High-End Regulated Buffered Inverted GC

Here it is, finally.
Trafo scavenged from an old amp.
Small box, 22cm wide.
Everything had to fit there.
Details of PSU construction, testing, listening, changing, listening again, etc. are here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=35025&perpage=10&pagenumber=1

Thanks to Pedja and Nuuk for some hints on the PSU.

Here it goes, first one:

This is not the best heatsink arrangement, but it's ok, and it had to be this way because of the limited space inside the box.
The heatsink is also dividing the amp in two seccions (PSU and amp modules), so some shielding is provided here.
Anyway, ABSOLUTELY no noise.

from the top

Sound is absolutely fantastic.

next step...

is to regulate this one.

Nuuk, if you separate things, like I did, and make a High-End preamp, you don't need to make the wooden knobs for this.
I don't open my pre for almost a year now.
Isn't it incredible?
It means that it's really good, I'm very satisfied.
This is a power amp, and this thing drives my difficult Epos 11 speakers like there's no tomorrow.
I have some CDs with extreme bass and on those tracks with ultrasonic bass I had some room resonances (I thought!).
Now they completely vanished.

This is a mini-Krell.
Mini just because of the size.

Guess what?

My wife likes the new amp!

Re: Re: question about circuit for rvbnigc

jackinnj said:

At best this will cause the regulators to shutdown, at worst, it will blow your regulators.
There is no need for regulating the chipamp power supply.

Click to expand...

Please go read the LM338 datasheet and come back later, ok?

Re: question about circuit for rvbnigc

ebijma said:

Hello everybody,
Got a question for CarlosFM.
You did a realy good job building your amp.
It looks very nice.
After allot of reading i made a plan for my amp.
You can see the circuit below.
Its based on Pedja regulated supply and Joe's vbnigc.
I want to build this Valve Bufferd Non Inverted Gainclone.
And ofcourse with the regulated supply.
I want to run the LM 3875 with 31 volts on each rail.
So my question is :
Can you tell me the value of the resistors in the LM338 ciruit?
And what kind of transformer can be used?
Hope you can help me out here.

Click to expand...

Hi ebijma,

You didn't identify the resistors, but to make it simple and quick (this site si sooooo slooooooow now... )look at the LM338 datsheet and use 180 ohm resistors for R1 and 4.7k trim pots for R2.
Don't bother to use resistors for R2, even if you match them, the regs are not matched and you'll always have a small difference between the rails.
May be that I'm too picky, but I like to precisely adjust for the voltage I want.
Adjust to 30~31v, and you can use a 2x25v to 2x30v transformer.
My trafo was scavenged from an old amp, it has 2x33v , it's on the limits of the regs, but no problem, it works fine.
BTW, use around 33~47uf caps on the LM3875 chips, I found out to be an optimal value with these regs.

Thanks for your nice words and I hope to get feedback from you when it's done and singin'.

It's good for two chips.
Nominal current 5A.
Max current 12A.
Just use a good heatsink.