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-input-Motorized-Remote-Volume-Control-ALPS-/141361329015?hash=item20e9cab377
Of course, it came with a schematic. In Chinese! :doh: 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! :steam: 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! :D
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! :rolleyes:
Oh, and rewire the balance control the right way round!
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20151120_134640_zpszjuy3hux.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20151120_134544_zpsz9zoysjz.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20151120_151045_zpsn1d1uihf.jpg

[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

15721

[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!

[Light Dependant Resistor]

Hi Richard
Is the 100k you are using a log or a linear type ? Your findings suggest leaving the gain
of the circuit as is. Boards since August have replaced former diodes with transistors
and more recently have rearranged components to greatly assist. I will try and get
yourself and Rupert one of these before New Year. Yes J2 control board ground now needs connection
to your star ground earth.

Cheers / Chris

[daddydj]

Excellent job, I was thinking of doing something similar with my LDR.
Was it worth the trouble would you say?

[awkwardbydesign]

Excellent job, I was thinking of doing something similar with my LDR.
Was it worth the trouble would you say?

NO! :lol:
After having to make a new case, bodging a fix to make a 5.1 remote into a true 5 way, discovering that adding resistors to a 100k pot to get a decent amount of travel changed the sound (for the worse; I have no idea why that is so!), getting up to change the volume or inputs doesn't seem so bad. I may even go back to manual!
A simple unit has now become over complicated for no real benefit, but I am retired and got bored, so the challenge was interesting. Don't bother, is my advice.

[awkwardbydesign]

Hi Richard
Is the 100k you are using a log or a linear type ? Your findings suggest leaving the gain
of the circuit as is. Boards since August have replaced former diodes with transistors
and more recently have rearranged components to greatly assist. I will try and get
yourself and Rupert one of these before New Year. Yes J2 control board ground now needs connection
to your star ground earth.

Cheers / Chris

Thanks Chris.
The pot is 100k log. I always did run a ground wire to the star ground, which is lifted from chassis ground with a 20 ohm resistor, like this.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Ground%20lift/Ground%20lift%202_zpszjyo97py.jpg
I will have to experiment with lifting or combining some of the ground wires, as it has more hum than my TVC. But at the moment I am concentrating on building a simple valve tester, as I have a load of old valves. http://www.valveheaven.com/wp-content/uploads/2015/03/An-inexpensive-easy-to-build-diy-valve-tester.pdf

[Light Dependant Resistor]

Thanks Chris.
The pot is 100k log. I always did run a ground wire to the star ground, which is lifted from chassis ground with a 20 ohm resistor, like this.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Ground%20lift/Ground%20lift%202_zpszjyo97py.jpg
I will have to experiment with lifting or combining some of the ground wires, as it has more hum than my TVC. But at the moment I am concentrating on building a simple valve tester, as I have a load of old valves. http://www.valveheaven.com/wp-content/uploads/2015/03/An-inexpensive-easy-to-build-diy-valve-tester.pdf


Hi Richard
My thoughts are to use the cathode returns J40 and J25 instead of the normal anode way of adjusting volume.
I will try it relative to 100k resistance and report back. Diagram attached shows how it may work.
15885

As the wiper being ground gets closer to say series cathode j40 it is in effect turning the internal led ON and causing the series pair to lower
their signal side resistances, and the shunt pair progressively off via 100k resistance, if volume was fully on. I think your 100k may be ideal then
as the voltage at the cathode is always lower than at the anode. So in effect you would rearrange j40 and J25 wiring to be
the upper and lower arms of the pot, and the wiper to be ground. Anodes would be fed straight from J1 control board out
via your balance control. Let me test it !

Cheers / Chris

[awkwardbydesign]

Thanks Chris. Bear in mind I have split the 2 halves of J27 and put a 470R balance pot across them. That would need to be re-organised.
(I think it's J27; without opening it it's hard to remember!)

[Light Dependant Resistor]

Hi Richard
The method of using J40 and j25 as connections to the pot and the
pot central leg grounding, works. I have tried it just observing resistance
so far, and it copies as a 100k pot to give, 36k travel for the shunts
and just over 40k travel for the series. This was with NSL32SR3

I need to listen to it connected this way, but from what I am measuring it is very
controlled in volume adjustment. ...and of course nothing better to do on Xmas day :)

Will give it a listen, and report back.

Cheers / Chris

[awkwardbydesign]

Thanks, Chris, and Merry Christmas. Or is it Boxing day there already? :D

[awkwardbydesign]

Hi Chris. Hope you had a good Christmas.
A question about wiring the cathode volume control. How do I connect the earth wiring? There are 2 connections each to J40 and J25, so is one of them still earth, and I only connect the pot to the other one? This is my layout at the moment, 2 boards piggybacked with the shunt LDRs on the top board. J27 is split for the balance pot. The star earth post is insulated from the case, with a switch to vary the connections.
I'm a bit confused as to how the earthing will be organised now. And have I got too many earth connections?
http://i1134.photobucket.com/albums/m604/awkwardbydesign/LDR%20pre/Cathode%20volume%20control%20for%20LDR_zpss6vflvcq .jpg http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20160215_101413_zpspl6xjb59.jpg http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20160215_101340_zpsy7owy9j0.jpg http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20160215_101405_zpstudl9idc.jpg

[Light Dependant Resistor]

Hi Richard
Very quiet Xmas , but very nice too lots of nice walks, hope yours went well.

