Could you please try a 12V battery instead of your wallwart? You may have something going on that none of us can know in your wallwart or in the power feeding the wallwart.
It truly is odd what you are experiencing and something wonderful can be attained with LDRs. Maybe together we can all figure out the problem.
Uriah
It truly is odd what you are experiencing and something wonderful can be attained with LDRs. Maybe together we can all figure out the problem.
Uriah
This is a great idea. Something latent seems to be the problem.
It is encouraging to hear that this seems to be an isolated incident. Of all the info there is to read about this great design, nothing has been found to confirm my observations.
As stated earlier, this is a very straight forward and innovative design.
What is more puzzling to me is that two identical units of the original Lightspeed design were assembled, with identical, pre-described PSU's and both exhibit the same sonic signature. Therefore your argument for possible contamination via the PSU/AC adapter is a valid one and quite an excellent idea.
I will try this and inform you on the outcome. It is good to know that no one else seems to have had similar experiences.
Thanks
Sorry to change the subject here, but I'm new to this thread, having just finished my first LDR attenuator just recently. It sounds lovely in my secondary system, but less so in my primary system due to the tube output stage of my DAC. Sooooo....I'm thinking of building Mr. Pass's buffered version (p137 of this thread - I thought the picture would appear in the quote, but I guess not). Before I go to the trouble of learning how to match complementary JFETs (not a prospect I'm relishing) - is there any reason that the 2SJ74/2SK170 pairs can't be replaced by an LM394 supermatched pair? Would any adjustments to the circuit be necessary? I know they're obsolete but they're still readily available on ebay. Thanks to anyone who can provide guidance!
Sorry to change the subject here, but I'm new to this thread, having just finished my first LDR attenuator just recently. It sounds lovely in my secondary system, but less so in my primary system due to the tube output stage of my DAC. Sooooo....I'm thinking of building Mr. Pass's buffered version (p137 of this thread - I thought the picture would appear in the quote, but I guess not). Before I go to the trouble of learning how to match complementary JFETs (not a prospect I'm relishing) - is there any reason that the 2SJ74/2SK170 pairs can't be replaced by an LM394 supermatched pair? Would any adjustments to the circuit be necessary? I know they're obsolete but they're still readily available on ebay. Thanks to anyone who can provide guidance!
It would be easier to buy matched jFets from Blues or Spencer here on the forum as the 2SJ74 are difficult to source nowdays. If you really want to match yourself:
Short the gate and source legs of the 2SK170. Connect these to the neg of a 9V. Connect the drain to the pos side with a 10ohm resistor. Use a DMM to measure voltage across the resistor. 0.1V=10mA Idss
THAT Corporation sells a 300 series that I have been thinking to try out. Its not expensive and it includes 4 transistors. Can get 4 matched PNP, 4 matched NPN or 2 PNP and 2NPN matched. Not saying you shouldnt try 2sj74 but man they are hard to come by and expensive, specially if doing your own matching.
ITs not hard at all to match the transistors by the way. Super simple. Go to pass' site and look up his articles. http://www.firstwatt.com/pdf/art_matching.pdf
You can literally get it done in 20 minutes. Including building the jig.
ITs not hard at all to match the transistors by the way. Super simple. Go to pass' site and look up his articles. http://www.firstwatt.com/pdf/art_matching.pdf
You can literally get it done in 20 minutes. Including building the jig.
if "matching" means selecting jFETs with the same or very similar Idss then the "selecting" process is very simple and very quick. And a smallish batch of devices will yield a fair number of selected pairs, triples, quads.
Matching transconductance is all together much slower. Yield of matched pairs is much lower. I have not tried to find matched triples nor matched quads. I know how much work would be involved to find a tiny proportion of triples or quads. From a 200batch I'd guess I might get one matched quad to better than 1% of Id over a range of Id from 25% to 100% of Idss.
In the B1 paper Nelson specifies that they only need Idss matched so it should be very simple. Now that I think about it I have not looked back at that LDR circuit Nelson designed in a long time. Maybe it does have PNP, but if you just need a buffer the B1 is cheap and easy.
If I recall the B1 does not need the PNP version, only the NPN.
Also, I think AndrewT sells matched devices and his prices are better than anyone else. I think you have to ask him because I have never seen him advertise it. But anyway, if I were buying matched devices it would be from Andrew. We all know how particular he is about things being just right and thats the way I would want my matching.
Uriah
If I recall the B1 does not need the PNP version, only the NPN.
