I have an audio friend down the road who isn't afraid to try the weird and wonderful to get answers, and possible solutions - and I've been visiting over many years now. He had a new toy he wanted me to appraise, so last night I toddled over for a listen ... for many years he has been using competent, pocket media players as his digital source, and he had just acquired a well recommended, lowish cost unit which he was pleased with. And I had been impressed with the previous units he had used - usually significantly better than the tweaked CD player that had served him for many years.
First impressions ... hmmm, okay, but there was something amiss - he is usually capable of getting very satisfying sound, sometimes after some judicious fiddling on the fly ... but it wasn't happening at the moment. There was a flatness, a lack of sparkle - the sound wasn't as good as as I had heard many times previously, with other configurations he had optimised.
Long story short, after many, many experiments, including swapping amplifiers, there was no major movement forward ... the dullness, lack of 'musicality' wasn't going away. Then, there was a period of inspired combining of our thinking, and intuition, which caused us to focus on the improvised damping of the top cover of the amplifier ... over time, it had been worked out that the typical, thin metal top plate had an audible impact, and adding some damping and weighting materials helped. But now, in a seemingly crazy way, removing that and just using some scraps of fluffy viscoelastic material on top was giving us the best sound! What's going on, ... ??!!
Then, the "Ah-hah!!" moment occurred: he had replaced the smoothing capacitors in the amplifiers - the manufacturer's parts were under-rated for the job, and failed early in the amplifier's life; my friend's replacements were better suited, but were significantly taller; he couldn't get higher voltage rated units that better matched the original profile. And now some experiments confirmed that adding the mild damping precisely over where those capacitors were situated under the cover plate was the key!
It appears that the top of those capacitors were now too close to the sheet metal of the covers, and there was a sound modulating interaction between those two parts. Okay, rip off the cover, and insert two circles of damping material between the caps and plate - so when the latter was screwed back on the material was under compression, slight but unnoticeable bulge to the cover now ...
And, the good sound was back, with a vengence! Full, sweet, satisfying music on every track - the system was now well and truly in the "zone" ...
An excellent example of how important it is, firstly, to acknowledge that an audio system is not up to scratch; and secondly, to start investigating all the possible causes, reasonable and unreasonable, to try and track down where the flaws in the reproduction are originating - dedication to this approach is so important to being able to conjure up convincing sound.
Addendum: for anyone who wonders why the amplifier swap didn't impact the sound quality issue- the two units were in fact from the same manufacturer, Naim: Nait models which were different versions, but had the same casing and essential circuitry within; the power supply capacitors in both had been replaced by my friend, so the same problem manifested in both units.
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