Matching LDR pairs
One way I sped up the matching job was to test 6 at a time. Basically, I took an IC socket and soldered a wire down each side of the pins. Then you can stick 6 ldr's into the socket and power the whole lot thru the pot. That way you warm up 6 all at once. Set the pot to 9 oclock and measure all six. then 12oclock and measure again etc. With 4 measurements and ldr's all from the same sorted lot, really close pairs emerged quickly. The measuring just took a few mins once the rig was set up.
One way I sped up the matching job was to test 6 at a time. Basically, I took an IC socket and soldered a wire down each side of the pins. Then you can stick 6 ldr's into the socket and power the whole lot thru the pot. That way you warm up 6 all at once. Set the pot to 9 oclock and measure all six. then 12oclock and measure again etc. With 4 measurements and ldr's all from the same sorted lot, really close pairs emerged quickly. The measuring just took a few mins once the rig was set up.
Harry3 said:
My sources:
Are Transport/DAC, Tentlabs clocked Teac VRDS-25 as a transport, (I'm the Tenlabs agent in Australia)
My own heavily moded Harman HD970 with discrete Transimpedance I/V stage and pure class A discrete output stage all dc coupled as the dac, and a stunning Tandberg 3001 FM tuner.
My preamp:
That's obvious, the Lightspeed Attenuator
My speakers:
Bi-amped Martin Logan Monoliths III Electrostatics
<100hz they have a 12" driver now tuned to -3db @ 28hz actively bi-amped with my own designed active xover and a revamped SV12 12" bass unit in the Monoliths, the Eminence one was a cheap sad driver, and badly implemented.
My amps:
Were my own 805 SET tube monoblocks for the stats,
now a moded heavily biased (50 watts) class A ME850 for the Stats and a stock ME850 for the bass, (modded inputs on both amps to 200k) also DC coupled.
This system is now dc coupled from dac chip (AD1955) output to the speakers, I have found that any coupling cap anywhere in this system no matter how good or esoteric is detrimental to the sound.
As for phono, from the dozen or so of my customers that use them, two of them use the Dynavector phono stages, and one uses his own design based around an opamp, the others I cannot remember, Lehman rings a bell though.
Cheers George
This is the best I've seen, one of the members here thought it up, no signal degradation at all. Going to be a b***h to build, but all others are a compromise, no matter which one you use.
If you don't want to use this, then your better off using a QED input switch box in front of the Lightspeed, then when your serious about showing off your system, go back to direct and forget the QED.
Cheers George
If you don't want to use this, then your better off using a QED input switch box in front of the Lightspeed, then when your serious about showing off your system, go back to direct and forget the QED.
Cheers George
Attachments
Has the member just thought or has he built it? If I understand this circuit right there is much attenuation of the active source in comparison to a relay (0,1 Ohm vs. 80 Ohm). I think it isn't the Silonex 2R part but what is it (with 1k)?
What is the mysterious of the QED device? I can't see nothing out of the box.
What is the mysterious of the QED device? I can't see nothing out of the box.
LDR for channel switching
Tolu,
Whilst the LDR produces a higher in series resistance than a relay or switch this should not be a problem with most devices today.
usually they have enough signal level to support this increased resistance (i.e voltgae drop) and if you add some additional circuitry to this circuity it is relatively easy to add channel level matching too (either manual or through software).
Tolu,
Whilst the LDR produces a higher in series resistance than a relay or switch this should not be a problem with most devices today.
usually they have enough signal level to support this increased resistance (i.e voltgae drop) and if you add some additional circuitry to this circuity it is relatively easy to add channel level matching too (either manual or through software).
I'll have a look into another solution...
Time for some more recruiting, to all the new posters please be good guys and vote here for a new Passive Preamp Heading
http://www.diyaudio.com/request/
Cheers George
http://www.diyaudio.com/request/
Cheers George
lightspeed
Hi george,
Think it's time to tell you my litlle story.
After having read more than 1200 messages ,and several days later, about musical optocouplers, Is thought my time had come!
So after ordering 12 litlle black 'S'marbles at Allieds I was able to match at least four out of a reasable average batch!
Put things together in your way, with a single motorised pot, remotecontroled. Tripple regulated 5volt. Noughty as I am, four 10uF simple el.condensors over the led-connections and go!!!
And go...means music! Must say sound improved, litlle sharpness from the first hour turned into smoother ver homogenous sound.
After 50years working with sound, I can tell you, it keeps me wondering. Some now and thens you meet things in toying with audio where you have no simple answers for!
Thanks for the great idea and for having me put on building one.
