View Full Version : New main board powers stereo coffee further than ever

Light Dependant Resistor
24-09-2018, 10:52
Hi AOS members
Sorry I have been away for quite a while developing the new main board, for the stereo coffee kits.
I regularly checked that three words Daily was still going.

I began research into this board about this time last year, and with many schematic drafts at easy EDA, it
started gathering momentum. A final all out effort saw the new printed circuit boards delivered here 3 weeks ago.
D16 though was strangely connected not per the schematic draft, but providence was with me because it
was better as the printed circuit boards had been made.

I am finally soon to send one of these to Marco to enjoy, and perhaps he will let you know
how it sounds. Peter too has already ordered the new kit with remote control , so he might let you know as well, in a month or two

The new board carries some very exciting developments in signal attenuation. On the signal side
as simple and as pure as it can get, just a L pad with a shunt pair and series pair of NSL32SR3 LDR's for each of the three inputs.
As usual contact-less switching of the three inputs.

But on the anode and cathode side much development. the images show a board set of about three weeks ago


A further 12 surface mount components are added under the board, bring the active components used to 45 on each main board.
The main board has its own active rectifier with N channel mosfets in the negative section of the full wave bridge. The board accepts
either 12v AC - I have tested it to 19v AC or as low as 12.5v Dc - great for battery powered and solar panel charging - or a plugpack
regulated at 15v Dc such as the ifipower unit. So lots of leeway on how it is powered.

How does it sound, well I will let forum members progressively comment on that, but put it another way I do not think I have
wasted 12 months developing it.

Cheers / Chris

Light Dependant Resistor
15-12-2018, 23:42
This how the boards look in casework

16-12-2018, 23:55

Nice neat and tidy work! It would look better, IMO, if the knobs were the same distance from the fascia; these little cosmetic details are important to me. Or is a photographic artifact?.

Light Dependant Resistor
17-12-2018, 04:29
Hi Barry
Thanks for your comments ,on the build pictured a alps pot was used, which has a metal shaft, yes agree the selector knob needs moving to match the spacing

17-12-2018, 17:35
Hi Barry
Thanks for your comments ,on the build pictured an alps pot was used, which has a metal shaft, yes agree the selector knob needs moving to match the spacing

Obviously sound quality is more important than build quality, but as you have already gone to the trouble of offering a well built and presented item, going the extra couple of millimetres (;)) would be worthwhile.

Light Dependant Resistor
18-02-2019, 17:16
A review and comments of the new board here: https://www.stereo.net.au/forums/topic/260371-2019-stereocoffee-ldr-preattenuator-kit/