Looks like the OP (in 2006) was talking about the 'lytics on board near the IC, not the supply main filter caps. These "local 'lytics" should be larger if the main filter caps are a good distance from the IC, which is often the case. The resistance/reactance of the long power supply leads can cause variation on the supply pins on the IC when it is driving a load at high current.
So good practice would be to use short and heavy wires from the supply board if separate from the amp board and use 100-220uf caps (per channel) on the amp board along with the .1uf film caps.
So good practice would be to use short and heavy wires from the supply board if separate from the amp board and use 100-220uf caps (per channel) on the amp board along with the .1uf film caps.
Your question is not gemane to the original post. It is what doesn't belong.
Replying to your post #20, Mike - I have a similar difficulty with the concept of just using the 1,500uF caps next to the LM3875 chip without any other smoothing after the diodes but I decided to just try it out for myself and see what happens
On the power supply, I've got a couple of over specced 300Va torroids, one per channel and separate windings (not Centre Tapped) and basically following the Chipamp system with no power caps after the Soft recovery diodes but sending the rectified sinewaves a short distance to the 1,500uF caps next to the chip - actually, 1,000uF/50V Silmics
Then, it's connecting a couple of 4,700 Nichicon GoldTones next to the diodes for a reduced ripple to the 1,000uFs and have a listen - then, the next step is to add a simple transistor C-multipliers (like the esp website ones) after the 4,700uF - it'll be interesting ...
It's pretty obvious that the chipamps have some quite different requirements when it comes to components, layout and power supplies so I'm not at all sure that the 'normal rules' for 'normal amplifier topologies' are correct here
About capacitors - they all have a slightly different colour and as this is very hard to describe in different applications, I wouldn't advise spending a lot of $s on boutique parts until you have the lm3875 up and operating in your system - I happen to have a wide variety of parts for this use and am starting with the Silmics and/or Nichicon Gts but will also try the Panasonic FCs, Rubicons, BGs, etc later on
Curiously, Uriah Daley used a thing called a 'Resistor Replacer' instead of the series input resistor of the similar chipamp and had quite an improvement in the sound, so it seems that all the parts have quite clear contributions to the overall result
Oh yes, this is for the 40 Watt Transconductance amp of Joe Rasmussen's, not the basic 'gainclone' but I think will showup similar results
I hope these 'rambling comments' are of some assistance ...
On the power supply, I've got a couple of over specced 300Va torroids, one per channel and separate windings (not Centre Tapped) and basically following the Chipamp system with no power caps after the Soft recovery diodes but sending the rectified sinewaves a short distance to the 1,500uF caps next to the chip - actually, 1,000uF/50V Silmics
Then, it's connecting a couple of 4,700 Nichicon GoldTones next to the diodes for a reduced ripple to the 1,000uFs and have a listen - then, the next step is to add a simple transistor C-multipliers (like the esp website ones) after the 4,700uF - it'll be interesting ...
It's pretty obvious that the chipamps have some quite different requirements when it comes to components, layout and power supplies so I'm not at all sure that the 'normal rules' for 'normal amplifier topologies' are correct here
About capacitors - they all have a slightly different colour and as this is very hard to describe in different applications, I wouldn't advise spending a lot of $s on boutique parts until you have the lm3875 up and operating in your system - I happen to have a wide variety of parts for this use and am starting with the Silmics and/or Nichicon Gts but will also try the Panasonic FCs, Rubicons, BGs, etc later on
Curiously, Uriah Daley used a thing called a 'Resistor Replacer' instead of the series input resistor of the similar chipamp and had quite an improvement in the sound, so it seems that all the parts have quite clear contributions to the overall result
Oh yes, this is for the 40 Watt Transconductance amp of Joe Rasmussen's, not the basic 'gainclone' but I think will showup similar results
I hope these 'rambling comments' are of some assistance ...
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