Understanding the SBR Power Circuitry

[04dgmsilv]

I have begun to explore the circuitry in the SBR and am going to take my time and make some modificaitons to it and try to learn a little along the way (er... maybe learn first then mod!!). First up is the power section, now it seams to me that the 9V wall wart feeds a 5V linear section and 3.3V and 1.2V switching sections. There are test pads located near each of the power supply sections. If one were to build a linear PS for each of these voltages and supply it to these test pads while removing the existing circuitry, would this be a workable solution. Has anyone figured out a block diagram for this section yet?

Does this seam reasonable? I have no concern for the case as I will just mount everything to a piece of wood for now.

Thanks

[nossaile]

I’m sitting with the same thoughts as 04dgmsilv, but I’ve not opened my SB Duet Receiver yet. Anyone that knows how to without damaging it? Anyone with a circuit diagram?

[04dgmsilv]

Its easy to open up, there are four screws at the corners below the foam pad on the bottom. Just feel for the hole and put a small slit. I think it was a torx screw, but can't remember now.

[TonyM]

Torx T10.

The little light-guide/button thing needs some teasing out (if you want to get the pcb out too) but it all comes apart (and goes back together) fine.

[nossaile]

I have now opened the box to get to know the power supply part and I must say it’s amazing that the sound can be enjoyable at all with such a minimalistic solution. However there is hope… for some reason they have provided us with two ready-to-use tweaking possibilities, one connection to 9Vdc and one to 5Vdc. I have not looked at the back side of the pcb, but I guess from the location that the 5Vdc is used for the analogue part. If anyone knows please verify, because it is horrifying low to be able to create an analogue amplifier stage of any quality! Anyway, based on this assumption I have made the following tweaks/improvements:
1st try: Add a 1000µF of ordinary quality between 5Vdc and ground. Result: Promising and definitely worth while and it is still possible to put the top cover on again. You will recognize improved dynamics and more details.
2nd try: Replace the 1000µF with a 10000µF RIFA of high quality with a 10µF audio grade in parallel. Result: I will not put the top cover on again as long as I have the Receiver in my possession! You will not be disappointed if you try this tweak! Everything is better and it is closer to my analogue source than I thought was possible.
3rd try: Add a 1000µF of ordinary quality between 9Vdc and ground. Result: A small improvement, but I will try to add a 10000µF RIFA here too.

[bartverwaaijen]

Is it possible for u to post some picture's? And what are the specs of the used materials?

Greetz

bart

ps, love to try it myself

[nossaile]

4th try: Replaced the 1000µF between 9Vdc and ground with a 10000µF RIFA of high quality and a 10µF audio grade in parallel. Result: Again a big improvement, more details, depth and dynamics. I will not switch back. I will try to post a picture of how my Receiver looks now.

[nossaile]

See attached...

[nossaile]

5th Try: Replace the two 10µF electrolytic capacitors on the analog output (see my picture above: the two small cans at the bottom left) with audio grade polypropylene SCR MKP 10µF (same as the black ones in my picture above).

Tip! Be very careful when you remove the old capacitors so you do not damage the print. My recommendation is to cut the body off with a cutting pliers before you try to unsolder its connectors.

Result: A much more relaxing sound for your ears. More details, depth and better bass.

Next: Replace the small PSU.

[nossaile]

1st try: I have now made my first try on replacing the original PSU. I took what I had:
A 13Vac 4A transformer connected to a rectifier bridge to 10000µF to a LM7809 (1A) to 50000µF and finally to the 9V on the print of the Receiver.

Result: Much better dynamics and details. A definite recommendation to do this tweak!

Next: I will do a proper replacement with separate 5Vdc and 9Vdc.