CarlosFM's Buffer. Is it correct?

[D_GR8_1]

Hi,

I created a schematic according to the information in this post:
High-end preamp for my GC

Below is the attached schematic.

Is this correct?

Carlos, can you shed some light on this?

[pete.a]

Hi,

Yes this is correct, just as Carlos stated later in his post's on this circuit. It's taken from the application footnotes from Nat Semi's web site..

Iv'e built the heaphone amp and it works fine , albeit with some minor fault's. But thats down to my circiut layout..it's got a small hummmm, apart from that im pleased with it.

Try Pavel Macura site...

[carlosfm]

Originally posted by D_GR8_1
Carlos, can you shed some light on this?

Me?
Oh.

C2, C4, C7 and C9 should be 100nf poly or ceramic, not 1uf.
Also, you need a cap between pins 2 and 6 of the OPA627.
200pf is fine, but you can test lower values, like 100pf, it also works fine.
Avoid ceramics here.
An importand thing is that all the PSU bypass caps (100uf+100nf) should be on each chip's PSU pins to ground.
You can also use a 100~330nf poly cap from - to + PSU pins on the OPA627, under the circuit.
It is very important that the layout is as small/tight as possible.
No big feedback loop, no PSU bypass caps far from the chip's PSU pins.

If you stricktly follow these instructions you will have a gorgeous sound.

[D_GR8_1]

Carlos,

I followed you suggestions and improved the schematic.

You mention to use a poly cap between - and + pins. Should it be polarized or non-polarized?

About the track length and distance, I will try and implement that onto the PCB design.

I will post the PCB here in the next few days.

Thanks.

[Swedish Chef]

The day you find a polarized poly cap you have indeed found a very exotic "audio grade" cap...

[carlosfm]

Originally posted by D_GR8_1
You mention to use a poly cap between - and + pins. Should it be polarized or non-polarized?

Are you sure you wanna do this?

Originally posted by Swedish Chef
The day you find a polarized poly cap you have indeed found a very exotic "audio grade" cap...

[D_GR8_1]

Doh, when you mentioned poly I associated it with electrolytic.

Too early in the morning for me. I need coffee...

[shusha]

Originally posted by carlosfm

C2, C4, C7 and C9 should be 100nf poly or ceramic, not 1uf.

You mean C2,C4,C3 and C5. Right?

Shusha

[carlosfm]

Originally posted by shusha
You mean C2,C4,C3 and C5. Right?
Shusha

No.
I meant what I meant.

[KT]

If I wanted to make an integrated preamp/GC in one chassis, I wouldn't need the BUF634T, right? Would I just leave off the BUF stage, or does the OPA627 need an output resistor as well?

Would this be the way to go or does the circuit sound better with the BUF behind the OPA?

Thanks,
KT