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FS: Lightspeed Attenuator matched LDRs
http://diyaudioprojects.com/Forum/viewtopic.php?f=13&t=785
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Author:  RiGuy [ 19 Jul 2009, 20:53 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

Just finishing up with matching. Probably will take me another 5 hours of matching work and then a few days of bagging and boxing etc. So, yep :) I have plenty of them. Shoot me an email at diyldrAT gmailDOTcom and I will send you an invoice. 38.42 for a stereo set single ended.
So how is your amp sounding!? Congrats on a successful build.
Uriah

Author:  megamahi [ 19 Jul 2009, 21:16 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

RiGuy wrote:
Just finishing up with matching. Probably will take me another 5 hours of matching work and then a few days of bagging and boxing etc. So, yep :) I have plenty of them. Shoot me an email at diyldrAT gmailDOTcom and I will send you an invoice. 38.42 for a stereo set single ended.
So how is your amp sounding!? Congrats on a successful build.
Uriah

Will do.

Amp sounds great. I placed the tranfo into a 6" PVC end cap assembly so it sits on the ground. From that I run both phases through a braided umbilical to the main chassis where the rectifiers are. As long as the speaker cables aren't sitting on top of the umbilical I get no audible 60Hz in the Polks (of which I'm impressed with so far). The pre-amp right now is my Presonus HP4, and hopefully by the end of the summer the B1 will be finished, cased, and powered.

Author:  RiGuy [ 19 Jul 2009, 22:19 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

So are you building a seperate Lightspeed or usig it in the B1?

Author:  megamahi [ 19 Jul 2009, 23:16 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

RiGuy wrote:
So are you building a seperate Lightspeed or using it in the B1?

Depends on what I feel like doing, many ideas popped in my head when I saw this thread.

Author:  Frank2 [ 22 Aug 2009, 16:40 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

hi, i would like to know what it really give to have balanced one? What can happen with an unbalanced set?
thx you
Frank

Author:  RiGuy [ 23 Aug 2009, 10:54 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

Balanced and unbalanced are just different ways to connect audio components together to pass signals. XLR is balanced and RCAs are single ended and also called unbalanced. If you are running short audio lines from your CD player to your amp/preamp then you dont need balanced. I assume your lines are under 25ft long. The standard is either 25ft or 25meters and I forget which it is. Anyway under 25ft for sure you dont need balanced.
Here is something to read
http://www.dself.dsl.pipex.com/ampins/b ... nced.htm#6
Unbalanced and balanced sets of LDRs are matched just as well. With balanced you need 8 of them rather than 4 and it is way harder to find a balanced match so they cost more.
Ri

Author:  Frank2 [ 23 Aug 2009, 11:06 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

aooow okay! Stupid me, i thought it was a special term for electronic... Thx you for your answer!

Author:  RiGuy [ 23 Aug 2009, 15:54 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

No Problem. If you want to try building one of these, which is an absolutely stunning and excellent increase over any other passive preamp that I have ever heard, I will help you to build the preamp either on the forum, or email, or phone. 100% guarantee you will build it to satisfaction.
Ri

Author:  jstevensiam [ 09 Sep 2009, 23:45 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

Can a lightspeed attenuator be made for 6 channel for HT? Thanks.

Author:  RiGuy [ 10 Sep 2009, 09:50 ]
Post subject:  Re: FS: Lightspeed Attenuator matched LDRs

You need two matched LDRs per channel to emulate a potentiometer. If you have 6 pairs that all match each other you can control them all easily with one potentiometer. If you have 6 pairs that have matched pairs but the pairs dont match other pairs you will have balance issues which can be sorted out by giving each pair its own personal control potentiometer. The only problem here is that it gets fiddly to have to turn up your volume with maybe one major control pot and then fiddle with each of six other control pots to get the balance right.
SO, if you were to buy LDRs to match for this project I would suggest buying them from me as there is NO WAY you will ever get 6 pairs that all match until you are into the hundreds of LDRs in matching. However if you wanted to match your own and just get 6 pairs that you would need to use balance pots with you could buy maybe 50 LDRs and accomplish this very easily.
For a balanced set (thats 4 pairs that all match) I charge 100.22 including shipping and all paypal fees, etc. For a regular single ended set which requires 2 pairs I only charge 38.42. Why more for the balanced? Because they are more rare and harder to find in a batch of matched LDRs. So 6 pairs would run you 171.28. I think you might be better off if you bought your own for matching or if you bought 3 single ended sets and just adjusted balance between 3 sets.
Just my suggestions. I hope this works out well for you. You will certainly be the first 6 channel Lightspeed I have heard of :)
Uriah

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