| Good supply for preamp, Comments? - Click HERE for Original Thread |
| Algar_emi |
I'm about to begin my new Classe Preamp Clone and I want your comments on my Power Supply. This is what can probably be called an overkill supply, but I got most of the parts in stock. Let me know want you think and how can I improve it further.
I will post two parts of the gif picture (before and after the regulator). The complete pdf file will also be posted.
Thanks in advance... |
|
|
| Algar_emi |
| Here the "after the regulator" gif file |
|
|
| Algar_emi |
| Complete Schematic in pdf |
|
|
| analog_sa |
No, it is not an overkill at all. PS transformer rating is way too low to qualify as an overkill. Caps following the regulators are really excessive. 317/337 provide some kind of minimal acceptable sound quality in general, but it really matters what exactly are they going to power in this case (sorry, unfamiliar with Classe circuits). There are many fast opamp- pass transistor based circuits on this forum, which will beat a 317 unconcious. There are also interesting shunt regulators. If you do some search you'll find a wealth of regulator info here. Just curious: why a Classe clone?
cheers
peter |
|
|
| Peter Daniel |
It simply seems overkill from the amount of parts used, when comparing for instance to a simple supply used in Pass preamps: http://www.passlabs.com/pdf/aleph/apserv17.pdf
Getting really good regulation doesn't necessarily have to produce good sound. Some people already commented that a simple pass trsnsistor provides for very good sonics.
I would imagine that the best ways to figure out the merits of a supply is to built few of them and check with a circuit how it sounds. Then you can add additional stages of filtering and bypassing. |
|
|
| analog_sa |
| quote: | | Getting really good regulation doesn't necessarily have to produce good sound |
Very possibly. But a set of 317/337, although ubiquitous in commercial amps sound positively 'grey' and dynamically challenged. |
|
|
| thylantyr |
Does Nelson Pass get credit for the pass transistor concept ?
;) :bigeyes: :clown: |
|
|
| millwood |
I am not familar with the Classe preamp as well. I assume that it draws minimual current just like an ordinary preamp (see 100ma?).
a few observations:
1) the R1/R2 (100ohm each) seem to be awefully big. With good ripple rejection of the 317/337 regulators, you probably don't need them.
2) if I have to, I would put big caps after the LM, not before.
3) I think overall the circuitry is complicated (too complicated?). |
|
|
| analog_sa |
| quote: | | 2) if I have to, I would put big caps after the LM, not before. |
And why exactly? Even the datasheet doesn't endorse that. |
|
|
| millwood |
| quote: | Originally posted by analog_sa
And why exactly? Even the datasheet doesn't endorse that. |
did the datasheet recommend BG caps, gold-plated RCA, aluminum pads, or heatsinks dipped in dielectric oil?
Seriously, my thinking or guessing is that a regulated PS will have high transiant internal resistance (it cannot output a lot of current for a very brief period of time). Having a large "resevoir" after the regulator will help cure that. |
|
|
| SY |
| Well, normally, preamps don't require sudden current draws. But the caps are often useful for noise reasons. |
|
|
| fdegrove |
Hi,
| quote: | | But the caps are often useful for noise reasons. |
Exactly.
And for most of their life the regulators won't have to regulate either.
It's wrong to look at this as a regulated supply, it is not.
The entire topology is exactly what I used in the PSU of one of my preamps, the juices come straight from the caps and the regs can be viewed as trickle chargers providing good isolation from the mains by the same token.
You'll often see tube amp tricks implemented in Classe designs.
At least I often spot them...
Cheers,;) |
|
|
| millwood |
both designs are foundamentally flawed as it has more capacitance after the regulators, something even the datasheet does not endorese.
:)
I don't know how much current a pre-amp draws (less than 100ma I guess?) but it cannot be too much. In that case, wouldn't it just be easier and cleaner to use unregulated one going through an R/C low-pass filter (with big caps)? |
|
|
| SY |
| millwood: As a practical matter, for class A preamps, a simple RC will work just fine. It's not as cool as active regulation, though. I look at it much the same way that Frank does. |
|
|
| Mad_K |
| quote: | Originally posted by millwood
both designs are foundamentally flawed as it has more capacitance after the regulators, something even the datasheet does not endorese.
:)
|
which datasheet? |
|
|
| fdegrove |
Hi,
The LM317T.
Not that it matters in this context, it doesn't.
Cheers,;) |
|
|
| Mad_K |
| quote: | Originally posted by fdegrove
Hi,
The LM317T.
Not that it matters in this context, it doesn't.
Cheers,;) |
Where are the LM317's in the TNT-designs:confused: |
|
|
| fdegrove |
Hi,
| quote: | | Where are the LM317's in the TNT-designs |
Haven't looked.
I was reffering to the Classe PSU...
