DIYHiFi.org

When carlosfm has gone from diyAudio, his schematics have left (fortunately) and continue to disturb brains of green DIYers, beget questions which need to be answered.
Every man who uses or just intended to use carlosfm’s schematics wants to be sure that their components value corresponds to his demands completely.
So, my inquiries are as follows.
Regarding a snubberized PSU MkIV SE Rev. 3.
1) Is there any need to bypass diodes on bridge rectifiers?
2) In my stuff I've found that amplifier when it's turned off discharge PS caps for about 5-10 minutes, so may I omit bleeder resistors in this design?
3) I wonder, may I use 2x(1mF+1Ohm10W+10mF) with 1 BR except 2x(4,7mF+1Ohm10W+10mF+10mF) with 2 BR PSU and 1mF+100nF+snubber on chip's PSU pins for one 100W channel with 4Ohm load and 400VA trafo for stereo amplifier?
4) Perhaps, will it be wise to use MOVes or some NTC thermistors to limit inrush current with big trafos.
5) What is a sequence of placing components 0,1Ohm+3.3nF, 100nF, 2,2mF to the IC?
Regarding a Non-Inverting LM3886 power amp version 4.
1) Might it be better to use C1-1uF and R1-47k for higher frequency performance sake?
2) What should be a DC Offset of such amp?
3) What tolerances resistors should have?
Regards.

I think you are refering to these schematics.
Amp:

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

PSU:

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

Be free to use them for your own and modify what you want but have in mind that:

- both were made and fine-tuned for each other, through several incarnations and extensive listening tests. (!!!)
- The amp is proposedly made with low value feedback/gain resistors (and it sounds better that way) but if you increase the input resistor to ground you will increase DC offset.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

Hello, Carlos.
Thanks for your answer.
As I remember, you said once on diyAudio that this PSU was calculated for 2-3 channels, based on LM3886 amp. Thus I suppose for 140-200W? How can I reduce power capabilities of this PSU down to 100W of continuous output power without any harm to sound quality which you achieved, if so is possible of course? I'm intended to build it for use with one 100W 4Ohm channel only.
What about resistor tolerances, sequence of placing components and bleeder resistors? Resistor tolerances, should have significant influence on DC offset I think.
Could you give recommendations for inrush current limiting for this PSU, which is to be used with 400VA trafo?
Did you ever update these schematics from “release date”?
Regards.

You can only achieve 100W at 4ohms with two paralleled chips, and in that case I would keep the PSU as is.
Resistor tolerances on the amp are 1% but I always measure and select a best match between the channels.
Sequence of placing components are exactly as the schematic indicates but it is really important to have the 100nF bypass caps directly across the bigger caps' pins.
There are a lot of inrush current limiter solutions, search around. But 250VA would be good for just one channel and it could work fine without inrush current limiter.
My PSU doesn't kick a big ass at startup, the first caps are relatively small.

I didn't update these schematics. It is what I'm using, since then.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

I have in mind to use two PSUs according to your schematic like a "quasi dual mono" configuration with one 400VA trafo with two secondaries.
I just wanted to know if you have updated versions.
Likewise, I guess your LM3886 schematic may be applied for use in parallel design combined with output resistors.
You recommend using 2.2uF as input cap. I have some spare 1uF MKP. Can I replace 2.2uF with 1uF?
What influence such substitution may have on audio performance?
Regards.

You can go up to 10uF for that cap, not down.
1uF is small, it will cut some bass.
I'm using a 10uF cap there.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

Thanks Carlos.
DIY without people like you would be pointless!
Regards.

Carlos is PRICELESS!!

BTW, Carlos, a beer, next weekend?

_________________
Pedro Martins

Playing with Canon EOS 5D mkII...

Do you come to Lisbon?
Ok!

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

I'll call you as soon as I get an answer from a guy out there.

Back to topic...

I got better bass with 4.7u @ input. Maybe the cause is what I have 'before' the amplifier... PGA2310.

_________________
Pedro Martins

Playing with Canon EOS 5D mkII...

Some will claim that DIY is pointless, period. Go look at the current mirror thread at The Pub.

I rest my case.

Maybe you should amend your statement to:

"People like you keep DIY from being a total waste."

That might be more accurate. Excuse me while I go make trouble somewhere.........


Jocko

_________________
"Because, I hate you guys. I hate you guys so very, very much.

Yours,
General Cartman Lee"

Hi, Jocko.
I didn't understand you completely what you mean by saying: "some will claim that DIY is pointless, period. Go look at the current mirror thread at The Pub".
I only wanted to show a respect to Carlos for his work he had done which became valuable for millions I suppose.
Likewise I deeply convinced that Carlos deserves to have a great fame not only for his work, but also for his unselfishness in doing things like that and I'm confident - I'm not alone with my opinion.
Regards.

AndriyOL, that's Texan humour.
Just read between the lines.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein