High Quality, Noise-Free sound output from the Sinclair Spectrum +2

If you have a grey-cased +2, you have probably noticed that its sound output is very noisy, both from the rear-panel "Sound" socket, and via the RF modulator TV output, and does not do justice to the AY-3-8912 sound chip.

However, there is a very simple modification that you can perform that will give you crystal-clear, noise-free sound output via the “Sound” socket.

I recently discovered, quite by chance, that nearly all of the noise on the +2's outputs is caused by the Datacorder, whose very sensitive amplifier is continuously switched on, even when the tape deck is not in use, and picks up noise from the +2's other circuitry.

If the Datacorder is disconnected from the main PCB, or even just the power is disconnected, the output from the "Sound" socket becomes beautifully clear, with almost no background noise whatsoever. (Even the TV sound output is dramatically improved, although there is still some background noise present on this.)

However, with the Datacorder disconnected or powered down, it is obviously not possible to load or save programs from tape, so I wired a small toggle switch in the Datacorder's power lead, and mounted this on the right-hand side of the +2's case, so that I could switch the tape deck on to load or save programs, but switch it off again to obtain noise-free sound output.

In the +2 I modified, the power wire was the red wire going to the centre pin of the 5-pin plug connecting to the main PCB. Please check which wire it is in your +2, as there may be differences between models, and while it's unlikely that you'll do any damage by disconnecting the wrong one, you might waste your time!

The only slight complication was that the power-on indicator LED is also powered from the Datacorder PCB, so I had to make other arrangements to ensure that this LED didn't go out when the tape deck was switched off. This required only one additional wire to be added - I chose to take this from one of the pins of my switch as this was the easiest place to solder.

By carefully cutting the wires going to the switch at the right length, I found it was possible to route them very neatly around the back of the tape deck motor, where they sit in the groove between the motor and the back panel of the case.

The simple modification is very effective, and I can highly recommend it to anyone who wants to obtain noise-free sound output from their +2. You only need basic soldering skills and the ability to handle a drill to mount the switch - it really is a piece of cake, and well worth the effort.

Another, slightly more involved, option is to solder some wires directly onto the output pins of the AY chip, and run these to an external amplifier. This has the advantage that the Load/Save tape noise is not routed through your amplifier, but neither are the 48K “beeper” sounds – this may or may not be desirable, depending on what you want.

Please note that these modifications are applicable to the "grey-case" +2 machines only, and may not be applicable to other models such as the +2A.

This page was last updated on 6th July 2006.
Copyright Tim Fardell.