Joseph K said:
Hi George,
Indeed, it is not really a tone control, I said that tongue-in-cheek, I thought that was clear. But it CAN be used to modify the speaker tonal balance.
What I meant on the ripple modulation (I think that is what you refer to) is related to large output levels. If you indeed have up to 10V ripple, with large output signals, the output level varies with the actual supply voltage which varies in a 100Hz (or 120Hz for those 115V mains voltage challenged countries
) rithm. That is plain signal modulation, aka as an AM signal. Just the frequencies are different from a standard AM radio station. Put a lf detector and headphone on the amp output and you can listen to the ripple! But you know all that.In another thread people worried about minuscule AM modulation resulting from PIM and TIM conversion. It seemed that it really ruined their enjoyment of music. Here you got many percentage points, maybe even tens of it, AM modulation depth, and people like it! Someone above, I think it was analog_sa, coined the term "audio virgins". Its a good term, although it probably wasn't what he meant.
Jan Didden
To Joseph K:
Joseph, I have just read your posts on this on the previous pages. Good posts. What I see in the graphs is that what you call "slowness" of the cap is of course a slow variation of the charging current pulses. It is wrong to relate that to "slowness" in sound reproduction. In the limiting case, if you would have a perfectly regulated DC power supply, this is infinitely slow, there is NO variation of the voltage on the cap. But surely an amp with such supply isn't "infinitely slow" or being able only to reproduce DC!
I maintain that the "slower" in this respect a power supply is, the better. Amplifiers are designed with the implicit assumption that the supply is DC, it is almost always also acting as a ground point for the signal. Any ripple or signal residue on the supply line messes up the signal fidelity to some degree. It may be a little in competently designed amps, but it is there.
Jan Didden
Joseph, I have just read your posts on this on the previous pages. Good posts. What I see in the graphs is that what you call "slowness" of the cap is of course a slow variation of the charging current pulses. It is wrong to relate that to "slowness" in sound reproduction. In the limiting case, if you would have a perfectly regulated DC power supply, this is infinitely slow, there is NO variation of the voltage on the cap. But surely an amp with such supply isn't "infinitely slow" or being able only to reproduce DC!
I maintain that the "slower" in this respect a power supply is, the better. Amplifiers are designed with the implicit assumption that the supply is DC, it is almost always also acting as a ground point for the signal. Any ripple or signal residue on the supply line messes up the signal fidelity to some degree. It may be a little in competently designed amps, but it is there.
Jan Didden
Upupa Epops said:P - A, it is about psychology ( in this case ). Man tends to take newest things as better, 'cos they are not still in his brain " wearing out "
This just shows total ignorance.
The "snubber" is used on audio amplifiers for some 35~40 years.
I just picked it up, tested it and optimized it for power op-amps, or chipamps if you like.
Because I knew it could be the answer to the problem of the high(er) inductance of the bigger caps.
Why would I be biased to listen for ghosts just because I wanted it to work?
Belive me, if it didn't work I would forget it and I would not even have opened the thread and reported it.
But you tend to call everyone stupid, as a dictator calls his own people stupid.
You are THE voice, you are THE reason, you know it all, you are GOD.
Amen.
PS: while you fail to understand that the PSU is also part of the signal, that everything is on the signal path, you fail to make a decent amp.
You blindly believe that the best you can do with a chip is what they say on the datasheet.
Carlos, I'm so tired by your snubber. You are permanent claiming, that for good sound is this circuit mandatory, my meaning is different. Let your opinion and I let mine. All is crazy stupidity and I can't talk about this, good amp make something quite different. I'm not God, I know, that I know nothing, but don't make my teacher, it's funny for me.
Upupa Epops said:
I don't need to talk about it, everyone talks, specially those who tried it.
And notice: I'm not selling or trying to sell anything.
Upupa Epops said:
You still don't understand what's this thing about, so yes, for you it may be stupidity.
Anyway, besides this, what I don't like to see is your way of posting:
Upupa Epops said:P - A, it is about psychology ( in this case ). Man tends to take newest things as better, 'cos they are not still in his brain " wearing out "
You can all see that without opening my mouth this guy posts like this.
You keep ridicularizing and calling psychos to those who TRIED and claim improvements, when you don't even have the guts to try it.
And if you do, you will not be honest enough to admit improvements.