Btw the remotecontrolething I did I can advice to anyone. It's the Remote1 with the 16-Alps motorpot. From: Dantimax.
So, for guys and girls who are still hesitating building a beautifull
volumecontrole, start now building one! You will not regret it..
Or buy one from George. Saves you at least the time of matching
the optocouples. Which is, thanks to this forum, the only hard part of the project.
Have though a small question. I prefer playing through an old, modified and beautfull sounding combination of two Quad ESL63 speakers, fed by a rejuvenated (Netaudio,England) quad 303 amp. Since this amp has a rather low input impedance(22Kohm)
athough very good sounding with the lightspeed,I wonder if you ,looking at the drawing, can advice changes in the inputc
irquitry.
Hi george,
Think it's time to tell you my litlle story.
After having read more than 1200 messages ,and several days later, about musical optocouplers, Is thought my time had come!
So after ordering 12 litlle black 'S'marbles at Allieds I was able to match at least four out of a reasable average batch!
Put things together in your way, with a single motorised pot, remotecontroled. Tripple regulated 5volt. Noughty as I am, four 10uF simple el.condensors over the led-connections and go!!!
And go...means music! Must say sound improved, litlle sharpness from the first hour turned into smoother ver homogenous sound.
After 50years working with sound, I can tell you, it keeps me wondering. Some now and thens you meet things in toying with audio where you have no simple answers for!
Thanks for the great idea and for having me put on building one.
Btw the remotecontrolething I did I can advice to anyone. It's the Remote1 with the 16-Alps motorpot. From: Dantimax.
So, for guys and girls who are still hesitating building a beautifull
volumecontrole, start now building one! You will not regret it..
Or buy one from George. Saves you at least the time of matching
the optocouples. Which is, thanks to this forum, the only hard part of the project.
Have though a small question. I prefer playing through an old, modified and beautfull sounding combination of two Quad ESL63 speakers, fed by a rejuvenated (Netaudio,England) quad 303 amp. Since this amp has a rather low input impedance(22Kohm)
athough very good sounding with the lightspeed,I wonder if you ,looking at the drawing, can advice changes in the inputc
irquitry.
lightspeed post 1256
Hi Georgehifi,
This message belongs to 1256.I don't succeed in bringing in the drawing of my amp
I have link here:.http://www.geocities.com/ResearchTriangle/Lab/6722/quad303cirb.html
Hi Georgehifi,
This message belongs to 1256.I don't succeed in bringing in the drawing of my amp
I have link here:.http://www.geocities.com/ResearchTriangle/Lab/6722/quad303cirb.html
Glad you bit the bullet and built one for yourself, as I say to everyone wait till you hear it, you will not believe what you were listening too before no matter how good a active or passive pre you've had the you know Lightspeed is something special when you first hear it.
I just got back from demo'ing another Lightspeed Attenuator, this guy has a massive 4 separate box Jadis 500 poweramps, top Alon speakers huge, Teac DV60 cd, and his pre was a very expensive Matisse Reference. The Lightspeed killed it blew it away, he bought immediately, and is now selling the Matisse Reference pre.
As for quick look at your circuit diagram of the Quad input, it looks to me like it's got a 220K for R100, that why it sounds good already. If that's an earth rail at the bottom.
Cheers George
I just got back from demo'ing another Lightspeed Attenuator, this guy has a massive 4 separate box Jadis 500 poweramps, top Alon speakers huge, Teac DV60 cd, and his pre was a very expensive Matisse Reference. The Lightspeed killed it blew it away, he bought immediately, and is now selling the Matisse Reference pre.
As for quick look at your circuit diagram of the Quad input, it looks to me like it's got a 220K for R100, that why it sounds good already. If that's an earth rail at the bottom.
Cheers George
Hey guys,
i was really tempted to ask george to build me one but changed ny mind because if i build it myself and make it work it will be very satisfying.
so i have purchased 20 ldr but do not know how to match it! so questions are as follows.
1. is anybody willing to match 4 ldr out of 20 for a fee and gets to keep the remaining ones?
2. how do i match it? ive read the threads and got some idea but i would like to know what equipments are needed?
i apologize for all the newbie questions.
thanks,
ivan
i was really tempted to ask george to build me one but changed ny mind because if i build it myself and make it work it will be very satisfying.
so i have purchased 20 ldr but do not know how to match it! so questions are as follows.
1. is anybody willing to match 4 ldr out of 20 for a fee and gets to keep the remaining ones?
2. how do i match it? ive read the threads and got some idea but i would like to know what equipments are needed?
i apologize for all the newbie questions.
thanks,
ivan
