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.
Two documents bear on the B, and they are 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 not held on this site.
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.