Being a tart (volume sensitive LED)

[mcai7et2]

I am about to start building a preamp based around PerAnders' diamond buffers and PSU. I want to use a motorised voume pot for remotability and because of this, to keep the outside looking nice and clean, I will only have a single LED and the remote receiver on the front panel (input switching will be by relays and will also be remote controlled).

So that I know roughly the volume setting, I am considering buying a 3 channel potentiometer (ALPS do them) and wiring the third channel in series with the LED (with a small circuit to get the resistance right) so that the LED will be brightest at high volume and very dim at low settings.

Will the presence of a small DC voltage through the POT cause any sound problems? I know this is a wanky sort of thing to do, but I want to to look exactly like a half height version of my power amp (they will both use the same case style, the power amp is 2U, the pre will be 1U).

Any thoughts or ideas?

Cheers,

Ed

[Magura]

Id use a seperate pot, or even better an attenuator.

Since you got your pants down anyway (making a remote), why not buy the kit that includes relay volme control and input relays?

Loads of people here have done so, look at the trading post thread, youll find it there.

Magura

[Peter Daniel]

Originally posted by mcai7et2

Will the presence of a small DC voltage through the POT cause any sound problems?

I wouldn't think so. Changing the brightness of the LED with a volume position seems like an interesting idea. You might play with different supply voltages to get maximum range. Don't forget additional series resistor to prevent the LED from burning.

[moamps]

Originally posted by mcai7et2
...buying a 3 channel potentiometer (ALPS do them) and wiring the third channel in series with the LED (with a small circuit to get the resistance right)....

Hi,

directly connected diode to pot isn't good solution because
a) diode current is little to high
b) diode transfer function (light/voltage) isn't linear or logaritmic (for dimming yellow LED from 0 to 100%, voltage change is ca 1.5 to 2V)
c) pot with 2 tracks (50K or so) for audio and third track for diode brightness control with ca 1k is hard to find


IMHO, the best solution is dimming diode with PWM source controlled by pot's third high resistance track. Second solution is maybe implementation some variable current source...

Regards

[Alexander Rice]

well asuuming you are going to use a microcontroller such as a PIC to implement the remote control, why not just use that to pwm the led, since it is going to be controlling the motor it should have a pretty good odea of where the pot is. For even better accuracy you could use the third track as a reference and just get a PIC with an analogue to digital converter and sample the actual position every second or so.

Regards

Alex