CarlosFM's Buffer. Is it correct?

[D_GR8_1]

Hi,

I created a schematic according to the information in this post:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=16928&perpage=10&highlight=&pagenumber=1

Below is the attached schematic.

Is this correct?

Carlos, can you shed some light on this?

 

[pete.a]

Footnote

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]

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]

improved it

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]

Re: improved it

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

Are you sure you wanna do this?

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

 

[D_GR8_1]

Doh

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

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

 

[shusha]

Re: Re: CarlosFM's Buffer. Is it correct?

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

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

Shusha

 

[carlosfm]

Re: Re: Re: CarlosFM's Buffer. Is it correct?

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

 

[shusha]

Re: Re: Re: Re: CarlosFM's Buffer. Is it correct?

No.
I meant what I meant.

Sorry Carlos I just realized that this is not your original schematics but modified one.

C2, C4, C7 and C9 should be 100nf poly or ceramic you said, while schematics shows that 7&9 are polarized.

shusha

 

[ShieldJaguar]

Re: improved it

Carlos,

I followed you suggestions and improved the schematic.

I would like to build this circuit as a Pre-Amp, would i need to change anything if i use a 50k pot?

 

[PMA]

Carlos,

my sincere congratulations to your circuit

Pavel

 

[carlosfm]

Carlos,
my sincere congratulations to your circuit
Pavel

It is not my circuit.
It's on the datasheet, and the first time I saw it here it was posted by you, as a buffer.
So, the credit must go to you.
I don't have any problem to give the credit to where it belongs, I don't understand your post.
I didn't open this thread, I didn't give it the title it has, I didn't claim anything.
Someone asked my help.
Is it clear?
Also, I'm not selling anything, and I find your "insinuation" offensive.

 

[ShieldJaguar]

Re: improved it

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.

I have a 50k Alps pot could i use it in this circuit? Would any changes be needed?
Was thinking of building this as a Pre-Amp.

 

[troystg]

I don't understand why would you consider a buffer like this and leave out an option for differential inputs?

I understand your "present" need may not require it, but it would be such a waste to not implement it for future use.

Especially considering the minimal cost to add differential inputs.

 

[peranders]

It isn't hard at all to understand. How many use balanced signals in home environment? Rather few I'll suspect.

 

[D_GR8_1]

Simulated

I just ran a simulation of this buffer circuit.

The input was 1V/50Hz sine, the output was 2.5V/50Hz sine.

Which means that the signal was multiplied by 2.5.

This being a buffer, there should be no multiplication, right?

Anyhow, here is the schematic:

 

[D_GR8_1]

Waveforms

And the results:

 

[aparatusonitus]

You have gain Av=1+R4/R3=2,42