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Lightspeed Attenuator a new passive preamp
Lightspeed Attenuator a new passive preamp
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Old 28th August 2014, 03:37 PM   #5221
udailey is offline udailey  United States
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Lightspeed Attenuator a new passive preamp
Yes, capacitors are the reason I didnt want to inject DC into the signal. With big enough transformer you could do that if the transformer is on the output of the ldrs.
Uriah
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Old 28th August 2014, 03:39 PM   #5222
udailey is offline udailey  United States
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Or use opamps after and a DC servo after first opamp.Of course then you're using opamps.
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Old 28th August 2014, 06:42 PM   #5223
Bigun is offline Bigun  Canada
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Lightspeed Attenuator a new passive preamp
My idea allows for the construction of multi-channel LDR attentuators without having to match any LDRs - but that would get expensive quickly if it required several high performance transformers. Capacitors is the only option for the idea I had.
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Old 28th August 2014, 06:52 PM   #5224
udailey is offline udailey  United States
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Well you should build it. Dont let me or George make you feel you shouldn't. It'll still sound good. Maybe not as great as not cap but good is good.
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Old 1st September 2014, 09:29 PM   #5225
vdi_nenna is offline vdi_nenna  United States
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Hi,

Was hoping someone could help me with this project. I didn't have the schematic for the board, so I used the basic schematic by George found online and in the thread.
The board says Design and layout Uriah Daily 2009.

I'm getting some audio from channel 2, but only hum from channel 1.
Think I might have the optocouplers in wrong.

Using 100 ohm for resistors and 5k pots. Volume adjustment is 100k.
Using 12v walwart and regulated down to 5v.

If I turn volume up all the way get audio from 1ch that's low but not distorted.
Other channel is just him.

Thanks for any advise or proper schematic would be helpful too.

Vince
Attached Images
File Type: jpg LS_01.jpg (149.2 KB, 332 views)
File Type: jpg LS_02.jpg (151.7 KB, 324 views)
File Type: jpg LS_03.jpg (152.9 KB, 321 views)
File Type: jpg LS_05.jpg (150.4 KB, 318 views)
File Type: jpg LS_06.jpg (149.6 KB, 314 views)
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Last edited by vdi_nenna; 1st September 2014 at 09:31 PM.
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Old 5th September 2014, 01:48 PM   #5226
udailey is offline udailey  United States
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Vince
I cant attach the file as its a few Kb larger than allowed.

Okay, linked pdf manual here:
https://drive.google.com/file/d/0B0N...it?usp=sharing

First schematic is George's original. Last is the schematic that represents the board you have.
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Old 5th September 2014, 02:58 PM   #5227
merlin2069er is offline merlin2069er  Canada
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Hey Uriah, have any of those boards?
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Old 5th September 2014, 03:40 PM   #5228
udailey is offline udailey  United States
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Hi
No I dont
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Old 5th September 2014, 03:56 PM   #5229
vdi_nenna is offline vdi_nenna  United States
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Thanks for the doc! I had since built a version based on George's schematic and it works fine. Hand wired it in 2.5 hours. But, now that I have this doc, I will build one for a friend using the board. Now just need to match some LDRs.

Thanks,

Vince
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File Type: jpg LS_Atten_02.jpg (161.3 KB, 117 views)
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Old 10th September 2014, 06:37 AM   #5230
dtses is offline dtses
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cheers!
a quick question about the wall wart, will this fit? I'll install LM317 after it and set the current to 150-200mA and then U7805 as advised.
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