Lightspeed Attenuator a new passive preamp - Page 344

sklimek · 23rd July 2010, 07:52 PM

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

udailey · 23rd July 2010, 08:05 PM

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

AndrewT · 23rd July 2010, 08:06 PM

PM to Trip & Uriah.

Marlowe · 27th July 2010, 07:32 PM

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.

ZUM911 · 30th July 2010, 01:58 AM

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.

AndrewT · 30th July 2010, 10:19 AM

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.

ZUM911 · 30th July 2010, 11:22 AM

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.

georgehifi · 11:39 AM

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

udailey · 30th July 2010, 12:13 PM

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

jameshillj · 30th July 2010, 12:36 PM

About post 1360, I think

23rd July 2010, 08:05 PM	#3432
udailey Passive Aggressive diyAudio Member Join Date: Mar 2008	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 __________________ You can purchase LDRs anytime to build a standard LDR attenuator or to build my new LDR Attenuator "A Lighter Note". Email me. diyldr@gmail.com

23rd July 2010, 08:06 PM	#3433
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	PM to Trip & Uriah. __________________ regards Andrew T.

27th July 2010, 07:32 PM	#3434
Marlowe diyAudio Member Join Date: Feb 2003	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. __________________ Here's looking at you, kid.

30th July 2010, 10:19 AM	#3436
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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. __________________ regards Andrew T.

30th July 2010, 12:13 PM	#3439
udailey Passive Aggressive diyAudio Member Join Date: Mar 2008	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 __________________ You can purchase LDRs anytime to build a standard LDR attenuator or to build my new LDR Attenuator "A Lighter Note". Email me. diyldr@gmail.com


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23rd July 2010, 07:52 PM	#3431
sklimek diyAudio Member Join Date: Oct 2004 Location: Arizona badlands	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

30th July 2010, 01:58 AM	#3435
ZUM911 diyAudio Member Join Date: Jan 2006 Location: Sydney	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.

30th July 2010, 11:22 AM	#3437
ZUM911 diyAudio Member Join Date: Jan 2006 Location: Sydney	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.

30th July 2010, 12:36 PM	#3440
jameshillj diyAudio Member Join Date: Feb 2005 Location: Melbourne, Aust	About post 1360, I think __________________ ... jh

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