Sorry if I confused you,;) |
|
|
| Mad_K |
| You're not so confusing as millwood... First he says: put more caps after the reg, then the tnt designs are flawed because of this? and still millwood; which datasheet (ref. tnt-psu's)? |
|
|
| millwood |
| quote: | Originally posted by Mad_K
You're not so confusing as millwood... First he says: put more caps after the reg, then the tnt designs are flawed because of this? and still millwood; which datasheet (ref. tnt-psu's)? |
Sorry, Mad_K. I was joking about the comment analog_sa made with regards to that the datasheet does not endorse the recommendation I made to move more caps after the regulator.
I agree with the TNT design. |
|
|
| Mad_K |
| OK, then I'm alright again:) |
|
|
| fdegrove |
Hi,
| quote: | | Sorry, Mad_K. I was joking about the comment analog_sa made with regards to that the datasheet does not endorse the recommendation I made to move more caps after the regulator. |
Well, you shouldn't for Analog_sa is right and, no joking here, so is the datasheet.
If you exceed the maximum allowed capacitance after the regulator it won't regulate anymore...it just can't because the caps become the dominant source of energy, not the reg., see?
The danger zone lies somewhere inbetween, as I'm sure you realise.
Cheers,;) |
|
|
| millwood |
On "the datesheet doesn't even endorse it" thing, I just checked LM317 datasheet on national's site.
The cap (0.1u) before the regulator is needed if the regulator is more than 6-inch away from the filter cap.
the caps after the regulator are optional - they "improves transient response. Output capacitors in the range of 1uf to 1000uf of aluminum or tantalum electrolytic are commonly used to provide improved output impedance and rejection of transients."
FYI. |
|
|
| fdegrove |
Hi,
| quote: | | the caps after the regulator are optional - they "improves transient response. Output capacitors in the range of 1uf to 1000uf of aluminum or tantalum electrolytic are commonly used to provide improved output impedance and rejection of transients." |
And which one would have the faster transient response?
The 1µF cap or the 1000µF one in this situation?
All else being kept equal of course.
Cheers,;) |
|
|
| millwood |
| quote: | Originally posted by fdegrove
Hi,
And which one would have the faster transient response?
The 1µF cap or the 1000µF one in this situation?
All else being kept equal of course.
Cheers,;) |
wouldn't they have the same transient response (if all else is truly kept equal) for small current drains and the larger one will have better transient response for heavier current drains.
That is my final answer, :) |
|
|
| fdegrove |
Hi,
| quote: | | wouldn't they have the same transient response (if all else is truly kept equal) for small current drains and the larger one will have better transient response for heavier current drains. |
Making your answer conditional doesn't help....sorry but you didn't pass.
Cheers,;) |
|
|
| SY |
| It's worthwhile to look at Bob Pease's wonderful little book. There's a nice analysis of capacitor effects on three-pin adjustable regulators. |
|
|
| Fred Dieckmann |
HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA HA.....
I haven't seen this much nonsense, bluffing, and utter confusion since Grey R. was posting.... I was going to make some comments but I wouldn't dream of breaking up the shear entertainment! I may have to dig out my Three Stooges DVD just to get back to something slightly coherent. I can hardly wait for AWL to see this thread.
"There's battle lines being drawn
Nobody's right if everybody's wrong
Young people speaking their minds
Getting so much resistance from behind*
I think it's time we stop, hey, what's that sound
Everybody look what's going down"
*and capacitance from in front and behind... |
|
|
| SY |
Well, set me straight, Fred. You know I enjoy cogent criticism; I'm just unclear about exactly what you're criticizing.
Woo-woo-woo! Spread out! Pick two! |
|
|
| fdegrove |
Hi,
| quote: | | Well, set me straight, Fred. You know I enjoy cogent criticism; I'm just unclear about exactly what you're criticizing. |
Dig out that good old 128 bit decryption engine... we're going to need it.
Cheers,;) |
|
|
| Peter Daniel |
| We're just lucky we have an Engineer in a house, who will set things straight. |
|
|
| millwood |
| quote: | Originally posted by fdegrove
Hi,
Making your answer conditional doesn't help....sorry but you didn't pass.
Cheers,;) |
Not exactly very helpful. Care to elaborate so the less fortunate and the mentally challenged like myself can at least start to comprehend, :) |
|
|
| fdegrove |
Hi,
| quote: | | Not exactly very helpful. |
Crystal clear to most of us.
| quote: | | Care to elaborate so the less fortunate and the mentally challenged like myself can at least start to comprehend, |
I'm starting to feel sorry for you already...
Yank another chain please,:( |
|
|
| millwood |
| quote: | Originally posted by fdegrove
Hi,
Crystal clear to most of us.
I'm starting to feel sorry for you already...
