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Chip Amps Amplifiers based on integrated circuits

Power Supply filter capacitors
Power Supply filter capacitors
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Old 4th December 2017, 09:06 AM   #11
JMFahey is offline JMFahey  Argentina
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The DD suggestion is quite clear to me:
Quote:
I suggest the following arrangement. About 10-100 uF after the bridge rectifier, and 1000 uF on each (power supply) pin of the chip amp.
Minimal filtering/storage just at bridge terminals, 2 to 8 inches away from the actual chipamp and 1000uF (which I guess way back then was maximum possible value to allow such connection) straight at Chip pins, no shorter path possible whatsoever.
Brushing away any significant wiring resistance/inductance.
I bet you can nowadays use 2200uF and even 4700uF there, just hanging from their legs and with some handy drop of silicone sealant so body does not move around and fatigue cut legs..

Quote:
If your speakers are a difficult load, you will need much more capacitance than this. But if you put say 10,000 uF after the rectifier, you will almost certainly notice that the chip amp loses some of its magic.
Chip amps in general *are* quite sensitive to wiring path and length, so doing things the opposite way, large filter caps away and puny "HF/RF only" local decoupling may cause audible problems ... but you can have your cake and eat it; 1000 uF to 2200uF local straight-on-chip-pads plus whatever you feel comfortable with just by the bridge.
Best of both Worlds.

I wouldn´t overthink it.

As of snubberizing, I does not convince me very much because it´s usually done far away from the chipamp, so negating its possible usefulness.

In any case, IF I considered it really useful, I´d connect the snubber straight from chip power pins to chip ground.
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Last edited by JMFahey; 4th December 2017 at 09:13 AM.
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Old 4th December 2017, 11:51 AM   #12
ggidzinski is offline ggidzinski  United States
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jM Fahey:

So you see the DD suggestion as bridge/up to 100uF - 1,000uF/chip amp with no 10,000uF caps anywhere?

George
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Old 4th December 2017, 12:02 PM   #13
00940 is offline 00940  Belgium
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That's it indeed. It was a trend a few years back, inspired by some audiophile designs.

Thankfully, the trend has shifted back towards more reasonable designs. Have a look at the neurochrome website. Tomchr has a good serie of articles on the lm3886, including power supply design.
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Old 4th December 2017, 01:54 PM   #14
Mark Whitney is offline Mark Whitney  Netherlands
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1000uF per rail as used by Labs47 in their gaincard and Audiosector in their gaincard (1500uF).
It only works because of the layout used.
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Old 4th December 2017, 02:31 PM   #15
00940 is offline 00940  Belgium
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This link is pretty good when it comes to establish the necessary parts for a supply.

Linear Power Supply Design

An aspect to consider carefully is the ripple current rating of the cap used. Good luck finding a satisfactory 1000uf cap under that respect.
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Old 4th December 2017, 03:22 PM   #16
DF96 is offline DF96  England
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The big snag with using a small cap after the rectifier and a big cap by the chip is that it significantly increases the area of the charging pulse loop, and potentially makes it harder to get a clean ground reference. Apart from this, it is slightly bonkers advice to use a small cap where science says to use a big cap (PSU reservoir) and to use a big cap where sciences says to ue a smaller cap (local rail decoupling). However, in audio there is no idea which is too daft for someone somewhere to promote it.
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Old 4th December 2017, 03:38 PM   #17
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by ggidzinski View Post
I understand decoupling vs smoothing as well as ripple etc. neither word is used in the tutorial. I am going to have to do further research
........into....YouTube)
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Old 4th December 2017, 05:25 PM   #18
Mark Whitney is offline Mark Whitney  Netherlands
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More info on gainclone.
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Old 4th December 2017, 06:54 PM   #19
ggidzinski is offline ggidzinski  United States
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I assume since there is not a single response in support of less than 1,500uF total capacitance (all functions) between the bridge and the chip amp power pins that this approach is no longer considered for new designs?

I am going to assume that 10,000uF for smoothing is standard and then you decide on decoupling/snubberizing/etc. In this area I will keep reading.

George
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Old 5th December 2017, 03:02 AM   #20
ggidzinski is offline ggidzinski  United States
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Quote:
Originally Posted by Mark Whitney View Post
Which design do you advocate, the one with the snubberized/35,000uF design or the last one with no filter caps at all and only the bridge output directly to the chip amp pins with the chip amp only decoupling?

George
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