SMD Preamp/Buffer design

[Wynand]

I've been working on this design over the last week.

It's a input buffer circuit with LM2940 and LM2990 voltage regulators.

The LP filter is set to approx 3hz and the HF Filter to 100-140 Khz.

These values were suggested by Peranders (thank you).

Any comments/suggestions?

The red is the top layer with all the tracks.
Blue is vias and green is the bottom layer(Ground plane).

Here's the PSU Schema

[Wynand]

Here's the Buffer schematic

[Wynand]

....and the layout.

[Nordic]

Wynand... if you are going to make some of those.. won't you make me a spare PBC too?

[Wynand]

I'm actually hoping there's enough interest to get them professionally made.

[Arius]

If you require professionally made PCB's, give www.pcbfabexpress.com a try. For a board like yours, it will cost US$13 each (minumum order of 5pcs) plus overseas shipping.

If you have one or two people interested, that ought to make the cost reasonable.

Disclaimer: My only relationship with them is that of a happy customer.

Back to the pre-amp, it seems fairly basic. Is that what you really want? Suggestions for improvement might be something like a buffer followed by the volume control, then an active gain stage (2 op-amps per channel). Other enhancements might be separate regulation (if not separate rails altogether) for each channel, use of good quality opamps and potentiometers, improved decoupling/filtering, relay-switched output, optional output coupling cap, etc.

[Nordic]

These look quite handy for multichannel applications because of the small size...

[Wynand]

Oops... seems I cant find most of the SMD components.

I'll have to revert to push through components.

I'll be a bit bigger but not by THAT much.
Another bonus would be being able to etch it myself!!!