Improving the Non-Inverting chipamp

[jeff mai]

Originally posted by carlosfm
And what value did you use from NI to ground?
R1 on my schematic (15k).

I used what I had: 22K

It doesn't much matter what is used here in my set-up because the driving source impedance is always much lower (a few hundred ohms.)

[carlosfm]

And how does it sound?

[jeff mai]

Originally posted by carlosfm
And how does it sound?

I'm terrible at describing what I hear, but I'll give it a shot.

Compared to the "standard" gainclone values (22K and 680ohm) I noticed a shift away from the HF, which I always thought was a little exaggerated before. I also noticed some separation and textures that I'd not heard before - and this was on music with which I'm quite familiar.

This was with only a couple of hours on the amp. It's certainly worth trying! I think I'm going to prefer it in the long run.

[carlosfm]

Thanks, I just had to ask, because I thought I was dreaming.

Let it -in.

PS: notice the wall-to-wall soundstage.

[jeff mai]

FYI - R3 in Carlos' schematic should be at least 1/4W and 1/2W rating would be preferred. 1/8W would be exceeded at full power.

[carlosfm]

Btw I use 0.6w 1% film resistors, from Philips.

[jeff mai]

Originally posted by carlosfm
Btw I use 0.6w 1% film resistors, from Philips.

I figured you had it sorted Carlos.

I just wanted to point this out to others who might build. I saw some people using 1/8W resistors in their photos of other projects.

I used a .6W Beyschlag metal film. It's the perfect size to fit between the pins on the underside of the board.

Listening some more this morning, I remain very impressed. Good work!

[carlosfm]

With the second snubber near the chip, there are advantages in using bigger caps than 100uf.
I started testing with 470uf and yes, extreme bass gets tighter.
Then I tested 2,200uf and...


This is it!
Midband and treble are gorgeous, as ever, but the bass is really on another league.

PS: If you are wondering, I do not test amps with choral music.
There's a good recording from the beginning of the 90's (!) that always was a good test: Counting Crows - "August and everything after".
Believe me, very few amps can drive my Epos speakers with this disc.
This one does it:

[carlosfm]

The PSU is, of course, the high-cap. snubberized.
3x4,700uf per rail, MBR16100 diodes, heatsinked.
The amp, with the new caps:

[carlosfm]

No, I'm not joking.
I have this at home.