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Old 21st November 2011, 09:53 PM   #4321
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Quote:
Originally Posted by udailey View Post
I understand what you are saying now. I wonder if we did something like this with a .1% SS amp and a .1% tube amp if we would hear the warmth of tubes left over.
Uriah
YES!
it's amazing idea - null audio, you can hear what device 'added', after nulling, you will get possibly some 'extra' distortions in upper freq.
generally you could check audio and be 100% sure
just noticed you mentioned amplifier - I don't know if speaker outputs of amp could be checked this way...
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Old 22nd November 2011, 03:20 AM   #4322
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Quote:
Originally Posted by AndrewT View Post
use a double pole double throw (dpdt) relay and use the other changeover contacts to reduce the currents through the LEDs.
This could be used to protect the LED/LDR from long term deterioration if left in the max or min volume by accident.

Invoke the Mute at power off. Use the Play to delay signal transmission at start up.

Now that extra contact in the signal route has a benefit.
There r other features I designed in the circuit that r not mentioned.

Preventing thump when changing input selector and preventing speaker relay arcing.

Not necessary. Put a resistor of your choice across the series (used) contact. U have to drive the shunt LED hard otherwise mute will not be effective.

Enjoy

Gajanan Phadte
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Old 22nd November 2011, 10:41 AM   #4323
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Default Mute logic design

The design is posted here

Mute Logic for LDR volume control

Gajanan Phadte
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Old 22nd November 2011, 11:45 AM   #4324
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Is there any LDR user who has ideal (say 0.5dB) difference between channels?
In my case it's not just 1 channel is louder - it's also inconsistent - changing from R 5dB louder to L 5 dB louder.
George, is it possible with LDR to have it equal less then 1db?
thanks for input
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Old 22nd November 2011, 12:14 PM   #4325
udailey is offline udailey  United States
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Hi gmphadte,
Wow, I wish I understood logic circuits. It is something that I do want to learn one of these years because it can replace the need for programming in some situations and can reduce circuit size in other situations.
For mute I use two more LDRs and a mosfet based optocoupler inbetween them.
It goes like this
Signal - LDR - photomos to ground (normally closed) - LDR - output
So when we apply power to the circuit the LDRs go to low resistance and the photomos turns on and goes open circuit so that we dont have any signal going to ground. There is no click or pop of course.
Its a simple idea but I managed to complicate it a bit
Here is a link to my Picasa album showing the implementation.
Of course the sound improvement is not huge but it is better than straight relays/contact switchers.
Uriah
https://picasaweb.google.com/udailey...eat=directlink
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purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
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Old 22nd November 2011, 05:26 PM   #4326
oenboek is offline oenboek  Belgium
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Quote:
Originally Posted by redmaster View Post
Is there any LDR user who has ideal (say 0.5dB) difference between channels?
In my case it's not just 1 channel is louder - it's also inconsistent - changing from R 5dB louder to L 5 dB louder.
George, is it possible with LDR to have it equal less then 1db?
thanks for input
I made a design where I can do an autocalibration of the resistance of each LDR. See here : Sylonex and Arduino preamp. And it has an LDR in the feedback loop of the DAC to compensate the nonlinearity and temperature drift. I guess it allows for nearly perfect linearity between channels, but I've never measured this.
I admit that it's a lot more complicated then the standard version, and for sure it has not better sound, that is impossible. But it was fun to make and design, and it allows me to play with input resistance etc. It's still working fine, and I'm still working from time to time on the Arduino side of the game.
I'm convinced that the sound of the optocoupler pot is one of the best available. I have it together with a salas DCB1 and a Hypex amp. This combination is really sounding great, the impact of the music is huge. I doubt I will ever move to something different.
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Old 22nd November 2011, 07:44 PM   #4327
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Quote:
Originally Posted by oenboek View Post
I made a design where I can do an autocalibration of the resistance of each LDR. See here : Sylonex and Arduino preamp. And it has an LDR in the feedback loop of the DAC to compensate the nonlinearity and temperature drift. I guess it allows for nearly perfect linearity between channels, but I've never measured this.
I admit that it's a lot more complicated then the standard version, and for sure it has not better sound, that is impossible. But it was fun to make and design, and it allows me to play with input resistance etc. It's still working fine, and I'm still working from time to time on the Arduino side of the game.
I'm convinced that the sound of the optocoupler pot is one of the best available. I have it together with a salas DCB1 and a Hypex amp. This combination is really sounding great, the impact of the music is huge. I doubt I will ever move to something different.


Hi Oenboek, I did watch your auto cal development closely, as I went down that path with a designer/friend of mine also years ago, and I think I may have posted on your thread, that while with unmatched ldr's we did get the channels very closely matched with a similar auto cal circuit, the problem was the I/O impedances were vastly different for each channel at all differing levels, and this effected to tonal quality of left vs right, so while the gains were correct it was as though we had two different speakers of the same efficiency.

Cheers George
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Old 23rd November 2011, 06:45 AM   #4328
oenboek is offline oenboek  Belgium
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Quote:
Originally Posted by georgehifi View Post
Hi Oenboek, I did watch your auto cal development closely, as I went down that path with a designer/friend of mine also years ago, and I think I may have posted on your thread, that while with unmatched ldr's we did get the channels very closely matched with a similar auto cal circuit, the problem was the I/O impedances were vastly different for each channel at all differing levels, and this effected to tonal quality of left vs right, so while the gains were correct it was as though we had two different speakers of the same efficiency.
Cheers George
Thanks for replying. I do an online calibration of the resistance of each LDR individually. This guarantees that each of the resistances is OK and perfectly linear. Therefor the total impedance is also controlled and stable, as the gain is. It could be easier to calibrate gain only, but I wanted to have control of the impedance as well. As you state, this is as important as the gain especially between left and right channels. The additional advantage is that I can adapt automatically the impedance for each different source. I haven't programmed this yet, and I agree it goes too far, but it's possible.
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Old 25th November 2011, 03:58 AM   #4329
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Use a quad pot and try.

Gajanan Phadte
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Old 25th November 2011, 08:07 PM   #4330
Tolu is offline Tolu  Germany
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Hallo Lightspeed fans,

I have a problem with my Lightspeed. One Optocoupler is damaged. The one of the right channel gives a variety of 30 to 19000 Ohm and the damaged one gives with the same voltage a range from 62 to 159 Ohm.

Does anyone of you have one 32SR2S in C or D grade left over? Please send me an email!

Thanks a lot!

Thomas
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