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-   -   plain Big caps on psu vs. carlosfm style Snubber (http://www.diyaudio.com/forums/chip-amps/128704-plain-big-caps-psu-vs-carlosfm-style-snubber.html)

shiraz 25th August 2008 10:56 PM

plain Big caps on psu vs. carlosfm style Snubber
 
What's the difference in sound between just having big smoothing caps (10,000 uf) after the rectifier, as opposed to a "full-fledged" carlosfm style snubberized psu?

P.S.:
If big caps are implemented in the psu, should the caps next to the chip be smaller (than say 1500 uf)? Why? :confused:

eeka chu 25th August 2008 11:14 PM

The only references I could find to clarlosfm snubberised psu's were just what appeared to be normal psu's with snubbers, so I'll assume that's what you mean.

Big caps are designed to deliver longer durations of power when the system demands it. Because of their physical size, they also usually have higher impedances and so lower current delivering capacity - limiting their use for removing or supplying power at higher frequencies. That's significant enough that most analog DIY'ers will say they can hear that difference even at audio frequencies. But chips that feature digital processing will place a requirement on the capacitor to supply power at frequencies many, many times higher.

Luckily, each ripples of power they must supply is small in size, just rapidly repeating. So a faster, smaller capacitance value component will work better.

The problem with smaller capacitance value, high speed caps is that putting them at the output of your PSU and then running tracks and cables to the IC's will create a capacitor / inductor circuit. This usually isn't a serious problem with big caps because they have more impedance. But the small value ones can create ringing oscillations with the inductance.

For that reason, board engineers will always bypass as IC's as close as possible to the pins of the chip - sometimes with the capacitors virtually on the pins. Adding some resistance to the tiny capacitors increases the time constant of the capacitor and so it's ability to form parasitic, resonant circuits with the boards, leads, pins etc of nearby components.

Essentially, the ultimate power supply is one that connects directly to the processing elements it supplies - with zero inductance / resistance between the two.

lanchile07 26th August 2008 01:17 AM

shiraz,I used to use 4.7uf/10uf caps.but, I was "experimenting"
and I started trying different values with alligator clips that way I can compare the sound with different caps fast and easily.
I noticed the big difference With the 10,000uf per rail, I got stronger,tighter bass.Just try different values with alligator clips that way you do not have to solder and desoldering caps to test them.(make sure to discharge the caps,specially the big ones before touching them).and after this test if you do not like the sound with the big caps....just put the usual 4,7uf or 10uf caps.
in my case and test! ...I like the sound with 10,000uf per rail better.

shiraz 26th August 2008 09:10 PM

eeka chu: thanks for the explanation. That was very informative. So the placement of the caps of different sizes has got a lot to do with the chip getting the power it needs, when it needs it, while still balancing the tradeoffs of small caps vs big caps. So if you're always going to be running at low volumes, doesn't all this become relatively less important? I mean then it should be enough just to have a couple of relatively small caps near the chip.

lanchile07: I think I'll try to do some experiments then. Are you using standard 10.000uf caps or Panasonic TS? Does it make a difference? I haven't been able to find any Panasonic caps where I live.

lanchile07 27th August 2008 03:01 AM

Well,I am using Black gate 1,000uf 50v x 2 on each "chip board" and on the power supply I am using Elna lp5 10,000uf 63v per rail. I am also using .01uf 400v 5% radial caps on each diode (8) to eliminate some impurity...(These 0.01uF, "103") caps subtract rectifier noise, which reduces heat and radio interference).so far I am happy with the result. I try many caps and capacitance 4,7uf,10uf,220uf,1,000uf,1,200uf,1,200 x 2x4x6 but at the end I liked the sound with "ONE" 10,000uf per rail ,I also try 10,000uf x 2x4...I am keeping this much capacitance(10,000uf per rail) on the power supply!.as I said before...Just give it a try and if you do not like the sound with "juicy" power supply...put the usual 4,7uf/10uf.

PS: let me know if you like the sound with more capacitance (I do).
:smash:

shiraz 27th August 2008 08:15 AM

Thanks, this is very helpful.

The caps on the diodes, are they just cheap ceramic caps?

The 10.000 uf caps, have you got them in a snubber network (with smaller caps and resistors in parallel with the big cap), or did you just put them there alone?

lanchile07 27th August 2008 03:29 PM

Shiraz, I am using .01 uF 400V 5% .4" LS Radial Film Capacitors .you can fin them in many places.try e-bay here http://cgi.ebay.com/01uF-01-uF-400V-...QQcmdZViewItem
and for the resistor (bleeder) I am not using them.they are for discharging the caps.maybe in the future I will put them but,for now I do not see the need to put them.
Make sure if you use big caps to be careful no to touch these "charged" caps,They can give you a real big punch.when you do the "test" you should be in a quiet room (no noise of any kind) and trust your ears no matter what.Get a CD that you know well , do not put attention to the words but to the tones....the lows,mid.highs, The bass should be strong and tight,the mid should be clear and effortless,the highs should be crispy but not fatiguing. You can trust your oscilloscope and instruments to test them but, the final and most important instrument that you have to test the sound is your ears. Trust your ears!.
good luck.:smash:

lanchile07 27th August 2008 04:35 PM

Before I forget! To achieve your goal ,you will need good speakers too. it is pointless to have a good amp and crappy speakers or viceversa.I am not an expert in this matters but,I can "still" hear well ( "listen" if it is music and "hear" if it is my wife lol) .
:D

Ed LaFontaine 27th August 2008 04:43 PM

Calculating Optimum Snubbers:

http://www.hagtech.com/pdf/snubber.pdf

shiraz 28th August 2008 02:21 AM

My speakers are ok but my biggest problem right now is that I just moved into a new appartment, and there's almost no furniture, so obviously there's a lot of reverberation in my living room which makes listening tests really difficult.

I'm using Peter Daniels' lm4780 boards (configured for stereo operation instead of dual mono). So from 1 set I'm getting 2 amps. The first one I've made with the included components. Appart from the weak bass, I think it sounds really good. I'm going to make the second one with big caps, and I've decided to start with that I'll just follow peters recommendations (http://audiosector.com/lm4780%20psu.pdf). With 2 amps, 1 with subberized psu and 1 without, I'm excited whether I'll be able to hear the difference.

Once I get the living room furnished I'm going to try different configurations with zobel, caps on the diodes, 3*4700uf in parallel per rail and small caps on the chip.


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