I bought one of these a few years back for the second bedroom amplifier. I could not get it to be quiet enough (< 15dB) from mechanical hum for this very quiet room (with noisy AC power) and also it seemed there was unavoidable hum from the speakers. So I moved it to my office, where I hardly ever used it. I got a better engineered Parasound Zamp for the second bedroom, and then I figured out the hum problem had been caused by the use of STP ethernet cable to connect the Sonos zoneplayer and NOT the Audiosource amplifier.
I think I paid $200 or less for the Audiosource. It feels quite heavy, almost as heavy as a Parasound HCA-1000A--a much more expensive and powerful amplifier, with much of the weight coming from a toroidal power transformer.
However, despite the apparent weight, specs do not suggest all that much power: 50W/ch into 8 ohms and 60W/ch into 4 ohms, both channels driven, at 0.2% THD.
With one channel driven, I got over 110W/channel into 8 ohms from 1kHz to 50kHz. I was surprised by the full power bandwidth to at least 50kHz. The power dropped slightly to 105W at 20Hz. A loss of power at low frequencies suggests softness in the power supply. But at twice the rated power (in one channel only).
Distortion measurements were way better than spec, with THD at 0.018% at 1kHz, 0.02% at 20Hz, and 0.07% at 20kHz. Hum and noise were about as low as I have seen in one channel, but not quite as good in the other. This amplifier meets audio objectivist high fidelity standards.
Unlike most more recent power amplifiers, it has a hardwired ungrounded AC connection. If the transformer were to develop a primary short, that could be a lethal problem. I see no UL, CSA, ETA, or CoLA approvals. However, note that virtually all hifi electronics up to 1980 were like that, and even since 1980 most "midfi" stereo or home theater receivers are also ungrounded. However, some major brand receivers DO have some kind of regulatory approval anyway, which I think requires something like double insulation (for example, the transformer is electrically isolated from the chassis). Lacking a ground connection often means that ground loop issues would not be as difficult as with fully grounded amplifiers, however this is not always true (and my own experience with this amplifier confirms that).
I now plan to use the quieter channel for small speaker testing purposes.
I think I paid $200 or less for the Audiosource. It feels quite heavy, almost as heavy as a Parasound HCA-1000A--a much more expensive and powerful amplifier, with much of the weight coming from a toroidal power transformer.
However, despite the apparent weight, specs do not suggest all that much power: 50W/ch into 8 ohms and 60W/ch into 4 ohms, both channels driven, at 0.2% THD.
With one channel driven, I got over 110W/channel into 8 ohms from 1kHz to 50kHz. I was surprised by the full power bandwidth to at least 50kHz. The power dropped slightly to 105W at 20Hz. A loss of power at low frequencies suggests softness in the power supply. But at twice the rated power (in one channel only).
Distortion measurements were way better than spec, with THD at 0.018% at 1kHz, 0.02% at 20Hz, and 0.07% at 20kHz. Hum and noise were about as low as I have seen in one channel, but not quite as good in the other. This amplifier meets audio objectivist high fidelity standards.
Unlike most more recent power amplifiers, it has a hardwired ungrounded AC connection. If the transformer were to develop a primary short, that could be a lethal problem. I see no UL, CSA, ETA, or CoLA approvals. However, note that virtually all hifi electronics up to 1980 were like that, and even since 1980 most "midfi" stereo or home theater receivers are also ungrounded. However, some major brand receivers DO have some kind of regulatory approval anyway, which I think requires something like double insulation (for example, the transformer is electrically isolated from the chassis). Lacking a ground connection often means that ground loop issues would not be as difficult as with fully grounded amplifiers, however this is not always true (and my own experience with this amplifier confirms that).
I now plan to use the quieter channel for small speaker testing purposes.
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