Pioneer RG-70
The Pioneer RG-70 is an RG dynamic processor. It expands the dynamic range of a signal instead of compressing it. It sold in Japan for ¥37,000, with pricing dated to around 1980, though at least one Japanese dealer listing places its production in the mid-1970s, so the exact era is a bit fuzzy. The "RG" in the name refers to the detector circuit, which works with a fast attack time to control dynamic range.
The unit could expand dynamics by up to 16 dB, switchable in five stages: 4 dB, 7 dB, 10 dB, 13 dB, and 16 dB. Each stage has its own gain range, from -2 to +2 dB at the gentlest setting up to -6 to +10 dB at the most aggressive. Pioneer's commentary recommended the 10-16 dB settings for jazz or rock, and the gentler 4 dB or 7 dB settings for classical. The RG-70 also offered a noise reduction effect of up to 6 dB, which helped reduce tape hiss and motor rumble. A dynamic expansion meter on the front panel shows how much expansion is being applied, and a processor ON/OFF switch gives an instant bypass comparison.
The circuitry uses low-noise differential transistors and an IC in the gain control amplifier section. One design detail stands out. To keep the gain difference between the left and right channel amplifiers from getting too wide, mixing is done at the input of the control circuit. This keeps the auditory image stable even when the two channels receive different input levels. The front panel also carries an expansion meter.
Known specifications are as follows:
- Maximum output: 6.5 V (1 kHz, 0.5% distortion, 16 dB expansion)
- Harmonic distortion: 0.05%
- Signal-to-noise ratio: 116 dB at 6.5 V output
- Impulse response: 0.3 msec attack, 120 msec release
- Input impedance: 50 kΩ
- Output impedance: 300 Ω
- Dimensions: 420 × 99 × 336 mm (W×H×D)
- Weight: 4.4 kg
Documentation on the RG-70 is thin. Nearly all specification data traces back to a single Japanese source, and no independent period reviews have surfaced. The record is also silent on production years, frequency response, and detailed input/output configurations. What survives is a well-specified dynamic processor from Pioneer's late-1970s/early-1980s lineup. A 100-volt Japanese-market version appears in secondary listings, which matters for anyone buying outside Japan.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.