carlosfm said:[snip]BTW I think that, as always, the cap must be NEAR the component (in this case the regulator).
If that's not practical, at least a small 0.1uf near the regulator.
Carlos,
You are right that the cap needs to be near the component. But we are not trying to decouple the regulator, we are trying to decouple the amplifier circuit. Therefore, logically, you want the cap as close as possible to the amp circuit.
If that is too far away, you may need an additional cap near the regulator to keep it stable, but that is secondary.
Jan Didden
i thought i can´t be wrong placing a small cap (200-300nF) and a larger (100-200uF near to regulator, small on direct to regulator pin, one pair at input and one at output, and one small + one larger cap at the amp/IC i want to supply with power. I did everything this way until now. Microcontrollers, audio ICs, DACs ....)
No, of course it isn't wrong. But the focus must be on whatever you are powering. If in addition you want to surround the reg with caps, sure. But it would not be the best solution if one would put the cap(s) closest to the reg, with the circuit to be powered a few inches away. If you want to do both, great.
Jan Didden
Jan Didden
Hmmm. Don't think there will be a problem. At the reg side, ringing *should* be adequately damped by the low Zout//cap. That cap should not have too little ESR to keep the thing, well, uhh, damped.
At the load side, you have the other cap. I think the ringing etc would come from improper termination, like end of the line left dangling. Both ends with caps would be OK, but you would want a couple of parallel caps to have good decoupling over a wide freq range.
Jan Didden
At the load side, you have the other cap. I think the ringing etc would come from improper termination, like end of the line left dangling. Both ends with caps would be OK, but you would want a couple of parallel caps to have good decoupling over a wide freq range.
Jan Didden
Yes, I suppose the lead inductance is perhaps often low
enough too, not to cause too much problems? Probably
this will depend a lot of the particular application too.
I just thought this was one of these cases where the obvious
answer is very obvious and simple, but at second thought
it isn't obvious if the answer is obvious. "Of course it is best
to have caps at both ends!! But wait, is it really so...?"
enough too, not to cause too much problems? Probably
this will depend a lot of the particular application too.
I just thought this was one of these cases where the obvious
answer is very obvious and simple, but at second thought
it isn't obvious if the answer is obvious. "Of course it is best
to have caps at both ends!! But wait, is it really so...?"
janneman said:
Jan, I meant that.
There must be a cap near the regulator.
But of course you don't take out the cap from the other chip just to put it closer to the reg.
Calm down, I was not generalizing on the engineers.
It's that I reminded of one I know, a friend of mine.
He was making an active crossover for his speakers.
He showed me once I went to his house.
His idea was to measure his speakers, because he was very worried something coud be wrong.
I said let's hear it.
The sound was not to my taste, he showed me the schematic and I said: change this 12k resistor for an 11k.
He did it, we listened again and
high end. He was impressed by my guess.
We couldn't stop listening to music.
But 30 minutes later we was talking again of measuring the speakers and making some changes to the crossovers.
Is this normal?
Hi,
Christer,
Well, if the decoupling is done right after the reg (which is what you'd want to decouple in the first place) I don't see where any stray inductance is going to come from?
Iso an electrolytic cap you may want to try a 1/10 smaller solid tantalum cap, these should have sufficent ESR to cause no oscillation from the reg.
As Jan said, the bigger chunk of the capacitance should be close to the circuit proper, not the reg.
That's where you could try out high quality (Low ESR) caps such as metalised film.
Cheers,
Christer,
Well, if the decoupling is done right after the reg (which is what you'd want to decouple in the first place) I don't see where any stray inductance is going to come from?
Iso an electrolytic cap you may want to try a 1/10 smaller solid tantalum cap, these should have sufficent ESR to cause no oscillation from the reg.
As Jan said, the bigger chunk of the capacitance should be close to the circuit proper, not the reg.
That's where you could try out high quality (Low ESR) caps such as metalised film.
Cheers,
Hey guys, I just wanted to report that removinig the caps from my regulated PSU actually improved the sound, not start WWIII
For the record, my preamp supply consists of transformer, bridge rectifier, smoothing caps and first stage of 317/337 regulation in one box which is connected to the amp with about a metre of cable.
In the amp is the second stage of regulation also using 317/337 regulators. There are 0.1 uF polypropylene caps on all the regs.
This works well but I put in the extra 220 uF caps after reading that they would decrease noise from the regulators. In fact the opposite was the case although I admit that the caps were some old cheapies that I just had lying around.
For the record, my preamp supply consists of transformer, bridge rectifier, smoothing caps and first stage of 317/337 regulation in one box which is connected to the amp with about a metre of cable.
In the amp is the second stage of regulation also using 317/337 regulators. There are 0.1 uF polypropylene caps on all the regs.
This works well but I put in the extra 220 uF caps after reading that they would decrease noise from the regulators. In fact the opposite was the case although I admit that the caps were some old cheapies that I just had lying around.
fdegrove said:
I was probably thinking wrong. I didn't write down any
equations or anything. The idea was that if we have one
cap at each end we could have an energy flowing forth and
back between these caps. Maybe the inductance would
rather work as a damper in this case?? Never mind. The
main point was, I guess, that one should question also
the simplest and most obvious things once in a while, to
see if they are simple and obvious.
Nuuk said:Hey guys, I just wanted to report that removinig the caps from my regulated PSU actually improved the sound, not start WWIII
Just wait till the electrolytics start exploding.
carlosfm said:
Jan, I meant that.
There must be a cap near the regulator.
But of course you don't take out the cap from the other chip just to put it closer to the reg.
Calm down, I was not generalizing on the engineers.
It's that I reminded of one I know, a friend of mine.
He was making an active crossover for his speakers.
He showed me once I went to his house.
