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 .
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.
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.
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.
Not reading them at all is an even bigger mistake, but I see your point, ALW.
Cheers,😉
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.
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.
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.
Not reading them at all is an even bigger mistake, but I see your point, ALW.
Cheers,😉
Sy
I quote: -
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
I quote: -
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
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.
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.
Who are you? Where am I
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
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
Attachments
Oh no they don't
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.
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.
Would Zout be the right answer ?? BTW this is my first post. Please dont bury me if that isnt right 🙂
I will say though that the AC performance is critical.
Can I say that again - AC performance is critical.
Chris
Can I say that again - AC performance is critical.
Chris
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.
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 😉
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 😉
Sy
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.
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.
fdegrove said:
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.
fdegrove said:
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?
fdegrove said:
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.
Re: Oh no they don't
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
ALW said:
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
Hi,
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,😉
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,😉
Help needed
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
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
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.
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.
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