pioneer er-420

Most Pioneer models from the late 1960s had names starting with the letters SX and two or three numbers after them. There were also SX models sold as LX. However, ER-420 had a completely different name. Visually, the ER-420 was similar to the SX-800 series models, except that it had a characteristic black and silver front panel. Electronically, the ER-420 was a newer version of the SX-40. The type of FM head has been changed, as well as the type of MPX decoder, and a few minor changes have been made. The audio path remained virtually unchanged. According to the manufacturer, the power was 15 W per channel in sine and 20 W per channel. 8 or 16 ohm column resistance. The power amplifier worked on two pairs of 6BQ5 / EL84 tubes in a Push & Pull arrangement with automatic bias. At the same time, the bias voltage was also used to stabilize the heating of the 12AX7 / ECC83 tubes in the correction preamplifier for a magnetoelectric turntable. The power stage was powered by a voltage doubler system. The output tubes drove another 12AX7 / ECC83. Pioneer used 6AN8A or 12AX7 drivers, depending on the type of bias. The preamplifier also featured the 12AX7, which greatly simplified the servicing of the receiver. The receiver had standard adjustments and filters - "High Filter" - is a high-cutoff, "Low Filter" is a low-cutoff and "Loudness" means dynamics. A separate switch was used to disconnect the speakers when connecting headphones - "Speaker On / Off". An interesting fact was the use of the "MODE Stereo / Left mono / Right mono" channel switch in the device. It probably resulted from the possibility of working with the so-called tape transport, i.e. a tape recorder with only heads - "Tape Head". The ER-420 had a modular MPX matrix decoder with the symbol AM0103A on two tubes 6AQ8 / ECC85 and one 6AV6 / EBC91 pentode. A neon bulb served as an indicator of the stereo signal. It worked properly with good separation. The FM head with the symbol AM0111U was also unified. 6C9 It was a double noval tetrode with an additional tenth output in the middle of this noval. Such a base - bore the symbols B10G or E10-73. This double tetrode enabled a three point VHF tuning which reduced the number of tubes from 2, e.g. ECC85 to one 6C9. The head for one "lamp" had excellent sensitivity and separation. 6C9 are still available and at the same time inexpensive. The receiver enabled also the reception of medium waves - AM. The design of the ER-420 is very correct, the amplifier confirms the positive opinions about Pioneer's Push & Pulls on the EL84, and the very characteristic look is eye-catching.

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