Category Archives: electronics

Renovating VideoLogic Sirocco Stereo Speaker System, Part II

Previously I started working on renovating an old speaker system that I have. See the article here: Renovating VideoLogic Sirocco Stereo Speaker System.

I left the project at the point where I was attempting to find replacement potentiometers for the controls of the amplifier. I tried suppliers like mouser and element14 and other similar ones looking for pots but found nothing that fitted as I wanted. It seems that digital controls are causing older analogue controls to become obsolete. I have also looked on eBay, and while I can find potentiometers of the right value, I have been unable to find ones with the same shaft length and type and I can’t be sure of the quality.

Therefore I have reconsidered my plan to replace to the potentiometers. Instead, I have determined that the “Sub” and “Attitude” potentiometers are in good enough condition to reuse. The volume potentiometer is not in good condition and the wiper makes intermittent contact which is a problem. Therefore I have determined the resistances across the pins of the potentiometer when it was near maximum and will use resistors to permanently set the volume. I don’t mind doing this for three reasons:
The first is that I use a separate DAC with a volume dial (ASUS Xonar Essence One) to connect my computer to my speakers so I will be able to have control over the volume that way.
The second is that the quality of the amplifier is enough that you don’t get that annoying static hiss as you often get with computer speakers which are turned up to the maximum.
And finally, I will be putting the amplifier out of sight so a hole in the front panel where the volume pot used to be won’t be too terrible.

I have used two 20k Ohm and two 50 Ohm resistors to join up the contacts in a way that was the same as if the wiper of the potentiometer was turned up to the maximum. I’ve also resoldered the other two potentiometers back in their places, soldered bridging wires onto the headphone socket (because that was causing intermittent contact issues and adding noise to the output) and replaced the blue led with a yellow one (personal preference).

With those small jobs done, I cleaned everything up and reassembled the amplifier enclosure. I attached all the cables and powered it up and it worked a treat. Turning either of the two remaining potentiometers does not produce any crackling sound through the speakers. Both channels are again working and producing even sound. In review the speakers I replaced are, I think, producing a slightly higher frequency than the original Audax ones. Previously I would have the attitude set somewhere between half way and maximum, but now I have it set much nearer to the minimum value which to my ear is now producing a more natural sounding audio. I will soon install the speakers in a more permanent location and be using them daily.

While I decided to make some compromises with my original intentions, I regard this project as complete. This is the first project I have completed in recent years (see this for why: Depression, Weight, Finance, Responsibility, Recovery) and completing a personal project is a goal that I have set myself. I’ll be writing more about setting goals and other things soon.