Also, I think AndrewT sells matched devices and his prices are better than anyone else. I think you have to ask him because I have never seen him advertise it. But anyway, if I were buying matched devices it would be from Andrew. We all know how particular he is about things being just right and thats the way I would want my matching.
Uriah
Well, I dont know that they will or not. I am working up a board to play with for the THAT devices right now. Dont know how these will work but its worth a shot. Yours are nice metal cans. I like that idea but pricey!! OMG Besides being out of production the cheapest I can find is 6.99 each plus 5 shipping. THAT is expensive to but at least you get 4 per package and can buy from Mouser when you get the rest of your parts. I think your idea with those cans will work but you might have different resistor values. Its worth playing with I think if you dont mind stuffing them into a protoboard and testing different combos.
Hmmm....that is a little expensive for a "maybe". I'll check out the souces for matched sets of 2SJ74 and 2SK170 first.
By the way, Uriah, the Lightspeed I put together using your board, LDRs and instructions sounds marvelous with my reclocked Sony CDP-710, Rotel RB-980BX and Cambridge Soundworks speakers. Thanks for making this possible.
By the way, Uriah, the Lightspeed I put together using your board, LDRs and instructions sounds marvelous with my reclocked Sony CDP-710, Rotel RB-980BX and Cambridge Soundworks speakers. Thanks for making this possible.
Here's an interesting snippet from the latest Stereophile review of the DCS Debussy Dac which has volume control in the digital domain. Yet two stage adjustable analogue level output stage 2v or 6v, this means you can use it straight into a poweramp and only use the top 25% of the digital volume control, this way you should not be "bit striping".
Sterophile Quote: The differences in sound between the Debussy into a preamplifier and the Debussy directly driving a power amplifier will depend on the preamp's transparency, dynamic capabilities, and overall quality. Sending signals directly to my Musical Fidelity Titan amp from the Debussy or through my reference preamp, a darTZeel NHB-18NS, I heard minimal differences. Given the darTZeel's price of $29,500, that's what you should expect. :Stereophile Quote
Guess what the Dartzeel uses as a volume control? you guessed it. A Lightspeed setup, they tried to patent when they first released it but I quickly put a stop to it showing proof to the patent offices in Eu and USA that I first did the LDR volume control back in early 1974.
Quote from the Stereophile Review of the darTZeel NHB-18NS
"For the first time in all audio history," said Delétraz, "the signal path does not pass through any physical switch, relay, or even transistor switch." Instead, inputs are enabled or disabled using electro-optical analog components. Because there is no physical input switch or FET-based analog switch, there is no "diode effect," either electrical or chemical (electrovalence differential), to alter the signal, he explained in an e-mail. Quote
Cheers George
Sterophile Quote: The differences in sound between the Debussy into a preamplifier and the Debussy directly driving a power amplifier will depend on the preamp's transparency, dynamic capabilities, and overall quality. Sending signals directly to my Musical Fidelity Titan amp from the Debussy or through my reference preamp, a darTZeel NHB-18NS, I heard minimal differences. Given the darTZeel's price of $29,500, that's what you should expect. :Stereophile Quote
Guess what the Dartzeel uses as a volume control? you guessed it. A Lightspeed setup, they tried to patent when they first released it but I quickly put a stop to it showing proof to the patent offices in Eu and USA that I first did the LDR volume control back in early 1974.
Quote from the Stereophile Review of the darTZeel NHB-18NS
"For the first time in all audio history," said Delétraz, "the signal path does not pass through any physical switch, relay, or even transistor switch." Instead, inputs are enabled or disabled using electro-optical analog components. Because there is no physical input switch or FET-based analog switch, there is no "diode effect," either electrical or chemical (electrovalence differential), to alter the signal, he explained in an e-mail. Quote
Cheers George
George,
Curious, how did you know they were about to patent this idea. Great that you caught it!!
In the 6 Moons review. The interview with Herve is after the review of the NHB-18NS.
6moons audio reviews: darTZeel NHB-18NS
Quote:
Q: What is wrong with conventional volume controls?
A: You lose something. I use a system that varies resistance with light. However, until all the patents are in place, I would prefer not to specify the details.
Quote:
Cheers George
6moons audio reviews: darTZeel NHB-18NS
Quote:
Q: What is wrong with conventional volume controls?
A: You lose something. I use a system that varies resistance with light. However, until all the patents are in place, I would prefer not to specify the details.
Quote:
Cheers George
Just finished building the Lightspeed kit I bought from udailey. Good news is it works! However the volume control is reversed somehow. The volume goes down when turned clockwise, and goes up when turned counter clockwise. Can I simply swap the leads going to main LDR and shunt LDR from the potentiometer?