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PostPosted: 25 Jan 2009, 12:21 
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MagMod93 wrote:
Sounds like Ri got so excited, he must have left a little puddle on the listening room floor. HAHAHA

LOL - ROFL

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PostPosted: 27 Jan 2009, 10:56 
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RiGuy wrote:
Oh, and some people have mentioned that they had less bass with this pre. I admit to having a stunted system in the bass arena recently, but this pre has restored quite a bit of bass. Weird. I dont know why.

Maybe they didn't pay proper attention to input and output impedance on their source, LDR attenuator and amplification? Interconnects with high capacitance can work together with impedance and make a nice LCR network. 8-)


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PostPosted: 27 Jan 2009, 11:23 
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Ahh. Hmm so basically a high pass filter. I am using the same interconnects and previously was using just 10k and also tried 25k and 50k pots. This is supposedly about 7k, though I havent measured it.
I think today I will wire in a 10k pot to the LED side of the attenuator and see if I cant control the balance a bit more. The image is a few inches to the left at higher volume with this particular pair of LDRs.
Just built another one last night and another little power supply. I have to test it today.
I should post the new and revised board...
There it is.
Ri


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 Post subject: interconnects
PostPosted: 27 Jan 2009, 11:56 
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Yeah, interconnects are a balancing act of inductance and capacitance. With high inductance highs are rolled off. With high capacitance lows are attenuated. If there is a large difference in the output impedance of source and input impedance of attenuator this effect is amplified -- if I recall correctly. I'm remembering this from my days of being deep into audio -- about twelve years or so ago. In that past life I made my own speaker cables by braiding 27 Cat5 conductors per channel. . . But back to the interconnects . . . according to the information that I found, Alpha Core Goertz and Nordost interconnects had a nice (ideal ?) balance of inductance and capacitance. I'm sure there are others with a good balance but those two stuck with me as a nice balance of price and performance. Also in interconnects, the size of the conductors becomes a factor because of the skin effect. You want a large enough conductor to carry the current but once beyond a size threshold a conductor begins to lose high frequencies due to skin effect.


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PostPosted: 27 Jan 2009, 14:27 
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Finished a second one today. Very impressed and its better than my previous, simply that the resistors track each other better.
I think for another I will remove the 1k pots and put in 5k 10 turn pots. It will allow lower volume as now the initial volume setting is low, but could be less and on super efficient speakers it might not be low enough. 5k would definitely allow super low volume adjustment. My speakers are I think 96db/spl to they notice the 1k and 5k would help. Anyway, this one tracks better and I was able to perfectly adjust the image. The proto is still off by a few inches.
Ri

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PostPosted: 03 Feb 2009, 02:39 
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Hey guys, stumbled on this forum when I Google my production Lightspeed Attenuator to see how the word is spreading, I thought I post up better circuit so you diyer's could get into it.
If anyone needs more history/pics info, I have quite a bit I can email, just email me with your email address and I can send it.
Attachment:
Lightspeed Attenuator MkII Circuit.JPG

Cheers George


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PostPosted: 03 Feb 2009, 13:08 
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Hi George, welcome to the forum.
I have not tried it yet, but do have plans to try it out. Thanks for sharing the project. Also, feel free to share any info you would like on the forum.
Cheers,
Gio

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PostPosted: 03 Feb 2009, 15:30 
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Thanks for the welocome Gio, always nice to see ones projects springing up. (if you want to see all my "propaganda" on the Lightspeed flick me your email address)
Allen "booangler" your email is not activated in the forum, I cannot send docs and pics via PM, so I sent all the info to your website email contact address.
EDIT: that did not work Allen it bounced back to me, I need another email address
Cheers George

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PostPosted: 03 Feb 2009, 15:41 
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Hi George!
So do you think its possible to make the equivalent of a 100k pot with these?
I have been considering using the LDRs to build an equalizer. Anythoughts or past experiences?
Uriah

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PostPosted: 03 Feb 2009, 15:47 
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RiGuy wrote:
So do you think its possible to make the equivalent of a 100k pot with these?
I have been considering using the LDRs to build an equalizer. Anythoughts or past experiences?
Uriah

I've had a similar thought -- because I need more input impedance than the PSMLS or the LS provides. I might try putting some high quality caddocks before the LDR attenuators.


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