Basic Technical Concepts for Tape Recorders

8. PART NUMBER FOR OTARI PRODUCTS↑ TOP

OTARI REFERENCE NUMBER↑ TOP

A○○○○○○○○ — 8 digits

• A: Amplifier
• BA: Bearing
• C: Capacitor
• I: IC
• LU: Lamp
• ME: Meter
• PB: PCB
• PN: Diode
• Q: Transistor
• R: Resister [sic]
• WH: Switch

⤢ zoomModel number to individual part numbers assembly tree

PART NUMBERS FOR PCB↑ TOP

• PB9○○○○○ : PCB without Components

• PB-1 (or 4, 6, 7)○○○○ : PCB with Components

• PB-1○○○○ : Amplifier PCB Assembly

• PB-4○○○○ : Control PCB Assembly

• PB-6○○○○ : Power Supply PCB Assembly

• PB-7○○○○ : Extension PCB Assembly

Ex. PB-1AAB — PCB Type, Renovation Number

9. OTARI CIRCUIT DIAGRAMS↑ TOP

⤢ zoomHow a set of Otari circuit diagrams is organized — list, wiring diagram, and per-board sheets with drawing and part numbers

BASIC TECHNICAL CONCEPTS FOR TAPE RECORDERS↑ TOP

1. TAPE TENSION↑ TOP

⤢ zoomTape path with supply and take-up reels, showing back force, back tension, take-up tension, drive force, heads, pinch roller and capstan shaft

2. HEAD CONTACT FORCE↑ TOP

⤢ zoomHead contact force produced by tape tension, and head gap with magnetic flux linking to the tape

3. HEAD GAP AND DEPTH↑ TOP

⤢ zoomHead gap length and depth, output null when wavelength equals gap length, level versus frequency lobes, and the wavelength formula with a worked example

4. TAPE DRIVE SYSTEMS↑ TOP

A. PINCH ROLLER SYSTEM

⤢ zoomPinch roller system with drive force passing from capstan shaft through the pinch roller to the tape

• Drive Force
  • ① Capstan Shaft → Pinch Roller
  • ② Pinch Roller → Tape
• Since the force is transmitted through elastic material, the tape tension tends to be unstable.
• More Drive Power

B. PINCH ROLLER SYSTEM

⤢ zoomPinch roller system with the tape driven directly against the capstan shaft

• Drive Force: Capstan Shaft → Tape → Pinch Roller
• Since the force is not transmitted through elastic material, the tape tension is stable.
• Less Drive Power
• Back Coating Tape
• Tension Servo System → MTR-10, BTR-10, etc.

C. PINCH ROLLERLESS SYSTEM

⤢ zoomPinch rollerless system with friction roller and direct drive capstan roller

• Direct Drive Capstan Roller
• Tension Servo System
• High Accuracy Transport → MTR-90 series, MTR-100A, DTR-900 series
• Same tape path for PLAY, FF, RWD → Quick Response

D. DOUBLE CAPSTAN SYSTEM

⤢ zoomDouble capstan system with small supply capstan and big take-up capstan enclosing the head area

• Tension: a > b > c
• Reel Tape Tension does not effect [sic] Head Tension. → Stable Head Tension
• Since tension servo technology has progressed, this system is not used much.

Servo Control↑ TOP

1. Reel Motor↑ TOP

• Tension Control
  • Open Loop Servo
    • Single Direction
    • Bidirection
  • Closed Loop Servo
• Winding Speed Control
  • Fast Winding
  • Controlled Pack (Winding)

2. Capstan Motor↑ TOP

• Speed Control
  • PLL (Phase Locked Loop) Servo
  • Voltage Servo
• Drive mode
  • Pinch Roller type
  • Friction Drive type
• Reference
  • Internal
    • AC Line
    • Voltage
    • Quartz
  • External (for Synchronizer)
    • Voltage
    • Frequency

3. Speed Accuracy↑ TOP

• Absolute Speed Accuracy
  • with Tension Servo: +/-0.05%
  • without Tension Servo: +/-0.1%
• Speed variation from begining [sic] to the end of reel
  • with Tension Servo: 0.05%
  • without Tension Servo: 0.1%

⤢ zoomTape speed drift from beginning to end of reel

5. RECORDING BIAS↑ TOP

BIAS CHARACTERISTICS↑ TOP

⤢ zoomBias characteristic — 1 kHz and 10 kHz output level and distortion versus bias

EXAMPLE OF RECOMMENDED OVER BIAS↑ TOP

MX-55N

Tape Speed (ips) Frequency (Hz)	3.75 10 k	7.5 10 k	15 10 k
AGFA PEM 469	8.0	5.0	3.0
AGFA PEM 468	8.0	5.5	3.5
AMPEX 406/407	7.0	4.5	2.7
AMPEX 456	8.0	5.5	3.0
BASF LGR50P	7.5	5.5	3.5
BASF SPR50LH/50LHL
BASF SM911	8.0	5.0	3.0
SCOTCH 206/207	7.0	4.5	2.7
SCOTCH 226/227	8.0	4.0	3.5
SCOTCH 250

(Unit: dB)

⤢ zoomDefinition of over bias — output versus bias current with peak bias point Bp and recommended bias point Br

⤢ zoomFrequency response with less bias, normal bias, and too much over bias

6. Dolby HX pro® HEADROOM EXTENSION SYSTEM↑ TOP

⤢ zoomDolby HX pro feedback system block diagram, bias versus frequency, and output curves with and without HX pro at 3.75 ips

7. BALANCED LINE AND ACTIVE BALANCED LINE↑ TOP

A. BALANCED INPUT/OUTPUT↑ TOP

⤢ zoomTransformer balanced input and output, unbalanced line versus balanced line noise rejection, and XLR connector wiring

Some standards assign Pin 2 as Hot, Pin 3 as Cold. (CAUTION: If the connection is mixed in one system, some problems might occur.)

B. ACTIVE BALANCED INPUT/OUTPUT↑ TOP

⤢ zoomActive balanced input and output op-amp circuits

Advantages

• Wide Band Frequency Responce [sic]
• Compact Size
• Low Cost
• High Impedance Input (10 kΩ - 1 MΩ) / Low Inpedance [sic] Output (1Ω - 5Ω)

PLAYBACK AND RECORD EQUALIZATION↑ TOP

Theory of Equalization

⤢ zoomTheory of equalization — (a) no EQ playback, (b) rec EQ, (c) playback EQ, (d) overall response

Constants of Playback Equalization

TAPE SPEED (cm/sec)

EQ Standard	76	38	19	9.5	4.8
AES	17.5	-	-	-	-
CCIR	-	35	35	-	-
DIN	-	35	70(DIN19S) 50+3180	90+3180	120+3180
IEC 1	35	35	70	90+3180	120+3180
IEC 2	17.5	50+3180	50+3180	-	-
NAB	-	50+3180	50+3180	90+3180	90+3180
BTS.NABJ	-	35+3180	50+3180	-	-
JIS	-	-	50+3180	90+3180	120+3180

Playback Equalization Curves

⤢ zoomPlayback equalization curves

METER RESPONSE CURVES↑ TOP

⤢ zoomTone burst signal with PEAK meter and VU meter rise and fall ballistics, and a VU meter scale with peak indicator

TAPE CHARACTERISTICS↑ TOP

⤢ zoomThird harmonic distortion versus input level at the 250 nWb/m standard operating level, and output versus input at 1 kHz and 10 kHz