Yank another chain please,:( |
What a waste of my time, :)
BTW, how did you think for the rest of the forum visitors? |
|
|
| fdegrove |
Hi,
| quote: | | BTW, how did you think for the rest of the forum visitors? |
That's the part that got it already,;) |
|
|
| SY |
| Frank, Millwood: C'mon, guys, this isn't useful. Say what you mean (technically, that is) if I may borrow someone else's sig. It could be quite enlightening. |
|
|
| millwood |
| quote: | Originally posted by SY
Frank, Millwood: C'mon, guys, this isn't useful. Say what you mean (technically, that is) if I may borrow someone else's sig. It could be quite enlightening. |
I should I asked a technical question and I got a non-answer. Oh well, no big deal. |
|
|
| fdegrove |
Hi,
| quote: | | I should I asked a technical question and I got a non-answer. |
A non-answer?
Don't think so.
How hard can it be to read a few datasheets on regs. and imagine real life situations as you read?
Milwood, if you stopped digging yourself into opposition, people might be more inclined to 'splain a little more.
So far you've been nothing more than a nasty wirewound corkscrew, how do you expect that is going to help you?
Cheers,;) |
|
|
| millwood |
| quote: | Originally posted by fdegrove
Hi,
A non-answer?
Don't think so.
How hard can it be to read a few datasheets on regs. and imagine real life situations as you read?
Milwood, if you stopped digging yourself into opposition, people might be more inclined to 'splain a little more.
So far you've been nothing more than a nasty wirewound corkscrew, how do you expect that is going to help you?
Cheers,;) |
fdegrove , I will not lower myself to your level.
I am fine with your inability to explain. and I don't expect you to be able to do that anyway. Good night. |
|
|
| fdegrove |
Hi,| quote: | | I am fine with your inability to explain. and I don't expect you to be able to do that anyway. |
Unable to explain? I explained this already anyway.
Maybe people shouldn't expect others to be able to read anymore either?
Buena notte a te bambino,;) |
|
|
| SY |
| Frank, I've read data sheets, I've read the app notes, I've read Bob Pease and Erroll Dietz's stuff, and I've built quite a few units using 117-family regulators. And I'm still mystified about what you're trying to get at. |
|
|
| Algar_emi |
Thanks for your comments everyones. Following some of your advices I found very intersting reading on the Jung Super Reg and the proper connections for the LM 317 (Kelvin Sensing), Thanks ALW.
Following Peter advice I will probably build two or three different supplies and compare their sounds, if difference there is.
First I need to build the Preamp channel to figure out its real power consumption, then we will see..
Thanks again everyones.
Bye. |
|
|
| Peter Daniel |
| quote: | Originally posted by Algar_emi
Following Peter advice I will probably build two or three different supplies and compare their sounds, if difference there is.
|
I would be quite interested in your findings, as I'm looking for a good preamp supply as well. Did you consider batteries? |
|
|
| millwood |
| quote: | Originally posted by SY
Frank, I've read data sheets, I've read the app notes, I've read Bob Pease and Erroll Dietz's stuff, and I've built quite a few units using 117-family regulators. And I'm still mystified about what you're trying to get at. |
I think I kind of see his point. But the fact that he didn't point out the usefulness of paralleling multiple caps in this design makes me believe that he is really not there.
Well, I am not going to kill brain cells trying to figure out what he knows or doesn't know. |
|
|
| fdegrove |
Hi,
| quote: | | I think I kind of see his point. But the fact that he didn't point out the usefulness of paralleling multiple caps in this design makes me believe that he is really not there. |
If you care to take a look at AN-1148 page 6 and following pages regarding ESR and its influence on the performance of the regulator.
AN-1148
Cheers, ;) |
|
|
| analog_sa |
I see i missed a lot of fun here. What i never realised was that the PS was also cloned from a Classe PS. Is this right? I'll have less trouble with the output caps if the 4700uF and 180uF are interchanged; the choke will then keep the 317 happy.
cheers
peter |
|
|
| millwood |
| quote: | Originally posted by tbla
first, read this......
http://128.121.162.80/other/LDOBk.pdf
and then built the superregs from jung/alw(and didden - allmost forgot)......as many as possible $$$
good luck...!
:) |
| quote: | Originally posted by fdegrove
Hi,
If you care to take a look at AN-1148 page 6 and following pages regarding ESR and its influence on the performance of the regulator.
AN-1148
Cheers, ;) |
I wish it hadn't taken you over 12 hours to come up with this answer. but better late than never, :)
So when you say everything else being equal, you didn't mean everything else, including ESR, being equal, right?
BTW, can you figure out why the original design had so many different caps in parallel? :)
Anyone? |
|
|
| Algar_emi |
Hi Peter. From what I red, the batteries have their own problem. According to ALW, the high internal resistance and noise seems to be the biggest. I will try the super reg. Bye...
SB |
|
|
| Algar_emi |
This supply is not from the Classe. It is rather a combination of few supplied from preamp considered to be good sounding, among them my own Simaudio preamp and I5 Amp. The parallel caps are to lower the ESR. I used the same combination that I found in my Simaudio I5 for before the regulator. My own Bryston .4B little preamp is using the LM317/337 and sounds quite good with my Aleph30 amplifier.
