The (high-cap.) unregulated PSU for chipamps

[wigginjs]

Sek:

Thanks very much, I appreciate the time you took to write that. I now have a much better understanding of why higher capacitance filters are better, even for smaller gainclone amps.

[sek]

Originally posted by m0tion
Thanks very much, I appreciate the time you took to write that.

Glad I could help.

I now have a much better understanding of why higher capacitance filters are better, even for smaller gainclone amps.

Well, that's the culprit! They should, but many report they aren't. Not because what I describe doesn't apply to chip amps, too. But because the sound in the midrange is reportedly compromised with a higher capacitance PSU. That's why Carlos is so happy about his results with a compensation circuit for higher capacitances. I suspect we'll have to wait until further investigation has been done... (unfortunately I don't have the time, nor the need at the moment)

There's also a neat article on TNT audio about designing PSUs. It also describes the method discussed in this thread.

Sebastian.

[carlosfm]

Originally posted by jackinnj
i wonder whether the effects you experience with the LM338 regulator for your GC's isn't compensating for a transformer which has poor coupling, or is overheating -- i don't think that the series inductance of the filter caps is going to materially affect the power supply impedance at the kind of frequencies we are talking about.

The first GC I made was with a 2x24V 384VA custom made toroid, unregulated PSU with MUR860s and 1,000uf per rail on each LM3875 board.
A typical GC, then.
This toroid didn't ever get hot, did never vibrate.
And it was quite a good trafo for two channels.
Unfortunately this amp, although good sounding, was not able to drive my speakers properly.
Bass was not tight, even at low volume.
I added 2x4,700uf caps on the PSU diodes and at first it seamed to sound better. At least bass was tighter.
Listening more carefully a week later, I found out that the amp was sounding like a cheap one. Low-level detail, midband, treble, "air", "ambience", soundstage, all went to the toilet.
I then made plenty of tests with capacitance and got my conclusions.
Then I made another modules with LM3886 and never looked back again to the LM3875.
But with the low capacitance unregulated PSU it was still not there as I wanted. There was more to be gained in driving ability, and I knew it.
Regulation did solve this problem in a way that I call my power amp a mini-Krell.
This test now with high-capacitance unregulated PSU is just because I felt that it could be made to work much better.
I don't say it's better than to regulate, in my oppinion it's not, but it will be enough to use with a much more variety of speakers tham the typical GC can cope with.
If one can't detect a difference for the worse in changing caps for bigger ones on the unregulated PSU with these chips, then there's a lack of transparency in the system that prevents it to be detected.
I don't ever take conclusions with my test speakers, the final and cruel test is always in my main system, where it gets all exposed.
Of course, I'm so used to it that I can detect any change for better or for worse.

[carlosfm]

Originally posted by sek
There's also a neat article on TNT audio about designing PSUs. It also describes the method discussed in this thread.

Have you really read my first post on this thread?
And also post #4?
No?
Yes?
Nah...

[wigginjs]

How about increasing the capacitance along with adding a voltage regulator? Is there some reason why adding a voltage regulator makes increasing the capacitance no longer useful? Or impossible? Anyone considering implementing these PS changes using BrianGT's kits?

[carlosfm]

You could search this forum instead of going all over it again.
As Pedja says, there's a "ground shaking thread" about this.

[moving_electron]

Originally posted by carlosfm
For a long time that I know this excellent article on power supplies:
http://www.tnt-audio.com/clinica/ssps1_e.html

I am having trouble making out the capacitor value in the figure 4 at the top of part Part 2. http://www.tnt-audio.com/clinica/ssps2_e.html

Does any body know what value the writer was recommending?

Carlosfm, I know you have tested and have a recommended value you like for chipamps, but I am curious as well about what the author of the article was recommending for (presumably) solid state amps.

[sek]

Originally posted by carlosfm
Have you really read my first post on this thread?

This one was addressed to m0tion. Although I could have choosen my words better, I only wanted to recommend him to really read it (as it appeared he hadn't, assuming he might not have noticed).

So, just add "in case you didn't notice" to my previous post...

Sorry to be redundant,
Sebastian.

[thomas997]

Originally posted by moving_electron


I am having trouble making out the capacitor value in the figure 4 at the top of part Part 2. http://www.tnt-audio.com/clinica/ssps2_e.html

Does any body know what value the writer was recommending?

Carlosfm, I know you have tested and have a recommended value you like for chipamps, but I am curious as well about what the author of the article was recommending for (presumably) solid state amps.

Going left to right after the rectifiers: 10,000uF, 10,000uF, 100uF, 100nF, 560nF (or 580nF not sure).

[carlosfm]

Originally posted by moving_electron
Carlosfm, I know you have tested and have a recommended value you like for chipamps, but I am curious as well about what the author of the article was recommending for (presumably) solid state amps.

He suggests a starting point, but he also says it can be fine-tuned in every implementation between 220nf and 560nf.
Check the link I posted on post #4 of this thread, as that article is a little more detailed.

I started with 560nf, then 330nf, then 120nf and...
That's it for now.
It's in'-in, sounds good.