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Optical Volume Control Professional PCB

Which soldermask colour do you prefer for future PCB´s?

  • red

    Votes: 66 13.3%

  • green

    Votes: 118 23.8%

  • yellow

    Votes: 54 10.9%

  • black

    Votes: 97 19.6%

  • white

    Votes: 52 10.5%

  • blue

    Votes: 108 21.8%
  • Total voters
    495
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#341
Its not really the Lightspeed design thats flawed is it Blues? The LDR wont go below 40R without slowly killing itself. If you design knowing that it will go to 40R safely and you get what you expected I fail to see the flaw. If you try to use this with a high gain system, the flaw is really in the expectation of complete silence in a situation in which thats impossible.
Ted, your best bets are to A: Lower the voltage like you talked about to get a higher series resistance B: Add a series LDR and set it at a resistance that yields a lower min volume with a 40R shunt C: Add a parallel shunt to get 20R
Uriah
 
#342
udailey said:
...The LDR wont go below 40R without slowly killing itself. If you design knowing that it will go to 40R safely and you get what you expected I fail to see the flaw. If you try to use this with a high gain system, the flaw is really in the expectation of complete silence in a situation in which thats impossible. ...Uriah
Click to expand...

It can be designed to go below 40R with device safety in mind. Complete silence is golden at times and this too is very possible and can be put into the design.

I don't want to disclose it just yet as this might be a nice competition to the LS...it's possible that the smart diyers here will figure it out.:idea:
 
#343
There are very few "high gain" amplifiers that will have the same sound signature when operated at low volume - they're not designed to do this, obviously, but this same situation crops up occassionally in pro-audio circles where you have to operate the system at levels far below it's designed levels and sounds rather "thin".

There is a device called a "power soak" that's a passive power attenuator that is fitted between the power amp and the speakers to "suck up" about 10dB - available at pro musician centres, PA hire, audio engineers, etc

You may have to build your own as the impedances (at both ends) has to be right for your own system to avoid mismatch loading and power compression - plenty of info about L-pads, T-pads, H-pads, etc, available on the net, etc

Not my first choice of solutions, but an "old days" non intrusive option.

I'm not sure about current LightSpeed cct variations, but the addition of o/p "mute" relay is simple and very useful.
 
#344
Personal announcement

Well my friends it is time to say thanks to all of you, who like and ordered my pcb´s.

Because i am no developer of electronic circuits but have the knowledge to design pcb´s, i wanted to give something back to the community.

Since i started with my 1st pcb, the Optical-Volume-Control on 15th October 2009, a small donation from every sold pcb goes to diyaudio.com

Today i am proud to say that your :grouphug: cumulated donation achieve

:worship: $ 1.500 :worship:

Keep on having fun with my pcb´s and best regards

Oliver​
 
#351
Hi Oliver,

How come I can't adjust the signal output of the unit when I adjust the (left or right) pot to balance the channel? I adjusted the pot on both extremes, still did not notice a slight change on the output voltage. I built two of these optical volume control both of them can't be balanced. Both of them respond to the volume control fine when I tested with dual trace O'scope.

Thanks,

Joe
 
#353
Marra said:
Could someone please advise me as to what value resistor to place across the output of the +5 volt shunt regulator to simulate the Optivol load so that I can set the voltage before connecting up the LDR's. TIA
Marra
Click to expand...

Did you use my +5V shunt reg?

If yes, you don´t need to simulate the load.
Just use a resistor between 22R and 10R to set the shunt current to ~90mA to 200mA and regulate the output voltage to +5V. that´s it.
 
#359
AndrewT said:
How does you regulator use Vref to determine output voltage?

I suspect that your Vref is a bit low. It can be left as is, or corrected by adding a diode for an extra 0.7V
Click to expand...

Thanks Andrew; I've decided to leave as is.
I plugged the optivol into my system and an quite impressed with the sound despite my Aleph 5 only having an input impedance of I believe 10k. I will listen for a couple of hours today and then try it as the VC in front of my DCB1.
My thanks to George for making his design public; Oliver for the pcb's and the advice from various people on diyaudio.:up:
 
#360
Marra said:
Thanks Andrew; I've decided to leave as is.
I plugged the optivol into my system and an quite impressed with the sound despite my Aleph 5 only having an input impedance of I believe 10k. I will listen for a couple of hours today and then try it as the VC in front of my DCB1.
My thanks to George for making his design public; Oliver for the pcb's and the advice from various people on diyaudio.:up:
Click to expand...

And not forgetting Uriah for his excellently matched LDR's
 
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