It's just too late for you.
snubberizing
Oh, and PS:
Those who understand it, encourage it's use.
Like here, check Phred's last paragraphs, before the links:
http://www.diyhifi.org/forums/viewtopic.php?p=3780#3780
Quote, Fred Dieckmann:
"Oh yeah........ before I forget, gratuitous snubberizing is welcome and encouraged, but not three weeks discussion about it."
He's just a PSU man...
Oh, and PS:
Those who understand it, encourage it's use.
Like here, check Phred's last paragraphs, before the links:
http://www.diyhifi.org/forums/viewtopic.php?p=3780#3780
Quote, Fred Dieckmann:
"Oh yeah........ before I forget, gratuitous snubberizing is welcome and encouraged, but not three weeks discussion about it."
He's just a PSU man...
Last night decided to double the 1000uF caps and the result was more solid base. The presentation though became somehow unclear. I thought the base was too much and masked the rest of the spectrum.
So I decided to try the "controversial snubbers" and to be honest I approached the modification with a dose of skepticism. Hey what if... I had my first lesson when I decided to change the opamp in my CD player. I didn't believe that it may sound different/better (I am an EE and we are talking 20kHz after all). Well, most of you who tried it know the answer.
The setup:
NITGC,
2x1000uF/rail/channel at the chip (lm3875),
(I don't need to go to more than 2000uF/rail/channel. There is plenty of base and loudness)
No 100n bypass caps on the rails.
One PS for both channels with a single bridge rectifier (600V/40A and 220VA CT transformer).
Snubbers 100n/1R.
I installed the snubbers as close as possible to the chip.
There is definitely a big improvement in the HF spectrum. The easiest way to explain it is to say that it removed a layer of HF grain. It makes the highs polished and more defined, more sparkly.
The improvement is quite obvious and not at all subtle.
It makes the whole picture more defined. It's like looking through a clean window rather than a foggy one.
For testing I used mainly Destiny's Child/Survivor. A lot is happening on that track. It tests the capability of the audio system quite well.
Mind you my ears are not the most sensitive. I really admire people that can catch some small differences in the sound. I think it takes a lot of time of listening to music to develop that kind of sensitivity.
So, the snubbers are staying for good. Thanks, Carlos! I'm a happier man now.
I didn't try just a 100n bypass cap instead the snubbers, but that'll be another day. May have a positive effect too. I don't know yet.
/Greg
So I decided to try the "controversial snubbers" and to be honest I approached the modification with a dose of skepticism. Hey what if... I had my first lesson when I decided to change the opamp in my CD player. I didn't believe that it may sound different/better (I am an EE and we are talking 20kHz after all). Well, most of you who tried it know the answer.
The setup:
NITGC,
2x1000uF/rail/channel at the chip (lm3875),
(I don't need to go to more than 2000uF/rail/channel. There is plenty of base and loudness)
No 100n bypass caps on the rails.
One PS for both channels with a single bridge rectifier (600V/40A and 220VA CT transformer).
Snubbers 100n/1R.
I installed the snubbers as close as possible to the chip.
There is definitely a big improvement in the HF spectrum. The easiest way to explain it is to say that it removed a layer of HF grain. It makes the highs polished and more defined, more sparkly.
The improvement is quite obvious and not at all subtle.
It makes the whole picture more defined. It's like looking through a clean window rather than a foggy one.
For testing I used mainly Destiny's Child/Survivor. A lot is happening on that track. It tests the capability of the audio system quite well.
Mind you my ears are not the most sensitive. I really admire people that can catch some small differences in the sound. I think it takes a lot of time of listening to music to develop that kind of sensitivity.
So, the snubbers are staying for good. Thanks, Carlos! I'm a happier man now.
I didn't try just a 100n bypass cap instead the snubbers, but that'll be another day. May have a positive effect too. I don't know yet.
/Greg
I don't see how you can get better high-end response from smaller capacitors (or that large capacitors have "worse" trebble). I do understand that undersized filter capacitors can hurt you in the bass region and a power supply input for the chip that is jumping around would make the op-amp's feedback network do some serious work to maintain the output. I can also see how the chip can maintain decent sound quality even with a very poorly regulated power supply (untill the rails sag dangerously close to the output) due to the action of negative feedback.
