Sansui RA-500 Solid-State Reverberation Amplifier

Switches and Controls

The front panel of the RA-500 includes the following controls:

• POWER SWITCH: Push to turn the unit on or off.
• POWER INDICATOR: Illuminates when the POWER switch is on.
• REVERBERATION INDICATOR: Illuminates when reverberation is active. The clarity of the multicolored geometrical figure increases as the reverberation time is shortened.
• REVERBERATION PUSHBUTTONS:
  • ON: Applies reverberation to all program sources (except tape decks) when the TAPE MODE selector is OFF.
  • OFF: Disables reverberation effects.
  • RECORD: Used with the TAPE MODE selector for reverberation effects during recording or tape-to-tape transfers.
• REVERBERATION TIME CONTROL: Adjusts the reverberation time. Turn clockwise to lengthen, counterclockwise to shorten, while observing the REVERBERATION INDICATOR.
• TAPE MODE SELECTOR:
  • OFF: Provides reverberation to control amplifier sources; disconnects the reverberation amplifier from tape deck circuits.
  • A / B: Selects the tape deck (A or B) for recording.
  • A → B / B → A: Selects tape-to-tape transfer direction (A to B or B to A) for recording with reverberation.

Connections

All connections utilize shielded cables with pin plugs. The upper row of jacks on the rear panel corresponds to the left channel, and the lower row to the right channel.

I. Reverberation of All Program Sources Except Tape Decks

Connect the RA-500 to your stereo control amplifier:

1. Connect the RA-500's left channel IN jack to the control amplifier's left channel TAPE RECORD output. Connect the right channel IN jack to the right channel TAPE RECORD output.
2. Connect the RA-500's left channel OUT jack to the control amplifier's left channel TAPE PLAYBACK (or TAPE MONITOR) input. Connect the right channel OUT jack to the right channel TAPE PLAYBACK (or TAPE MONITOR) input.

Operation:

1. Set the control amplifier's Tape Monitor switch to PLAYBACK or ON.
2. Depress the REVERBERATION ON button on the RA-500.
3. Turn the TAPE MODE selector to OFF.
4. Adjust the REVERBERATION TIME control for desired effect.

II. Reverberation of Tape Decks

A. Recording and Playback

Connect tape decks with built-in preamplifiers for reverberation effects during recording and playback.

Connection:

1. Connect the tape deck's left channel input to the RA-500's left channel TAPE REC A (or B) jack. Connect the right channel input to the right channel TAPE REC A (or B) jack.
2. Connect the tape deck's left channel output to the RA-500's left channel TAPE PLAY A (or B) jack. Connect the right channel output to the right channel TAPE PLAY A (or B) jack.

Recording:

1. Set the control amplifier's Tape Monitor switch to PLAYBACK or ON.
2. Set controls on the tape deck as needed.
3. Depress the REVERBERATION RECORD button (or REVERBERATION OFF if no reverberation is desired).
4. Set the TAPE MODE selector to A or B.
5. Adjust the REVERBERATION TIME control.

Playback:

1. Set the control amplifier's Tape Monitor switch to PLAYBACK or ON.
2. Set controls on the tape deck as needed.
3. Depress the REVERBERATION RECORD button (or REVERBERATION OFF if no reverberation is desired).
4. Set the TAPE MODE selector to A → B (or B → A).
5. Adjust the REVERBERATION TIME control.

B. Tape-to-Tape Reprinting

Connect two tape decks to the TAPE DECK A and TAPE DECK B jacks for transferring recordings with optional reverberation.

To Record from Tape Deck A to Tape Deck B:

1. Set Tape Deck A to playback mode.
2. Set Tape Deck B to recording mode.
3. Depress the REVERBERATION RECORD button (or REVERBERATION OFF).
4. Set the TAPE MODE selector to A → B.
5. Adjust the REVERBERATION TIME control.

To Record from Tape Deck B to Tape Deck A:

1. Set Tape Deck A to recording mode.
2. Set Tape Deck B to playback mode.
3. Depress the REVERBERATION RECORD button (or REVERBERATION OFF).
4. Set the TAPE MODE selector to B → A.
5. Adjust the REVERBERATION TIME control.