His idea was to measure his speakers, because he was very worried something coud be wrong.
I said let's hear it.
The sound was not to my taste, he showed me the schematic and I said: change this 12k resistor for an 11k.
He did it, we listened again and
He was impressed by my guess.
We couldn't stop listening to music.
But 30 minutes later we was talking again of measuring the speakers and making some changes to the crossovers.
Is this normal?
Carlos,
I'm impressed. You're way above anyone of us.
Jan Didden
janneman said:
Joking?
You don't know the circuit I was talking about, so why comment?
Just op-amps, nothing special.
If you listened to that I thing and with the circuit at hand you would probably give the same suggestion.
You understand my words as you like, I was joking but at the same time telling a real situation.
A madness that some people have to measure everything.
I'm not above anyone, I think that YOU think you are.
I don't want a fight with anybody, I take this as a hobby and you're a professional.
Either way we all learn here, including me, including YOU.
I hope you have the honesty to admit this.
Yes, even the genious have always something to learn.
Otherwise they wouldn't come here loose their time.
No.
No way.
Maby because english is not my native language I may sometimes be misunderstood, but who knows me a little better will understand I don't ever claim that.
When I'm absolutely sure I say it, but when I'm not, I may make a suggestion.
I made a suggestion to Nuuk and this degenerated in some guys making jokes, but they DON'T EVER GIVE THE ANSWER.
It's like saying that it doesn't work, and don't say how it should be done.
Some people here would be good in politics.
No way.
Maby because english is not my native language I may sometimes be misunderstood, but who knows me a little better will understand I don't ever claim that.
When I'm absolutely sure I say it, but when I'm not, I may make a suggestion.
I made a suggestion to Nuuk and this degenerated in some guys making jokes, but they DON'T EVER GIVE THE ANSWER.
It's like saying that it doesn't work, and don't say how it should be done.
Some people here would be good in politics.
carlosfm said:
Joking?
You don't know the circuit I was talking about, so why comment?
Just op-amps, nothing special.
If you listened to that I thing and with the circuit at hand you would probably give the same suggestion.
You understand my words as you like, I was joking but at the same time telling a real situation.
A madness that some people have to measure everything.
I'm not above anyone, I think that YOU think you are.
I don't want a fight with anybody, I take this as a hobby and you're a professional.
Either way we all learn here, including me, including YOU.
I hope you have the honesty to admit this.
Yes, even the genious have always something to learn.
Otherwise they wouldn't come here loose their time.
Carlos,
Be reasonable. You look into a piece of equipment, you just say: change this from 12k to 11k and the circuit transforms from bad to hi-end. That IS impressive. I'm not a professional engineer, I wish I had your abilities. So, what's your problem? I mean, this WAS a true story, no?
Jan Didden
Carlos,
The reason I made the joke in the first place was that I
thought you were trying to be funny. I understand that
your recommendation was serious, but the way you
expressed it sounded to me as if you intended it to
sound amusing at the same time. One can be both
serious and joking at the same time.
Making small changes to component values and see what
happen can be reasonable if you have a fair idea of how
the circuit works. Any major change should be done only
after analysing the technical consequences of changing
the component. To take an extreme example, you can't
try a single op amp instead of a dual one (without
changing the PCB). Even for simple things you need to
check details. If you make a resistor smaller, will it need
to be able to handle more power? If you change it either
way, how does it affect the working conditions of other
components?
When I was some 14-15 years old, I tried to understand
how amplifiers work. I read a lot of books, but I still didn't
have the necessary understanding of math and physics to
understand it. I eventually decided to try the empirical way
of figuring out resistor values, using pots for all resistors.
I learnt two things from this experiment:
1) How to convert a TO92 BJT into one diode and the novel
one-pin collector device.
2) The empirical way of understanding the basics of amplifier
design doesn't work.
The reason I made the joke in the first place was that I
thought you were trying to be funny. I understand that
your recommendation was serious, but the way you
expressed it sounded to me as if you intended it to
sound amusing at the same time. One can be both
serious and joking at the same time.
Making small changes to component values and see what
happen can be reasonable if you have a fair idea of how
the circuit works. Any major change should be done only
after analysing the technical consequences of changing
the component. To take an extreme example, you can't
try a single op amp instead of a dual one (without
changing the PCB). Even for simple things you need to
check details. If you make a resistor smaller, will it need
to be able to handle more power? If you change it either
way, how does it affect the working conditions of other
components?
When I was some 14-15 years old, I tried to understand
how amplifiers work. I read a lot of books, but I still didn't
have the necessary understanding of math and physics to
understand it. I eventually decided to try the empirical way
of figuring out resistor values, using pots for all resistors.
I learnt two things from this experiment:
1) How to convert a TO92 BJT into one diode and the novel
one-pin collector device.
2) The empirical way of understanding the basics of amplifier
design doesn't work.
janneman said:
Ok Jan, I said you don't know the circuit, why comment?
But you insist, I'll tell you.
The speakers are the crappy Kef Q7 (yes, you heard me well, CRAPPY).
The tweeter is the weak point on these speakers (uni-Q new generation metallic (titanium?) dome).
The treble doesn't go high, it's just a splash.
At 20khz these tweeters are more than 6db down.
Making an active crossover and tri-amping
my friend thought it was possible to make something better out of these speakers.His schematic was not bad at all, and it worked fine.
One of the op-amps was making a slight treble lift to account for the tweeter loss in output around 14~15khz.
And it was on this op-amp that I told him to change the resistor.
Deam, a resistor and a cap across it before an inverted op-amp is a simple circuit, don't you think?
Change the resistor or the cap and you're changing the treble lift, right?
It happens that the value I suggested him was right on spot, BECAUSE the sound I was LISTENING suggested a small correction in that direction.
Clear now?
What's impressive here?
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