Pedja Rogic Buffer and component choice for PCB design

[Nuuk]

Where is the 270R on that diagram?

[justblair]

Originally posted by AndrewT
Hi,
caps become the biggest space/pin pitch problem when you start experimenting.
Try to make sure every capacitor location has at least two (useful) pin pitch options and leave adequate space for physically large caps. PP are always bigger than PES/PET.
I would prefer to see 0.1inch pitch connectors alongside/under the 0.2inch pitch terminals you have shown. Then you have a choice of how you make the on/off board terminations.

What do the regs need for caps around the pins?

I will work around the caps issue, I need some more space on the board. I will add the .1 connector choice as well. I stuck on .2 cause thats whats in my parts box for screw connectors.

The caps for the regs, I have sized for 47uf.

Originally posted by Nuuk
Where is the 270R on that diagram?

I built my schematic with an adj resistor. However I am going to replace that with a fixed one. That will allow me some more space or the pp cap choices as well.

I also spent some time last night matching the J310's I have some exact pairs and a lot within 0.1 milliamps of each other. I Can get 6 matched to within .4 milliamps of each other. What constitutes a matched pair in peoples opinions?

I got a case made today for my measurement mic, I gues I have less than 45 mins to get it completed then I will work flat out on the design above.

Regards

B

[justblair]

Oops double post.

[Nordic]

Here are mine... not useing them anymore though... gone down the passive route...

[Dxvideo]

What about this one?

I'll try this very soon. I've got the components.
There are some differences;
- 2u2 used as DC decoupling instead of 4u7.. Why? because I already have 2u2.. However the space is suitable for 4u7 also.
- 2SK170 used as J2 as Pedja said. But without R2, bias current increases 10mA. Then to keep it 6mA I put 20R source resistor to SK170..
- Added gate (1K) and input load (100K) resistors to J1...
- +/-30v will be used for LM3875... Because I've sold my wharfedale 9.6s.. Now I have only 9.1s and theyre 86dB. So I will need more power..

Thats all. If anybody request, then I can send the eagle files..

[dodo]

Well I would stay with the J310 or 2SK246BL

Jfets with high Vgs are more suitable as a curren sources
have better rejection
more about - W.Jung Current sources in audio circuits.

[Dxvideo]

2SK170 is also a JFET as you know.. So whats the difference?

[Dxvideo]

Means, I coulndt find data about 2SJ310.. Does it have really big diffrerence by meaning of Vgs?

[justblair]

My latest PCB design.

Tidied up the component sizes, for the 1 uf I have designed for the sonicap Gen1

I have moved the cap to the underside of the board, but printing one sided board

Dimensions work out at 43.18x 29.21mm (1.7' x 1.15')



Whats the thoughts? Any errors or better design tips?

Had considered a signal earth plane?

[Nordic]

bypass before and after the reg... get those pins as close to the reg legs as you can... looking nice otherwise I would route the ground plane a little further from the sk170.... I think it is a high impendance point...