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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: my experiences posted by Joelt on March 29, 2004 at 07:01:50:
Hi Joel,I'm looking at the 01A for a few reasons not least of which is that is has 250mA filament current. A 45V supply can be used to heat and bias both the tubes.With the filament current running through the filament bias resistor the AC impedance of the 01A filament to ground would be 15ohms and 130ohms for the 71A filament. No bypass caps, and no fixed bias source.
It is great that the 01A was quiet enough for you as an input, this is what I need to know. I will go ahead and breadboard it.
Regarding the RC coupling, I was considering a DRD type arrangement with the plate choke of the input tube being fed from the cathode of the driver, and direct coupling the two. Unfortunately the B supply for the 71A would be too high. The filter CCS that biases the VR tube string needs a few more volts across it than that. The driver will be xfmr coupled to the PP output stage though. The neat thing is that the AC impedance of the VR string at HF adds to the Rp of the driver. Measurements suggests that it right in the ball-park for the LL1660S.
regards,
shane
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Follow Ups
- Re: my experiences - shane. 03/29/0422:22:56 03/29/04 (4)
- Re: my experiences - Joelt 10:34:22 03/30/04 (3)
- Re: my experiences - filament bias schem. - shane. 19:38:46 03/30/04 (2)
- probably not a big deal for you - Joelt 08:02:00 03/31/04 (1)
- Re: thanks Joel (nt) - shane. 21:52:42 03/31/04 (0)
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