Thanks for your PM to steer me to your post. With cathode volume control, we are just chassis grounding
the signal ground, and you have correctly wired that at j25 lower. the other ground connections are
control board J2 also star grounded, but we have a new ground to make which is now the wiper of the pot.

You can do all of this without lifting the upper LDR board to reveal the lower board, by knowing exactly
the wire from j40 upper and J25 upper which are the cathodes. hopefully your wire length will be
suitable to extend J40 upper (previously ground ) from each board now to the RHS of Pot , and
j25 upper from each LDR board to the LHS of pot.

So disconnect j40 upper each board -2 wires and J25 upper - 2 wires
from your very neatly wired star earth, these need to go to J40 RHS leg of the pot
and J25 LHS of the pot.

Where previously you wired Right Hand Side leg of pot to pole of switch then via contacts to series anodes
and Left Hand Side of Pot to the Shunt anodes you would now have J1 control board OUT with a wire directly to
shunt anodes - yours running via a 2.5k pot to balance current left to Right across the shunt LDR's
so its wiper wire this to J1 ..... next the same for the series LDR now by the looks of it running to common of the relays
NO ( normally open ) connecting to each anode- when coil is activated. .... wire this also to J1

you should be able to steal these off the RHS and LHS of the pot... all now wired to J1
and central leg of pot wire --- this is now grounded.

With cathode volume the steering of current to shunt and series LDR;s is being done via the separation
on the LDR board of shunt cathode completely separate to series cathode. So just at the other end of the circuit.
How this works is that there is a potential difference between ground ( now wiper of the pot ) and the current
seeking ground ( really a potential difference ) from the cathodes. Voltage at the cathodes is going to be
J1 less the LDR forward voltage. so likely about 6.7 volts at the cathodes as J1 on model of control board will be
7.5-8v

So with some forward planning you should not have to make too many alterations to wiring ut there will be some,
rather you should be able to rearrange same wires to do different wiring for cathode volume.

I am online for another few hours and will help you tomorrow when I wake up.

Cheers / Chris

[Light Dependant Resistor]

Hi Richard.

Where I said, you should be able to steal these off the RHS and LHS of the pot..
I of course mean the wiring you have there at the moment that is going to
LDR shunt anodes and to your relay common... . both are now wired to J1
as we want current continually at one series LDR pair - switched via your great relay
improvement, and current at the shunt pair via your 2.5k pot wiper.

The central leg of pot wire --- this is now grounded, so make a cut at the J1 end of
that wire and provide it instead to your star ground.

J40 and J25 cathodes - that were previously grounded are now commissioned
to be on the RHS and LHS of the pot legs.

Cheers / Chris

[awkwardbydesign]

Thanks Chris. I'll try and get my head round that later!

[awkwardbydesign]

Right, here goes. On the control board, J1 goes to J27 (L and R, via the balance pot), also to the relay common (which goes via the relays to the the series anodes). J2 still goes to the star earth. J3 still goes to 12v.
On the LDR boards, both J40 (series cathodes?) goes the top* leg of the pot. The other J40 terminals are not connected (they run to J25 anyway). J25 (shunt cathodes?) goes to the bottom* leg of the pot. The other terminal on J25 (linked to J40) goes to the star earth, because that is signal ground. Have I got it right? If it works, I will tidy up the wiring later. Honest!
* You say right and left legs, I say top and bottom legs of the pot. I was assuming right equalled top (as in full volume when wiper reaches it), but I suspect that is the wrong way round.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20160221_131654_zps0sfnjwvx.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/20160221_140931_zpsv7snntjv.jpg

[Light Dependant Resistor]

Hi Richard
Yes you have it right, but you need also to ground the central leg of pot to star ground.

The attenuation ability occurs in this revised method, because a potential difference
same as was with the usual anode method, now exists on the LDR cathodes.
Same as cathodes all grounded previously, ground is needed to steer attenuation.
In this case the series or shunt arranged LDR is progressively turning on as current
is being instructed toward, and away as the case may be from that pair.

So lessening volume the shunt cathodes seeking ground via wiper progressively turns on the shunt pair
and increasing volume the series cathodes seeking ground via wiper progressively turns on the series pair.

Have volume midway when you audio test to ensure pot is wired correctly, your
description suggests it is right already. :)

Cheers / Chris

[awkwardbydesign]

Thanks Chris. The white wire from the star earth goes to the pot wiper. I forgot to mention that, as it wasn't something I was confused about, the only thing I wasn't! I'll give it a try later; at the moment I have borrowed a Primare integrated (as a fairly neutral reference) to try to sort my speaker crossovers. They have been waiting nearly 2 years!