MX-5050B: specifications
Specifications for the MX-5050B line — the synchronous-capstan 2H, 2L and 4L and the DC-servo 2HD, 2LD, 4LD, FHD and FLD — with sources noted; this page prefers gaps over guesses. Not sure which machine you have? Start with Identify.
The figures below come from two different kinds of paper. Otari's September 1979 brochure is a full specification sheet, but for one machine: the two-channel MX-5050-B with the DC capstan servo. The OS2-004 maintenance manual covers the whole line, but it has no specification table of its own; its figures are the limits its performance tests hold a machine to. The B's instruction manual, OS1-011, is also available as a 61-page Library of Congress scan (PDF).
The brochure's specification↑ TOP
The two-channel MX-5050-B, from the 1979 brochure:
| Parameter | 1979 brochure |
|---|---|
| Tape width and channels | ¼″ (6.3 mm); two channels, 0.075″ (1.9 mm) track width |
| Tape speeds | Three speeds, in internally switchable pairs: 15 and 7½ ips, or 7½ and 3¾ ips |
| Speed deviation | Maximum 0.15% with 1.5 mil tape |
| Rewind time | Less than 90 seconds for a 2500 ft reel |
| Reel size | 10½″ EIA or NAB; 5 or 7″ plastic |
| Heads | Four stacks: ½ track erase, ¼ track reproduce, ½ track record, ½ track reproduce |
| Motors | Capstan: three-speed DC servo, variable ±7%. Reels: two induction torque motors |
| Flutter and wow, NAB weighted | 15 ips less than 0.05%; 7½ ips less than 0.06%; 3¾ ips less than 0.10% |
| Line input | Minimum −15 dBm, unbalanced 50 kΩ; balanced 10 kΩ with optional transformer |
| Mic input | Minimum −70 dBm, unbalanced, nominal 50 kΩ (usable 150 Ω to 10 kΩ); 20 dB attenuator |
| Line output | Variable or fixed; fixed +4 dBm or −10 dBm switchable; maximum +28 dBm; 24 dB headroom; 600 Ω load, 50 Ω output impedance, balanced |
| Headphone | −24 dBm, 8 Ω or higher |
| Equalization | NAB; IEC rear panel switchable |
| Record level | 185, 250 or 320 nWb/m, rear panel switchable |
| Signal-to-noise, record/playback, unweighted | 15 ips 66 dB; 7½ ips 66 dB; 3¾ ips 65 dB — measured against 520 nWb/m |
| Signal-to-noise, playback electronics | 72 dB unweighted |
| Crosstalk | Greater than 55 dB at 1000 Hz, adjacent tracks |
| Frequency response, record/playback | 15 ips (0 VU) 30 Hz to 22 kHz; 7½ ips (−10 VU) 25 Hz to 20 kHz; 3¾ ips (−10 VU) 30 Hz to 12 kHz; all ±2 dB |
| Frequency response, playback only | 15 ips 31.5 Hz to 20 kHz; 7½ ips 31.5 Hz to 16 kHz; 3¾ ips 31.5 Hz to 10 kHz; all ±2 dB |
| Distortion | Less than 0.7% at 1000 Hz at 250 nWb/m |
| Test oscillator | Nominal 1000 Hz |
| Metering | VU meters plus peak LEDs set at +9 dB (adjustable), based on 185 nWb/m |
| Power | 117/220/240 V, 50/60 Hz, 100 W |
| Operating environment | 40° to 104°F (5° to 40°C), 20 to 80% RH |
| Weight | Cabinet 53 lbs (24 kg); portable case 62 lbs (28.2 kg) |
| Size | 21⅞″ (55.6 cm) high and 21½″ (54.6 cm) wide including reel overhang; 8⅛″ (20.6 cm) deep |
What the maintenance manual holds it to↑ TOP
OS2-004's performance tests run on "high quality low-noise tape such as Ampex 406, 407, 456, or Scotch 206, 207, 250" — a list that includes every tape the brochure names. Its limits:
| Test | OS2-004 |
|---|---|
| Tape speed | 3000 Hz test tape to read 2994 to 3006 Hz (±0.2%) |
| Flutter and wow, NAB weighted | 15 ips 0.06%; 7.5 ips 0.08%; 3¾ ips 0.12% |
| Crosstalk | 55 dB, half-track and quarter-track |
| Depth of erasure | More than 70 dB |
| Distortion, at 250 nWb/m, 1000 Hz | Second harmonic not to exceed 0.1%; third harmonic typically 0.4% on low-noise high-output tape |
| Reproduce response, from a test tape | 15 ips 31.5 Hz to 20 kHz; 7½ ips 31.5 Hz to 16 kHz; 3¾ ips 31.5 Hz to 10 kHz; all ±2 dB |
| Record/reproduce response | 15 ips 30 Hz to 20 kHz; 7½ ips 20 Hz to 18 kHz; 3¾ ips 20 Hz to 10 kHz; all ±2 dB |
