MARK III: specifications
Specifications for the four machines Otari sold as the MARK III series — the MARK III/2, MARK III/4, MARK III/8 and the upright BQ-II — with sources noted; this page prefers gaps over guesses. Not sure which machine you have? Start with Identify.
The sourcing is uneven, and the page says so rather than smoothing it over. Two of the four have a full factory specification table transcribed on this site. One has two data sheets. The III/8 has neither, and its section is short for that reason.
The four machines at a glance↑ TOP
This grid is Otari's own, from the 1984 series brochure, and it is kept to that single source on purpose. It is the only document that measures all four machines the same way — and, as the sections below show, the way it measures is not the way the service manuals do. Treat it as the sales comparison it is, not as the machines' specifications.
| MARK III/2 | MARK III/4 | MARK III/8 | BQ-II | |
|---|---|---|---|---|
| Channels | 2 | 4 | 8 | 4 |
| Tape width | ¼″ | ½″ | ½″ | ¼″ |
| Tape speeds | 15/7.5 or 7.5/3.75 ips | 15 & 7.5 ips | 15 & 7.5 ips | 15 & 7.5 ips |
| Equalization | IEC/NAB switchable | NAB | IEC | NAB |
| Headphone amp | 8 ohm impedance | 4-channel selectable | 8-channel selectable | 8 ohm impedance |
| Frequency response | 25 Hz to 22 kHz | 30 Hz to 20 kHz | 40 Hz to 25 kHz | 30 Hz to 20 kHz |
| Signal-to-noise | 72 dB | 70 dB | 68 dB | 66 dB |
| Wow and flutter | <0.04% | <0.04% | <0.04% | <0.04% |
| Distortion | <0.5% | <0.3% | <0.7% | <0.7% |
Four more rows in the brochure's grid are printed once across all four machines rather than per machine: nominal I/O level +4 dBm, −10 dBV; an hours/minutes/seconds real-time display with zero return; a built-in 1 and 10 kHz alignment oscillator; and a single multipin synchronizer connector. The brochure's own note above the grid sends the reader elsewhere for anything more — "For full specifications, see individual machine data sheets."
The wow-and-flutter row will not survive contact with the manuals. It gives every one of the four machines less than 0.04%, but both service manuals that state the figure give worse ones — 0.05% and 0.06% for the III/4, 0.06% and 0.08% for the BQ-II, both NAB weighted and both stated per speed. The brochure quotes one number, at neither stated speed nor stated weighting, for four different transports. It is a best case.
MARK III/2↑ TOP
No service manual for the III/2 is held here. Otari's own figures come from two printings of the data sheet, both on this site as scans: the 1983 sheet and the 1987 sheet (BP6872.5K).
The two printings are not the same document with a new date on it. Otari restated several of the machine's headline numbers, and every change makes the machine look worse on paper:
| Parameter | 1983 sheet | 1987 sheet |
|---|---|---|
| Signal-to-noise, 15 ips | 72 dB unweighted | 68 dB unweighted |
| Signal-to-noise, 7.5 ips | 72 dB unweighted | 71 dB unweighted |
| Signal-to-noise, 3.75 ips | 70 dB unweighted | 69 dB unweighted |
| How that ratio is defined | "Third Harmonic to noise", 30–18 kHz, NAB EQ | "3% Third Harmonic to noise floor", 30–18 kHz, NAB EQ |
| Frequency response, 15 ips (0 VU) | 25 Hz to 22 kHz ±2.0 dB | 30 Hz to 20 kHz ±2.0 dB |
| Frequency response, 7.5 ips (−10 VU) | 20 Hz to 20 kHz ±2.0 dB | 30 Hz to 20 kHz ±2.0 dB |
| Reference tape | 3M #226 | Ampex #456 |
| Power requirements | 100/117/220/240 V | 110/117/220/240 V |
| Shipping weight | 89 lbs (40 kg) | 105 lbs (48 kg) |
The signal-to-noise change is the one that matters, and the definition beside it explains most of it: the 1987 sheet measures to a 3% third-harmonic point and names a noise floor, where the 1983 sheet just says "third harmonic to noise". That is a different measurement, not a different machine.
The 1984 brochure agrees with the 1983 sheet, not the 1987 one — 25 Hz to 22 kHz and 72 dB are the 1983 figures, at 15 ips. That is what you would expect of a brochure printed between the two.
