Pioneer | Classic Receivers

In 1980 Pioneer introduced the Pioneer SX-D7000 and made a statement that it was heading into the digital future. It's similar in many ways to the SX-3900 except that Pioneer did away with nearly all of the knobs - replacing them with push buttons. There are no analog meter or dials either as Pioneer utilized their Fluroscan technology for the power meter and digital tuning display. The SX-D7000 retailed for about $800.

Aesthetically it's a beautiful receiver. It has a modern, clean look to it and the symmetrical layout of the controls give it balance to the eye. It's rated at 120 watts per channel and 0.005% total harmonic distortion.

The power output and tuning meters are Fluroscan and the Treble and Bass controls are adjusted via sliders with 11 click stops. The Adaptor switch allows the user to patch in a signal processor such as a graphic equalizer or reverb unit.

The SX-D7000 was the bigger brother to the Pioneer SX-D5000 and was slightly bigger and a little heavier. Pioneer also added a C speaker switch, Tone on/off control, a display dimmer and a second phono input. The SX-D7000 was one of the first receivers to incorporate a preamp section that could handle both a moving magnet and a moving coil cartridge. The user could switch between cartridges with the push of a button just to the right of the volume knob. Switching to the MC position boosts the phono gain by 20dB and reduces the impedance to 100 ohms.

The SX-D7000 also features:

Non-switching DC power amp design
Quartz PLL Synthesizer Tuner
6 FM and 6 AM station memory for easy tuning
High Gain FET phono equalizer
Attenuator type master volume control

To set the memory for a station you tune to the station using either the autoscan or manual scan and then push the memory along with one of the station call buttons.

Pioneer SX-D7000 Ad

The power amp is a Direct Current configuration. Coupling capacitors are used at the input of the amp to safeguard the circuits and speaker systems. Ultra-low-frequency signals which might be picked up from a warped record can cause annoying Doppler distortion in drivers, adversely modulating the audible frequencies. Pioneer's DC configuration removes signal-delaying capacitors from the negative feedback loops to reduce phase distortion. This contributes to a "sharp and densely-textured sonic imagery in the final reproduction".

Pioneer avoided the problems associated with Class A or Class B amps by designing a special circuit they called Vari-Bias. According to them it is:

"An inspired breakthrough that led to the Pioneer Vari-Bias circuit, which constantly monitors the amplitude of incoming signal, then automatically controls the amount of bias fed to the power transistors. While they 'rest' during no-signal periods they get only a trickle - just enough to keep them from switching off. Actually, this circuit is so simple it does not limit the transient response of the transistors in any way."

The Pioneer SX-D7000 has three power transformers. One is toroidal, for the non-switching power amp, and the other two are of conventional design.

It has three speaker outputs as well as two Phono inputs and one Aux input. It even has an AM Stereo out.

The SX-D7000 is the beginning of the end for silver faced receivers. It wasn't long after its introduction that audio manufacturers, including Pioneer, moved toward cheaper black plastic components. The receiver has a distinct look to it that some like and some don't. It's still very popular for its performance level can usually be bought for a reasonable price. In good serviced condition they will sell for $500 to $600.

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Pioneer SX-3700 Front

From that slightly awkward time that lies between the fully analog and fully digital eras come the Pioneer SX-3700. It was 1980 and digital displays were just catching on and Pioneer sought to capitalize on the movement with its Fluroscan technology. The SX-3700 produces 45 watts per channel and incorporates a direct coupled amplifier design.

Pioneer SX-3700 Meter

There is a variant of the SX-3700 labelled the SX-820. Apparently it is a European version but has a black dial face and white Fluroscan. A couple other SX-3000 series receivers also had European variants in the SX-620, SX-720.

Pioneer SX-3700 Knob

The Fluroscan display shows the tuning for the AM or FM bands depending upon AM or FM selector button is pushed. The analog dial shows both FM and AM tuning as well. The power output meter is also a Fluroscan display. Pioneer utilized a 3 gang FM tuning capacitor and quartz servo lock technology to create a very good FM tuner section. The Fluroscan FM display is backed up by a quartz crystal oscillator that provides a stable time base so that the correct numbers will always be displayed for a given frequency selection. The display is also 5 digits as opposed to many other manufacturers that used only four digits. Pioneer referred to all of this as their P.D.Q. or Pioneer Digital/Quartz tuning technology.

Pioneer SX-3700 Inside

The SX-3700 was a mid range receiver and had bigger brothers in the SX-3800 and the SX-3900. But, those receivers had more complicated designs and are more difficult to work on than the SX-3700.

Pioneer SX-3700 Inputs

If you like the Fluroscan display then the Sx-3700 (or SX-3800, SX-3900 depending upon your budget) might be the way to go. They do look very nice in the dark and are a good representation of the technological shift from analog to digital. They are also very good performers and can be found for a price that is within most budgets. A fully serviced unit will sell for around $300 while the average working unit will sell for $150 to $200.