Lightspeed Attenuator a new passive preamp

[rocosr]

"not one has gone faulty, drifted or changed it's characteristics"

The only way this can be true is if you have measured ALL of them year after year. The fact of the matter is that these devices drift, some more than others. Just ask the component manufacturer.

[udailey]

Well you should be an expert by now rocosr. As I recall you were going to buy a bunch of these and test them over a 1-2 month period and that was back in September of last year.
So please share your results.
Uriah

[rocosr]

I confirmed the inherent drift characteristic of LDRs with manufacturers, as I mentioned. No point making measurements, unless of course, they would have said these LDRs "don't drift", "they're stable", blah blah blah...

[tinitus]

If they really drift that much there would be a clearly audible channel imbalance, right ?

[georgehifi]

Rocosr you seem to be the only one talking about drift in the 6 only posts you have contributed, it sounds thou like you have not even built one.
If you punish them, drive them over their rated 20mA you will do damage and yes they will change, also if they are overheated (soldered) this will also change them, and also if they are not kept uniformly temperature coupled by close proximity potting as I do, this may also cause drift on different days. Something does smell of fish.
Cheers George

[udailey]

Tinitus,
No. An individual LDR could only drift up or down. Obviously not left or right. So when we have 4 LDRs that are matched to all track the same, all made out of the same material with the same propensity to drift being part of physics then matched LDRs would drift in the same way.
For instance the resistance will change about 4% with a 1F degree change in the room. But if all 4 change 4% in the same direction... then our voltage divider pretty much gives us the same voltage so impedance would have changed a tiny amount but there would be no problem with channel balance.
Also, if I use the word drift, my definition is a change in resistance. This is what they do. The whole idea is for them to change in resistance. If we use the word drift to mean that they would change their resistance at a given voltage and current to a different resistance at the same voltage and current then we can talk about something undesireable. So considering this is probably what you guys are talking about lets consider this. What exactly could happen for one to drift without its couterpart drifting? Its, again, a voltage divider. So if a shunt LDR's value at one measured point drifts it would have to happen because of the environment and usage. If the environment and usage are the same for both shunt LDRs then why would one change and the other not change? Circuit is the same for them both. So if one changes and the other changes, why would they change differently. So if they dont change differently but they change the same, then what will change for the audience? Its a voltage divider and both shunt LDRs are always equal to each other so if both shunt LDRs change equally there is no change for the audience.
Uriah

[anubisgrau]

interesting logic.

[rocosr]

You're right George, I haven't built one. I went no further after discussing the unspecified change in resistance vs. bias drift that occurs on these devices over time per the component vendor. So as always, Caveat Emptor.

[rocosr]

hornperfect....yep...that is interesting logic....LOL...

[tinitus]

Gentlemen, please dont make me consider this as intentionally obstructive

You contribute nothing positive

Its free to build or not
It is about building Lightspeed
To debate whether it works or not makes no sense

I am willing to go very far to protect a popular thread from going down, make no mistake about it
I really dont like to interfere, but if you push it I will
If you want to take this further, I suggest to do it in http://www.diyaudio.com/forums/analo...ml#post2060163