Lightspeed Attenuator a new passive preamp

For some inexplicable reason I seem to have much less control over the volume. It gets loud very quickly which it didn't do before. Do these things go off? Is it likely to an LDR or PS issue? I am using exactly the same PS as previously.

I take it the system is exactly the same, nothing has changed to vary the system gain?

If so and the difference you get (gets loud very quickly) is happening in both channels, then the dual 100kohm log pot has gone faulty, replace it.

Cheers George
 

Attachments

  • Lightspeed Attenuator MkII Circuit Diagram.jpg
    Lightspeed Attenuator MkII Circuit Diagram.jpg
    99.8 KB · Views: 716
My Lightspeed started to develop a crackling noise on the left channel. Any idea what could it be? Thanks.

Is this a production "Lightspeed Attenuator" or a diy one?

As the led/ldr's in the production Lightspeed Attenuator can't make a crackling noise, not even if the front volume pot is bad.
It must be a bad interconnect connection or the rear rca sockets have a loose center pin contact, check this get an old rca plug break off the outside contact so you only have the pin, and see if it's a loose fit in all 4 of the rca sockets on the back.

Cheers George
 
Is this a production "Lightspeed Attenuator" or a diy one?

As the led/ldr's in the production Lightspeed Attenuator can't make a crackling noise, not even if the front volume pot is bad.
It must be a bad interconnect connection or the rear rca sockets have a loose center pin contact, check this get an old rca plug break off the outside contact so you only have the pin, and see if it's a loose fit in all 4 of the rca sockets on the back.

Cheers George

Hi George. It is a production Lightspeed. I will try what you suggesting and will report back. It is only doing it only in the Left Channel out. If anything I think I have a spare RCA jack. Thank you.
 
I cleaned the rca sockets with Deoxit and that seemed to fix the problem. ��

If that fixed it, then they have weak pressure inside for the center pin of the rca plug, re-new all 4 of the rca panel sockets, with good quality ones.
I have seen slightly oversized center pins on interconnects, and these stretch the inside of the socket, so when a correct size one is inserted you get this problem.

Cheers George
 
If that fixed it, then they have weak pressure inside for the center pin of the rca plug, re-new all 4 of the rca panel sockets, with good quality ones.
I have seen slightly oversized center pins on interconnects, and these stretch the inside of the socket, so when a correct size one is inserted you get this problem.

Cheers George

Yes. I will replace them accordingly when I finish listening to some music :)
 
Scratch that with the PC817C. Couldn't get it below 3K resistance. Can't source L-32SR2S, except from one shop in AU, and getting and sorting through L-32SR2 would still be pretty expensive for 40 of them. So I'll be trying LCR-0203 which I can get locally for about $0.75 each. The spec says it'll go down to 50 ohms at 20ma, so if I am lucky and can get 2 quad matches, I'll be able to bring the total resistance down to 25 by running them in parallel.