1973, analog voices
Voices (10): bass drum, high conga, low bongo, high bongo, rim shot, cow bell, clave, cymbal, high hat, snare.
Patterns (27): each with A and B variation. "Auto" mode alternates between variation A and variation B. You can press multiple pattern buttons at once to combine rhythms.
Sound: round and warm. Think lounge, not aggressive electronic dance music. The TR-66 is not "angular and tight" like the snappy CR-78, it's softer. The kick is a winner, mellow but with a cleanly defined thump at 60Hz (decay is tunable via an internal trimmer, but not the pitch). The high conga, low bongo, and high bongo are simple but recognizable classics (both decay and pitch are tunable via internal trimmers). The rim, clave, and cow bell are all tight and highly usable (they take reverb well). The snare is fine but can be a bit crude, but good if you get a nice sample (amount of white noise adjustable via internal trimmer). The hat and cymbal are a bit trashy sounding; need processing to get rid of annoying frequencies. The top end on this unit extends beyond 40kHh.
Balance knob: adjusts the relative levels of the kick and hat/cymbal (it’s not an EQ tone knob), while holding the midrange sounds constant. So if you turn counterclockwise you get more kick and less annoying hat. Around 9-10 o'clock is a balanced sound between the kick/hat, that's pretty much the usable range of this knob. Note you can not get isolated hits this way, as the hat/cymbal will not mute.
In/Outs: the low impedance out (10k Ω) gives line -10 dBV levels for recording, and there’s also a high impedance out (100k Ω, lower-gain). There’s also a “start” input for connecting a foot switch.
Notable use: Dust Brothers Fight Club score "Corporate World." Roxy Music "Dance Away."
These rhythms were sampled 24/44.1k into a Metric Halo LIO8 using its DI input, then converted to MP3 320. No effects, just the dry rhythm box. Tuned using just intonation: bass drum 1/1, snare fundamental 9/8, high conga 5/3, low bongo 5/3, high bongo 9/8.
HOW TO SAMPLE IT
The 1973 service manual can be a bit hard to decipher, here is how you trigger individual sounds for creating your own samples. First remove the four screws on the base. The TR-66 will then slide out the rear of the wood case.
Conveniently located on top you will see the Sound Generator Board. There is a cut out section in the metal platform on which the Sound Generator Board is attached, which allows you to access a small portion of the Rhythm Switch Board below. That is where you will find "terminal 5" (which is referenced in the service manual). Term5 is outputting a trigger at the tempo set by the front knob. Put the box in play, no rhythm buttons engaged, and run a wire from term5 to the sound you want to trigger. This generates a waveform at the 1/4" outs, at the same volume and sustain as the box normally outputs.
Note: best not to use your own external trigger as this can produce lower gain sounds with erratic sustain, I experimented with this using my modular trigger outs, but ended up using the built in one.
Situated around the edge of the Sound Generation Board are nine terminals, which trigger ten sounds. Moving clockwise starting with the snare drum you will see terminals labeled: SD, HH, CY, C, RS, HB, LB, HC, BD. The RS terminal normally outputs a cow bell, but if you push the "bossa nova" button in around 3/4 (without actually making it click in) this terminal will output a rim shot (the service manual mentions something about grounding/ungrounding the CB SHUNT terminal to get these two sounds).
On the sound generator board you will find eight off-white trimmers for tuning the sounds. These are labeled: BD DT, HC DT, HC FRQ, LB DT, LB FRQ, HB DT, HB FRQ, and CY.HH.SD VAR.
"FRQ" trimmers: these give you some control over the pitch of the three toms (HC, LB, HB), however the available range is narrow. If you go too low the drum may start to become a lump of noise with no definitive pitch, and if you go too high it may start feeding back. Interestingly the snare sound contains the low bongo sound within it (the SD fundamental is fixed at around 280hz, and the LB is adjustable around 400hz). So tuning this bongo also changes the sound of the snare (I tune it to a just intonation relationship).
"DT" trimmers: these give you control of the decay time of the bass drum and the three toms. It is especially useful for the bass drum; you can get anything from a tight 65ms snap, and a long 650ms boom.
"CY.HH.SD VAR" trimmer: this controls the level of the white noise. Turning this adjusts the snappiness of the snare, from completely muted (this could be considered a secret 11th sound!), to bright and raspy. Also, when sampling the HH/CY turning up this trimmer gives you a better signal to noise ratio.
This old box uses a two prong ungrounded power plug and can be noisy.