Lightspeed Attenuator a new passive preamp - Page 344 - diyAudio
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Old 23rd July 2010, 07:52 PM   #3431
sklimek is offline sklimek  United States
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Hi Uriah, I just received your board today w/ 4 matched LDR's plus parts. Amazing value with the matching printouts and pre-bent LDR leads. I haven't wired it into the board yet just wanted to thanks for making it available.

Stan
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Old 23rd July 2010, 08:05 PM   #3432
udailey is offline udailey  United States
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Stan, Thanks for the thanks. Make sure you bend those leads the right way to get the dot on the side of the LDR to match up with the board before you solder them in. The LDRs are bent to fit in my matching jig. Wish I could claim I prebent them for the board
Uriah
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Old 23rd July 2010, 08:06 PM   #3433
AndrewT is offline AndrewT  Scotland
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PM to Trip & Uriah.
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Old 27th July 2010, 07:32 PM   #3434
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Dears,

I just done a mod in my Lightspeed attenuator and the result is good to me.
I added a decoupling cap for each LED on the board. The caps are Elna Silmic II 10uF.
With this mod, the sound is warmer, smoother, and more forgive. The bass is also extended. The background is darker and cleaner. An easy and nice mod overall. Highly recommended.
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Old 30th July 2010, 01:58 AM   #3435
ZUM911 is offline ZUM911  Australia
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Has anyone put together the Nelson Pass version with the buffer? I made one and I've got a slight channel imbalance and I can't get my head around how to level it out. Any ideas would be appreciated.
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Old 30th July 2010, 10:19 AM   #3436
AndrewT is offline AndrewT  Scotland
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Buffer? is this the B1 by Nelson Pass?

A buffer passes the signal straight through without inversion and without gain.
The output is very slightly lower than the input and the lower the load resistance/impedance the bigger the voltage loss through the buffer. Expect 99% of the input voltage across a normal output load.

Any imbalance between channels must be due to an error, either elsewhere in in the B1 assembly.
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Old 30th July 2010, 11:22 AM   #3437
ZUM911 is offline ZUM911  Australia
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Hi Andrew, thanks for the input. Nelson had Lightspeed version with a jfet buffer to help drive amplifiers with lower input impedance. It has +/- power supply so there is no provision to trim the ldr's with a pot to ground like George's original. He has a schematic somewhere in here I just can't point it out at the moment. I'll have to wade through to find it.
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Old 30th July 2010, 11:30 AM   #3438
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From Nelson for the Lightspeed Attenuator to use with lower input impedance power amps, but still rather high output impedance at 1k.
Whats good is that it's dc coupled.
Cheers George
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Old 30th July 2010, 12:13 PM   #3439
udailey is offline udailey  United States
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While Nelson has provided a position for a regular pot to be in control of the volume, the LDRs values will still alter the volume. Have you implemented the circuit for the LDRs power just as George has shown us? If so you will have two 1k trimmers in series with two of the LDRs. Turn the system on, play some music, and change one of those trimmers til you get a good balance.
Uriah
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Old 30th July 2010, 12:36 PM   #3440
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About post 1360, I think
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