Adding remote control to an LDR pre.

[awkwardbydesign]

I decided to add a remote control to my LDR pre, just for the hell of it. A new box was donated by Dan (loosend) and after searching ebay I decided on this remote control kit - http://www.ebay.com/itm/MV-06-6-Way-...item20e9cab377
Of course, it came with a schematic. In Chinese! A request for an English version got no reply, so I searched for help. DIY Audio had an old thread which helped, so I built it on a breadboard, and it all seemed fine. I drilled the case to fit the remote and the LDR attenuator, to which I added a 5th input, and fitted the remote kit, with a set of LEDs. As I was using only one channel of each relay, to switch the control voltage for the LDRs, I had to figure out how to wire it up to suit.
This was when I realised there was a problem; relays 1-4 switch on and off as expected, but switching on relay 5 (and 6, they are linked) left relay 4 on! It turns out that this isn't a true 5 way switching kit, but a 5.1 AV kit! Eventually I worked out that if I diverted the output from relay 4 through relay 6 to the normally closed pins, then switching on 5 (and 6 - linked) would cut the output of 4! So at last I had a true 5 way switch. Phew!
Then I had to configure the charging system so that when the battery was charging, it would cut the power to the remote and the LDRs.
Did I mention it's battery powered? A 12v 1.3 Ah battery lasts about a week before it needs recharging. I have an LED voltmeter mounted on the front panel to keep a check; switchable to avoid current drain.
And it works! With the Squeezebox Duet and ReadyNAS I no longer need to move. Ever!
Except to cut the red transparent Perspex front panel (like an Albarry) and fit a flashing LED so I don't overcharge the battery; it seems to sound best between 12v and 12.3v. And as I have a newer control board from Chris to try (version 6?) that will go in after I have got used to the sound again. And I would like to work out how to get more travel on the pot (at the moment it is running at the 9 o'clock position; it's 100k as opposed to the 250k it used to be).
Now I just have to finish the speakers, the Velleman K4000 power amp (1 channel low output) and modify the Velleman K8020 pre I picked up recently!
Oh, and rewire the balance control the right way round!

[Light Dependant Resistor]

Hi Richard
Nice work ! , does the pot have a second gang ? I recall similarly
building a remote version and to get what was then 200k I routed
the series anode through the second gang like an added series
resistor, but still being addressed by the wiper.

If just one gang, you can also arrange a 56k resistor across the shunt side
of the pot. So wire a 56k resistor central leg, to left hand side of pot - legs down
shaft facing you. which diverts more current to the shunt LDR's .

Looking great

Cheers / Chris

[awkwardbydesign]

Can you sketch the layout of the 200k option? I can't quite visualise it. Someone else mentioned it, but I didn't understand it then, either.
And the 56k resistor; does that go to J27 or J36?

[Light Dependant Resistor]

Can you sketch the layout of the 200k option? I can't quite visualise it. Someone else mentioned it, but I didn't understand it then, either.
And the 56k resistor; does that go to J27 or J36?

Hi Richard
I have attached a diagram. Method is to join the wiper ( central leg ) of the first gang
to the left hand side ( legs down shaft facing you ) terminal of the second gang then
take the output from the right hand side terminal of the second gang = 100k + 100k

Yes J27 shown in the diagram it needs to go back to control board J1
in effect forming a lower resistance across the shunt circuit.

You could also try a combination of the two ( = Janis Joplin album Cheap Thrills first track )
where you have more current to the shunts via the 56k and more series resistance
wiring both gangs, as described above. ending up at the series LDR's J36 , J38 and J39 ,
one at a time, via your well thought out relay system.

Cheers / Chris

Richards Volume.pdf

[awkwardbydesign]

I tried the 56k resistor across the shunt side, and it sounded awful! Tizzy and recessed in the midrange, strange. It reminded me of the time I tried a law faking resistor on the pot before going to a 250k log pot. I've gone back to the original wiring, just using the 100k pot in the remote kit. The control is so slow it is easy to set it where I want it anyway. I will experiment further at a later date.

[Light Dependant Resistor]

Hi Richard
Thanks for your observations, it would be good then to extend the resistance to 200k via the method I outlined,
as it is getting closer to the 500k normally used.

Cheers / Chris

[awkwardbydesign]

Thanks Chris. I assume simply adding a 100k resistor in the link to the switch would do the same job? Using the other half of the pot would be awkward to implement, and add extra wiring. But would the volume still drop to zero when the pot is turned fully left? I will be doing something similar to my Velleman K8020 pre, but at the input end of the pot, which would stop it going to full volume; I do understand that the LDR volume control works differently.

[Light Dependant Resistor]

Thanks Chris. I assume simply adding a 100k resistor in the link to the switch would do the same job? Using the other half of the pot would be awkward to implement, and add extra wiring. But would the volume still drop to zero when the pot is turned fully left? I will be doing something similar to my Velleman K8020 pre, but at the input end of the pot, which would stop it going to full volume; I do understand that the LDR volume control works differently.

Hi Richard
Adding 100k, but not as part of the pots wiper travel will work, it will add approx 7k resistance to the signal side of each inputs series LDR
I will see if I can come up with a better solution for you if you are just going to use 1 gang. Yes volume should be very quiet when fully left
if adding series resistance in the link to the switch.

Cheers / Chris

[awkwardbydesign]

OK, thanks.

[awkwardbydesign]

Update. I took the LDR pre along to a bake-off, and with the 100k resistor added to the pot the sound was flat and undynamic (compared to a Trilogy valve pre into Trilogy valve monoblocks). I came home and removed the resistor, and it improved! I have no idea what's going on. But there is a point on the volume setting, above which the sound changes for the better. Maybe I will have to go back to manual control.
I also put in the last control board Chris sent me (the 2nd one that Rupert also had, and IIRC, quite liked). Will have to do some swapping around when I feel up to it.
And Chris, you say the new board will need careful placing and connecting, more than the old ones; I will have to send you some pics of my layout so you can explain it to me in words of one syllable!