Everything else is common to both printings:
| Parameter | Value |
|---|---|
| Tape width and channels | ¼″ (6.3 mm) tape, 2 channel |
| Tape speeds | 15 and 7.5 ips, or 7.5 and 3.75 ips — internally switchable speed pairs |
| Maximum speed deviation | ±0.2% |
| Reel size | ¼″ × 5, 7 or 10.5″, EIA or NAB |
| Heads | Four, in-line: erase (half track), play (quarter track), record (half track), play (half track) |
| Motors | DC servo-controlled capstan motor, two induction reel motors |
| Rewind time | Less than 90 seconds for a 2,400′ reel |
| Pitch control | Variable within ±7% |
| Wow and flutter (NAB weighted) | 15 ips less than 0.04%; 7.5 ips less than 0.07%; 3.75 ips less than 0.08% |
| Connectors | Line input, mic input and line output: standard three-pin XL type. Headphone: standard ¼″ phone jack |
| Inputs | Line: active, balanced, 10 kΩ. Mic: active, balanced, usable 150 Ω to 10 kΩ, switchable 20 dB pad and mute |
| Outputs | Active, balanced, 5 Ω source impedance; +27 dB (ref. 0.775 V) into 600 Ω or more |
| Equalization | IEC or NAB, switchable |
| Crosstalk | Less than 55 dB at 1 kHz on adjacent track |
| Frequency response, 3.75 ips (−20 VU) | 20 Hz to 12 kHz ±2.0 dB |
| Operating level | 250 nWb/m |
| Distortion | Less than 0.5% third harmonic |
| Test oscillator | Nominal 1 kHz and 10 kHz |
| Operating environment | 40 to 104 °F (5 to 40 °C), 20 to 80% R.H. |
| Storage environment | −5 to +113 °F (−20 to +45 °C), 10 to 80% R.H. |
| Mounting | Vinyl covered wood case; RK-32 rack mounting kit and ZA-52L roll-around pedestal optional |
| Dimensions | 28.25″ (718 mm) wide × 18.75″ (476 mm) high × 18.1″ (460 mm) deep |
For the tolerances a technician holds this machine to, rather than the ones Otari advertised, see the 1988 alignment procedures — written for the B-II and the MKIII-2 together, and transcribed here in full.
MARK III/4↑ TOP
The III/4 is the best-documented of the four. Otari's factory table is transcribed in full from the OS3-035 instruction and maintenance manual: Table 1-3, Specifications. The headline figures from it:
| Parameter | OS3-035 |
|---|---|
| Tape width and tracks | ½″ (12.7 mm) tape, 4 tracks, 0.037″ (1.9 mm) track width |
| Tape speeds | 7½ and 15 ips, maximum deviation ±0.2% |
| Heads | Three, four-track in-line: erase (ferrite), record and reproduce (both hard permalloy) |
| Frequency response, REC/PLAY | 15 ips: 40 Hz to 20 kHz ±2 dB; 7½ ips: 30 Hz to 18 kHz ±2 dB |
| Frequency response, SEL/REP | 15 ips: 40 Hz to 16 kHz ±3 dB; 7½ ips: 30 Hz to 12 kHz ±3 dB |
| Signal-to-noise (NAB or IEC) | 71 dB weighted, 69 dB unweighted, at both speeds |
| Wow and flutter, NAB weighted | 15 ips less than 0.05%; 7½ ips less than 0.06% |
| Distortion | Less than 0.5% at 1 kHz at 250 nWb/m |
| Crosstalk | Greater than 60 dB |
| Erase efficiency | Greater than 70 dB |
| Bias and erase frequency | 200 kHz |
| Power | 100/117/220/240 V, 50 or 60 Hz, 110 watts |
| Dimensions and weight | 438 mm W × 662 mm D × 488 mm H (17.3″ × 26.1″ × 19.2″); 32 kg, 71 lbs |
| Operating position | Horizontal, tabletop |
Set against the brochure's column for the same machine, the pattern is consistent — the manual states a speed, a tolerance and a weighting, and the brochure states none of the three:
| Brochure (1984) | OS3-035 | |
|---|---|---|
| Frequency response | 30 Hz to 20 kHz | 40 Hz to 20 kHz ±2 dB at 15 ips; 30 Hz to 18 kHz ±2 dB at 7½ |
| Signal-to-noise | 70 dB | 71 dB weighted / 69 dB unweighted |
| Wow and flutter | <0.04% | <0.05% at 15 ips, <0.06% at 7½, NAB weighted |
| Distortion | <0.3% | <0.5% at 1 kHz at 250 nWb/m |
The brochure's frequency response is the wider of the manual's two speeds at its low end and the narrower at its top, which is to say it is neither. Its distortion figure is better than the manual's, and its wow and flutter better than either speed the manual gives.
MARK III/8↑ TOP
No manual and no data sheet for the III/8 is held on this site. The card for the MARK III/4, III/8 and BQ-II data sheets records them as not held, and the OS3-035 manual is the III/4's book, not the III/8's. What follows is what the brochure claims, and it is marketing copy.
