? - jyourison 17:13:45 04/26/13 (15)

RE: Would any of these triodes also work? - Eli Duttman 18:08:07 04/26/13 (14)

O/P Stage - Eli Duttman 08:06:52 04/29/13 (4)

Bias - Eli Duttman 12:45:52 04/29/13 (3)

RE: Bias - jyourison 19:01:42 04/29/13 (2)

RE: Bias - Eli Duttman 19:43:49 04/30/13 (0)

RE: Bias - Eli Duttman 22:57:18 04/29/13 (0)

Small Signal Hen Scratches - Eli Duttman 04/28/1320:11:16 04/28/13 (0)

B+ PSU Hen Scratches - Eli Duttman 00:36:32 04/28/13 (6)

RE: B+ PSU Hen Scratches - jyourison 03:32:34 05/6/13 (1)

RE: B+ PSU Hen Scratches - Eli Duttman 05:44:53 05/7/13 (0)

Capacitor Value - Eli Duttman 17:50:51 04/28/13 (0)

RE: B+ PSU Hen Scratches - jyourison 08:48:21 04/28/13 (1)

RE: B+ PSU Hen Scratches - Eli Duttman 09:41:50 04/28/13 (0)

Addendum - Eli Duttman 01:30:02 04/28/13 (0)

RE: Would any of these triodes also work? - Eli Duttman 21:45:46 04/27/13 (0)

CCSs fix a whole host of problems. 12AT7s with CCS will be more than up to the task. - Chip647 12:02:45 04/25/13 (1)

RE: CCSs fix a whole host of problems. 12AT7s with CCS will be more than up to the task. - jyourison 19:04:32 04/25/13 (0)

Follow Ups

Small Signal Hen Scratches - Eli Duttman 04/28/1320:11:16 04/28/13 (0)

Small Signal Hen Scratches

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