Members tedmich Posted September 24, 2008 Members Share Posted September 24, 2008 I am very impressed by Randall Aiken's tech stuff; very even handed and not crazy voodoo audionutish (if only the Corsair links weren't dead...) and Randall asserts that the ultra FREDs he uses in the bridge rectifier circuit help the tone (bass especially I believe). Is this anyone else's experience? I have run across tube heads who actually do tricks to "slow down" SS rectifiers to produce "sweeter audio" also put a cap across bridge to limit RFI...etc. so should I get some Ultrafast 1000v 3A rectifiers or bag it? They're only 47c x 4... Link to comment Share on other sites More sharing options...
Members Casey4s Posted September 24, 2008 Members Share Posted September 24, 2008 I think Randall is a very informative guy and a really great amp builder and I am sure there is something to it. But I just use 1N4007 diodes for just about everyting. Link to comment Share on other sites More sharing options...
Members el_tonto Posted September 24, 2008 Members Share Posted September 24, 2008 Low-drop rectifiers diodes (e.g. schottkys, or higher-rated "normal" rectifier diodes) could provide more headroom, which would give a bit more power. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted September 24, 2008 Members Share Posted September 24, 2008 I would think once the AC is converted to DC and smoothed out a bridge has zero to do with how audio sounds so long as its smooth DC with constant current and voltage. The only thing I can think of is having A cap across the rectifyer might be done to mimick a littel like a tube rectifyer creates under high power conditions. I have an old Sunn amp that did something simular with coils throughout the power amp circuit to mimick tubes. Its has a closer attack/feel of tubes then any other I've tried when playing through it. Link to comment Share on other sites More sharing options...
Members tedmich Posted September 25, 2008 Author Members Share Posted September 25, 2008 Thanks for the input guys, makes sense... I guess I'll save the money for the tantalum resistors... (kidding... they're $7 each see: http://www.angela.com/catalog/resistors/Resistors.html)) Link to comment Share on other sites More sharing options...
Members Randall Aiken Posted September 25, 2008 Members Share Posted September 25, 2008 and Randall asserts that the ultra FREDs he uses in the bridge rectifier circuit help the tone (bass especially I believe). I think you are reading a bit too much into my statement: "The rectifier uses massive 3-amp 1000V ultra-fast recovery diodes (Ultra-FREDs), for utmost reliability and a tight low end, without the RF noise interference "spikes" inherent in standard rectifiers" What I meant was that the benefit of using fast-recovery diodes is that they eliminate RF noise and spikes. By "tight low end". I meant they have tight low end in contrast to tube rectifiers. They will not magically give you tighter low end if you use them in place of 1N4007's. Their only benefit is that you don't have to use "swamper" caps or snubber networks across the diodes to prevent radiated or conducted switching noise from the diodes. The high voltage and current rating are used for improved reliability. Randall Aiken Link to comment Share on other sites More sharing options...
Members tedmich Posted September 27, 2008 Author Members Share Posted September 27, 2008 I think you are reading a bit too much into my statement:"The rectifier uses massive 3-amp 1000V ultra-fast recovery diodes (Ultra-FREDs), for utmost reliability and a tight low end, without the RF noise interference "spikes" inherent in standard rectifiers"What I meant was that the benefit of using fast-recovery diodes is that they eliminate RF noise and spikes. By "tight low end". I meant they have tight low end in contrast to tube rectifiers. They will not magically give you tighter low end if you use them in place of 1N4007's. Their only benefit is that you don't have to use "swamper" caps or snubber networks across the diodes to prevent radiated or conducted switching noise from the diodes. The high voltage and current rating are used for improved reliability.Randall Aiken Sorry to have paraphrased so inaccurately Randall! I do want to avoid switching noise as my circuit is very high gain; any noise would be bad. As long as I have such a learned ear available: where would metal film resistor do the most good? Is it just temp stability on the B+ feeds or perhaps a little noise could be removed in the signal path, or at the cathode resistor? And what caps do you favor for cathode bypass? I swear I saw a Tantalum in a Egnater design... Link to comment Share on other sites More sharing options...
Members bruce_egnater Posted September 27, 2008 Members Share Posted September 27, 2008 Randall Aiken is probably the smartest guy I know. His website is the most down to earth informative site about tubes, bar none. The information he presents is quite technical and is 100% accurate and, as you said, no voodoo nonsense. aikenamps.com is first on the list of suggested reading in our amp building class manual. As you can see, because of the depth of information there, things can be misinterpreted. Read carefully and be sure to not take specific statements out of context. Anyone interested in tube amps should visit his site. egnater Link to comment Share on other sites More sharing options...
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