Pioneer SX-780 Receiver review

“Silver Era” Pioneer SX-780 Receiver


  • Continuous Power Output: 45 watts per channel (8 ohms from 20Hz-20kHz with no more than 0.05% total harmonic distortion), 45 watts per channel (4 ohms from 20Hz-20kHz with no more than 0.08% total harmonic distortion)
  • Damping Factor: 30 (20Hz-20kHz, 8 ohms)
  • Line Input Sensitivity/Impedance: 150mV/50k ohms Phono Input Sensitivity/Impedance: 2.5mV/50k ohms Frequency
  • Response (Line): 5Hz-80kHz +0,-1dB Frequency Response (Phono): 20Hz-20kHZ ±0.2dB Hum and Noise (IHF, short-circuited, A network, rated power): 76dB (phono), 95dB (line)
  • Bass control: +8dB, -7dB (100Hz) Treble control: +7dB, -6dB (10kHz)
  • Loudness Contour (volume @ -40dB): +6dB (100Hz), +3dB (10kHz)
  • Low Filter: 15Hz (6dB/oct.)
  • Power Requirements: 120V, 60Hz
  • Power Consumption: 150W
  • Dimensions: 18-7/8(W) x 5-1/2(H) x 12-5/8(D) in. Weight: 24lb. 11oz

The first real audio system I ever experience was on a family vacation to my Uncle’s home. I don’t recall much about his system other than lots of silver faceplates and analog meters, but the look and sound stuck with me all the way home. After a year’s worth of cutting lawns and washing dishes I purchased my first stereo system—a Pioneer SX-680 receiver, EPI 100 speakers and a Technics SLB3 turntable (the receiver and speakers are long gone, but the turntable still does its thing in my basement system).

So perhaps I was simply trying to recapture my youth when I began searching online for old Pioneer “silver era” receivers a few months ago. It wasn’t long before I came across several SX-780 receivers available for local pickup—I’m reluctant to ship these large, heavy components both due to cost and potential damage. Nostalgia and an itchy auction trigger finger got the best of me and I was soon sneaking 3 of them through my front door, ranging in price from $40 to $100 each. I didn’t mind paying a bit extra for the last one since it was recently bench-tested and serviced, an important consideration when buying vintage equipment. Speaking from experience, it also seems that many sellers do not know the true definition of “mint condition.” Be wary if there are no close-up photographs showing all angles of the receiver, and even if there are does not guarantee it is operationally mint.

The SX-780 seems to be one of the more prevalent vintage Pioneer receivers available today. Whether this is due to their durability or popularity I’m not sure, though my guess is this was one of Pioneer’s higher volume models. It sold from 1978 to 1980 with a list price of $325 to $399 depending upon the year. Initially built in Japan, production switched to S. Korea at some point as evidenced by the varying tags on the back of my units. The original Pioneer literature rates continuous power output at 45 watts per channel into both 8 and 4 ohms, with hum and noise at 95 db through the line level inputs (see specifications for details). After 25 years, I was finally moving up to the next model in the lineup!

Pioneer SX-780 review

The “Silver Era” Look

There is something about the glitter and glow of these silver era receivers with their brushed metal faces, bulb-lit displays and bouncing VU meters that is mesmerizing and a bit like sitting in front of a fireplace in the dark. Not quite the warm embrace of tubes reflected off of polished chrome, but comforting just the same. The SX-780 is the middle-of-the-road model from one of Pioneer’s last series of receivers (denoted by the “80” in the model number) before they switched to digital meters and black faceplates/casework. The sides and top are finished with a faux vinyl woodgrain (real wood was used on some upper models and older series receivers). The woodgrain film on one of the receivers I purchased was peeling off to reveal the horrid beige color of the laminate underneath. Since the case was not dented or gouged, a can of spray paint transformed it into a rare, one-of-a-kind, flat black SX-780.

Behind the front display window there are dual analog power meters, the AM/FM tuning meter and radio station frequency scale. A quick twist of the heavy tuning knob at the far right sends the station pointer smoothly across the scale, but only if it is properly lubed (I had to disassemble one of the receivers and lubricate the tuning knob which had frozen up). Across the bottom are the various control levers and knobs, all of which feel much smoother and more substantial than the plastic pushbuttons of modern designs. There are controls for bass, treble, low filter, FM muting, source selection, stereo/mono, tape monitor, balance, volume and the era’s ubiquitous “Loudness” switch as well as a headphone jack. If they have not been used in a while, the switches and pots can become noisy or even inoperative due to dust and oxidation and may need to be cleaned.

