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Old 28th September 2010, 12:25 PM   #3531
Ted205 is offline Ted205  United Kingdom
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Quote:
Originally Posted by wapo54001 View Post
If one wanted to "preattenuate" before the LDR attenuator in order to reduce overall signal level to match a high gain amplifier and efficient speaker system, would it be best to use a two-resistor voltage divider before the series LDR, or just a single series resistor in line with the series LDR?

Any opinions?

This is something i'm interested in too.

I was thinking of lowering the 5 volts but have not yet tried it.
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Old 28th September 2010, 09:28 PM   #3532
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There are two way of gain reduction without impacting on the sound of the Lightspeed Attenuator if your up to it, reduce the gain of the source in it's output stage, or reduce the gain of the amplifier.

Cheers George
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Old 4th October 2010, 06:48 AM   #3533
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For those who follow Stereophile, the Lightspeed Attenuator has made it into "Class B" with a $$$ value tag in the October issue.
I received an anonymous email saying if your wondering why it didn't get into "Class A" just have a look, nothing below 10K, it will never happen.

Cheers George
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Old 4th October 2010, 07:21 AM   #3534
soongsc is offline soongsc  Taiwan
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It's well known what magazines have to do.
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Old 4th October 2010, 01:25 PM   #3535
udailey is offline udailey  United States
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Nice job George. You deserve the high praise. Must feel absolutely great to be getting reviews and respect from Stereophile.
Congrats
Uriah
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Old 5th October 2010, 04:23 PM   #3536
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Uriah Hi

I'm your latest UK customer.
Hurry up an send me the kit - reading this is killing me !!!!!
Can't wait

Andrew
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Old 5th October 2010, 04:32 PM   #3537
udailey is offline udailey  United States
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Andrew,
It went out today after I dropped my daughter at school!
Uriah
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Old 5th October 2010, 08:58 PM   #3538
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Hi

Thanks Uriah - a nice family image

I have a Monovolt PK 30 5 volt pro rack mount SMPS spare.
Would this be too noisy and should I stick to a 5 volt wallwart
for starters ?

If it's in the thread already I apologise - I have not read it all... yet

Does buying matched pairs of LDR's from you mean there'll be no channel imbalance issues at all ?

Have all the bits ready now as you suggested - many thanks for your great e mails and help.

Regards

Andrew
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Old 5th October 2010, 09:33 PM   #3539
udailey is offline udailey  United States
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Andrew,
I would not use a SMPS or wallwart. George uses a wallwart but he uses a linear one and it will be hard to find a linear wallwart. While waiting you might want to put together a 5VDC supply with a toroid, plenty of capacitance on input and output of voltage regulator.
I match the LDRs at 4 commonly used points. They will match those 4 points and presumably almost all points between. I tested at 5 points for a while but it didnt produce any fewer matches than 4 points which would indicate 4 is optimum.
Feel free to shoot questions to my email or keep them coming here. Its good to keep the thread active to.
BTW the better your supply the better the sound quality. Do a bit of research on google and find maybe some app notes that will help you build something with low noise. You will need to build a supply capable of at least 50ma as max draw will be about 40ma.
Uriah
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Old 5th October 2010, 11:22 PM   #3540
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Thanks Uriah

So, a 0v - 12v toroid ( 20VA ) 7805 reg and heatsink plus 100 uf 16v caps on each side of the regulator - would this do it ?
Bigger caps maybe ?
I have these parts now - it'd be great to use them on this.

Let me know when you can

Andrew
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