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Old 5th June 2012, 08:25 AM   #4711
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There are light's being turned on in all circles now even Paul McGowan is seeing them.

The preamp conundrum | PS Audio

Cheers George
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Old 5th June 2012, 11:52 AM   #4712
djn is offline djn  United States
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Hi George, is your type of volume control affected by other components in the preamp such as B+ and such? At first I was thinking that I would do a stand along light control V-pot and selector switch but my audio rack is running out of space. I am now thinking of replacing the Alps pot in my preamp with the lightspeed style and use the Alps pot for controling the 5v. How isolated does it have to be?
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Old 5th June 2012, 09:45 PM   #4713
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Hi DJN, the only time I have seen any effect of extra noise on the scope with the ldr's of the production Lightspeed Attenuator, is when a switchmode wall wart was used, this raised the noise level double. But it is still very low (micro volts), and still ok to use if a linear cannot be found.
This noise was probably radiated from the entry wires into the internal second stage 5v regulation, as the power supply floats as is isolated it could not have come in through the audio ground plane.

Cheers George
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Old 6th June 2012, 12:11 PM   #4714
djn is offline djn  United States
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Thanks George. I was tweaking my pre amp last night and it actually has more room under the hood than I remember. I also use small coax wire from the inputs to the pot to the preamp so if there where a possibilty, that would negate it.
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Old 5th July 2012, 01:24 AM   #4715
JoeyGS is offline JoeyGS  Philippines
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Default Lightspeed as volume potentiometer

Have been using the Lightspeed for quite a while now.

Has anyone used or integrated the Lightspeed attenuator into their active preamp as a volume potentiometer?

Any results?

Thanks
JoeyGS
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Old 5th July 2012, 10:37 PM   #4716
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You can do this Joey, but you have to be very careful of temperature changes especially if the integrated or pre has tubes as this may not allow you to keep them in a matched arrangement. In the production Lightspeed Attenuator I pot all ldr's together in hard wax to keep them at better temp co. between the four of them. This still may not work within a environment such as an amp or pre.

Cheers George
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Old 5th July 2012, 11:48 PM   #4717
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Just to let you Lightspeed Attenuator owners know, Stereophile have just released their August 2012 Recommended Components and the Lightspeed has once again made it with highest $$$ value.
2012 Recommended Components Preamplifiers | Stereophile.com

Cheers George
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Old 6th July 2012, 10:52 AM   #4718
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I am using the LSA as volume control in my aikido preamp (LSA is the input stage).

What is the input impedance of the LSA, as I am selecting a suitable output capacitor size for my dac.

Thanks

---
edit; CONGRATULATIONS GEORGE!! I think we can all agree!
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Old 6th July 2012, 10:10 PM   #4719
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If the stage after the Lightspeed is 100k input impedance then the input impedance of the Lightspeed is between 10k-15k,
Here is the Graph that Tom Gootee plotted for the input impedance of the Lightspeed Attenuator (how I make them) for three different poweramp input impedances.
Thanks again for the graphs Tom!
Lightspeed Attenuator a new passive preamp

Cheers George
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Old 7th July 2012, 03:08 AM   #4720
JoeyGS is offline JoeyGS  Philippines
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Quote:
Originally Posted by studiostevus View Post
I am using the LSA as volume control in my aikido preamp (LSA is the input stage).

What is the input impedance of the LSA, as I am selecting a suitable output capacitor size for my dac.

Thanks

---
edit; CONGRATULATIONS GEORGE!! I think we can all agree!
What would be a good solution is to put an Aikido ACF between your DAC and the Aikido preamp/LSA combo. This would eliminate the impedance matching on any preceding component to your Aikido Pre/LSA.
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