Gainclone Power Supply Design

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J

jarkaa

Member
Joined 2004
Hi,

I´ve been listenig to gc with regulated supply for three weeks now and I am amazed of it´s performance. I have 7000uF before regulators and 100,1uF on rails and it is excellent. Even though that the gc is based on opa549.

The soundstage is very clear and especially the stereo imagining is excellent.

I am yearing to get a tube buffer in front of the amp but I am not capable of designing that myself.

The amp is NIGC

One more thigng...

I found that 2.2uF input cap for each block gave the best results for opa549.

Still waitin for a good schematic for tube buffer...

Jarno
 
Variac

Variac

diyAudio Editor
Joined 2001
BurningAmp.org
Paid Member
This isn't close?
He says that the conversion to non inverted is probably not big deal.

http://www.diyaudio.com/forums/showthread.php?s=&postid=403693#post403693

I like the tube buffer/ regulated power supply combo.
More is better- in this case it just might be!!
I'ts possible that with a buffer, the inverted sounds better than the non inverted- one more experiment:rolleyes:
 
S

Sheldon

Member
Joined 2003
D

Dr.H

Member
Joined 2002
POwer supply set-up

Carlos,

Can you confirm your PS set-up? As far as I can see you have

MUR860 diodes
Some smoothing caps
LM3xx regulator for + and -
No cap after regulator
A small cap on the LM3875

Please state your cap sizes. I tried the regulated PS cometime ago, but the sound was tizzy and overwhelmed by bass. Maybe it was because I was using 1000uF on + and - legs of the chip at the same time as using the regulator.

Does the use of the regulator require less capacitance on the LM3875?

Thanks
Ryan
 
moving_electron

moving_electron

Member
Joined 2004
Nuuk said:


Carlos, do you mean on the output as in between the output pin of the reg and the cap on the input of the 3875?

Or do you mean bypassing the adjust pin?

And what is the length of the wire between the output of the 338 and the 3875?

(Yes, mine is still progressing slowly) ;) (Like a good port)
Click to expand...

Since the info is throughout the thread I also feel compelled to make sure I really am interpreting Carlos' implementation correctly. I am comparing the comments to the regulated power supply design on Predja's site mentioned in one of the early responses:

http://users.verat.net/~pedjarogic/audio/gainclone/supplies.htm

I interpret Carlos' comments to be that he obtained his best results with 47nF for C3 and C4 and changed the 1000uF caps on the gainclone board to 33Uf.

But I am not sure if that is correct or if he still uses the 100uF-470uF caps in Predja's design. But it sounds like he does not use the 100uf-470uF on the power supply board since there are 33uF caps on the gainclone board.

And I am pretty sure he likes the sound! :)
 
C

carlosfm

Member
Joined 2003
Nuuk said:
Carlos, do you mean on the output as in between the output pin of the reg and the cap on the input of the 3875?
Click to expand...

:confused:
No Nuuk, I mean on the regulator, I used a 47nf cap.
Between the output pin and ground.
Check the datasheet, page 6.
I use 47nf for C1.:eek:
They usually recommend 100uf cap here, but that sounds bad to me.

Look at the photos of my amp on my thread, the amp is in a small case (22cm wide), the regs are not far from the LM3886s, let's say some 10~15cm of wire.
 
moving_electron

moving_electron

Member
Joined 2004
carlosfm said:


:confused:
No Nuuk, I mean on the regulator, I used a 47nf cap.
Between the output pin and ground.
Check the datasheet, page 6.
I use 47nf for C1.:eek:
They usually recommend 100uf cap here, but that sounds bad to me.
Click to expand...

OK so looking at Predja's schematic a summary of changes that describes your implementation is:

- MUR860 diodes
- C1 and C2 = 47nF
- No caps for C3 and C4 although there are 33uF caps instead of the 1000uF caps at the amp chip power ins
- Variable resistor to be able to precisely set voltage
- Resistor changes to provide different voltage target than Predja's
 
N

netgeek

Member
Joined 2003
According to National the CMRR is so good that regulated supplies may not be needed - which would make sense for most of their target market (in order to reduce costs). Does it really make that much difference - in the opinion of people who have tried both ways? And has anyone actually measured the effect (positive or otherwise) on the output and performance?

Regards,
Bill
 
Nuuk

Nuuk

Member
Joined 2003
decdun.me.uk
No Nuuk, I mean on the regulator, I used a 47nf cap.
Click to expand...

Sorry Carlos, I meant on the output between the regulator and the chip but connected to ground!

You hadn't mentioned the cap on the adjust pin. Pedja had suggested removing the cap on the output of the reg, and just using a 100 uF on the pins of the amp chip, hence I was wondering if the 47 uF talked of was on the output of the regulator or on the adjust pin. It seems that you have both!

It can get very confusing talking about circuits, especially for those that haven't built one.

I'm sure that Pedja won't mind if we put his circuit here to show exactly what we are talking about (even if some of us have used slightly different values).

An externally hosted image should be here but it was not working when we last tested it.


BTW, do you use the second protection diode as suggested in the application notes for the LM338? I have included it on mine. ;)
 
C

carlosfm

Member
Joined 2003
Nuuk,

Looking at Pedjas' schematic, I used 47nf polyester for C3 and C4.
I don't like to leave a regulator without a cap on the output, but that's me, and this is a very small one.
For C1/C2 I used 47uf, and a diode from Adv pin to Output pin.
I didn't use D1.

On the amp's PCBs I used 33uf instead of the 1000uf I had.
The result is to :bawling: for.
:D
 
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