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Chip Amps Amplifiers based on integrated circuits

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Old 13th August 2007, 03:40 AM   #1
dezzz is offline dezzz  Denmark
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I have been wondering where the best place would be to run the long wires from an external power supply to, in my case a GainClone. I could place only the toroid in a case of its own, and then run wires to the rectifying board, or I could include the rectifying board in the external supply. What would be the pros or cons of either solution? I am currently running a snubberized version if that has any impact on result, but have plans for one regular as well, so input on both would be nice.

In case it is a bad idea to have the retifying take place to close to the amplifier chip, what is the most efficient way of shielding, and still keep things very compact, and hardwire compatible.

Hope you can put an end to my speculation.
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Old 13th August 2007, 05:48 PM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
keep the rectifier and first stage smoothing beside the transformer.

Keep the main current supply capacitors beside the amplifier.
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Old 13th August 2007, 08:39 PM   #3
scottw is offline scottw  United States
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Quote:
AndrewT wrote:
keep the rectifier and first stage smoothing beside the transformer.
That's what I did the last time I built an outboard PSU and it works fine. My thinking was that the diodes can radiate some RFI, so it keeps them further from the signal, and having mostly DC through the umbilical would be better than hum inducing AC.

Was thinking if I were to do it again would likely put the rectifiers in the amp case. Use a shielded cable for the umbilical and put an aluminum or copper shield between the rectifier and the rest of the amp. The thinking here is to prevent the current loop of the power supply, that runs from the rectifiers to the amp, from running through the umbilical. This sounds good in theory and in the past I've read a number of threads on current loops but I'm not sure how important this is to the sonics or function of a chipamp PSU.

Andrew, any thoughts on the importance of maintaining short current loops in PSU's?


Scott
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Old 13th August 2007, 09:43 PM   #4
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RE: Short Current Loop. Explains why Star Ground is popular.

In my mind, and experience, good ripple filter caps (4700uF) right where AC rectifaction occurs is the smartest solution. You achieve the goal of getting the diode ripple out at the source. Now comes the concern about induced noise and surge current response right at the chipamp. This is why you always want some more low value (.1uF) and High Value (1000uF) right at the chipamp itself. Nothing says you can't have more caps in parallel as parallel banks of caps are common in many of the designs seen here.

BTW: I NEVER worry about RFI harmonics from the diodes... it comes from too many other places with much more punch.
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