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Lightspeed Attenuator a new passive preamp
Lightspeed Attenuator a new passive preamp
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Old 7th November 2015, 07:03 AM   #5511
kffern is offline kffern  Australia
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Lightspeed Attenuator a new passive preamp
I have found myself a set of udaileys matched LDRs.
Can someone advise me as to how I should select them in the circuit.

From the attached image should I use one from each pair for the the left and right series LDR and the remaining 2 for the shuntsas the image below? Or have I completely misunderstood this.
Thanks,
Kffern

Lightspeed Attenuator a new passive preamp


Lightspeed Attenuator a new passive preamp

Last edited by kffern; 7th November 2015 at 07:04 AM. Reason: delete attachments
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Old 7th November 2015, 07:20 AM   #5512
georgehifi is offline georgehifi  Australia
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[QUOTE=kffern;4508578]I have found myself a set of udaileys matched LDRs.
Can someone advise me as to how I should select them in the circuit.

From the attached image should I use one from each pair for the the left and right series LDR and the remaining 2 for the shuntsas the image below? Or have I completely misunderstood this.
Thanks,
Kffern


These matched pairs.
The lowest ohmage matched pair should be used as the L&R shunts to get the lowest minimum volume
And the higher ohmage pair as the L&R series

Cheers George
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Last edited by georgehifi; 7th November 2015 at 07:23 AM.
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Old 7th November 2015, 09:21 AM   #5513
kffern is offline kffern  Australia
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Lightspeed Attenuator a new passive preamp
Thanks George,
So in my case #147 and 159 should be the L&R shunts and the 189,197 the series?
Are they so close it probably makes little difference?
I plan to buy a bunch and match someday....

Regards,
Kffern
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Old 7th November 2015, 10:27 AM   #5514
AndrewT is offline AndrewT  Scotland
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What are the black figures (under the k values) telling us?

what about values for 10k and 5k?
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Old 7th November 2015, 01:00 PM   #5515
udailey is offline udailey  United States
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147 and its match for series because at low volume it wont match as well in shunt.
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Old 7th November 2015, 01:03 PM   #5516
udailey is offline udailey  United States
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Youve got it right in the pic.
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Old 14th November 2015, 06:38 AM   #5517
sugano is offline sugano  Hong Kong
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Dear all,

I'm really interested in making the Lightspeed Attenuator. Can I possibly buy 4 matched 32SR2S' from someone who has spares? Hopefully quad matched instead of 2 pairs?

Thanks!
Peter

Last edited by sugano; 14th November 2015 at 06:52 AM.
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Old 14th November 2015, 06:53 PM   #5518
georgehifi is offline georgehifi  Australia
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Hi Peter, you can get them in Hong Kong get the $5 led tester I posted in the 1st post of this thread. Get a friend and yourself to buy 20 pieces from here, you'll get enough for two quad matched sets and sell the left overs ones.

Hong Kong Nsl-32sr2s, Hong Kong Nsl-32sr2s Manufacturers and Suppliers on Alibaba.com

Cheers George
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Old 19th November 2015, 10:08 PM   #5519
thesavage is offline thesavage  Australia
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Quote:
Originally Posted by georgehifi View Post
Hi Peter, you can get them in Hong Kong get the $5 led tester I posted in the 1st post of this thread. Get a friend and yourself to buy 20 pieces from here, you'll get enough for two quad matched sets and sell the left overs ones.

Hong Kong Nsl-32sr2s, Hong Kong Nsl-32sr2s Manufacturers and Suppliers on Alibaba.com

Cheers George
Hi George,

I followed the link you supplied for the LDR's but they didn't have any in stock.

I managed to locate a different supplier but the model number is slightly different. Are they still suitable?

NSL-32SR2. - ADVANCED PHOTONIX - OPTOCOUPLER, RESISTIVE O/P | element14 Australia

Appreciate your assistance,

Cheers,

Tim
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Old 19th November 2015, 10:28 PM   #5520
georgehifi is offline georgehifi  Australia
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Quote:
Originally Posted by thesavage View Post
Hi George,

I followed the link you supplied for the LDR's but they didn't have any in stock.

I managed to locate a different supplier but the model number is slightly different. Are they still suitable?

NSL-32SR2. - ADVANCED PHOTONIX - OPTOCOUPLER, RESISTIVE O/P | element14 Australia

Appreciate your assistance,

Cheers,

Tim
Yes Tim, they won't be as close to each other as the "S" version, so get another ten to get quad matching, you'll probably end up with 2 x quad matched sets so you could sell one set here.

Also the "S" version is typical 40ohms (on resistance) @20mA, so the "S" gives better attenuation at minimum level.
Where the "non S" does not specify (on resistance) @20mA, and can be a bit of pot luck, minimum level could be a bit loud for background music.

Cheers George
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Last edited by georgehifi; 19th November 2015 at 10:38 PM.
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