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Lightspeed Attenuator a new passive preamp
Lightspeed Attenuator a new passive preamp
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Old 10th May 2010, 10:37 AM   #3231
georgehifi is offline georgehifi  Australia
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Quote:
Originally Posted by fbee View Post
George,

my setup is way off your recommended source/amp impedances.
Source 300R out / activeCrossover 10k7 in.

However, it seems to work (very well).
Am I missing something?
How could I recognise the need for a buffer?

Furthermore I cant recognize any added distortion in my LinkwitzOrion system.
Are there some special recordings, that would help discover (eventually present) distortion?

Thx;Frank
Hi Frank, my recomendations of the source to be less than <200ohm output impedance and the poweramps to be more than > 50kohm input impedance, are just that, recomendations for the Lightspeed Attenuator to work at 100%It will work fine with what you have with no stress or damage to any component, however you are not getting the full 100% of what the Lightspeed Attenuator is capable of sounding like, saying that you still say and probablly are getting better than anything else active or passive preamp you've tried.
The input resistor 10.7kohm to ground on your active xover can most probablly be changed to 100kohm if there's a fet input opamp after it, then your sound will improve even more.
Cheers George
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Old 10th May 2010, 12:19 PM   #3232
3GGG is offline 3GGG  Australia
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Just finished my lighter note. Wow is all I can say.
Big thanks to Uriah and George
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Old 10th May 2010, 01:22 PM   #3233
udailey is offline udailey  United States
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Lightspeed Attenuator a new passive preamp
Hi 3GGG,
Glad you like it. However its not a Lightspeed so this really isnt the forum for it. I apologize but would rather not clutter George's thread with it.
Thanks and sorry, not trying to come off as rude.
Uriah
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Old 10th May 2010, 02:24 PM   #3234
joemana is offline joemana  United States
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my setup is way off your recommended source/amp impedances.
Source 300R out / activeCrossover 10k7 in.

However, it seems to work (very well).
Am I missing something?
How could I recognise the need for a buffer?

Furthermore I cant recognize any added distortion in my LinkwitzOrion system.
Are there some special recordings, that would help discover (eventually present) distortion?
Thx;Frank[/QUOTE]

Hi Frank,

Would you mind to let us know what brand of pre Amp did you replaced? I'm interested to find out because I have similar experience as you have using the same speaker. Thanks.

Joe
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Old 10th May 2010, 10:37 PM   #3235
georgehifi is offline georgehifi  Australia
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Frank, you will not get any extra distortions the way you have it, but from my experience you will lose a bit of dynamic range, this is what I meant by not 100%. But even this will be more dynamic rage than your probably used to. Just that when the Lightspeed Attenuator works at 100% of it's capability it's dynamic range and soundstage is outstanding, in a big wholesome enveloping way, not forced/squeezed or shot out at you like actives can do. Or lush out like some TVC do.

Cheers George
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Old 12th May 2010, 05:44 PM   #3236
roke2468 is offline roke2468  Ireland
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Hey.

I'd like to try and build this lightspeed attenuator to put between my DAC and monoblocks. What strikes me is that I'd like to use the same philosophy of using LDR's to control tone also - probably just bass and treble.

Now, please forgive my ignorance. I did not (a) read through this whole thread (b) have too much experience at this apart from building a set of speakers (c) anticipate reasons this cannot be done because of something very obvious to most on here that I have not taken in as yet...

But I'm wondering is there a design or kit out there to do this? Is it achievable? Is it a worthwhile thing to do? (I like tone controls to adjust for room characteristics and particular music).

Thanks.
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Old 12th May 2010, 05:52 PM   #3237
troystg is offline troystg  United States
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Quote:
Originally Posted by roke2468 View Post
Hey.....

But I'm wondering is there a design or kit out there to do this? Is it achievable? Is it a worthwhile thing to do? (I like tone controls to adjust for room characteristics and particular music).

......Thanks.
It is doable.. But I think most will agree it would go against the popular concept of as little circuitry as possible.

With that said I would suggest shunt components with series LDR's in the branch controlling the resistance but that would most likely be low order roll offs, and you would "probably" need gain to compensate for the losses.
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Old 12th May 2010, 06:07 PM   #3238
roke2468 is offline roke2468  Ireland
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Quote:
Originally Posted by troystg View Post
It is doable.. But I think most will agree it would go against the popular concept of as little circuitry as possible.

With that said I would suggest shunt components with series LDR's in the branch controlling the resistance but that would most likely be low order roll offs, and you would "probably" need gain to compensate for the losses.
Well, say I include a high quality switch to bypass the tone section.

But back to a hypothetical tone section - if building with LDR's is it not the philosophy that it is a better way of building it since you are able to do away with the feathering contact between the wiper contact of the potentiometer and the side contact - that introduces 'wobble' into the signal etc.
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Old 12th May 2010, 06:12 PM   #3239
troystg is offline troystg  United States
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Originally Posted by roke2468 View Post
Well, say I include a high quality switch to bypass the tone section.

......
You wouldn't have to. If the LDR's we set for max resistance the affect of the frequency dependent component would be minimized and the signal would be unaffected by that branch.

"Theoretically" of course...
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Old 12th May 2010, 06:31 PM   #3240
fbee is offline fbee  Germany
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Hi joemana,

I used to have a Roku M2000 Soundbridge connected to a Advance Acoustics Mpp505 Preamp with internal DAC.

As I upgraded my source to Linn Akurate DS, I thought a middle-class preamp could only worsen the signal.

So I choose to go via attenuation with as little elements in the signal path as necessary.

Beside the LDRs Im presently checking a fixed inline attenuation soldered in the plug of the active crossover. 4k7 series and 2k4 shunt gives me about 9,5dB fixed attenuation. Volume is controlled digitally in the Akurate DS (incl dithering).

Next step is to compare the inline att/ digital VolCtl with the LDR attenuation mounted in the digital XO cabinet (maybe with wax or heat sink "cream" between them). Here , Im still trying to find out how to
increase input impedance to 50 or 100k without messing up things in this sophisticated XO-design.


Cheers, Frank
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