Important Notes on Connections and Power

• Use shielded cables (four connecting cords supplied) for all connections to prevent hum or noise. Ensure all connections are firm and properly seated.
• The two AC outlets on the rear panel are always live and rated for a maximum total capacity of 300 VA. Do not exceed this capacity.
• Power Fuse: If the unit does not power on (POWER indicator does not light), the power fuse may be blown. Replace it with an identical fuse. For 100–117V operation, use a 0.5A fuse. For 220–240V operation, use a 0.3A fuse. Never use a substitute wire or fuse of a different capacity.
• Grounding: Connect the GND terminal on the rear panel to an underground copper plate for optimal Signal-to-Noise (SN) ratio. Grounding the entire audio system by connecting each component's grounding wire to this terminal is recommended.

Voltage Adjustment

The RA-500 can be operated at different voltages. To adjust:

1. Remove the two screws from the rear panel nameplate to access the voltage selector.
2. Set the voltage selector arrow to the required voltage (100, 117, 220, or 240 volts).
3. Important: The power fuse must be changed according to the selected voltage. Use a 0.5A fuse for 100-117V and a 0.3A fuse for 220-240V.

The voltage selector can also help mitigate issues caused by voltage fluctuations by setting it to the peak voltage.

Specifications

• RATED OUTPUT VOLTAGE: 300 mV (at 1,000 Hz, minimum reverberation time, 200 mV input level)
• MAXIMUM INPUT VOLTAGE: 3 V (at 1,000 Hz, minimum reverberation time)
• HARMONIC DISTORTION: Less than 0.2% (at 1,000 Hz, minimum reverberation time, 300 mV output level)
• FREQUENCY RESPONSE: 20 to 30,000 Hz ±2 dB (at minimum reverberation time); 20 to 30,000 Hz ±10 dB (at maximum reverberation time)
• SIGNAL TO NOISE RATIO: 65 dB (at 300 mV output level)
• REVERBERATION TIME: 1.9 to 3.2 seconds (at 1,000 Hz)
• INPUT IMPEDANCE: Greater than 200 K ohms (at 1,000 Hz)
• INPUT AND OUTPUT JACKS: INPUT, OUTPUT, TAPE RECORDING-A, TAPE RECORDING-B, TAPE PLAYBACK-A, TAPE PLAYBACK-B
• LOAD IMPEDANCE: 100 k ohms
• SWITCHES AND CONTROLS: REVERBERATION MODE (ON, OFF, RECORDING), TAPE MODE (PLAY BACK-B, PLAY BACK-A, A→B PRINT, B→A PRINT), REVERBERATION TIME
• POWER REQUIREMENT: 100, 117, 220, 240 V, 50/60 Hz
• POWER CONSUMPTION: 10 VA
• SEMICONDUCTORS: Transistors: 11, Diodes: 3
• DIMENSIONS: 11 1/2" (302 mm) W, 6 7/8" (162 mm) H, 10 11/16" (265 mm) D
• WEIGHT: 11.4 lbs. (5.2 kg)

Specifications are subject to change without notice.

Accessories Included

• Operating Instructions and Service Manual (1)
• Operating Sheet (1)
• Connection Cords with Pin-Plugs (4)
• Polishing Cloth (1)

Block Diagram and Internal Components

The RA-500 utilizes a block diagram illustrating the signal flow through various amplifier stages, including buffer amps, audio driver amps, low frequency amps, and reverberation units. The internal components are organized on printed circuit boards, such as the AUDIO DRIVER BLOCK (F-1232) and MODE SWITCH BLOCK (F-1263). A parts list details resistors, capacitors, diodes, and transistors with their respective values and positions on the circuit boards.

The unit features a power circuit with a power transistor (TR511) and a reverberation unit. Disassembly procedures are outlined, showing the removal of the front panel, knobs, and screws to access internal components. Dial threading is also illustrated.

Key components include:

• F-1232: AUDIO DRIVER BLOCK
• F-1263: MODE SWITCH BLOCK
• TR501-TR511: Transistors
• D501-D503: Diodes
• C501-C528, C901-C902: Capacitors
• R301-R356: Resistors
• PL001: Fuse
• SO01: Power Switch
• Sx(u~g): Tape Mode Switch
• REV001: Reverberation Unit
• PT001: Power Transformer
• PU001: Voltage Selector
• CO001, CO002: AC Outlets