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In Reply to: RE: That what my guess in that it was for spike suppression. posted by JKT on August 30, 2016 at 18:17:38
M.Jones point out that this arrangement does degrade the ability of the choke to filter higher frequencies.
Ok but that choke is only filtering 120hz and even if it had to filter far above the fundamental at the 10th harmonic,you are still only talking 1.2khz which is low.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Follow Ups:
If you perform a Fourier analysis on the rectified output (the rectifiers perform a non-linear transformation of the mains AC 60Hz) you will see that there are many harmonics of 120Hz that need to be filtered. Also, HF noise from the AC mains (do a spectrum analysis of your incoming AC, it will not be pure 60Hz) can couple through parasitic capacitance (interwinding capacitance?). Also the voltage spikes generated by the choke if not snubbed will produce HF harmonics of the 120Hz fundamental. While the best of human ears can't hear past 20kHz, ultrasonic noise can and will degrade audio signals in ways that are unpleasant to the listening experience.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
They use dual rectifiers. I wonder if transient current supply is an issue. There is an article I read, about smoothing out current demands using an input cap (prior to choke). I suppose the amount of mfd is critical to what this input cap is doing.
Amps I've seen use a 1-8 mfd cap prior to the choke. With usual caps after the choke.
Maybe historical note. When higher current power transformers, plus GZ34 and better 5U4GB became more available and affordable... cap before choke wasn't needed (?).
Edits: 08/31/16
Steve
Keep in mind that the Mac Mc60s also use two rectifier tubes. When you are running the output tubes at 150ma plus for the pair, and then have 5 other tubes to feed as well,you are going to be on the edge of static current with just one rectifier in the case of the GZ34.The transient current you speak of is the reason for running two rectifiers as opposed to one.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
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