JBL SG620
¥ 460,000 (around 1980)
Commentary
A preamplifier that integrates JBL sound policy and circuit technology.
As a control center, the SG620 is designed to satisfy all types of input signals and to improve sound quality.
Class A push-pull operation is adopted for all stages of the MC head amplifier.
The first stage, which handles input signals, consists of large low-noise devices connected in parallel, and is DC-coupled so as not to degrade sound quality.
The first stage of the Phono amplifier has high input impedance to minimize distortion for any input. The variable switch of input resistance and input capacitance can be used for all MM cartridges.
The equalizer stage is made up of a semi-passive filter for dynamic distortion to achieve a wide dynamic range. In addition, a subsonic filter is installed between the first stage and the equalizer stage to cut out the harmful 3 to 7 Hz band below the audible frequency that occurs during disc playback.
The high-level amplifier uses a class A push-pull and complimentary service configuration. The first stage uses a unique floating cascode connection using a high-speed dual FET to realize a response with good linearity.
The tone control circuit is located inside the high-level amplifier and consists of only passive elements.
The adjustment is step-by-step and the tone circuit is completely lost when set to the flat position.
A symmetrical low-noise device with excellent regulation is used for the power supply section to provide a stable power supply to each block.
Gold-plated connectors and contacts are used to reduce aging degradation and contact strain.
The gain of the MC head amplifier, the input resistance of the equalizer stage, and the input capacitance can be changed.
It is also equipped with control functions such as changing the loudness sensitivity and using a processor circuit.
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Model Rating
| * If not specified, output 3 V, load 10k Ω | |
| Type | Control amplifier |
| <MM Input(Tape out)> | |
| Gain (1 kHz) | 37dB |
| Total harmonic distortion factor (20 Hz to 20 kHz, 3 v output, 600 ohm load) | 0.008% |
| Hum & Noise (A Network) | Equivalent to 0.35 μ V input |
| Channel Separation (10 kHz) | 65dB |
| Maximum Allowable Input (1 kHz, THD 0.02%) | 250mV |
| RIAA deviation | ± 0.25 dB |
| <MC Input(Tape out)> | |
| Gain (1 kHz) | 60dB(Low gain) 69dB(High gain) |
| Total harmonic distortion factor (20 Hz to 20 kHz, 3 v output, 600 ohm load) | 0.008% |
| Hum & Noise (A Network) | Equivalent to 0.04 μ V input (High gain) |
| Channel Separation (10 kHz) | 60dB |
| <High Level Input(Pre out)> | |
| Gain (1 kHz) | 19dB |
| Total harmonic distortion factor (20 Hz to 20 kHz, 3 v output, 600 ohm load) | 0.008% |
| Hum & Noise (20 Hz to 20 kHz) | 3 μ V Input Equivalent |
| Channel Separation (10 khz, Volume Max) | 60dB |
| Frequency response (maximum volume) | 2 Hz ~ 350 kHz + 0 -3dB |
| Accessory function | Input resistance Switch (33/47/100k Ω) Input Capacitance Switch (High/Low) |
| Tone control | Bass/Treble : ± 8 dB |
| Subsonic filter | 15Hz cut |
| Loudness control | High/Low |
| Pwer | 100 VAC, 50Hz/60Hz |
| Rated power consumption | 40W |
| External dimensions | Width 432x Height 98x Depth 334 mm |
| Weight | 9kg |
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