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Old 16th April 2009, 10:35 PM   #2001
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Quote:
Originally posted by ptysinn
Hi George,

But what I am saying is using the LDR also in series configuration but set at a fixed resistance, the same series resistance (eg 3kohm) in mk II at your listening level. So it will be the same Cadmium Sulphide or Cadmium Selenide chemical. With same impedance level at the listening level, it should sound the same, theoretically. Seems like Mr. ondesx finds differently.

Maybe something else is affecting the sound.

Philip
Exatctly what I did.

Cheers George
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Old 16th April 2009, 10:53 PM   #2002
jkeny is offline jkeny  Ireland
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Leaving impedance issue to one side, it does come down to the quality of the resistor in the series position. It would then seem that Cadmium Sulphide/Selenium is an audibly great material for resistors. Silonex gave distortion graphs for the LDR , I wonder how many resistor manufacturers have done the same (Resista distortion graph attached)?

It seems that anything that modulates the electrical parameters of a resistor will introduce distortion, so low tempco & mechanical configuration (nude Vishay). I wonder how LDRs fare in these considerations, tempco & mechanical?
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Old 16th April 2009, 10:53 PM   #2003
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Not only does the MkII sound better because of the chemical make up of the LDR's resistance element compared to carbon or metal film/oxide resistors. I have not compared to smd resistors, but I have done Beshlage Vishay and a couple of others, in metal oxide/film.
It still remains that the MkII configuration has a better (lower) off volume, and more importantly it has much more stable/consistent output impedances, were going back over old discussed things here, that were said a year or so ago.
There is no comparison, MkII (ldr series / ldr shunt) kills the MkI (series resistor / ldr shunt) do you guys think I would recall all the MkI's to upgrade them to MkII for nothing? And also have the big hassle matching all 4 ldr's building the MkII when it was so easy to build the MkI's, my profit margins dropped by 20% because to MkII is so expensive to make.

Cheers George
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Old 17th April 2009, 01:25 AM   #2004
jkeny is offline jkeny  Ireland
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George,
I hope all these investigations don't appear ungrateful to your efforts in bringing this unique & great sounding Vol control circuit to attention here. Your generosity in doing this is much appreciated. I have no doubt you have done all these tests before & have proven the MKII is superior to any all combinations.

The spirit of DIY & investigative minds are, I'm afraid, what is in evidence here rather than any doubt about your tests or outcomes.

I am, however, sensitive about the possible commercial repercussions of these investigations! With this in mind I'm happy to go off-line with these posts but I don't know what your thoughts are on this?
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Old 17th April 2009, 07:27 AM   #2005
ptysinn is offline ptysinn  United States
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Quote:
Originally posted by Tolu
but if you use a LDR for series R, why don't you build MKII? I have done these tests also as I wrote some posts above! Even a third LDR in the signal way doesn't disturb the quality. It is the opposite!
Well, my thought was using those unmatched LDR in the series position, be green. Since according to people, you may need to buy 10 or 20 to get 4 matched LDR. I was hoping that if you only find one matched pair of LDR unluckily in your 20 of them, you can use 2 others in the series position setting it at a optimum value for your system. However from George, it seems like even using a fixed LDR in series R position sounds worst than using a variable LDR in series R position. So we have to buy some more to get a 4 matched to make mkII.

Philip
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Old 17th April 2009, 09:13 AM   #2006
Tolu is offline Tolu  Germany
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The first time I bought 12 pcs which gave me 4 well matched LDRs. The remaining 8 pcs are perfectly used for signal switching. So you have per channel 2 LDR for about 5$ which are far superior in relation to any kind of relay!

So, for about 30 $ you'll get the best sounding preamp (I dislike the word preamp regarding to a vol control; in Germany is a better word for it: Vorstufe ~ pre stage) you can imagine. And I have heard so many of them...
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Old 17th April 2009, 09:35 AM   #2007
AndrewT is offline AndrewT  Scotland
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call it a passive pre-amp.
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Old 17th April 2009, 09:40 AM   #2008
Tolu is offline Tolu  Germany
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Quote:
Originally posted by AndrewT
call it a passive pre-amp.
how can an amp be passive?
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Old 17th April 2009, 10:00 AM   #2009
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A pre amp means it pre amplifies, this it is not.
It is called a passive attenuator.

Cheers George
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Old 17th April 2009, 10:18 AM   #2010
AndrewT is offline AndrewT  Scotland
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an attenuator is an attenuator.

A box containing a host of undefined components with selector switches and attenuator knob that is placed between a group of sources and the power amp/s is conventionally referred to as a pre-amp.

If it has active components inside it then it's an active pre-amp. The fact that the gain can only be -ve does not affect the colloquial title.

If the pre-amp has no active components inside then we usually call it a passive pre-amp.

Most of us understand the difference between these.

A gain stage with no gain that presents different impedances at it's input from it's output is a buffer. A buffer inside a preamp box makes the pre-amp the active type but it still has no voltage gain. It probably has current gain as a by product of the differing impedances on its terminals. It's still a pre-amp.
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