I got the little chokes from an audio equipment that I disassembled. I was curious to try these hearing so many good comments from the choke supply used in the Musical Fidelity gear.
I planned to used this supply to try not just the Classe clone but also 2-3 other preamp desings and compare the sound. But don't get to excited just yet. I will take me propably a year to go the full circle of my little experimentation. I'm not as fast as Peter :cool:
I bying most of the parts right now. Bye... |
|
|
| millwood |
| quote: | Originally posted by Algar_emi
This supply is not from the Classe. It is rather a combination of few supplied from preamp considered to be good sounding, among them my own Simaudio preamp and I5 Amp. The parallel caps are to lower the ESR. I used the same combination that I found in my Simaudio I5 for before the regulator. My own Bryston .4B little preamp is using the LM317/337 and sounds quite good with my Aleph30 amplifier. |
I am just curious about how they sound. Do they sound positively grey and dynamically challenged?
Yeah. you can lower ESR by paralleling them. But there is more to that when you parallel different caps.
| quote: | Originally posted by Algar_emi
I got the little chokes from an audio equipment that I disassembled. I was curious to try these hearing so many good comments from the choke supply used in the Musical Fidelity gear.
|
resistors do similar things than chokes in this application. Actually when I first started in electronics, all PS, regulated or unregulated, had little chokes straddling large caps to smooth out ripples. It makes a lot of sense since current through a choke cannot change suddenly. Over the years, cost cutting forced people to replace those chokes with resistors and then completely got away with the resistors at all. |
|
|
| janneman |
| quote: | Originally posted by millwood
I wish it hadn't taken you over 12 hours to come up with this answer. but better late than never, :)
So when you say everything else being equal, you didn't mean everything else, including ESR, being equal, right?
BTW, can you figure out why the original design had so many different caps in parallel? :)
Anyone? |
...to impress DIY-ers and customers?
Jan Didden |
|
|
| fdegrove |
Hi,
| quote: | | I wish it hadn't taken you over 12 hours to come up with this answer. but better late than never, |
Do you mind???
| quote: | | BTW, can you figure out why the original design had so many different caps in parallel? |
Assuming they are all of the same value and technology...
For economic reasons....and yes they lower total ESR, in theory.
| quote: | | So when you say everything else being equal, you didn't mean everything else, including ESR, being equal, right? |
The caps were the only variable, no one said anything about ESR being a constant so there you go.
Cheers,;)
P.S. I hope you slept well... |
|
|
| ALW |
:cannotbe:
Fred, let them believe what they want to believe.
Anyone who wants to use their ears can tell the truth, but I nearly wet myself with Sy's statement that an RC is fine for a class A amp :)
Might be fine for some class A amps, but definitely not for all.
Ok then guys, your starter for ten: -
What's most important in an audio PSU?
The closest answer (judged by Fred and myself) gets a free super-reg to play with, donated by me.
Any of my existing private email correspondants need not apply ;)
Andy.
P.S. don't forget you can store significant energy in a choke, it's a bit difficult in a resistor, FWIW.
P.P.S. remember most reg's have zones of stability against ESR - be very wary adding low ESR to reg's without deliberation. |
|
|
| UrSv |
| quote: | Originally posted by ALW
:cannotbe:
Fred, let them believe what they want to believe.
Anyone who wants to use their ears can tell the truth, but I nearly wet myself with Sy's statement that an RC is fine for a class A amp :)
Might be fine for some class A amps, but definitely not for all.
Ok then guys, starter for ten, what's most important in an audio PSU, closest answer (judged by Fred and myself) get's a free super-reg to play with, donated by me.
Any of my existing private email correspondants need not apply ;)
Andy. |
How could I possibly know?
I'll still try:
Regulation and regulator stability with respect to an interference/signal induced by the load from the load end for both negative and positive interference voltages. |
|
|
| ALW |
None of the stuff you'll read in data sheets, application notes or any other reference work I've seen will give you the answer.
In order to understand the answer, I strongly reccomend building a simple discrete linear reg.
Nothing exotic, but it will tell you more than any amount of fiddling with 3-terminal devices ever will, as you now have control over internal operational parameters.
UrSv, not nearly specific enough ;)
Andy. |
|
|
| millwood |
| quote: | Originally posted by janneman
...to impress DIY-ers and customers?
Jan Didden |
That could very well be reason #1, :)
| quote: | Originally posted by fdegrove
Hi,
Assuming they are all of the same value and technology...
For economic reasons....and yes they lower total ESR, in theory. |
Making your statement contingent doesn't really help, Frank. Sorry that you missed (by about a mile and half), :)
| quote: | Originally posted by fdegrove
The caps were the only variable, no one said anything about ESR being a constant so there you go.
