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Old 19th July 2012, 06:30 PM   #51
tsiros is offline tsiros  Greece
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Quote:
Originally Posted by OnAudio View Post
something close to D.C.
don't want to sound like an ***hole, but: DC doesn't mean "constant voltage/current". Even after the rectifier it is DC. As long as it doesn't change direction, it still is DC.
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Old 19th July 2012, 06:31 PM   #52
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by tsiros View Post
yeah the capacitors themselves will cost at least twice as much as the IC
I think you made a wise choice because I read a lot of people found the quality of caps in the psu to be very important.
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Old 19th July 2012, 06:31 PM   #53
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by Ian Finch View Post
Andrew posted (about a month ago) that he was taking an extended holiday. Just how extended we don't know but best wishes to him.
Thanks for that Ian.
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Old 19th July 2012, 06:34 PM   #54
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Default improved capacitor technology

There are very interesting caps now available
Click the image to open in full size.

B41456B8109M EPCOS Inc | 495-4224-ND | DigiKey
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Old 19th July 2012, 06:50 PM   #55
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Quote:
Originally Posted by OnAudio View Post
TThese capacitors are sweet as they respond fast enough in the high frequency region to buffer the interconnecting cables. Thus What the amplifier sees is a stable DC supply.
Okay Harrison, everyone describes that the power supply should produce good DC over a wide frequency range, but what affects your choice of value capacitor, it is surely not just an arbitrary number. Mind you I have seen comments on the forum like and I have xx 0000 uf caps..... results in solid bass, surely it is not just trail and error and you stop adding caps when you either run out of space or money.

Question is what made you choose these values why 33uF not 47uF or 10 uF. I would accept if you say from experience 33 uF sounds better than 47uF or if you have some formula (excuse the pun ) to calculate a specific value for a specific purpose, or a rule of thumb that has some historical significance.

So far we have a few mathematical representations and several arbitrary choices of values, then we have some including myself that feel distributed power should be used and others that disagrees - we still do not have widely accepted set of rules that confidently indicates that the amplifier/power supply combination lives up to expectations?
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Old 19th July 2012, 07:08 PM   #56
gootee is offline gootee  United States
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Quote:
Originally Posted by OnAudio View Post
Attached is an example of a power supply
Click the image to open in full size.
The 10NF capacitor ensures that some high frequency noise is cleaned up. The rectifier exibits good high frequency behaviour (it isnt switched by the remaining high frequency noise) because the large 10,000uF shouldnt have low impedance at those frequencies. Thus we have a well behaved supply giving us something close to D.C.

Something close to D.C. will not mind interconnecting cables and will safely charge the on board 33uF capacitors. These capacitors are sweet as they respond fast enough in the high frequency region to buffer the interconnecting cables. Thus What the amplifier sees is a stable DC supply.
It will depend on the amplifier being supplied, but...

There will not be constant current from the power supply. So the supply and ground conductors will have voltages induced across their parasitic inductances and resistances, by the time-varying currents. The only question is how much.

The 33uF is quite small. With a smaller decoupling capacitor like that, the rail voltage needs to drop more in order to cause any given increase in demanded current to be supplied by the cap. Also, if a demanded increase in current is too large for the cap to supply, the circuit will attempt to pull more of the current through the power rail conductor, which will likely have significantly more impedance than the cap, causing an even larger disturbance in the power rail voltage. Whether or not any of that will be significant depends on your application.

This setup might be OK (and more like you have desribed it) for a low-power amplifier that is for high frequencies only.

Otherwise, it should perform better with more attention given to implementing lower-inductance rail conductors (shorter, or multi-parallel) and more and/or larger-value caps in parallel at the load. It would also be improved by using multiple parallel caps in place of each 10k uF cap.
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Old 19th July 2012, 07:16 PM   #57
gootee is offline gootee  United States
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Quote:
Originally Posted by Nico Ras View Post
Okay Harrison, everyone describes that the power supply should produce good DC over a wide frequency range, but what affects your choice of value capacitor, it is surely not just an arbitrary number. Mind you I have seen comments on the forum like and I have xx 0000 uf caps..... results in solid bass, surely it is not just trail and error and you stop adding caps when you either run out of space or money.

Question is what made you choose these values why 33uF not 47uF or 10 uF. I would accept if you say from experience 33 uF sounds better than 47uF or if you have some formula (excuse the pun ) to calculate a specific value for a specific purpose, or a rule of thumb that has some historical significance.

So far we have a few mathematical representations and several arbitrary choices of values, then we have some including myself that feel distributed power should be used and others that disagrees - we still do not have widely accepted set of rules that confidently indicates that the amplifier/power supply combination lives up to expectations?
Determination of the minimum capacitance value needed at the point of load, and the maximum inductance in the cap and its connections to the load, are done using well-known methods. Well, they are well-known to the high-speed digital guys, anyway (see Henry W. Ott and Bruce Archambeault, for example). See the links I posted earlier, for the specific method(s).
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Old 19th July 2012, 07:48 PM   #58
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Default Minimum cap size

Here we go
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Old 19th July 2012, 08:05 PM   #59
djk is offline djk
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NVMOS amplifier
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Old 19th July 2012, 08:17 PM   #60
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Default wattage has nothing to do with capacitor bank

Heres why
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