Around back are input jacks for phono and auxiliary sources (this is before CD players) as well as two tape loops. These jacks will likely need to be cleaned and deoxed, especially if the receiver has been stored in an attic or basement for years. Also, the push-type speaker terminals found on the SX-780 have a common problem in which the button gets stuck in the “in” position making it difficult (or impossible) to attach speaker wires. Luckily, with two sets of terminals you can always use the “B” speakers. Other features include an AM bar antenna, connections for external antennas and switched/unswitched power outlets. The upper Pioneer models give you more inputs as well as a preamp/amp loop out.

The Sound

Call me biased, but I had no illusions that the SX-780 was going to displace my current preamp/amp combination consisting of a Reference Line Preeminence One passive pre and PS Audio HCA-2 power amp. Moreover, no one in their right mind is going to pair the SX-780 with the Magnepan MG1.6 speakers. But I never claimed to be sane, so that’s exactly what I did. Source music in my 13’x18.5’x8.5’ listening room came from a Squeezebox SB3 with an Elpac linear power supply as a transport running through a Cary 306/200 CDP/DAC.

Bass was impressively powerful and plentiful though not necessarily tight and controlled. While there are conflicting views regarding the actual auditory effect of damping factor on bass control, the SX-780 is relatively low by today’s standard for solid state amps at only 30 into 8 ohms, which would theoretically drop to only 15 with the 4 ohm Magnepans. The potent yet somewhat loose deep bass combined with a midrange and upper bass that seemed forward and tipped up a bit gave the SX-780 a pleasantly warm and punchy sound with a lot of body and heft. This was most noticeable (and enjoyable) on small scale, acoustic stringed instruments as it seemed to enhanced their resonance and presence in the room. However, engaging the “Loudness” contour simply delivered too much of a good thing and the sound became excessively bloated and overpowering in the lower registers. Fun for parties and head-banging, but I keep it turned off most of the time.

In the upper frequencies, I became aware of a grittiness and increased sibilance which on vocals seemed to mask the singer’s nuances. Jeff Tweedy on Wilco’s “Jesus, etc” (Yankee Hotel Foxtrot), a song I greatly enjoy for the emotion he imparts, lost some feeling as his subtle inflections were made more difficult to hear. Likewise, Tori Amos’ voice on Strange Little Girl lacked the details in her breaths and sighs between lyrics that communicate the emotion of the songs. It also caused cymbals to take on a fuzzy shimmer as sharp transients tended to get lost in the mix. The sound was not nearly as sweet and open on the top end as I am accustomed to with the Maggies, and imparted a slightly uncomfortable edginess. Turn the volume up, and it became difficult to follow individual instruments and vocals as this edginess jumped forward, especially through complex passages. That also meant that when pressed with big dynamic swings, things got somewhat blurred and confused.

The soundstage was clearly flatter, reduced in depth and never seeming to reach beyond the width of the speakers. Rather than transporting you into the venue, the feeling became more intimate in which the performers seemed to be in the listening room with you. While this perspective was not unpleasant, the speakers and walls just never seemed to completely disappear. Part of this may be because the SX-780 lacks the low level detail and ambience retrieval needed to portray a truly enveloping soundstage. For example, Medeski Martin and Wood’s “Paper Bass” and “House Mop” (Friday Afternoon in the Universe) begin with percussive instruments that usually sound like Billy Martin is playing them right next to you and as he moves about the room. But on the SX-780, the little auditory cues which create that sense of space and movement were reduced, thereby keeping the instruments anchored between the speakers. Likewise, although it did a great job portraying the body and richness of California Guitar Trio’s Invitation (especially “Apache” and “The Good, The Bad and The Ugly”), the fantastic ambience of this recording felt greatly restricted.

Pioneer SX-780 Receiver backside

This may all seem like harsh criticism of the SX-780, but to be fair it sounded much better than I expected on the Maggies. To keep things in perspective, it is almost 30 years old and produces only 45 watts compared to the 225 watts generated by my PS Audio HCA-2. Many of these issues may simply be the result of trying to push it too hard with a pair of low impedance, inefficient, current hungry speakers. Even so, throughout the listening I was surprised that the SX-780 never got excessively hot or balked at any of the gymnastics I put it through on the Maggies. Would the SX-1080, -1280 or even the enormous -1980 be a better match? Probably, but they are also comparatively rare and much pricier.

Back to Reality

Switching to a saner set of speakers proved to be a much better match. I recently purchased a circa 1994 new-old-stock pair of KEF Coda 9.2 speakers. Evidently a supply of these still in their original boxes were found in the back of a warehouse somewhere and sold them off for about $100-150 a pair shipped (there goes my itchy trigger finger again). I initially thought the darker, full-bodied house sound of KEF speakers would be too much with the SX-780 and tend to overemphasize the upper bass and midrange. But such was not the case, which may be due to the fact that the Coda 9.2 are relatively small consisting of only a 6.5” midrange/woofer with a 1” soft dome tweeter. They actually seemed to tame the top-end edginess I heard on the Maggies.