Cheers,;) |
so if the only thing that varies is the capacitance, everything else (including ESR) should stay the same right?
Now you see how unclear your orignal question was. so before blasting others for giving your the wrong answers, you may want to look at how you present your questions first.
| quote: | Originally posted by ALW
:cannotbe:
P.P.S. remember most reg's have zones of stability against ESR - be very wary adding low ESR to reg's without deliberation. |
yeah. low ESR isn't always a good thing for regulated power supplies.
| quote: | Originally posted by ALW
None of the stuff you'll read in data sheets, application notes or any other reference work I've seen will give you the answer.
Andy. |
engineers build staff and geeks read datasheets, :) |
|
|
| Peter Daniel |
| quote: | Originally posted by ALW
Nothing exotic, but it will tell you more than any amount of fiddling with 3-terminal devices ever will, as you now have control over internal operational parameters.
UrSv, not nearly specific enough ;)
|
I remember from reading your posts that Kelvin point (or whatever it's called) was very critical. |
|
|
| ALW |
| quote: | | I remember from reading your posts that Kelvin point (or whatever it's called) was very critical |
That is important to getting the best performance / noise spec. from a given regulator, but is in no way remotely fundamental for audio.
Andy. |
|
|
| SY |
| quote: | | Sy's statement that an RC is fine for a class A amp |
Try to quote me accurately next time. I said no such thing. The discussion is about preamps, not amps. A well-designed Class A preamp (note the all-important three letter prefix) can be made absolutely inaudible in a bypass test using simple RC supplies- unless you've got evidence to the contrary that goes beyond assertion and anecdote . |
|
|
| fdegrove |
Hi,
Milwood,
| quote: | | so if the only thing that varies is the capacitance, everything else (including ESR) should stay the same right? |
Since ESR is an inherent characteristic of the caps and the regulator will respond to this it of utmost importance to take this into account.
In the real world a 1µF cap or a 1000µF cap will not have the same ESR.
I see ALW has pointed to the dangerzone as well.
| quote: | | yeah. low ESR isn't always a good thing for regulated power supplies. |
There you are...you do understand it after all.
This is why I pointed to the app. note from page 6 downwards in the first place.
IMHO, a well designed reg should exhibit reasonably low Z, across the audioband and beyond.
More important than lowest possible Zo is that it should not change too much with frequency.
| quote: | | None of the stuff you'll read in data sheets, application notes or any other reference work I've seen will give you the answer. |
Not reading them at all is an even bigger mistake, but I see your point, ALW.
Cheers,;) |
|
|
| ALW |
I quote: -
| quote: | | millwood: As a practical matter, for class A preamps, a simple RC will work just fine. It's not as cool as active regulation, though. |
Yes, I know we are talking preamps and that is what I meant, despite my lack of clarity. Very few class A preamps have truly constant current drain.
You didn't state (or define) 'well designed' though, hence my assertion, which I stand by.
To counteract my argument, you will need to define what's important in an audio PSU - you can win a prize ;)
Andy |
|
|
| SY |
| Actually, a quick scan of Dietz's work (it's probably on the NS site somewhere) measuring capacitor effects on noise and output inductance is EXTREMELY enlightening. Especially so when you see how these parameters vary with output current. |
|
|
| SY |
| quote: | | you will need to define what's important in an audio PSU |
That's much too general to answer. We've been around that one before. Different circuits and different applications have different requirements. Otherwise, we wouldn't need engineers. |
|
|
| Fred Dieckmann |
I really shouldn't be so flippant on the subject of audio power supply design but......
It is not a slam dunk on any particular of the design approaches. There have been many threads devoted to three terminal regulators, capacitors, high speed diodes, transformers (and how to optimize small ones if you have to use them)
There are a near infinite number permutations and approaches and one has to narrow it down to a starting point for a basic topology and start from there. There are some pretty decent possibilities and definite tweaks for three terminal regulator designs but that is obviously not to best one can do but not the worst approach either. I get frustrated at starting from square one every time someone ask a (very reasonable) question. It is like getting comfortable with understanding something and waking up from a coma to start from scratch every time someone comes along. I really wonder if a forum is even the right format for education on design, since this seems to be a regular occurrence. I will not cheat someone out of AWL's great looking design by giving away any more than the hint that this subject has been discussed to death on the forum and the Web. I am still waiting for mine as well as working on some other related designs as well. Search engine anyone?
Nyuk, Nyuk, Nyuk... Certainly,
Fred |
|
|
| ALW |
| quote: | | Different circuits and different applications have different requirements. |
One single aspect dominates sonic performance, that's the answer I need, others have an effect, but can be varied by orders of magnitude with less subjective effect.
This is for analogue supplies only, BTW.
