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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: If you are reading Crowhust posted by Ralph on June 21, 2024 at 09:25:57:
The input stage that I'm employing is a half mu stage. The plate resistance of the tube(s) is canceled in the gain equation. It''s a low distortion stage. Another poster mentioned transitory instabilities. That was the whole point of the Crowhurst article that I sited. The 150pF cap from the plate of the input tube to ground creates a dominate pole at ~9.6uS. That puts the open loop gain down about 10dB at 75kHz, the 90 degree shift point. Now the freq. response is not as "pretty" as it was for Eico. They reported +-0.5dB from 5Hz to 100kHz. I'm down 1dB at 50kHz and 3dB at 75kHz. The rolloff is smooth with no peaking. I'm listening to the amp now and it sounds wonderful. I listened to jazz music with some percussive, discordant piano cords and they sounded clean. The most trouble that I had getting the amp up and running was dealing with some issues with the phono stage after four years in storage. One tube just quit with a bang and another was destroyed by a bad solder connection. Damn, Russian 6N30s with sections matched for plate current are difficult to come by.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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Follow Ups
- RE: If you are reading Crowhust - JKT 21:19:30 06/24/24 (1)
- +1 - Ralph 08:42:55 06/25/24 (0)
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