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Old 30th January 2004, 06:53 AM   #31
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Yep.....If TEK and others have to use the bicuit tin concept for general screening ....Now one knows what one is in for !! to get it right.

I'm no prophet of doom using SMPS....I can recommend it and it's brill't when designed right for the appl.

Viva PFC !

rich
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Old 30th January 2004, 10:03 AM   #32
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/me raises his hand in anxious interest of our new switching overlords.
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Old 30th January 2004, 01:18 PM   #33
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there have been some complaints in ham circles about switchers -- first of course -- the noise

more importantly, one guy reported that the instantaneous current demands for CW transmission place a great challenge on the feedback loop.
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Old 30th January 2004, 06:58 PM   #34
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Default SMPS DIY

Just pointing out another thread on this same topic:

http://www.diyaudio.com/forums/showt...101#post252101

By the way, the "CUK" (pronounced shuk) SMPS converter does not produce output ripple, unlike other SMPS converters. Still have to pay attention to radiated and conducted noise shielding though. More complicated to design however, not well known even by most SMPS designers. A couple of books are (or were) available on the design: "Advances in Switched Mode Power Conversion" Vol. I,II & Vol. III. 1983 published by TESLAco (Pasadena Ca. 213-795-1699) 534 pages/353 pages. They even discuss the "CUK" class D amplifier too.
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Old 30th January 2004, 09:38 PM   #35
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Yes, hams may complain of excess noise in radio amplifier circuits using an SMPS but is it relevant in audio amplifier design? (I don't know I am just asking). Remember they are trying to do different things with their tubes. I understand they use high voltage tubes to amplify very high frequency signals thus their 'noise' may be a completely different thing and irrelevant to the audio frequency. I would more readily accept the fact that SMPS were noisy and relevant to us audiofiles if someone could directly that efi, rfi, ripple, or other noise produced by an SMPS directly influenced the reproduction and amplification of the audio signal in the actual set and that it had nothing to do with radio transmission or reception.
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Old 30th January 2004, 10:10 PM   #36
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orangedog...As a SMSP designer I can well understand why US Rad Hams complain about SMPS noise.......my answer to that is simple: ....the bull in a china shop approach.....When did SMPS designers in the US ever care about electronic /mag emission and standards ? I've seen SMPS in the US without input filter circuits, a legacy from the past. Now that's changed but there's alot of old stuff still about.

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Old 30th January 2004, 10:18 PM   #37
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Quote:
Originally posted by orangedog
Yes, hams may complain of excess noise in radio amplifier circuits using an SMPS but is it relevant in audio amplifier design? (I don't know I am just asking). Remember they are trying to do different things with their tubes. I understand they use high voltage tubes to amplify very high frequency signals thus their 'noise' may be a completely different thing and irrelevant to the audio frequency. I would more readily accept the fact that SMPS were noisy and relevant to us audiofiles if someone could directly that efi, rfi, ripple, or other noise produced by an SMPS directly influenced the reproduction and amplification of the audio signal in the actual set and that it had nothing to do with radio transmission or reception.
Just think of all the modulation byproducts.

There is a real "brouhaha" emerging in the US over BPL -- internet over the power lines -- even the emergency services and military are getting upset with the FCC over this -- it only takes a couple microvolts of spurious emission to wreak havoc with radio communications.
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Old 30th January 2004, 11:22 PM   #38
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Hi there.....designing hard and soft switching SMPS without moddy problems to ajacent equipment is a tough situation to confront.. There is a catch....it does require a massive amount of R&D prototyping especially in Telecoms apps........Thing is.......

< not all SMPS designs are noisy.....> far from it- however as someone else mentioned >peak current designs are often the worse, true, discontinuous mode operation isn't liked by compliance houses as it's the worst for capacitively charge injection into chassis and will radiate down power cables etc.
There are remedies, it may take many attempts to get a commercial SMPS design right. With a tube amp (anyone who has done this before) can get a design up and running first time, or nearly. Simplification has advantages......

As for switching noise in power amps using SMPS technology....the situation is tougher than one makes it out to be......loudspeaker leads and input cables are like long antenna......they will emit commonmode crap and harmonics present in a chassis. Understandably many are against ferrite ring cores for suppression with the view of signal distortion.
e.g Take the metal lid off a CD player and put an FM tuner in the vicinity. (okay thats software noise, but it's just as broadband with signals that have fast rise and fall times.).......and one has the worst of all worlds....the radio has an antenna........see what I mean!

Getting to grips with beastly SMPS problems is an experienced business...radio and SMPS are similiar......the biscuit tin does work with double sided PCD approach......If one is doing design ideas, don't throw away those old equipment chassis which have ceramic feed throughs.........they are worth every bit.

Viva PFC......
rich
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Old 31st January 2004, 12:53 PM   #39
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Quote:
Originally posted by richwalters

As for switching noise in power amps using SMPS technology....the situation is tougher than one makes it out to be......loudspeaker leads and input cables are like long antenna......they will emit commonmode crap and harmonics present in a chassis. Understandably many are against ferrite ring cores for suppression with the view of signal distortion.
But, if your overall goal does not require maximization of efficiency you can work around the problems.

Two of the most perplexing noise sources for ham radio operators are loose electrical connections and cheap Chinese handheld telephones. I don't know what it's like in Helvetia, but here in the U.S. you can take the public utilities to the FCC over power line interference. (but we digress).
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