SOUNDBOXES XVI: RESTORING THE NEC A-520E INTEGRATED
AMPLIFIER
As a matter of preference, this blog admires Japanese
made Hi Fi of the 1970s. The following is a restoration report volunteered by a
reader, Mr Robert Fry.
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Here are its specifications:
Power output: 50 watts per channel into 8Ω (stereo)
Frequency response: 5Hz to 70kHz
Total harmonic distortion: 0.008%
Input sensitivity: 0.25mV (MC), 2.5mV (MM), 150mV (line)
Signal to noise ratio: 87dB (MM), 105dB (line)
Output: 140mV (line)
Speaker load impedance: 8Ω to 16Ω
Dimensions: 430 x 110 x 340mm
Weight: 9.5kg
Years of Production: 1978-80
Having owned a couple of NEC CD players, whose sound
exceeded my expectations, I decided to go with the A-520E as an experiment.
It was very modestly priced at £70 so I clicked the 'Buy It
Now' button and began this journey.
Upon arrival, I was pleased with the general condition of
the amplifier. There were no significant
marks on the case or the control knobs.
Initially, the sound was rather dry and unfocused/tizzy. It had a pretty dynamic sound while also
seeming somewhat constrained at the frequency extremes. Bass was indistinct and the treble a little
flat and grainy. Here is a picture before restoration of the interior.
I gradually collected together the parts needed to do an
extensive restoration. I felt the
amplifier had potential, so I went all-in!
I purchased replacements for all electrolytic capacitors, mostly Nichicon
FG 'Fine Gold' due to their clean and neutral sonic signature. I also replaced the bridge rectifier and the
OP-AMP, resistors and some small capacitors in the Phono stage. Each part was carefully considered for
quality, physical fit and a neutral sound quality. The parts also had to look right!
Upon beginning the mammoth task, I noticed the solder joints
were failing and many exhibited signs of cracking. So, I added to the list a reel of Multicore
62/36/2 LMP solder which makes lovely shiny, tight solder joints - far superior
to the generic solder NEC had used 45 years ago.
Work eventually began, taking each board out for best access. Every solder joint was drained with MG chemicals Superwick and reflowed neatly with the Multicore LMP solder. Absolutely every joint - including those of parts I did not need to change. I had to banish the ongoing decay of the original solder completely.
At first power-up, it worked well and sounded pretty good, painting a smile across my face. This thing sounded totally different. The bass was now cleaner and well defined, the treble detailed and delivered with finesse - without being fatiguing, revealing subtleties of detail and ambience which I had previously not heard. The last thing to do was set up the idling current to 13.2mV as detailed in the service manual. I left it for an hour or so to settle before checking and re-adjusting again about an hour later. One channel was significantly off, the other was nearly correct.
After the setup, the sound improved further, tighter and even more neutral. My Sony CDP-X559ES CD player's sound was reproduced faithfully.
Listening to John Holt's '1000 Volts of Holt' delivered a
natural, highly realistic vocal and superb reggae bass lines with seemingly no
effort. The sweet treble embellished the
soundstage with natural detail that injected life into the performance.
Playing Cusco's 'Desert island' CD showed off the fine
instrument placing this amplifier is capable of. 'Galapagos' was delivered into the speakers
with pulsing pace and sparkling detail, a real thrill to listen to.
I highly recommend restoring one of these if you get the chance. It is a lot of work, but it pays off.
The 'Active Drive' design and care in layout makes for
excellent sound quality at a modest price.
Also, I noticed the background noise is very, very low - almost
inaudible with no signal at max volume. (AUX/CD source).
NEC are a semiconductor manufacturer and clearly know how to
optimally implement the devices they make.
I take my hat off to the NEC engineers.. The A-520E truly is a hidden
audio gem of yesteryear!
Contributed by:
ROBERT FRY
August 2026
[Please post any comments or reactions in the comment space
below. I will put you in touch with Mr Fry if necessary.]
