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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: It's a Myth posted by Triode_Kingdom on September 24, 2021 at 16:38:32:
Lynn Olson"Absence of rectifier switching noise. The noisiest circuits of all are solid-state bridges driving large values of electrolytic capacitors. (As found in almost all transistor gear and the DC supplies for heaters and filaments.)
The commutation noise of the diodes shock-excites the RLC of the stray L in the cap bank and the stray C in the power trans secondary. The resonance of this tank circuit is typically anywhere from 4 to 20KHz and the Q's are large, anywhere from 5 to 100, depending on the DCR of the caps. This is why paralleling large values of electrolytics with "better", faster polypropylenes can frequently result in worse sound. It is also the reason power cables are audible ... they act as antennas for the small Tesla coil that most power supplies resemble. The supply radiates noise into the chassis, the power supply B+ lines, the audio circuit, and the power cable. This broadband noise can be filtered and shielded (at considerable trouble), but it is much easier to eliminate the commutation switch-noise right at the source.
Choke-fed supplies are much quieter due to the choke slowing down the rate-of-charge of the main cap bank. I use a hybrid choke-fed/pi-filter to minimize the shock-excitation of the main PS choke (this tip from the Radiotron Designers Handbook, Fourth Edition).
In terms of ragged waveforms, solid-state diodes are the worst, followed by Schottky diodes and HEXFRED's, followed by conventional tube rectifiers, followed by TV damping diodes, which are the smoothest of all in terms of the AC waveform on the power trans secondary. This, along with 2 amp peak current, is why I use them. The 30 second warmup is just a bonus."
Tre'
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Follow Ups
- RE: It's a Myth - Tre' 09/25/2105:59:24 09/25/21 (10)
- RE: It's a Myth - Triode_Kingdom 09:52:43 09/25/21 (9)
- For the Sake of Clarity - - Triode_Kingdom 18:39:19 09/27/21 (3)
- RE: For the Sake of Clarity - - sony6060 17:54:26 09/28/21 (2)
- RE: For the Sake of Clarity - - Triode_Kingdom 22:18:06 09/28/21 (1)
- RE: For the Sake of Clarity - - sony6060 01:07:17 09/29/21 (0)
- I didn't make the claim. Talk to Lynn. nt - Tre' 11:31:05 09/25/21 (3)
- Not necessary - Triode_Kingdom 12:41:52 09/25/21 (2)
- What about these claims? - Tre' 14:14:55 09/25/21 (1)
- RE: What about these claims? - Triode_Kingdom 15:18:42 09/25/21 (0)
- RE: It's a Myth - sony6060 10:20:23 09/25/21 (0)
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