[barkas]

Okay, it has become a PIMETA with discrete diamond buffers. So what.

Only the power section for now, and the diamond buffer, I'm waiting for a bit of feedback for the amp, since L and R are probably very similar to VGROUND.

first, the diamond buffer (note, I'll use BC3x7, not BC3x8, but the eagle package for BC3x7 is a bit fubar)

then, the vground. (note, the buffer right of the opamp is the above diamond buffer, and I used the other channel of the opamp for layout reasons. R1, R2 and C1 may be optional, depending on opamp stability, and may be replaced by bridges)

EDIT: here the boards

 

[ATAT]

First, it looks like you're making all your routing one sided.. intentional?

On your bottom one,
1. you want to avoid 90 degree angles.. use the miter command in eagle to make them all 125 degrees..

2. there's no reason your lines should be crooked.. take straight lines and 45 degree angles.. its just alot more aesthetically pleasing, and it shows thought =p

3. R1 and R2 wont fit. it intersects with the cap, check it out yourself

4. It really just looks like you're using one channel.. why use dual opamp?

Layout for your ground channel looks fine. I've no qualms.

Also, why not groundplane?


As for the buffer.. I suggest you replace that ressistor with a CRD, it'll make your bias voltage independent.. its "better" after a fashion.

 

[barkas]

One sided is intentional. And why not? Etching is a bit simpler, then.
If it gets too crazy, I'll go double sided. Up to now, I've managed with some strategically placed bridges.

Do 90 degree wires generate reflections? It is no problem changing them, I'll do them round or something.

Dual opamp because it is no more expensive than a single one. At least I think so, and it really doesn't matter. I may change that, too.

R1 and R2 - I thought they would fit, but I'll recheck that.

No groundplane because I don't know how yet in eagle

.

The buffer - I guess I could use a resistor and a jfet, like in cetooles diamond buffer design in the other thread, it would make it bigger, though. I'll check that.

Thanks for the advice.

 

[ATAT]

groundplane is easy.. just draw a big polygon around the entire thing.. name it "GND" and set isolate to 16.

 

[ozshadow]

Just a questions, on those transistors, I have seen them as 16's, 25's, 40's etc. Whats that mean ?

 

[steinchen]

the numbers designate the gain classes, refer to the datasheet for the ranges

 

[barkas]

Updated power channel layout

I still can't do a ground plane ;/
And I don't know how to get a CRD implemented, I can't find CRD diodes at reichelt.de and I wouldn't know which FET to use

.

@ozshadow: sijosae marked them as -25 types in one of the schematics, but I think you could use whatever type you want, I tend to the -40 since they have the highest gain (danger: I don't really know what I'm doing

)
Datasheet: http://www.ortodoxism.ro/datasheets/...on/1-bc337.pdf

 

[barkas]

updated with full schematics and boards

 

[mono]

Quote:

Originally Posted by barkas Updated power channel layout I still can't do a ground plane ;/ And I don't know how to get a CRD implemented, I can't find CRD diodes at reichelt.de and I wouldn't know which FET to use .

The CRD would just be a drop-in replacement for the resistors. Do you know what bias current you want? If so, then you start to choose the JFET.

part# min max (mA)
5484 1.0 5.0
5485 4.0 10
5486 8.0 20

So for example if you weren't picky, and could accept (on average?) somewhere between 2 and 5mA, you might buy a handfull of 5484 and test their IDSS, finding matching pairs for each without need for the resistor.

If you are more picky, you can use the resistor to limit current more and for less need to use very fine tolerance, low value resistors you would choose a higher # JFET. For example in a past project I used 2N5486 & 1K resistor for 2.4mA result but that would vary some based on what your specimen of JFET's IDSS is. With a CRD this testing is avoided but if you can't find any (or at reasonable prices) maybe someone can help there but the JFET is fine if you have the space for it. I wouldn't worry much about a resistor either if that's what you want to use... it is your design.

Why all the separate boards though?

 

[barkas]

All the boards so I am modular and can swap things out.

I fear I can't easily get 2n548x in germany. Can somebody recommend an easier to get replacement?

 

[steinchen]

BF244 a/b/c BF245a/b/c, please note the reversed pinout compared to 2n548* JFETs