The EL-POR with dual amplifiers and 6 controls

This page includes facts and photos about the Gerinvex EL-POR Discomatic featuring dual amplifiers and 6 control knobs.

Not an official version!

Although it looks very convincing at first sight, the EL-POR version with 6 controls was not made in the factory by Gerinvex. Instead, it appears to have been quite a popular conversion in the day to modify an EL-POR to incorporate a second amplifier. The dual amplifiers can then drive two external speakers in stereo.

If Gerinvex had made this version they would certainly have marked the control panel correctly with dual volume, treble and bass legends that matched the control functions. The first photo shows the 6 control example which has a standard EL-POR control panel. The second photo is a mock-up of how the control panel should probably have looked if Gerinvex had designed it.

Who made the control panels?

The control panel is the standard control panel from an EL-POR. Conveniently, the spacing between the Channel 1 and Channel 2 line output sockets is exactly the same as the spacing between the amplifier controls. If the line output sockets are removed and the holes opened out slightly, the bass and treble controls of a second amplifier can be fitted here with no problem. That just leaves a new hole to be made for the volume control and the second amplifier can be mounted on the control panel.

Who supplied the spare amplifier?

I would guess the amplifier was removed from a broken Discomatic. The amplifiers in my example have noticably different component types so are almost certainly from different generations of Discomatic.

How are the connections made for the two speakers?

To complete the modification, speaker connection has to be provided for the additional amplifier. There are a few ways in which this can be done.

• Mount an additional minijack on the control panel.
• Convert the existing speaker minijack to a 3 pin stereo minijack.
• Add dual speaker outlets somewhere less visible, perhaps on the back panel.

In the case of my example in the photos, the engineer chose Option 1. You can see there is an additional minijack mounted between the two amplifiers. An extra hole was cut to enable this to be fitted. There are two minor disadvantages to this method. Both sockets on the control panel are now feeding speakers so there is no longer a line output socket. The internal speaker can only connect to one audio channel. Neither of these issues would be of concern if the Discomatic is to be permanently connected to a pair of extension speakers the conversion will work well.

Option 2 has a slight advantage over Option 1. The original speaker output will now carry both left and right channels. The line output socket can be left off the control panel for a cleaner look or can be fitted, converted to stereo using a stereo, switched minijack. One minor negative is that both speaker cables will wire into a single minijack cable.

Option 3 is probably the neatest as the speaker cables would connect to sockets at the back of the cabinet, rather than to the top control panel. The speaker socket on the control panel would probably be disconnected to save any confusion.