Bass continued to be SX-780’s biggest strength even with the much smaller Coda 9.2, and the midrange maintained its pleasantly forward and punchy presence. As mentioned earlier, I found the SX-780 particularly enjoyable with solo or small group acoustic instrumentals, particularly guitar and other stringed instruments. Ode to a Butterfly from the young bluegrass band Nickel Creek’s first self-titled album was wonderfully fleshed out and full bodied. Even the sharp plucking on the mandolin came through clear and bright, which I thought might be a problem based on the edginess detected earlier. The excellent compilation recording of Hawaiian Slack Key Guitar Masters (Vol. II) sounded great and the rich harmonics of this guitar style were well represented, though here again I anticipated problems with the crisp finger-picking. It would seem that the harshness on the SX-780’s topend manifests itself primarily on vocals.

However, with the taming of the top-end came a commensurate reduction in detail, ambience and soundstage. The decay and air around instruments lessened and the sense of space took another step back. Of course, this may just be the result of going from large dipole planars to small ported box speakers, but that is a much more likely pairing for the SX-780. More expansive recordings did not fare as well in these circumstances, especially with big dynamic shifts. On Empire Brass Quintet’s “Hopper Dance” (Passage 138 B.C. – A.D. 1611), the deep percussion coming from the far back of the venue remained powerful and strong, but lost its sense of location and was pushed forward into the same plane as the more delicate horns, even overpowering them at times. The horns themselves became a bit indistinct as individual instruments in the space. This also occurred on orchestral pieces like Saint-Saens’ “Danse Macabre” (Jean Fournet, Tokyo Metropolitan Orchestra), where once again the soundstage narrowed and flattened and the percussion section occupied the same area as the other instruments.

I did not spend a great deal of time exploring the phono and AM/FM functionality of the SX-780 as I viewed these as “bonus features” at this price. Brief comparisons with my Monolithic Sound PS1/HC1 phonostage showed the SX-780 to be much less detailed and relatively thin sounding, not what I would expect from vinyl. As for FM radio, it pulled in stations quite well (which is never a problem in my area) and was quite listenable, but I am not a fan of radio other than for background music and news.

Enter the Sonic Impact T-Amp

At around $30 plus the price of a good power supply (either a 12v plug-in supply or rechargeable SLA battery), the tiny Sonic Impact T-Amp is nearly the same price as a decent Pioneer SX-780. So how do these wildly different components compare?

Sonic Impact T-AmpThe first thing that became apparent was the difference in background noise. The Sonic Impact is dead quiet, and I do mean DEAD. Not a peep. The SX-780 had a noticeable hiss from the tweeters, though this could not be heard from the listening position even with the 91db (2.83v) efficient KEF Coda 9.2. Comparing the two, the Sonic Impact provided a much blacker background from which the music emanated.

Vocals through the Sonic Impact sounded considerably clearer and smoother, with all of the performer’s inflections and nuances coming through without any excess sibilance. It seemed much more delicate, providing a greater portrayal of subtleties and details in each recording with a much more spacious soundstage. All-in-all, it is closer to the PS Audio HCA-2 though lacking in bottom-end weight and extension. Whereas the SX-780 was not as well-controlled on the low end, you felt the drums and bass lines which are only hinted at on the Sonic Impact.

Compared to the Sonic Impact, the best way to describe the combined effect of the SX-780’s upper edginess, midrange forwardness and powerful bass was that ultimately the music seemed forced and did not simply flow. There is a lack of coherence from top to bottom with certain frequencies and instruments tending to jump to the fore. The Sonic Impact had a much smoother, more refined and open sound that I preferred for extended listening, but it also lacked the powerful bass and midrange of the SX-780.

In the end, I’ve decided to leave the SX-780 on iPod duty paired with the KEF Coda 9.2 speakers for background music in the living room and dining room. I also have one in a spare bedroom with a treadmill for use while exercising. The SX-780 does a fantastic job of filling the room with music, whereas the Sonic Impact is better for kicking back, relaxing and actually listening to the music.

Conclusion about Pioneer SX-780

On nostalgia points alone I love the SX-780 or any of the silver era Pioneer components for that matter. As long as you are not overly critical, it is perfect for an inexpensive second (or even third or fourth) system, especially when coupled with a pair of warmer sounding speakers with a soft top end. Plus, you get an AM/FM tuner, phonostage, tape loops and headphone amp all in one unit.

With its powerful bass and room filling sound, the SX-780 is a great receiver for entertaining. It is also quite the conversation piece, often garnering more attention than the Maggies among both my audiophile and non-audiophile friends. When guests see the SX-780 all lit up they can’t help but lean in, touch the knobs and give the tuning dial a spin. Now if I could just find an old pair of EPI or Polk speakers.

from affordableaudio, by Craig Johnson