Surely, 4 watts of single-ended power is better than any magic stone or $2000 power cord. And as the circuit would require only two connections to the existing amplifier, most audiophiles could install it. Frosting on this cake would include a temperature sensor to attach to the amplifier's heatsink to monitor the effect of the increased load current. Furthermore, a small high quality fan (i.e. a quiet fan, with serrated blades and quality bearings) could be added to blow on the existing amplifier's heatsink. The self-contained power supply could incorporate a multi-tapped power transformer, which would allow adjusting the power supply voltage to match the amplifier's rail voltage. (Of course, a connection could be made to the amplifier's negative power supply rail, eliminating the need for the independent power supply.) Unfortunately,  many amplifier are so flimsily made that the 1A load would cause them to overheat. (Bear in mind that many transistor amplifiers have an output stage idle current of only 50mA, which would make the 1A represent a twentyfold increase in conduction and a tenfold increase in heat dissipation.) One possible work around would be to rewire the power transformer's connections to the line voltage, if the transformer has two primaries.

    Amplifier often contain power transformers meant to be used in either 230 VAC or 120 VAC countries. Where 230 VAC is used, the transformer's two primaries are wired in series; where 120 VAC is used, in parallel. Thus if you live in a 120 VAC country, you could wire the primaries in series, halving the power supply rail voltages, but doubling the current delivery capacity. Now, it would be unlikely that the solid-state amplifier's output devices would leave their safe operating area (SOA).
   However, such as modification to the power supply could upset the amplifier internal voltage references. But anyone familiar with solid-state circuit design should be able to evaluate the amplifier's suitability in just a few minutes of schematic perusal. However, such a modification would certainly quarter the available output power. But would you rather have four plates of bad food or one plate of tasty food? Another advantage to the lower rail voltage is that the amplifier's electrolytic capacitors should last forever because of the reduced voltages.
   All in all, this idea is definitely worth experimenting on. And should anyone experiment along these lines, please share your results with us.

The SA-1 makes a great addition to any audio test bench. It can also be a complete preamp solution for audiophile "purists". Consider the advantages of using a Passive Preamp like the SA-1 between your CD/DVD player(s) and your power amplifier(s): The SA-1 adds no distortion to your signal path while performing the major task of most preamps - signal level control. (Active preamps add in at least some distortion.) It uses a precision 24 position stepped attenuator for low noise and excellent channel-to-channel signal level tracking. And it costs a fraction of what an active preamp costs.

Arn Roatcap, Inc.
1248 Valerian Court #4    Sunnyvale, CA 94086
Phone: (408) 737-3920  E-mail:

            Phone: (408) 737-3920   E-mail:

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