25 February 2016

The dark side...pioneer sx-580 to NAD c370

The stereo thing seems to have gotten popular,
prices of marginal units linger in the triple digits,
and monster receivers are out of reach.
Recently deals have been rare.
Not much time for the swap meet lately,
but a quick Friday walkabout found this,
a scruffy $35 Pioneer SX-580.
A starter BOTL unit at 20 wpc,
perfect for an outside work setup,
needed since I gave away the little Kenwood.
Under the peeling wood vinyl case,
the inside was a dustball.
A quick vac & brush left it really clean.
Lights on and clear sound,
not bad for 1978 era!
Time to experiment.
The 1971 Sansui 2000a was ok,
but a little hissy when warned up,
most likely a recap needed.
I had also hooked up the Sansui qrx-8001,
and there was a light hum.
An issue with too efficient speakers,
magnifying the faults in the system.
Many people get these horn speakers
to crank small wattage amplifiers,
in the 3-5 watt range.
The little pioneer actually sounded just fine!
A smooth tone with a bit thumpy bass,
but at least no underlying hum.
Then an ad popped up for a free amp,
sound dead in one side.
A morning email went unreplied til night,
and I rushed out the next day.
A new era NAD C 370 integrated amp,
even with the original box and remote!
A bit dusty,
maybe I'd get lucky and it'd just need cleaning...
The inside layouts haven't changed much,
just the components.
Mysterious black boxes replacing transistors.
After a spray and screw of all the pots,
(behind the volume and tone knobs)
no luck.
The underside was one big circuit board,
not much to do there.
Luckily this had a pre-out/main-in option,
making it easy to test 
if the amp or preamp was faulty.
After some wiring trickery,
the problem was in the amplifier section.
Like that would help me!
There were no obvious burns or bulging caps.
As a last resort,
I started wiggling wires while it was on.
Yeah dangerous I'm sure....
But...Hey...there was sound!
The main amp plug was loose!
The fix was twisting the wires one turn more,
creating force on the plug.
Heck yeah!
Reminded me of the kid 
blowing into the playstation plug to get it to work!
What a boring looking amp!
Hooked up it sounded very new,
no more tube-like warmth,
a crisp clinical sound with distinct separation.
Makes mp3 recordings sound like a$$!
Can't complain for free!
And the best part is this new fangled remote!
The volume knob turns with the button,
I'm sure that was a huge selling point.
Good enough for now,
giving time to fix the oldies...
Now where to put the box!?

1 comment:

  1. Great write up - liked the twister fix, will remember that one!

    I just got busy and deoxit'd my Hafler and Yamaha last weekend, now back in the garage system.