Poly 800 Moog Slayer Mod

The inspiration to perform this mod came from visiting this site:

Having recently obtaining a Poly 800 cheaply I couldn't resist added some real time tweakability to this charming little synth :-)

The Moog Slayer mod adds real-time filter Cut-Off frequency and Resonance controls. Remember, the Poly 800 has one and only one real analogue filter for all 8 voices!

This is not an extensive How to and is just meant as a guide.

Poly-800 with innards on display

First you have to open it up by removing all the screws in the base.

Poly-800 and no keys

Remove the keyboard.

This is also a good opportunity to clean the conductive contacts under the rubber strips. I used several cotton buds (Q-tips) and Isopropryl Alcohol (IPA) - acetone or nail varnish remover will work just as well.

Poly-800 main board
A view of the main PCB.

no variable resistors and new battery

Remove the variable resistors. I also took the opportunity to replace the ageing original 3V lithium memory backup battery.


The Poly 800 is now mostly gutted!

new pots

Holes were drilled above the joystick and the new pots were added.

new wires

A Shot of the new wires coming from the board and going to the pots.

keys back in place

The mod is now complete, now put the keyboard back.


Close up of the new controls


The completed Moog Slayer Poly 800

It took around two hours to do but I was going very carefully and methodically. Costs were 1.50 for each pot as I used high quality conductive plastic types. 1.50 for each knob as they were high quality aluminium types and 1.00 for the new battery. A bargain really for the added functionality it brings.

I got the knobs from a company called CPC which is a division of Farnell.
I got better than usual pots so that could take a fair bit of use too.

Audio examples

OK that's all well and good but how does it sound?

A little echo and reverb was used too :-)

Remember when recording you need a hell of a lot of compression to tame that wild resonance!

Video example

Here's a short clip of me putting it through its paces - it'll help if you pretend for now that your name is Mike - OK?

If you have a Poly 800 - Just do it!

Free download

64 new presets and a new sequence for your Poly 800 298kB.

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