Monday, July 19, 2021

Update On The Pioneer SX-780 and Speakers

 Sooooo....I dragged the two speakers I made some time ago out of the basement, and set them up with the SX-780. When I used these speakers before, I used them with my turntable, preamp, and a small, PylePRO PCA2 "40 Watt" amplifier. your dreams, maybe. For one-half cycle at some given frequency. While cooled by LN2.....

The first no-no I did was to have the speakers about 18" from the turntable. Yes, I know better, but in my haste I used the model car workbench to set things up quickly, there wasn't much room, and I wasn't planning on listening at high volume.

Nope, doesn't work. Even at moderate volume, having the speakers that close to the turntable causes a form of audio feedback, where the sound pressure waves from the speakers vibrate the turntable at variable frequencies, which get picked up by the stylus,  fed to the amp, and then the speakers, and then the turntable again, and presto! TERRIBLE sound.

So I set the SX-780 on the den coffee table, set the speakers up a few feet away and 6' apart to see what kind of separation they have, connected things up, and brought the receiver up.


YOWIE-ZOWIE! This thing sounds GOOOOOD! I had a clip lead about 29" long (1/4-wavelength!) that I used for an antenna, and I could get just about every station on the dial. The stronger stations ("Full Quieting" in FM-Speak) sounded spectacular, WAY better than they do on our home theater system when I use the FM tuner. I knew this was a premium grade receiver when it was new, but I was surprised how good my home-built speakers sounded now that they have a clean signal "with enough amp" to drive them to good levels. You can compare speakers to air pumps, and I was running 45 Horsepower air pumps with 15 Horsepower motor s when I was using the little amp.

Now I've got like 60 Horsepower, which gives me plenty of reserve capacity, or "Headroom". Makes a huge difference.

All the rotary switches and controls turn smoothly, and quietly, with no scritchy-scratchy sound, and all the lever controls do the same. The FM dial calibration is a bit off to my eye, but it's off a consistent amount from the bottom to the top of the band, so that's usually caused by the dial cord having slipped a bit. Easy-Peasy fix, and I'll do that when I take the cover off to replace a burned out dial lamp, and blow any dirt and dust out of the chassis.

This is the first "High End" FM Stereo Receiver I've ever owned although I've heard plenty. When some of my friends were buying things like this, I was buying things like Carillo connecting rods. Different priorities for different folks.


  1. Yeah, that's something the idjits with the massive speaker systems in their cars don't understand. Feedback.

    Feedback sucks.

    My dad, when in Korea, scored some really nice Japanese made speakers because the room the owner used them in was just a tad wider than the width of a bed.

    Move them to a larger room and the sound was, as you found out, spectacular.

    1. Usually the stereos installed in Boom-Boom Cars have other issues, like loose hardware in the doors, trunk, and other places, and severe problems with a lack of damping.

      Hey, moron.....Ever hear of Dynamat?

      The test setup I had worked fine at low volume levels. The problem happened when I turned the volume up, like for sitting across the room, and that's when the turntable started vibrating.

      I have some "Speaker Spikes" to put on the bottom of the speaker boxes, but I'll probably wall mount the speakers so I can get them off the same shelf as the receiver. I need the space on the shelf for the turntable, and possibly a reel-to-reel deck.

  2. Glad to hear it all worked out!

    1. Thanks, NFO! I'm quite pleased with how the speakers sound. I was really bummed at first, and figured the amp wasn't big enough to drive them. The acoustic feedback from the speaker/turntable closeness was expected, but I didn't think things would sound as bad as they did.

      They'll blow you out of the basement now.

  3. Ah, SOUND! I used to be into it and still am, in a way, some of my old friends do it for a living, even. But these days? I pull stuff off the internet and put it through a bluetooth speaker, mostly.

    I know, I know, bad practice. You've inspired me to up the game!

  4. One of my Hot Rod buddies from where I grew up saw my post, and went to his storage unit and dug out the exact same Pioneer SX-780, his turntable, cassette deck and speakers. He set it up in his garage/Man Cave, and said he'd forgotten how good it sounded.


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