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Old 13th September 2012, 12:38 AM   #1101
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I concur with AndrewT on acceptable voltage drop range.
We should firstly filter noise off a basic power supply to reduce voltage fluctuations from HF noise/nuisance charge. And, with decent filtering (filters on transformer primary, secondary and diodes) the voltage fluctuations are reduced to fit his 1v to 5v range.

Noise is a weak current source that charges caps extraneously higher until load pulls down the extra, and thus noise IS the primary cause of extraneous voltage fluctuations. So, first we filter that. Later, after filtering off HF noise, we can consider series filters, such as CRC. I've constrained my CRC to 1.4v drop (at most), and the results still fit within AndrewT's guidelines.

P.S.
There are possible exceptions:
It is possible that a Class D power amplifier has insufficient idle load to pull down noise/nuisance charge, and in this case the voltage fluctuation could be a bit higher (so of course one should filter harder--no free lunch). Unrealistic non-music testing conditions applied to audio amplifiers (inapplicable test), over-current management (retail current dumper), undersize transformer (bad design), and diodes that list a more aggressive voltage drop at current in the datasheet graphs (abused rectifier) are other possible causes of discrepancy that may exceed the 1v-5v range. As you can see, most of what looks like exceptions is really just noise. Meanwhile, back to filtering off the noise.
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Last edited by danielwritesbac; 13th September 2012 at 12:45 AM.
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Old 13th September 2012, 12:59 AM   #1102
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you should look at the Pioneer SPEC2 amp psu, standby rails of 91 volts drops to 75volts at full power.....these are actual measured data....not something imagined.....

link.....Pioneer Spec-2 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
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Old 13th September 2012, 01:58 AM   #1103
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Quote:
Originally Posted by Tony View Post
you should look at the Pioneer SPEC2 amp psu, standby rails of 91 volts drops to 75volts at full power.....these are actual measured data....not something imagined..... link.....Pioneer Spec-2 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
Long thin cable from transformer to board and other creative current management (current dumpers) is standard for most retail builds. It is extra cheap protection. Necessarily, decreased return/defect and lower cost is very important for retail mass market amplifiers. The disadvantage is that mass market style current dump protection makes a given transformer act like a bit smaller transformer.
Suggestion: build your own hi-fi instead.
Alternative suggestion: it should be possible to alter a current dumper retail supply into a CRC supply without losing protection--just relocate the loss, more usefully, into the CRC resistors; however, this guess needs double-checked for safety. And I would also use the Fairchild Stealth 1200v diodes to make a bridge rectifier with an attractive little bit more current dumping protection. Anyway, I think we can do better than a retail current dumper cable. But doing better means the costs are not suitable for mass production--and that is something to remember when you are shopping retail audio.
EDIT:
Also a 250 watt per channel (total 500w) amplifier can be expected to have a larger voltage drop.
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Old 13th September 2012, 04:23 AM   #1104
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what's with the 1 to 5 volt drop anyway? how was it arrived at?

i know that the same amp circuit using different sizes power transformers will have different voltage sags.....

for full power sine wave testing, for as long as the power transformer can deliver required voltage and currents at the same time, then that should be a valid design....i have been building power transformers longer than amplifiers, since 1970, i think i have something to say...

maybe the more knowledgeable members here can investigate further....

Quote:
Also a 250 watt per channel (total 500w) amplifier can be expected to have a larger voltage drop.
to make this amp drop rails in the 1 to 5 volt range i estimate that i need to build a transformer at least 3x as heavy as what i have in my super leach amp....
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Old 13th September 2012, 06:53 AM   #1105
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I believe that the 1 to 5 volt drop is "average home amplifiers" and not referring to big PA amplifiers. And I guess that the 1 to 5 volt drop is using excellent filtering (snubbing the transformer primary, secondary and rectifier) to minimize HF nuisance charge voltage fluctuation. It just seems to be a quality control check.
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Old 13th September 2012, 07:01 AM   #1106
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my big amp is not a PA amp....it is a hifi amp.....i used it at my home set-up years ago....
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Old 13th September 2012, 02:09 PM   #1107
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Tony,
I understand what you are saying when you say that your amplifier is not a PA amplifier. The discussion has been generally revolving around amplifiers of lower output in the 50 to 100 watt range and like you I feel that in some applications this is not realistic. With high efficiency loudspeakers then those power levels are fine, but with low efficiency speakers of say 84 to 86db per watt output then you are looking at much more power to drive them to any kind of high level of output. I think that we can all agree that with low efficiency speakers you will be doubling up the power output for each 3db of increase in sound level at a fast clip. But at the same time I think that the conclusions drawn from the lower powered amps should still follow the same rules and you will have to scale the application to your power requirements. The filtering and smoothing of the transformer will not change and the component layouts will still follow the same pattern, just much more current and or voltage will be needed to get there.

Steven
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Old 13th September 2012, 04:40 PM   #1108
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Quote:
Originally Posted by Nico Ras View Post
My point from the outset, mains related ripple is one issue that manifests itself as hum, signal related ripple masks low intensity detail without knowing it. It does not show up measuring the amplifier output or using FFT, it is only detectable by ear if you know what a good amp sounds like.

This afternoon I fooled with two extremes, 80 000uF per rail capacitors versus a single 4700 uF per rail. Now here is were I get shot down. Bass is better with the big caps but on the other hand the small cap allows me to hear so much more music.
Very interesting thread, I've only read the first 15 pages so far in one seating, will need to do more later after work.

Now, my question is.

What is the reason behind the sound being more "musical?" with smaller caps vs bigger caps? Shouldn't the sound be the same with the big caps, vs the smaller ones not being able to handle the demands for lower end?

thanks!
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Old 13th September 2012, 06:09 PM   #1109
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if we put instrument's in subjective position, i think is end of the world.
Instrument measure it very well,maybe...not ear.
I agree that this thread contain many good info and good job of gotee,as others have post formulas,idea, etc. but i feel that at end, with new measures (with real instrument's) and comparition, we return at begin of questions.
We all know that multi small caps are better, instead one big. this is old (but can not reduce drop voltage at 1-5V). (or i not have indagate well..
Is my opinion that: 50-100w without crossover in loudspeaker, can work well with good job on psu.
----------------------------
With 200w and crossover (this mean peak 750w) medium level at home. please, if someone have (as me) mosfet amp 200w8R and 3 way B&W or other loudspeaker, measure it while listen a good Jazz.
Obviously I do not want to listen to all musical instruments, soft, with the dynamics far from the reality.
in a few days, I'll put the measures, and the photo of psu + module mosfet amp.
we can use as the comparative with others.
...while I wait to see the measure on psu 1-5V

regards
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Old 13th September 2012, 11:26 PM   #1110
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Quote:
Originally Posted by Jean View Post
Very interesting thread, I've only read the first 15 pages so far in one seating, will need to do more later after work.

Now, my question is.

What is the reason behind the sound being more "musical?" with smaller caps vs bigger caps? Shouldn't the sound be the same with the big caps, vs the smaller ones not being able to handle the demands for lower end?

thanks!
not NICO, but i believe there is no explanation that can satisfy everyone....Nico's opinion is true for himself only....YMMV...
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