I think that for the maximum sound quality, the power supply should be as stiff as possible at all frequencies. I have typically used large main reservoir capacitors (several 1000's of uF, such as 4700 or more per rail), mounted whever makes the most sense in the mechanical layout. These are supported by capacitors of a few 100's of uF mounted on the same board as thr chip(s), as close to the chips(s) as possible, perhaps one set per chip in a stereo or bridged unit that shares the power supply. And finally I would bypass the rails with a 0.1 uF capacitor RIGHT AT THE CHIP. these capacitors (I've used both ceramic and the green "chicklet" film capacitors) should be mounted as close to the chip as practically possible. Either right in front of the chip in a PCB layout, or perhaps under the board, hanging off of the chip's pins in a DIY protoboard layout. Sometimes I'd also use a small capacitor at the chip between the positive and negative supply rails. I always make sure to bypass my chips at the chip with a .1 capacitor or so, since I have had some bad experiences (with a PICmicro and some op-amps) by leaving it out.
The only bownside to a large capacitor (besides size/cost and inrush current) would be that a single large capacitor might have a somewhat higher internal resistance and inductance (taken care of by the smaller board mounted capacitor). Annother solution to this problem would be to use several smaller capacitors. For example 3 2200 uF units in parallel rather than one 6800 uF cap.
I think that for the maximum sound quality, the power supply should be as stiff as possible at all frequencies. I have typically used large main reservoir capacitors (several 1000's of uF, such as 4700 or more per rail), mounted whever makes the most sense in the mechanical layout. These are supported by capacitors of a few 100's of uF mounted on the same board as thr chip(s), as close to the chips(s) as possible, perhaps one set per chip in a stereo or bridged unit that shares the power supply. And finally I would bypass the rails with a 0.1 uF capacitor RIGHT AT THE CHIP. these capacitors (I've used both ceramic and the green "chicklet" film capacitors) should be mounted as close to the chip as practically possible. Either right in front of the chip in a PCB layout, or perhaps under the board, hanging off of the chip's pins in a DIY protoboard layout. Sometimes I'd also use a small capacitor at the chip between the positive and negative supply rails. I always make sure to bypass my chips at the chip with a .1 capacitor or so, since I have had some bad experiences (with a PICmicro and some op-amps) by leaving it out.
The only bownside to a large capacitor (besides size/cost and inrush current) would be that a single large capacitor might have a somewhat higher internal resistance and inductance (taken care of by the smaller board mounted capacitor). Annother solution to this problem would be to use several smaller capacitors. For example 3 2200 uF units in parallel rather than one 6800 uF cap.
Note that I'm not arguing how much good the snubber does just what it does electrically.carlosfm said:
We agree, no matter what Pavel says.
The resonance peaks are much attenuated by the snubbers, and the bypass caps serve, as you should know, to provide a low impedance path to ground at high frequencies.
The resonace peak is dampend at the left part of the PS but, Carlos, what do you say about the local decoupling very closely to the supply pin where you have an additional 100 uF// 100nF? There you must have some resonance too and what about it? Isn't that resonance even more important?
My point is that you have two resonance peaks but treat only one of them which has the least influence and the most important peak is untreated.
P - A, how is value ( amplitude ) of this oscilations ? 10 mV ? 100 mV ? 1 V ? What is ratio of this amplitude related to DC ? 1 % ? Or less ? How is theoretical mechanism of penetration to signal path ? And PSRR ? In every my amps I'm using bypasing rail to ground, but also rail to rail - these oscilations have theoretical oposite phase, will they in this case by bypasing shorted ? Etc... - many questions are here, but any answer, only with postcoital smile declared claims. 
The peak is reallly, really small..... and not to many dB either 3-6 dB! in the lower MHz region.
I'm trying to sell in that the first and only snubber doesn't do much good at the supply pins, still the effect is big or even huge!
My "product" here is to snubberize also the supply pins. How much this peak has any real influence, I have no idea becasue I can't detect it and I don't want to hear any degrading remarks about that over at "the other" forum, please.
I'm trying to sell in that the first and only snubber doesn't do much good at the supply pins, still the effect is big or even huge!
My "product" here is to snubberize also the supply pins. How much this peak has any real influence, I have no idea becasue I can't detect it and I don't want to hear any degrading remarks about that over at "the other" forum, please.
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