Like many I started messing with EDM production in the 90s using ReBirth and Reason and absolutely adored the 303 suimulation, but of course original 303 prices were too much for me in 1998. I got a Korg EA-1 in 2001 and still have it. Bought a TD3 in April '25. Within 5 minutes of messing with it (particularly after feeling the reassurring quality of the filter pots) I decided to order this (along with an RD8 MkII). I have only taken off one star out of 25 for quality due to the light plastic construction. I would happily pay more for a metal enclosure if it were an option, this circuit is worth it imo. All pots are firm, smooth and accurate. Buttons are plastic and rattle a bit when the unit is shaken but all work positively with no issues. The mini switches are perfectly serviceable. The connectivity is superb - MIDI, USB, sync in, multiple patching options, headphones and audio out - all work perfectly and are correctly and solidly mounted. It seems to have flashing LEDs underneath (bottom half is opaque black plastic) that seem to synchronise with the pattern. The basic 303 type sounds are slightly different to the TD3, somehow smoother and more refined (which could be good or bad depending what you want) and I cannot make it sound identical to the TD3. The TD3 is forgiving, mid-rangey and seriously good fun. Basically as long as you do not accidentally turn the tuning pot you can't really mess up. However, this version is much more sensitive and less forgiving. It is very easy to make it choke out or squeal/chirp simply due to the fact that it is considerably more powerful than the basic model. There are some online guides to help one set it up to get close to standard 303 territory, but the range of control provided by the MO's pots is waaaaay wider. It can also completely change the groove and even the programmed pattern itself as certain notes may get squeezed (or chirped!) out with extreme filter settings. It compliments the TD3 perfectly for me. I use the TD3 for the main rubbery/squelchy sort of typical acidic basslines and the MO for special effects or a deeper lower pitched bassline. The 'square' wave oscillator sounds a bit better on the MO to me, deep and smooth. The saw wave becomes hysterically unhinged with the right distortion circuit. Most reviewers I have read that own both synths usually recommend you get both and I heartily concur. If you only want the classic 303 sound then a TD3 will be absolutely fine (with an option to lightly modify if you are unconcerned with warranty). If you want a much more versatile instrument with a strong 303 flavour but many more options, then this is the one. Love it.