Oh S*** I said the 'S' word, cue thread degradation into long winded and pointless discusion :)
Andy. |
|
|
| skp112233 |
| Would Zout be the right answer ?? BTW this is my first post. Please dont bury me if that isnt right :) |
|
|
| tbla |
| quote: | | What's most important in an audio PSU? |
well...:scratch: |
|
|
| chris ma |
I will say though that the AC performance is critical.
Can I say that again - AC performance is critical.
Chris |
|
|
| SY |
| quote: | | One single aspect dominates sonic performance |
You know, it's funny, I know a fellow up in Canada who is absolutely cracked on wine made from hybrid grapes (like Concord). He's a terrific guy with a good palate, a great attitude, but EVERYTHING is filtered through his passion for hybrid grapes. You can start talking about any wine or wine region in the world and he'll have something pertinent to say, but his question always is, "Is anyone making any wine there from hybrid grapes?" A wonderful monomania, since he's got a sense of humor about it and understands that other people have reached different conclusions based on their experiences. |
|
|
| ALW |
Chris,
Not bad!
But not quite specific enough for a dominant factor, but the best answer yet.
Andy.
P.S. it should also be noted that if any genuinely PSU insensitive preamp designs exist, they will have had this issue dealt with, whether the designer realised or not ;) |
|
|
| ALW |
If anyone gets the answer right, you'll have chance to find out for yourself whether my views are filtered, or not :)
FWIW, I've never seen the aspect I'm after discussed directly, w.r.t. PSU's
Andy. |
|
|
| millwood |
| quote: | Originally posted by fdegrove
Hi,
Milwood,
Since ESR is an inherent characteristic of the caps and the regulator will respond to this it of utmost importance to take this into account. |
the point was that you had presumed that your audience would agree to that in the specific context of your question. To me, 'everything else being equal" in the context of "1u cap vs. 1000u cap" truly means that other than the capacitance, everything else including ESR (and the other ES) is equal.
| quote: | Originally posted by fdegrove
In the real world a 1µF cap or a 1000µF cap will not have the same ESR. |
and in the real world, there is also no assurance that a 1000uf cap will have higher ESR than a 1uf cap. So how do you get an unqualified answer to your question?
| quote: | Originally posted by fdegrove
More important than lowest possible Zo is that it should not change too much with frequency. |
you are onto the right track to answering my question but you aren't exactly there. the focus should be on the word "different". Think a little bit harder. |
|
|
| tbla |
| ripplerejection.....:bulb: |
|
|
| janneman |
| quote: | Originally posted by ALW
One single aspect dominates sonic performance, that's the answer I need, others have an effect, but can be varied by orders of magnitude with less subjective effect.
This is for analogue supplies only, BTW.
Oh S*** I said the 'S' word, cue thread degradation into long winded and pointless discusion :)
Andy. |
Very, very good Andy! May I predict that when you give the "right" answer, you're in for quite a lot of flak. But you know that...
Jan Didden |
|
|
| fdegrove |
Hi,
| quote: | | you are onto the right track to answering my question but you aren't exactly there. the focus should be on the word "different". Think a little bit harder. |
Actually, it was not meant as an answer to a question you put.
99% of the regulators I designed so far are with tubes, some series some shunt, some simple some rather complex.
What I usually design for in a preamp PSU is total ( well as much as I can) independance from the mains supply.
To many engineers it looks like complete overkill untill they actually hear what it can do.
The only time I use a solid state reg a la LM3xx is for heater suppy regulation, both voltage and current regs.
In this application, I doubt whether pushing reg performance to the extreme would push the performance of the preamp proper further but it may well be worth investigating.
Cheers,;) |
|
|
| chris ma |
Can someone please briefly explain the transfer function of a simple circuit like a power supply here for me? Or am I barking up the wrong tree here?
Thanks,
Chris |
|
|
| skp112233 |
| Assuming a power supply is just a dc amplifier would slew rate qualify ? |
|
|
| millwood |
fdegrove, the principle works with regulated and unregulated power supply and here is my understanding (it is full of holes I am sure).
Each real capacitor is a combination of three devices, an inductor (ESL), a resistor (ESR) and an ideal capacitor (C).
Putting aside for a moment the regulated power supply case, you want to reduce ESR and ESL relative to C. One simple answer is to parallel the capacitors so the ESL of the combined capacitor array is 1/nth of each capacitor, and ESR is also 1/nth.
What that does is to flatten the impendance vs. frequency curve. But you still have a dip (at the resonnace frequency where the imaginary part of the ESL impedance equals to the imaginary part of the C impedance, and the capacitor functions just like a resistor of ESR).
But we can certainly do better than that! by paralleling different capacitors. Different capacitors will resonnate at different frequencies, and by paralleling those "impendance", you can get a flatter and lower ESR over the working frequency range: think of a ceramic cap as one that is closer to an ideal capacitor than an electrolytic. and you certainly benefit from paralleling a lower ESR cap with a higher ESR cap, just as you do with resistors of different values.
