Online Parts International

The Best Audio Circuit pages

Recently I wrote a column for a site which specialises in audio repair and did some research on randomly selected forums which covered same.  Sadly, much of the information is misleading and for a novice, this could cause more damage in the long run.  This article hopefully will set the record straight. I’m prone to rambling but let’s hope I can keep on track.

Tube Amplifier


Some Background….

First of all an amplifier of ten watts is loud if played through an efficient loudspeaker system in a fair sized room. To double the power would mean a build of 100W. Here I assume we are looking at the same rating of measurement – sine wave, same frequency, same drive level, no distortion. A 10W amplifier driven full power into a 20W loudspeaker will do more damage than a thirty watt amplifier dissipating 25W into the same load because the distorted signal causes a lot more heating around the voice coil which cannot be dissipated cleanly as opposed to a voice coil being driven cleanly but slightly over the rated current handling.

Loudspeaker designs belonging to the majority of big names are not going to be easily beaten by the home builder – however, your ears may tell you another story entirely when you build your own. My personal preference are big drivers, 15″ bass, 8″ middle and so on. And lots of power, clean power.


Most high end amplifiers still use unregulated power supplies – there are theories as to why they are better than regulated supplies. I built a regulated supply for a Sansui many years back and I can promise you the bass sounded better. “Sounded better” for me, but not to two other listeners. I have repaired quite a few big name PA amplifiers for big band use and they did not have regulated power supplies. Plenty of safety built in from temperature to over current to loudspeaker protection. Never once a burnt transformer.  In most cases user neglect was the cause of failure – professional musicians will normally not lie about the reason for failure and often know a lot about the electronics inside although more on a technical level than practical level.

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