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Correct Path: Diodes Or Rectifier Tube?
Correct Path: Diodes Or Rectifier Tube?
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Old 30th December 2010, 12:57 AM   #41
Eli Duttman is offline Eli Duttman  United States
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Quote:
Originally Posted by andyjevans View Post
I'm no expert in ss diodes, so could someone fill me in on the difference in quality of a IN4007 to a UF4007 to a SiC Schottky diode rated 1A and 1,000v?

Is there a big or a small step up with a IN4007 to UF4007 for instance, and so on to a Schottky?

Price differential is substantial.

Andy

Andy,

The step up from 1N4007 to UF4007 is substantial and well worth the cost differential. The 1N part is very noisy and (IMO) should not be used in HIFI equipment, either hollow or solid state. OTOH, the UF part is darned quiet on its own and it can snubbed into near silence.

Diminishing returns has set in in the case of the 5 A./1200 PIV Schottky. For supplies in that part's range, I suggest a "cockeyed bridge" that uses snubbed UF4007 stacks on the ends of the rectifier winding and a single Schottky on the CT.

Infineon makes 600 PIV/3 A. Schottkys that are reasonably priced. A 4 diode bridge from those parts is quite affordable and "noiseless".


----------------------------------------------------------------------------------------------------------------------

All,

Distinct warnings from Cree against stacking high PIV Schottky diodes are fairly well known. Stacking the parts seems to lead to cascading failures. Don't do it!
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Last edited by Eli Duttman; 30th December 2010 at 12:58 AM. Reason: fixed typo
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Old 30th December 2010, 07:50 AM   #42
Jen-B is offline Jen-B  United Kingdom
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Quote:
Originally Posted by Eli Duttman View Post
Distinct warnings from Cree against stacking high PIV Schottky diodes are fairly well known. Stacking the parts seems to lead to cascading failures. Don't do it!
Thanks for the info Eli.
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Old 30th December 2010, 08:47 AM   #43
andyjevans is offline andyjevans  United Kingdom
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Thanks to Eli seconded. Very useful.

Andy
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Old 30th December 2010, 11:08 AM   #44
M Gregg is offline M Gregg  England
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Jen-B,

I guess we agree to disagree.
Just for info I am not a hifi person that moves in hifi circles.
Have a good New Year!

Regards
M. Gregg
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Old 30th December 2010, 11:26 AM   #45
DF96 is offline DF96  England
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our ability to describe everything 100% numerically
Who said everything? I just said that sensitivity to rectifiers will vary with capacitance, according to the laws of physics. To the extent that you can hear the PSU, there is something wrong with the PSU and/or the amplifier. This is simply because the job of the PSU is to deliver DC at a low source impedance. If it does anything else it shouldn't!

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road feel
I thought someone would mention this. It comes back to the purpose of driving. Is it to get safely and reliably from A to B? If so, a little road feel may help the driver be aware of poor surfaces so he can drive accordingly. If the driving itself is the purpose of driving, then lots of road feel may enhance the experience. However, this is then using the vehicle not as a mode of transport but as apparatus for an experience - an expensive, dangerous type of fairground ride? Motoring magazines and journalists seem to prefer the latter, and pour scorn on those who simply want to travel. Audio is not much different!
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Old 30th December 2010, 11:27 AM   #46
SY is offline SY  United States
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Correct Path: Diodes Or Rectifier Tube?
Quote:
Originally Posted by DF96 View Post
To the extent that you can hear the PSU, there is something wrong with the PSU and/or the amplifier.
Or even more often, grounding schemes!
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Old 30th December 2010, 12:17 PM   #47
analog_sa is offline analog_sa  Europe
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Quote:
Originally Posted by Jen-B View Post
[COLOR=black][FONT=Verdana]Facts such as a rock solid power supply is more suitable for accurate amplification than a flimsy supply which allows you to “hear” the rectifier!

IME no amount of regulation seems to be able to hide the signature of a rectifier. Probably because regulators don't regulate so well in the MHz region. Passive filtering may be more successful but requires extreme attention and nice measurement equipment. Oversimplifications as seen in your post are just dandy for mid-fi but really out of place for more serious audio. The suggested stacking of Shottky diodes in order to achieve higher PIV is plain humorous.
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Old 30th December 2010, 12:32 PM   #48
DF96 is offline DF96  England
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It is fortunate then that most of us don't hear too well "in the MHz region"!

I realise that intermodulation allows us to 'hear' things which our ears can't detect. This emphasises the importance of individual amplifier stages being reasonably linear, as stray RF does not necessarily take the same path through the circuit as our intended audio signals.
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Old 30th December 2010, 12:41 PM   #49
bobrown14 is offline bobrown14  United States
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This is an interesting thread.

I'm not sure why no one mentioned ripple and which method is best used to reduce this from the power supply output. After all isn't that where the noise would be coming from, be it tube rectified or SS??

Two paths to the same goal here. Good clean harmonic free DC output.

Tube rectified power supplies use filter caps, resistors and a choke to eliminate/reduce ripple, where as solid state power supplies use filter caps, bridge rectifier (diodes), resistors and voltage regulators.

If you can hear anything from the power supply, wouldn't that be RIPPLE frequency in the form of 2nd, 3rd etc. order harmonics? As an example: if you had ripple in a TV power supply you could see it in the form of wavy picture..

So to summarize my thought here, since the goal is good clean DC output from an AC line, proper use and design of either SS or tubed PSU should both "sound" the same and that would be a transparent sound. If the listener can hear differences, wouldn't that be and indicator the design needs to be looked at further, be it SS OR tube designed?

I'm talking AUDIO here not guitar gear, I know that some guitar players like sag etc from the amp to give it a specific sound.

Cheers,

Bob
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Old 30th December 2010, 01:27 PM   #50
DF96 is offline DF96  England
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Ripple is not the whole story, although until that is right it is not worth getting too excited about second-order effects.

Rectifier switching can induce interference into adjacent circuits, especially when people wire their PSU as though it only handled DC. If the underneath of your amp looks very tidy, with straight wires and right angle corners, then it is likely to have huge loops sending and receiving interference. With normal SS rectifiers your PSU is handling RF (due to charge storage) so it should be wired like an RF circuit. This is less of a problem with better SS or valve rectifiers but there will still be fast transients.
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