So, it is good to have multiple but smaller caps and it is better to have multiple but different caps. |
|
|
| millwood |
| quote: | Originally posted by skp112233
Assuming a power supply is just a dc amplifier would slew rate qualify ? |
actually one of the lm3xx datasheet had an amp based on a regulator.
yeah, I would think slew rate matters. |
|
|
| ALW |
| quote: | | Assuming a power supply is just a dc amplifier would slew rate qualify ? |
I doubt it in the context we're talking about here.
It would be one hell of a preamp to be able to present a load in which slew-rate becomes relevant :bigeyes:
Andy. |
|
|
| ALW |
| quote: | | Very, very good Andy! May I predict that when you give the "right" answer, you're in for quite a lot of flak. But you know that... |
Yeah, I know.
It is fun though, and it gets people thinking and since few, if any, will have considered this, it should keep people busy for a while afterwards proving me wrong.
By which time I'll have fled the country ;)
Andy. |
|
|
| ALW |
| quote: | | Would Zout be the right answer ?? BTW this is my first post. Please dont bury me if that isnt right |
I shall not bury anyone, you're not right;)
It's certainly a relevant parameter though, but fairly large variations in it though are not subjectively dominant, within the context we're discussing here (i.e. preamps, primarily class A).
Andy. |
|
|
| fdegrove |
Hi,
| quote: | | So, it is good to have multiple but smaller caps and it is better to have multiple but different caps. |
Thanks for the lecture Milwood.
That's what I meant when I said "in theory".
Unfortunately, my ears don't always agree with theory.
Cheers,;) |
|
|
| millwood |
| quote: | Originally posted by fdegrove
Unfortunately, my ears don't always agree with theory.
Cheers,;) |
I think that's more than theory. a typical opamp by-passing for example requies both a large electrolytic and a small ceramic cap; and multiple capacitors are used and located throughout motherboards for precisely the same reason. |
|
|
| fdegrove |
Hi,
| quote: | | and multiple capacitors are used and located throughout motherboards for precisely the same reason. |
My motherboard doesn't sound all that great though...:bawling:
I'll tell you once more, I'm well aware of the theory behind the mixing of the caps and I also know what different technology caps do etc.
Knowing that, I also know that it doesn't necessarily make for a
good sounding PSU.
In fact, I never apply the theory of decoupling caps to lower ESR, and if I need multiple caps on the same rail I use exactly the same value and type throughout.
According to Peter Daniels' experiments with his gainclone, a single cap of appropriate value sounds better to him.
From past experience, I'd agree with him.
Just my experience, YMMV.
Cheers,;) |
|
|
| analog_sa |
| quote: | | I think that's more than theory. a typical opamp by-passing for example requies both a large electrolytic and a small ceramic cap; and multiple capacitors are used and located throughout motherboards for precisely the same reason. |
Very true in the case of motherboards, really not applicable to quality audio. Bypassing with ceramics?! Most of the better sounding gear uses bypassing carefully; you may achieve improvement in sound but it takes a lot of effort. Using quality caps in appropriate locations is a much cleaner solution if you care about the sound. All these different resonances of multiple caps you mention can really mess up the natural timbres.
Talking of which, has anyone tried the bypassing method Audio Research uses, with a small inductor in series with the bypasing cap? |
|
|
| millwood |
| quote: | Originally posted by fdegrove
I'll tell you once more, I'm well aware of the theory behind the mixing of the caps and I also know what different technology caps do etc. |
maybe you do. But you didn't come out that way, :)
| quote: | Originally posted by fdegrove
In fact, I never apply the theory of decoupling caps to lower ESR, and if I need multiple caps on the same rail I use exactly the same value and type throughout. |
maybe if you follow the theory next time, your amp will sound better. If you don't try, how do you know that it doesn't work for you, right? |
|
|
| Fred Dieckmann |
"I think that's more than theory. a typical opamp by-passing for example requies both a large electrolytic and a small ceramic cap; and multiple capacitors are used and located throughout motherboards for precisely the same reason."
I think you might find dozens of people who disagree with that and have built and sold products in contradiction to this. I avoid ceramic caps whenever possible as they usually sound nasty. Indiscriminate use of multiple caps leads to resonant behavior that can result in resonant frequencies at undesirable frequencies. The use of very low ESR electrolytics in the 10uF to 1000uF range for op amps in the 30MHz and under GBW is becoming very common. If you are going to HF bypass, I like 0.1 uF metalized polypropylenes. I often see people use things like 0.01 uF foil and film caps which can sound pretty bad.
