If you're into vintage gear, you've probably come across our website. We've been buying, refurbishing and selling vintage synths and other electronic musical instruments for close to 30 years now. We're perfectionists and take our business, our gear, and our customers very seriously, so buy with full confidence - we won't let you down.

Our prices here may seem high, but we are a legit business with real business expenses, not your typical amateur seller with a Reverb store. Please click on our user name to read more about our shop so you better understand our prices & high standards. Reverb and merchant fees are of course already added into our prices here.


Here's an interesting one-of-a-kind synth. We bought this from a customer who was into DIY electronics. He always admired the design of the ARP 2500 but couldn't find one, so he built his own! Well, kind of. He bought MFOS Music From Outer Space circuit boards and assembled the circuits. He made his own front panels to look similar to those on the arp2500 and wired them up. They're installed in a nice wooden cabinet he made as well.

This system is a real pleasure to play. If it doesn't sell, we're going to use it in our studio as a secret weapon, as it sounds great and quite different from our other synths.


Oscillator 104
Dual LFO 103
8 Stage Phaser 111
Oscillator 104
Dual T/G/T/S/H (We believe this circuit is the Ian Fritz module aka Threshold/Gate/Trigger/Sample/Hold Circuit)
Oscillator 104
Low Pass Filter 107
Dual Envelope Generator 133
Dual VCA 106
Clocked Sequencer 116

DIY synths often have lots of problems due to the fact that some of the people who build them have never had any prior experience assembling electronics, and even when they have, there are often mistakes that the builder didn't bother to correct. Fortunately, the person who assembled this unit had good soldering and decent assembly skills and, for the most part, this unit is working quite well and sounds amazing - we were very surprised by how good it sounds!

There are a few anomalies, most of which seem to be wiring errors that should be easy to correct or features that were never implemented. We are selling it as is, though we could probably have our tech fix any issues for an additional fee:

-The dual T/G/T module's LED is not working, but the module itself works fine. A couple of the other modules that have spaces for an LED never had LEDs installed.
-In reverse mode, the sequencer's step 1 does not play, and the sequencer's random mode triggers step 16 a lot more than it should if it was truly random, but we suspect this may be normal operation.
-There are 3 volume pots for each of the 3 audio inputs in the VCF module. Pots 1 and 2 do not seem to work unless something is plugged into input 3. The signal going into input 3 seems a bit muffled.
-VCF trigger and gate input jacks do nothing as they were never wired. This function may not be possible with this circuit.
-The LFO sawtooth and reverse sawtooth jacks (or panel labels) seem to be reversed on both LFOs.
-The phaser distorts when the input is high, but this is likely normal and is an interesting effect.
-We noted that VCO2's pitch was drifting in the past but we didn't notice this when this unit was tested recently. It's possible we fixed this a long time ago or that this may be intermittent.
-VCO2 sine wave sounds like a sawtooth - we suspect the wiring was wrong.
-Each of the oscillator modules has a waveform mixer on the front panel, but there doesn't appear to be a circuit for this function in vco2 or vco3. This function in vco1 results in lower level volumes than the direct waveform outs. There's a connector inside that's not attached and this may or may not have something to do with this.
-The resonance CV pot seems to pass a signal when it's at zero position but works as expected throughout the rest of its range.
-Envelope trigger 1 jack triggers envelope 2 and trigger 2 jack triggers envelope 1.
-VCA audio input pots seem like a simple tone control, which may be normal. Both pots crackle a bit.
-The VCF's audio input signal seem to frequency modulate the filter when the resonance is high.
-There could be more, but that's all we noticed when going through it.

It's hard putting a price on this. We're guessing the parts costs for everything - circuit boards, panels, components, power supply and cabinet may have been around $1000, but all the time spent building these things is valuable. We asked our tech what he felt it should be worth and he valued it a lot higher than its current price, but as someone who builds things like this professionally, he also knows how much time and effort these things take. If our asking price is too high, feel free to make a reasonable counter-offer, though we're also tempted to keep it and use it in the studio, so this unit is valuable to us.

PLEASE CONTACT US AND WAIT TO DISCUSS BEFORE ATTEMPTING TO BUY so we can calculate shipping and adjust it accordingly. The amounts here are a rough estimate.

eBay only allows us to post 12 pics. There are many more detailed photos on our website, just search it for MFOS so you can see it in greater detail. There are also more videos on our Instagram.


-Please read our shipping policy & terms before buying. They are firm.

-We are an online-only store and are unable to allow local pickups.

-Quality control and customer satisfaction are our top priorities. We go to great lengths to test, service and even future-proof most of the items we sell so they’re better than others you may find. We test most items multiple times and overlook nothing. When items are not working perfectly, they are accurately described. Physical imperfections can be seen in the detailed photos present here. Please search our website for additional photos.

-All sales are final. We do not accept returns or issue refunds, so please be sure you know you want this item before buying it.

-Due to the vintage and electronic nature of our items, we sell all items strictly as is, only because we cannot control what other people do to our items once they leave here, we cannot offer warranties on parts that are decades out of their original warranties, and we don’t want to be scammed or inconvenienced by people who abuse return policies or have buyer's remorse.

-In the extremely unlikely event that there’s a problem with an item we sell you, please contact us immediately so we can try to help.

-Thank you so much for your time, interest, and support. We look forward to doing business with you! If you need anything, please don’t hesitate to ask.

-Any date of manufacture shown here is just a guess.

-We generally set our condition ratings to "excellent", but please refer to the photos and writeup so you can have a better understanding of this items condition.

This item is sold As-Described

This item is sold As-Described and cannot be returned unless it arrives in a condition different from how it was described or photographed. Items must be returned in original, as-shipped condition with all original packaging.Learn More.

Listed5 months ago
ConditionVery Good (Used)
Very Good items may show a few slight marks or scratches but are fully functional and in overall great shape.learn more

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Astoria, NY, United States
Joined Reverb:2019

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