LDR Attenuator

[awkwardbydesign]

My Stereo Coffee LDR pre is now working. 4 inputs (3 on a piggyback board) and the front panel is now finished. I used a piece of Ipe (Brazilian Walnut) flooring; it's really hard! I had to cut it down from 18mm to 10mm thickness, not easy to do. The knobs are American walnut, turned on my little metalworking lathe, and I had to turn a shaft extension for the 500k log pot, as it has a very short shaft.
The digital voltmeter is normally switched off with the push switch below it, to save power, as this is run from a 1.2Ah battery, charged by a small solar panel. There is a mains charging circuit installed, but I haven't quite finished that yet.
I seem to have muddled up the wiring somewhere, as although it works OK and sounds very dynamic, when I switch the battery over to the charging circuit, which should switch off the LDRs, there is a fixed medium level audio output still feeding the power amp. The volume control has no effect on this. Oh well, I will have to work through the circuit; it didn't do this before with the single output board.
The sound is promising, but of course it shows up deficiencies elswhere in the chain. And I wonder if these components need to burn in, the way others do.
I will add more pics when I pull it out to modify it, and plan to veneer the aly lid too.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/LDR%20pre/P1000298_zps13470a41.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/LDR%20pre/P1000298_zps13470a41.jpg.html)
http://i1134.photobucket.com/albums/m604/awkwardbydesign/LDR%20pre/P1000295_zpsc8a32d14.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/LDR%20pre/P1000295_zpsc8a32d14.jpg.html)

The centre LED is purple BTW.

[Ali Tait]

Very nice, like the wood.

[Sovereign]

Very nicely done Richard !

[Light Dependant Resistor]

My Stereo Coffee LDR pre is now working. 4 inputs (3 on a piggyback board) and the front panel is now finished. I used a piece of Ipe (Brazilian Walnut) flooring; it's really hard! I had to cut it down from 18mm to 10mm thickness, not easy to do. The knobs are American walnut, turned on my little metalworking lathe, and I had to turn a shaft extension for the 500k log pot, as it has a very short shaft.
The digital voltmeter is normally switched off with the push switch below it, to save power, as this is run from a 1.2Ah battery, charged by a small solar panel. There is a mains charging circuit installed, but I haven't quite finished that yet.
I seem to have muddled up the wiring somewhere, as although it works OK and sounds very dynamic, when I switch the battery over to the charging circuit, which should switch off the LDRs, there is a fixed medium level audio output still feeding the power amp. The volume control has no effect on this. Oh well, I will have to work through the circuit; it didn't do this before with the single output board.
The sound is promising, but of course it shows up deficiencies elswhere in the chain. And I wonder if these components need to burn in, the way others do.
I will add more pics when I pull it out to modify it, and plan to veneer the aly lid too.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/LDR%20pre/P1000298_zps13470a41.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/LDR%20pre/P1000298_zps13470a41.jpg.html)
http://i1134.photobucket.com/albums/m604/awkwardbydesign/LDR%20pre/P1000295_zpsc8a32d14.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/LDR%20pre/P1000295_zpsc8a32d14.jpg.html)

The centre LED is purple BTW.

Hi Richard
There should be 0v -no voltage across the series and shunt LDR's during charging - if you are switching in your external charger. A diode or diodes can assist to define current in desired direction. Can you send me a diagram please of how the external charger is connected.

Probably the simplest is to just leave your solar panel connected permanently to your battery , as current draw on the stereo coffee is minimal approx 8ma. The solar panel should maintain the battery at about 12.2-12.8v which will indicate the solar panel as a charging source is slightly in front and enabling charging, rather than allowing the battery to dip below 12v

Let me know if I can help further.

Cheers / Chris

[awkwardbydesign]

Hi Chris. Actually, I discovered that the volume slowly fades to nearly nothing when I switch off. It doesn't make any difference whether the charger is connected or not; I only have the solar panel wired in at the moment. Only nearly nothing though, I suspect I have an earth loop, especially as there is a slight hum when the pot is half way round (when it is turned on, that is). Silent at min and max volume settings though.