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Old 3rd April 2012, 11:08 AM   #4471
soongsc is offline soongsc  Taiwan
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Recent notice indicates Cd in pro audio equipment analog circuits is exempt from RoHS till end of 2013. So it's good news.
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Old 3rd April 2012, 08:25 PM   #4472
DRONE7 is offline DRONE7  New Zealand
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Originally Posted by soongsc View Post
Recent notice indicates Cd in pro audio equipment analog circuits is exempt from RoHS till end of 2013. So it's good news.
eh..? What does this have to do with Lightspeed Attenuator.
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Old 3rd April 2012, 09:20 PM   #4473
fotios is offline fotios  Greece
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Originally Posted by georgehifi View Post
Glad it got to you safe and sound it's a long way from Australia to Greece, thanks for doing such a professional job on Johns new Lightspeed Fotios, he will be pleased when you forward it to him in freezing Norway, and if I decide to go remote with the production version I will be sure to contact you, it's far better than some of the rubbish available.
I have something in the oven for a Lightspeed Attenuator no expense spared version with your remote with contactless input switching, volume setup, balance and active unity/+6db gain buffer for those who need it or passive for the purists as it is now, contactless all the way through from input to output.

Cheers George
Thank you George. Oz to Greece distance is just 9 days. Parcel dispatched at 19 March and i received it at 28 March. And i live in north Greece, 600km far away from Athens. I did the modification with each respect to your work as you can see in pictures. I asked the LightSpeed to pass from my hands (it was a good oportunity, Greece is located at the middle of the travel from Oz to Norway) because i needed the case dimensions to draw the PCB to fit exactly inside Lightspeed.
Now the PCB layout is available for any DIYer.
Please feel free to contact directly with me in my e-mail address.
The same of course, for everyone else.
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Old 3rd April 2012, 11:26 PM   #4474
soongsc is offline soongsc  Taiwan
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Originally Posted by DRONE7 View Post
eh..? What does this have to do with Lightspeed Attenuator.
The LDR contains Cd.
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Old 4th April 2012, 12:43 AM   #4475
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Hehe good to hear that Drama is actively creating awesomeness

I finished building Uriah's lightspeed version a few hours ago, now it s 3:30AM and I simply cannot stop listening to music... I just hope the neighbours do not call the police on me

Congrats George on an amazing idea. On my setup, it completely embarasses an ARC LS-25 and a Klimo Merlin.

Only issues for now are the expected non-mute lowest volume, the fact that I connected the pot the other way around and volume increaseas when I turn it CCW, and the steep slope that the volume increases.

I plan on handling them all very soon with a simple redesign of the pot circuitry that will even render LDR matching unnecessary. I won t say more now, I want to try a few things first before I publish my protoboards.

Fotios' solution is also in my todo list. I do not really like the idea of digital stuff in there, but the lack of remote volume is very annoying for me because I listen to music on weird hours and I change the volume very often so that I do not disturb the neighbours.

Anyway
I will post some photos once I manage to find some decent looking knobs
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Old 4th April 2012, 02:19 PM   #4476
udailey is offline udailey  United States
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Dimitri
If you plan on some circuit to get rid of matching WOW that will be awesome! You must know that you can not just get the circuit to match them at one point and expect it to work from there on out. There are infinite points and the circuit must make up for the 'unmatching' at each point. I truly feel that a cpu is the only solution. Perhaps this is the route you are going or perhaps not. Good luck on it.
I could also see another circuit that samples the signal and matches to the signal on the other channel but you have to insert a stable signal into both channels to do this and then filter that signal out before it goes to the amp. DC would be the option here and this involves caps or a transformer in the signal which kind of kills the advantage of the LDRs.
Uriah
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Old 4th April 2012, 03:21 PM   #4477
BFNY is offline BFNY  United States
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Originally Posted by dimkasta View Post
I plan on handling them all very soon with a simple redesign of the pot circuitry that will even render LDR matching unnecessary. I won t say more now, I want to try a few things first before I publish my protoboards.
The only simple re-design I can see is to use a balance control.
This could be easily adjusted with headphones and a mono switch/source (most of my FM tuners have a mono button).

Of course, remote control balance would be best, so you can adjust in your chair. A direct wired solution is probably not that hard if you are handy and use a source like "Small Parts" (now amazon supply) for shaft extenders pulleys, motor, etc AmazonSupply.com: The Hardware Store for Researchers and Developers

I also mentioned using a step attenuator with adjustment pots as needed at each step in the "other" LED/LDR DC bias thread that goes into this concept more.
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Old 4th April 2012, 03:27 PM   #4478
udailey is offline udailey  United States
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The stepped way you are talking about I heartily agree with. Should work well but they still have to be moderately matched because when temp changes and they change resistance you want them to change in the same direction/rate. Also I wondered if people would put up with soldering 24 3 legged pots that cost about 84 cents each for each LDR. You might get away with 24 for each channel but it would also require a few more parts per channel. I just though its to much money and to much soldering for an enjoyable kit.
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Old 4th April 2012, 03:50 PM   #4479
AndrewT is offline AndrewT  Scotland
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fit fixed resistors.
Then trim (by adding a parallel resistor) one or other of the pair to bring the LDRs to similar attenuation.

The trimming could be by using a variable resistor (1M0 or 2M2) and replace with a fixed once measured.

The big advantage of switched & fixed resistors, is the ability to choose the attenuation to suit the listening conditions.
You could have coarse steps from -1dB to -100dB or finer steps from -1dB to -30dB or again finer steps from -20dB to -50dB, or finally from -40dB to -80dB. Just get a ball park attenuation range that suit your equipment and range of listening levels. Then choose the fixed resistors to suit.

You could use a 3step attenuator:
background music / answering the doorbell.
listening attentively
party !
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Old 4th April 2012, 03:57 PM   #4480
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by AndrewT View Post
fit fixed resistors.
Then trim (by adding a parallel resistor) one or other of the pair to bring the LDRs to similar attenuation.

The trimming could be by using a variable resistor (1M0 or 2M2) and replace with a fixed once measured.

The big advantage of switched & fixed resistors, is the ability to choose the attenuation to suit the listening conditions.
I would think a stepped attenuator that also selected the appropriate trim resistor at each position would make the match better since LDR curve shape may not be the same.
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