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Old 8th March 2011, 04:14 PM   #4031
markusA is offline markusA  Sweden
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Ah, when I said consumer product I was thinking about the budget market, not the high end segment.

And yeah, I'm doing a balanced version as well.
The case is nothing special really. I just found a extruded aluminum case lying around and decided to be cheap. Instead of buying a new case I'll fix the end plates for free.
Two knobs at the front, Balance and Volume. Four XLR connectors in the back, nothing fancy. AC wall wart with local regulation and ccs for the LDR's.
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Old 8th March 2011, 08:47 PM   #4032
pubul57 is offline pubul57  United States
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Question power supply

Udailey (and others), how do you power your LSA. I use a lineaer regulated AC/DC adapter, 400mA. Is there a better aprroach? Does it make a difference.
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Old 8th March 2011, 11:15 PM   #4033
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I got a smile out of this one.

Edgar Krammer of reviewer of 6 moons & Reviews Editor, Sound+Image, Australian Hi-Fi sent this to me.
"Remarkable resemblance to the Lightspeed’s maker…"


Cheers George
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Old 9th March 2011, 12:11 AM   #4034
udailey is offline udailey  United States
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George, Maybe you should have had your coffee this morning. I know that keeps the grumpys away from me.

Pubul57, yes it makes a remarkable difference. I love any implementation of LDRs. They sound really good just about no matter what. The only time I can say they sounded bad was with 6V through the resistor side of them.
Things that make improvements are : Ultra quiet supply (skip the switching supplies), use current sources to power them, use a lot of capacitance around the regulators, snub the LED side of the LDRs with 10-100uf (not more) and a small film cap, use as low of a Rtot as you can manage ( I dont think this goes for just LDRs. Any attenuator with a low output impedance sounds better than the alternative)
If this is your first try at LDRs then build George's circuit just exactly how it is. It is remarkable and it is easy, it is proven and it works. Then if you feel the need to tweak you can start with more capacitance and snubbing which will both yield great results. Some people have used Salas shunt regulator to power the LDRs and have really enjoyed the results so really you have a huge amount of options when powering LDRs but I strongly encourage you to try the circuit that this thread is about first. You cant go wrong. Its the gold standard by which any other implementation will be compared.
Uriah
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Old 9th March 2011, 01:23 AM   #4035
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Quote:
Originally Posted by ua100k View Post
... At the risk of offending all the audiophiles, at the end it comes down the ability of your equipment to resolve the differences. ...
I know of no true audiophiles who would be offended by that comment. It's a fundamental principle of the art and the hobby both.
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Old 9th March 2011, 05:39 PM   #4036
ua100k is offline ua100k  United States
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Quote:
Originally Posted by udailey View Post
If a lightspeed owner wants complete silence then a relay to ground will do the trick. Mute.
If a lightspeed owner wants lower min volume then they can take a 100k trimmer and use it as a variable resistor. Put in from the line feeding the series LDRs LED to ground. Adjust to taste. The lower the resistance then the higher the max resistance on the series LDR. This resistor wont effect most resistances much until the LDRs is into higher resistances anyway, so the Rtot wont change a lot simply because of the trimmer until it is required to which is when there is hardly any power going to the LDR at all at which point the amount of power going to ground via the trimmer is large compared to that feeding through to the LDR and so the LDR goes even higher in resistance when volume is turned down all the way and voila, you have nearly zero volume.
Uriah
And the other point of view is there is are much more elegant solutions out there, with less components that will get absolute results without adding relays, trimmers, resistors or any other components just to get "nearly there" results. KISS. KISS.

Time to move from the bi-plane to the jet plane..... If you would excuse my bluntness... or not.

On power supply's. Adding a choke really improves a power supply ripple. Since the current draw is sufficiently small, this is not too expensive a proposition.
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Old 9th March 2011, 05:47 PM   #4037
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Originally Posted by ua100k View Post
And the other point of view is there is are much more elegant solutions out there, with less components that will get absolute results without adding relays, trimmers, resistors or any other components just to get "nearly there" results. KISS. KISS.

Time to move from the bi-plane to the jet plane..... If you would excuse my bluntness... or not.

On power supply's. Adding a choke really improves a power supply ripple. Since the current draw is sufficiently small, this is not too expensive a proposition.
The real elegant solution would be a precision made LDR with not only unit-to-unit consistency, but adding an illuminator less responsive to micro-current levels, eliminating the need for all the filtering and regulation. If there was a demand I'm sure the semi-market would produce it, but our collective needs don't even peak their interest.
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Old 9th March 2011, 05:58 PM   #4038
udailey is offline udailey  United States
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Guess I will have to try an inductor to
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Old 9th March 2011, 08:48 PM   #4039
Blues is offline Blues  United States
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Quote:
Originally Posted by sepolansky View Post
The real elegant solution would be a precision made LDR with not only unit-to-unit consistency, but adding an illuminator less responsive to micro-current levels, eliminating the need for all the filtering and regulation. If there was a demand I'm sure the semi-market would produce it, but our collective needs don't even peak their interest.
I'm quite satisfied with Silonex. I have matched quite a few and just 2 units so far I found that retain some resistance even after power on the LEDs was removed. Battery power powers my 'ship...pure dc and very quiet.
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Old 9th March 2011, 09:10 PM   #4040
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Originally Posted by Blues View Post
I'm quite satisfied with Silonex. I have matched quite a few and just 2 units so far I found that retain some resistance even after power on the LEDs was removed. Battery power powers my 'ship...pure dc and very quiet.
Battery power is the best most purest form of powering the Lightspeed bar none.
During A/B listening test with a dozen "golden eared Audiophiles" it was very hard to tell the difference between the battery or the supplied wall wart on the production Lightspeed Attenuator.
I did measurements (high end Tektonics Scope) and the supplied wall wart produced no more than 200uV!! (that's not millivolts) of noise on the Lightspeed's output, this is undetectable to the human ear, and the reason why in the A/B test the difference was not detectable.
Yet as with all Audiophiles myself included, we all thought there was a very very slight preference for the battery, yet no one could say why, it was that small.
So the motto is, don't waste time money and effort on the power supply, a good linear 12vdc regulated wall wart with a secondary 5vdc regulated power supply as I've posted is more than adequate to get the best out of the Lightspeed "KISS"

Cheers George
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