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-   -   Final doubt on CarlosFM like PSUs ("light" or "complex v3")? (http://www.diyaudio.com/forums/chip-amps/229528-final-doubt-carlosfm-like-psus-light-complex-v3.html)

tent 7th February 2013 10:08 AM

Final doubt on CarlosFM like PSUs ("light" or "complex v3")?
 
Hello,
after too many readings about Chipamp PSU implementation examples I'v come to one fundamental question that still seems unclear to me, that probably is very subjective but that still would like to hear opinions of listeners that compared them.
There are different CarlosFM PSU like implementations like for example a "light" version like the interpretation of BrianGT
http://i29.servimg.com/u/f29/13/29/14/73/lm388610.gif
and the v3 von Carlos itself
http://i29.servimg.com/u/f29/13/29/14/73/cfm_ch10.png
rather complex and that even uses a resistor on the line (R4 1ohm@10w), probably like an inductance more than else...
And the question is indeed if some of you tested some of those and could explain sonic differences he felt.

Thanks,
tent:wq

blu_glo 8th February 2013 08:46 AM

So we have a power supply with a static series reistance of 2 ohms within the rails. This will do wonders for your output power figure into 4 ohms speakers (NOT). At least 1 of these will be dissipating 1/4 of your available output power per cycle, as well as slowing down the charging of your reservoir capacitors ultimately leading to more power loss through droopy rails. Can someone please show me the advantage I'm so obviously missing?

tent 8th February 2013 09:01 AM

I mean I also have always seen lots of discussions about this two opposite philosophies: a) trying to reduce resistance and inductance as much as possible, as well as b) introducing resistances and inductances claiming it will perfectly fit that specific chip/amp/application.. and I also always have found those discussions weird from logical PoV.. so I was now trying to go the pragmatic route and try to evaluate only with experience by listening or by collecting other users' listening/testing opinions.. so like if all is more subjective or application dependant than "logic" dependant.. anyway who know what is wrong? ;)

tent:wq

wintermute 8th February 2013 09:04 AM

1R does seem a little excessive, I'm not really sure what the normal current draw of a chip amp is I know my LM3886 only uses around 11W at idle... Lets say it is 3A when running fairly hard. if so then you will be dropping 3V across that resistor. so if you had a 30V supply it would drop to 27V when pushed (just from the resistor without taking into consideration any other contributors to voltage sag).

The reason for putting the resistor in is to reduce the ripple on the supply, but typical power amp PSU's I have seen have 1/2 ohm or less for the R. preamp PSU's are a different story.

At the time of the release of this PSU there was a lot of controversy, and I think that was in large part of the reason for CarlosFM departing here. The controversy was more around the snubber part of the circuit and the claims being made as to it's effect on the sound.

The general thinking at the time was that large amounts of capacitance in the PSU had a negative effect on the sound of the chipamp. Low capacitance PS's were the in thing. But Carlos claimed that this "snubberising" allowed you to use lots of capacitance in the PSU without the degredation in sound quality.

As is often the case here, people wanted theory and proof to back up the claims and the whole thing spiraled out of control.

I hope that this time around that this is not the result. (and if it is the thread will not last long).

Tony.

tent 8th February 2013 09:14 AM

Hi Tony,
absolutely: what my intention is, would be to keep it on the experience side more than on the "theory" or "proof" side.
First of all to my ears and my tests, I definitely and of course subjectively, perceive it as an improvement to have bigger capacitance, but snubberized, in the PSU (esp. if compared to smaller capacitance.. that has also negative effect on noise/ripple for me). Additionally the snubber is of mandatory importance to be (also?) present at the very close end where the amp PSU imputs are (V+ and V-).
But not wanting to discuss that.
Wanted to discuss if further improvements suggested that time by Carlos with those resistances in series and those further added caps would mage a difference in your HEARING tests..
For instance it could benefit the noise floor but be a hindrance in rapid music passages? <- real question then...

tent:wq

blu_glo 8th February 2013 11:42 AM

I think the first schematic (without the 0.1uF/ 1R "snubber") is perfectly adequate and has everything going for it. Double up the the reservoir uF for 4 ohms ann leave it at that. And if you must put snubber in, put it across the AC input of the bridge rectifier where it *might* help with switching ringing of the diodes (although to date, with such heavy electrolytic filtering already going on, I've never seen the necessity...).

BTW - why not rig it up and try it? You're welcome to prove ME wrong!

JMFahey 8th February 2013 12:17 PM

There's no way a puny 100nF , even less a microscopic 1.5nF , and with a series resistor to boot, can have *any* measurable or audible effect on an amp which at the same time is being fed from multiple 10000uF caps.
Seems like worrying about what a mosquito would do to an Airplane Carrier or Freight Train by moving its wings one way or another.
Gimme' a break !!!

tent 8th February 2013 01:18 PM

JMFahey, so you think no help even in preventing ripple noise and similar?
And what your opinion about R3/4 resistors for instance?
Even if in the end I agree with blu_glo: I'd try to setup some PSU made with "crocodiles" and test it out myself.. ;)

tent:wq

blu_glo 8th February 2013 01:41 PM

Quote:

Originally Posted by tent (Post 3361050)
JMFahey, so you think no help even in preventing ripple noise and similar?
And what your opinion about R3/4 resistors for instance?
Even if in the end I agree with blu_glo: I'd try to setup some PSU made with "crocodiles" and test it out myself.. ;)

tent:wq

Give it a go, but we all seem to be agreed - we don't expect you to hear any real difference at all.... :spin:

tinitus 8th February 2013 01:54 PM

I never thought much of bypass film caps in ordinary power supply
or the snubbers for that matter
people can use them if they want
I don't care about it at all

but lately Keantoken drew my attention to their use in connection with small regulators that can be sensitive to low impedances
might be the use of snubbers makes more sense there


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