Analog filth or digital clean? Most of us go for the analog, if only for the fun of twiddling actual knobs. I can't believe I've had a KORG Monotron Delay* for three years now, but have never written about it.
Not much bigger than a deck of cards, the Monotron Delay (like the original Monotron and the dual-oscillator Monotron Duo) makes sound with an analog engine. The built-in delay effect is digital, but don't let it bother you, as it really delivers the goods.
Here is a little snippet I made by connecting the stereo headphone output of the Monotron Delay to inputs 1 and 2 of my Steinberg UR22 mkII* audio interface and recording the results of my noodling in Ableton Live Intro 9.6*.
WARNING: The audio contains some rather loud and abrasive sounds!
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My way of connecting is a regular cable with a 3.5" male stereo jack on one end, and two RCA plugs with 6.3" plug adapters. The Monotron Delay output level is fairly low, so turn up its volume and the input gain on your audio interface. There is some background noise, but the type of sounds you will be making will mask it.
I may also try using the Monotron Delay as an external effect through its AUX IN jack. Logic Pro X has a handy I/O utility plug-in that can handle the routing, but I need to use an audio interface with more than two outputs, like my trusty old Focusrite Saffire Pro 24 DSP.