Every cap and combination of caps will have a (several for more than one cap) resonant frequency and where that resonance lies can be critical in both analog and digital design. Don't take my word for it.
http://www.sigcon.com/pubsIndex.htm#bypass capacitors |
|
|
| Peter Daniel |
Recently I tried to bypass a cap in a tweeter network with silver mica cap, as someone mentioned it some time ago as an easy way to improve the sound of a speaker. I couldn't believe the sound it made. I quickly removed silver mica cap and will never try it again;)
I also don't think that millwood is really qualified to discuss sonic issues of PS, as he doesn't even believe that resistors sound differently. |
|
|
| millwood |
| quote: | Originally posted by Fred Dieckmann
I think you might find dozens of people who disagree with that and have built and sold products in contradiction to this. |
and if we judge a product on the basis that someone is selling them, we would all be drinking snake oil by now, :)
| quote: | Originally posted by Fred Dieckmann
I avoid ceramic caps whenever possible as they usually sound nasty. |
they may indeed sound nasty to you. But I just haven't seen any statistically significant study on their sonic characteristics.
| quote: | Originally posted by Fred Dieckmann
Indiscriminate use of multiple caps leads to resonant behavior that can result in resonant frequencies at undesirable frequencies. |
indiscriminate of anything, no matter how good they are, will result in bad things. Isn't that the definition of "indiscriminate"? |
|
|
| millwood |
| quote: | Originally posted by Peter Daniel
I also don't think that millwood is really qualified to discuss sonic issues of PS, as he doesn't even believe that resistors sound differently. |
Peter, first of all, I am not sure if I am talking about sonic issues of PS. 2ndly, I fail to see the link between resistor sound and by-passing caps. Enlighten me please? |
|
|
| fdegrove |
Hi,
| quote: | | If you don't try, how do you know that it doesn't work for you, right? |
Maybe it's because I tried already ages ago already.
| quote: | | Talking of which, has anyone tried the bypassing method Audio Research uses, with a small inductor in series with the bypasing cap? |
Never tried it. I assume they choose the L carefully with repect to C?
Worth a try, I reckon.
| quote: | | Recently I tried to bypass a cap in a tweeter network with silver mica cap |
Although on its' own a siver mica of good quality is said to be amongst the best sounding caps around.
They're often used in RIAA correction ccts.
Ceramics and tantalum caps on the other hand should stay well away from audio circuitry unless you know exactly what you need them for.
Cheers,;) |
|
|
| Fred Dieckmann |
"Talking of which, has anyone tried the bypassing method Audio Research uses, with a small inductor in series with the bypasing cap?"
For moving the resonance I suppose? Changing the value of the decoupling cap might be an easier way to achieve this.
can you tell us the source of this information?
I have been looking at a small resistance in series for one cap in multiple cap applications. |
|
|
| ALW |
| quote: | | Although on its' own a siver mica of good quality is said to be amongst the best sounding caps around. |
Whilst mica is a pretty good dielectric, having low DA and low loss at HF, for audio use I would prefer polystyrene, polypropylene or polyphenyl sulphide, where HF performance wasn't critical.
Judicious application could be beneficial in certain areas though.
Andy. |
|
|
| Peter Daniel |
| quote: | Originally posted by millwood
Peter, first of all, I am not sure if I am talking about sonic issues of PS. 2ndly, I fail to see the link between resistor sound and by-passing caps. Enlighten me please? |
This was my impression. If we are talking about PS for audio applications, I assume that sonic performance would be actually the dirving force behind any PS design. If not, I don't know what this thread is all about indeed.
The link between resistors sound and bypassing caps looks simple to me. For someone who treats resistors as electrical parts only, without any consideration for possible sonic aspect, will talk about bypassing caps in a similar way, from measurements POV, concentrating on best measured performance but without any regard as to sonic aspect again. |
|
|
| millwood |
| quote: | Originally posted by Peter Daniel
Recently I tried to bypass a cap in a tweeter network with silver mica cap, as someone mentioned it some time ago as an easy way to improve the sound of a speaker. I couldn't believe the sound it made. I quickly removed silver mica cap and will never try it again;) |
that should give you enough reservation about those sonic tweaks floating around the net. |
|
|
| analog_sa |
Fred, Frank, anyone else not auditioning ceramic caps in motherboards
Somewhere in the back of my memory i recall Audio Research had a patent for something remotely sounding like 'distributed PS decoupling". Looking at the PS of a PH3 one sees a 470uF in series with a parallel combo of a 2.7uH and 54R9. The resistor is presumably to damp the inductor and the result is a predictable impedance behaviour (rising) at high frequencies. All this is bypassed with a 2,0uF and 0.01uF. Seems like a reasonable way to achieve bypassing and at the same time decrease the sonic signature of the electrolytic at HF.
cheers
peter |
|
|
| Peter Daniel |
| quote: | Originally posted by millwood
that should give you enough reservation about those sonic tweaks floating around the net. |
This makes one thing certain for me, I will try everything myself, before incorporating it in a circuit. From what I see both on a forum and in general, not too many people are really into trying things for themselves and doing their own R&D's. ;) |
|
|
|
|
