Questions which keep me up at night ---
What is the terminal velocity of a penny coin?
or,
What is the temperature of a lightning bolt?
-RNM
What is the terminal velocity of a penny coin?
or,
What is the temperature of a lightning bolt?
-RNM
p.s. If enough measures to reduce noise are taken in the led driver circuit including quite large caps across the LEDs - LDRs can sound good . . . but dunno about prize winning good 🙄
I suspect it would take as many as 100 LDR's to get down to the resistance range desired. The lowest listed on the Advanced Photonix Canada, Inc.: Products: Audiohm Optocouplers site is 40 Ohms. 10 in parallel with the LED on hard may make it. The on to off lag and hysteresis may compromise any precision desired. Worth an experiment.
John makes a very reasonable point, "zipper" noise (midscale transition for example) like from some digital pots at that point in the circuit could cause 200W spikes at the speakers.
I would think a Gray scale ladder might be better.
You only get excess noise from passing current through the resistor, if we are talking the same term.
Well, John, if it were me who needed such a control, I would use an optical system.
Maybe start with the 'lightspeed attenuator' concept? But that's just my opinion. 🙂
Thx-RNMarsh
Maybe start with the 'lightspeed attenuator' concept? But that's just my opinion. 🙂
Thx-RNMarsh
If JC is refering to excess noise in LDR's then I can get that - when we were working on LDR volume control we were taking every possible measure to reduce noise - every measure showed an audible improvement and that was at line level. In the end I thought it was a pretty good pot - quite clean - but not as clean as a DVC so I dropped them.
So I can see that at MC coil levels this could be a show stopper
So I can see that at MC coil levels this could be a show stopper
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These are just engineering issues, if it's an all-out assault then simply incorporate the refinement, and protection circuitry to stop such things happening.
Mikelm --- BenchMark's newest VC is now analog -- used to be a DVC. [Lower distortion.]
You can go direct to a suitable semiconductor with its body/top cut off with the light pipe.
?
-RNM
You can go direct to a suitable semiconductor with its body/top cut off with the light pipe.
?
-RNM
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Yes, the light to electrons mechanism is subject to different mechanisms for noise in fact it gets quite non-intuitive at times.
and they're using LDRs ?
I've been thinking to build a new analog preamp for a while now - Perhaps I'll try LDRs again.
Mikelm, I am putting this variable resistor in front of a phono preamp (one of the most expensive in the world) with a gain of 10,000 at 10Hz. Do you think that an active variable resistor will be adequate for this application?
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