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
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
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.
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.
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.
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
cumulated donation achieve
$ 1.500
Keep on having fun with my pcb´s and best regards
Oliver
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
cumulated donation achieve $ 1.500 Keep on having fun with my pcb´s and best regards
Oliver
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
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
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.
Thank you Oliver; yes its one of your +5V regs. I'm using 20R. I will plug in and set the voltage. Thanks again.
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.
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.
And not forgetting Uriah for his excellently matched LDR's
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