LIGHTSPEED ATTENUATOR diy

[Light Dependant Resistor]

Readers will notice or should notice signal ground is also led cathode ground in this implementation

[georgehifi]

Readers will notice or should notice signal ground is also led cathode ground in this implementation

So sorry guys this was an old circuit, I've amended it in the first post diagram.
The led cathodes go to negative of the power supply, and that negative is not part of chassis ground. So in fact the positive and negative floats, and is not part of the signal or chassis ground. Again very sorry.

Also here is the NSL32SR2S (sorted) data sheet should anyone want it.

Cheers George

[Cobra2]

I have searched..(!) but cannot find any data about how much attenuation the Lightspeed can give (range) ?
And input impedance?

Arne K

[georgehifi]

I have searched..(!) but cannot find any data about how much attenuation the Lightspeed can give (range) ?
And input impedance?

Arne K

In most 99% of systems the attenuation can go right down to a whisper, as the Lightspeed as built cannot go down to absolute zero.

The only time it may be at minimum volume and still be at very low level from the speakers, if the system has very high gain and the speakers are >105db efficient horns.

The Lightspeed mimics a 10kohm logarithmic potentiometer.

Cheers George

[georgehifi]

If you want a full to min range figure from sine wave bench test.

Then with a constant sine wave input of 800mVpp, the full volume output is naturally 800mVpp being unity gain passive. The minimum volume with the same input is under 2mVpp more like 1

Which works out to around 52db-58db of attenuation range.

Hope this helps Cheers George

[Cobra2]

Thanks
Unfortunately, this means that it will be unsuitable for my use
(as are all TVC units I have seen)

Arne K

[georgehifi]

Thanks
Unfortunately, this means that it will be unsuitable for my use
(as are all TVC units I have seen)

Arne K

Wow, this means you either have amps or source with abnormally high gain and or >110db speakers. Or you have a baby sleeping in the same room
Cheers George

[Cobra2]

Close...
Altec Model 19, Hypex UcD400HxR, or Yamaha M-4, or Yamaha PC2602M, + various preamps...
Used for analog, digital & TV/video. (24/7)

Arne K

[georgehifi]

Yep big gain there, in these situations the Lightspeed's volume will only get down to back ground (dinner party) levels.

Cheers George

[r100]

why not just add a mute switch ?