From the 1984 brochure:
| Parameter | Value (brochure) |
|---|---|
| Channels | 8 |
| Tape width | ½″ |
| Tape speeds | 15 and 7.5 ips, with 60 minutes record time at 7.5 ips |
| Equalization | IEC |
| Frequency response | 40 Hz to 25 kHz |
| Signal-to-noise | 68 dB |
| Wow and flutter | <0.04% |
| Distortion | <0.7% |
| Headphone amp | 8-channel selectable |
| Reference levels | +4 dBm or −10 dBV, independently switchable per channel |
| Heads | Plug-in optimized three head design, hinged head cover |
| Electronics | Plug-in, one card per channel, with a full complement of adjustments each |
| Pitch control | ±7% (+50%, −100% via external control) |
| Floor stand | ZA-52L-38 (optional) |
Given the wow-and-flutter row's history above, the 0.04% here should be read as the series claim rather than a figure anyone measured on a III/8.
One piece of genuine factory documentation does reach this machine. The addendum bound into the OS3-035 manual is headed for the BQ-2, MK-3-4 and MK-3-8, and describes external capstan speed control through the rear-panel LOCATOR connector: a DC voltage across pins 1 and 2, range ±13 V, with −13 V giving minimum speed, 0 V nominal, and +13 V (or +8 V at 15 ips) maximum.
Otari's own sales copy sets the machine against the company's MTR-90 for features and against 1″ eight-channel machines for performance, and claims its 7.5 ips audio specifications surpass other eight-channel machines at 15 ips. No independent measurement of that claim is held here.
MX-5050 BQ-II↑ TOP
The upright four-track of the series, and the other machine with a full factory table transcribed — from the OS3-031 instruction and maintenance manual: Table 1-3, Specifications.
| Parameter | OS3-031 |
|---|---|
| Tape width and tracks | ¼″ (6.3 mm) tape, 4 tracks, 0.037″ (0.94 mm) track width |
| Tape speeds | 7½ and 15 ips, maximum deviation ±0.2% |
| Reel sizes | 5, 7 or 10½″ plastic or metal, EIA or NAB |
| Heads | Four head stacks: ¼″ erase × 2 (1–3, 2–4 CH), ¼″ record, ¼″ reproduce |
| Frequency response, REC/PLAY | 15 ips: 30 Hz to 20 kHz ±2 dB; 7½ ips: 20 Hz to 18 kHz ±2 dB |
| Frequency response, SEL/REP | 15 ips: 50 Hz to 18 kHz ±3 dB; 7½ ips: 30 Hz to 12 kHz ±3 dB |
| Signal-to-noise (NAB or IEC) | 69 dB weighted, 66 dB unweighted, at both speeds |
| Wow and flutter, NAB weighted | 15 ips less than 0.06%; 7½ ips less than 0.08% |
| Distortion | Less than 0.5% at 1 kHz at 250 nWb/m |
| Crosstalk | Greater than 55 dB |
| Erase efficiency | Greater than 70 dB |
| Bias and erase frequency | 200 kHz |
| Power | 100/117/220/240 V, 50 or 60 Hz, 100 watts |
| Dimensions and weight | 438 mm W × 269 mm D × 527 mm H (17.3″ × 10.6″ × 20.8″); 27 kg, 60 lbs |
| Operating position | Vertical or at angle |
Against the brochure's column, the disagreement runs in both directions this time:
| Brochure (1984) | OS3-031 | |
|---|---|---|
| Frequency response | 30 Hz to 20 kHz | 30 Hz to 20 kHz ±2 dB at 15 ips; 20 Hz to 18 kHz ±2 dB at 7½ |
| Signal-to-noise | 66 dB | 69 dB weighted / 66 dB unweighted |
| Wow and flutter | <0.04% | <0.06% at 15 ips, <0.08% at 7½, NAB weighted |
| Distortion | <0.7% | <0.5% at 1 kHz at 250 nWb/m |
Here the brochure quotes the BQ-II's unweighted signal-to-noise, 66 dB, where for the III/4 it quoted a figure close to the weighted one — and its distortion figure is worse than the manual's, not better. The comparison grid was built to rank four machines against each other, and the numbers in it were chosen to make that ranking come out; they are not a consistent set of measurements.
The BQ-II's own dimensions are the clearest statement of what it is. At 269 mm deep and 527 mm high it is the upright of the series — half the depth of the III/4's 662 mm, and taller than it.
Sources↑ TOP
- The MARK III Series brochure (1984) — the four-machine comparison grid, and the only figures held here for the III/8.
- MARK III/2 data sheet, 1983 — the III/2's transport, electronics and physical figures as first printed.
- MARK III/2 data sheet, 1987 (BP6872.5K) — the same sheet reprinted, with signal-to-noise, frequency response, reference tape, supply voltage and shipping weight all restated.
- MX-5050 MKIII-4 instruction and maintenance manual, OS3-035 — Table 1-3, the III/4's factory specification, and the addendum covering external capstan speed control on the BQ-2, MK-3-4 and MK-3-8.
- MX-5050 BQ-II instruction and maintenance manual, OS3-031 — Table 1-3, the BQ-II's factory specification.
- MX-5050 BII and MKIII-2 alignment procedures, 1988 — the III/2's service tolerances, as distinct from its advertised figures.