Lightspeed Attenuator a new passive preamp

[georgehifi]

Vatofale, I have only called them Lightspeed for the last year, and I sell in small quantity here in Australia $500au. through word of mouth.



Your missing the point Chewrock, it's got nothing to do with oxidization of the wiper or the track, rather the contact of the wiper being a feather weight pressure on the track that makes it easy to be slightly disconected when a fast rise time transient comes along, this is what I mean by becoming a diode, it's got nothing to do with oxidization, but that can be bad also if things get that old. Time to get rid of that pot.

Cheers George

[st2_998]

Nice topic!
Georgehifi: I don't believe you are losing customers here. I don't think everybody is willing to do the same trial and error research on LDRs you did. Perhaps this could happen only to start a business like you.
Why don't you develop a variant of your design with a servo control? More "natural-minded" people like me could buy the former and the "picky men" the latter. I think you could cut through a thick slice of customers.

As for relays... are the inner contacts gold-plated too? I read about Omron relays. Are they good?

Smooth power supply for LEDs... the same SLAs I'm going to power the outbut buffer on! LED consumption is minimal, I believe.

Mumble... what's the quality of the LDR as a resistor? No point using Dale or Vishay (I don't) in a design and then end up with something not up to the situation.
Bye

[georgehifi]

Ok, here is a ruff of the circuit, just give it a clean +5vdc to the pot and ground the otherside of the supply, as for the Led/Ldr package it looks to me as though the Perkinelmer VTL-5C3 will do the trick you will have to match them up, the ones I use are from a different company that are matched for me, but I still have to match them again, the 1k 25 turn trim pot is for final calibration you only need the one on the strongest channel to match it to the weaker one to get perfect channel tracking. Enjoy

Cheers George

[st2_998]

lightspeed-clear george

[Cortez]

http://www.silonex.com/audiohm/levelcontrol.html

[powerbecker]

Thank`s!
Non linearity is a issue!
Regards
Heinz

[georgehifi]

Heinz,I read this paper a while back, I'm sure they are talking about non-linearities in the time (ms) it takes for the LDR to react to the LED brightness, not non-linearities in the sound quality. Who cares if it takes 2 milli seconds to reach the level once you have turn up or down the volume, by the time you have sat down it's at the volume, to be honest the time delay cannot be detected at mid levels, only at low level, but like it said, it is milli seconds, it's like having a built in shock absorber in the volume control.

Cheers George

[powerbecker]

snip
non-linearities in the time (ms) it takes for the LDR to react to the LED brightness

George,
of course that`s not a problem!
I mean the distorsion a high level
voltages over a LDR (see below: green line, left side)
Regards
Heinz

[powerbecker]

and here from PE:

[georgehifi]

Originally posted by powerbecker
Thank`s!
Non linearity is a issue!
Regards
Heinz

If was'nt an issue with you why post it (read above), as for the distortion, I challenge you to hear the difference between .001% and .1% on a system, and that .1% distortion is at 2volts rms, show me a cd player or dac that gives 2vrms, while playing music, it would blow an amp to kingdom come.
Heinz you have yet to hear one of these. Do yourself a favour and listen to one, I'm sure you'll change your views towards them.

Cheers George