| Standard reference levels | L 185, M 250, H 320 nWb/m, each giving 0 VU and +4 dBm (or −10 dB with the output level switch low) |
Signal-to-noise, from Table 4-1, by track format, each pair NAB / IEC:
| Tape speed | ½ track weighted | ½ track unweighted | ¼ track weighted | ¼ track unweighted | Full track weighted | Full track unweighted |
|---|---|---|---|---|---|---|
| 15 ips | 65/63 dB | 62/60 dB | 62/60 dB | 59/57 dB | 68/66 dB | 65/63 dB |
| 7½ ips | 65/63 dB | 62/60 dB | 62/60 dB | 59/57 dB | 68/66 dB | 65/63 dB |
| 3¾ ips | 63/63 dB | 60/60 dB | 60/60 dB | 57/57 dB | 66/66 dB | 63/63 dB |
The manual reads these against 0 VU at the L record level, 185 nWb/m, and then adds 9 dB — "peak recording level-520 nWb/m-is 9 dB above SRL-185 nWb/m" — so the figures are referred to 520 nWb/m.
Where the brochure and the manual disagree↑ TOP
| 1979 brochure | OS2-004 | |
|---|---|---|
| Signal-to-noise, two-channel, unweighted | 66 / 66 / 65 dB, against 520 nWb/m | 62 / 62 / 60 dB (NAB), against 520 nWb/m |
| Flutter and wow, NAB weighted | Less than 0.05 / 0.06 / 0.10% | 0.06 / 0.08 / 0.12% |
| Speed | Maximum deviation 0.15% | Within ±0.2% |
| Record/playback response, 15 ips | 30 Hz to 22 kHz, at 0 VU | 30 Hz to 20 kHz, at 0 VU |
| Record/playback response, 7½ ips | 25 Hz to 20 kHz, at −10 VU | 20 Hz to 18 kHz, at −20 dBm |
| Record/playback response, 3¾ ips | 30 Hz to 12 kHz, at −10 VU | 20 Hz to 10 kHz, at −20 dBm |
Speeds are given as 15 / 7½ / 3¾ ips throughout.
The signal-to-noise figures are measured to the same level. Both refer them to a 520 nWb/m recording — the brochure directly, the manual by adding 9 dB to a reading taken at 185 nWb/m. On that common reference the brochure claims 4 dB more at 15 and 7½ ips and 5 dB more at 3¾ ips than the manual accepts. The two describe their unweighted filters differently — the brochure a 30 Hz to 18 kHz band, the manual its own filter circuit — but the gap is the familiar one between an advertised figure and a service limit.
Playback agrees; record/playback does not. The manual's reproduce limits, checked from a test tape, are exactly the brochure's playback-only figures at all three speeds. The record/playback figures differ at every speed: the brochure claims more at the top of the band at all three, and less at the bottom at 7½ and 3¾ ips — where it also measures at −10 VU and the manual at −20 dBm.
Flutter and wow is measured NAB weighted in both, and speed as a plain percentage deviation, so both compare directly, and here the pattern is the familiar one: the brochure advertises a tighter figure than the manual accepts in service.
The brochure's 0.7% distortion and the manual's second-harmonic limit are not the same measurement, and are not set against each other here.
Four-track and full-track machines↑ TOP
The brochure covers only the two-channel B, so for the 4L, 4LD, FHD and FLD the manual's limits are all there is: the quarter-track and full-track columns of the signal-to-noise table above and the 55 dB quarter-track crosstalk figure. The manual's other limits — speed, flutter, erasure and response — are not broken out by track format. It notes that the test and alignment procedures for the MX-5050B-F and MX-5050B-4 "may be carried out in essentially the same manner". The four-track B's channel count is not printed in either document — see Identify.
The manual's brake adjustment gives a mechanical figure as well, checked with a spring scale: braking force of 3.6 to 4.5 ounces (100 to 125 grams) in one direction and 7.9 to 9.7 ounces (225 to 275 grams) in the other.
Sources↑ TOP
- MX-5050-B brochure, 107-9-79 — the two-channel machine's full specification.
- MX-5050B maintenance manual, OS2-004 — the performance-test limits in section 4-4, the response limits in section 4-6, and the braking force in Table 3-1.