Wednesday, November 27, 2013

Amp-100 to be sent back

I've felt good about Audiosource equipment I've bought in the past.  Their small speakers (recommended by my uber Audiophile brother-in-law) were sufficiently good to outshine a pair of Polk's which cost and weighed twice as much.  Their Amp One is currently in service as my office amplifier, and seemed like an excellent value for an amp with 100W RMS output.  But there was a problem with the $119 (at Parts Express) Audiosource Amp 100 I noticed from the moment I plugged it in that made me want to send it back.  The chassis makes a quite noticeable hum, which I measured as around 53dBC (approximately 45dBA).  I did mostly dBC measurements because the sound is mostly low frequency, and improperly tossed by the A weighting, and too close to the meter and room residual when measured in dBA.  I could measure as high as 55dBC within 2 inches of the unit, reducing to 53dBC at 6 inches which is a more fair weighting.  The highly tonal nature of the sound makes it more noticeable than the dB ratings would suggest, and it is especially noticeable in the remodeled second bedroom with it's sound blocking wall and door (I would guess ambient noise level below 20dBA).  Actually, I haven't always paid attention to chassis noise, I wouldn't notice it in my office filled with computers and other noise making machines.

While I decided this noise level was unacceptable, and an hoping for better performance from a Parasound Zamp V.3, it wasn't much more than a transformer type Tensor lamp.

On the whole, I don't believe audiophiles have paid enough attention to chassis noise.  They may obsess (as I do) about the difference between 16 bit audio, with a 96dB S/N ratio, and 24 bit audio, which in practice gets to about 120dB S/N ratio.  Meanwhile, chassis hum at 55dB with listening level around 70dB (and often less, this is a room for a lady and they generally keep the spl low), you have a 15dB S/N ratio--very unacceptable.

I wouldn't be surprised if many of my older amplifiers, including my two currently unused Parasound HCA-1000A amplifiers have even more chassis noise than the Amp 100 either.  It does seem like equipment gets noisier as it gets older.  And I'd be absolutely certain my McIntosh MC225 tube amplifier makes more chassis noise.  I'm hoping a brand new Parasound Zamp will be better.  It seems like Parasound made their zone amplifier as small as possible, and in this case small is good for a lot of reasons, including less chassis to vibrate.

Parts Express has a 45 day return option and quickly issued me an RMA.

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