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LONG TERM TESTING
SPCR does not have a standard test procedure for such an unusual
product, so we tested the Kama Bay Amp slowly over the course of two months
so we could really get to know its ins and outs. Initially, it replaced a cheap
Sony mini-system amplifier (I know, I know) that was feeding a pair of Pro-Linear
PL3.5B bookshelf speakers. This arrangement required heavy EQ in Realtek's
driver software to sound even close to normal but that's what you get
when you use a mini-system with mismatched speakers. We'd have been very disappointed
if the Kama Bay Amp did not outperform the Sony amp. In both cases, the source
was the integrated audio on a Soltek SL-K8T Pro-939, powered by Realtek's ALC850
When powered by the included power brick, the Kama Bay Amp sounded
terrific a night-and-day improvement over the crappy Sony mini-system.
The bookshelf speakers still sounded a bit boomy and cramped, but that had more
to do with the speaker itself and their position too close to my ears than any
fault of the amp (we do recommend taking care when positioning your speakers
regular bookshelf speakers aren't designed to be listened to from three
feet away). A little EQ quickly smoothed out the low end.
For the most part, the audio in this setup sounded crisp and pristine;
the relatively full-range Pro-Linear speakers proved their worth by delivering
clearer, more dynamic audio than I have heard from almost any powered computer
speaker. Some might lament the lack of subwoofer support, but for listening
to music this was a blessing; I've never yet encountered a well-balanced 2.1,
4.1 or 5.1 speaker setup for computers, and the relatively large bookshelf speakers
provided a richer low-end than most computer speakers are capable of.
Although the Pro-Linear speakers are not particularly inefficient
or hard to drive, I did notice occasional clipping when the volume knob was
above halfway. The clipping was most noticeable in tracks with heavy, synthesized
bass the Portal soundtrack was particularly bad. This is no surprise
sustained bass notes require the most power to amplify, and, at times,
the 10W per channel rating didn't quite seem to be enough.
Unfortunately, we discovered one major drawback. While the audio
quality was excellent, we noticed that our wireless keyboard and mouse stopped
working whenever the amp was on. Some experimentation revealed that the effective
range between the peripherals and the wireless receivers dropped to about a
foot or less from six feet or more. A second, more robust wireless keyboard
and mouse dropped to about three feet from twenty. The range dropped even further
when the volume was cranked up high.
Clearly, the Kama Bay Amp has EMI shielding issues, and not small
ones either. According to Yamaha's
spec sheet, the switching frequency of the amp is in the realm of ~500 kHz,
and this is where you would expect the worst interference to occur. This is
two orders of magnitude lower than the 27 MHz band used by wireless peripherals,
so obviously the interference is not restricted to the 500 kHz band.
This interference was a rather serious problem, so we attempted
to solve it by wrapping the power brick in several layers of aluminum foil.
While this helped a little, it was nowhere near enough to allow ordinary operation
for our keyboard and mouse.
Next, we sought to eliminate the power brick entirely by using
the Molex adapter to power the amp from the system power supply. Unfortunately,
not only did this not solve the problem, it also revealed a truism about amplifier
design: an amplifier is only as good as the power supply that feeds it. With
the amp sharing the same power supply as the rest of the system, every drive
seek, every mouse click, and every spin of the scroll wheel was amplified audibly
as the electrical effect of each action propagated through the system. Using
a power supply with lower ripple and better voltage regulation might have helped,
but we're hard pressed to recommend the Molex adapter to anyone who wants clean
audio. To top things off, eliminating the power brick from the equation still
did not solve our interference issues.
Our testing concluded by throwing the Amp into the deep end: It
was substituted into our lab home theater system, replacing Panasonic SA-HE200
receiver and driving a pair of transmission-line speakers built and tuned by
SPCR's editor-in-chief, Mike Chin. The source? A Chaintech AV-710 sound card.
Differences between the Panasonic receiver and the Kama Bay Amp
were small but noticeable. The Kama Bay Amp sounded less cohesive and "focussed"
than the Panasonic; at times, the music sounded like a collection of instruments
playing at the same time rather than a band (or an orchestra) playing together.
On the other hand, bass-heavy drums and loud thumps were more dynamic and "impactful"
on the Kama Bay Amp possibly because it lacks the subwoofer crossover
that is active (even in "Direct Mode") on the Panasonic, and therefore
allows the speakers to perform at their full frequency range as is desireable
in a setup with no subwoofer.
The Kama Bay Amp is not for everyone, but it does open up possibilities
for a new market segment. Gamers and avid movie fans will probably pass on it
because it is stereo only, and those used to the mandatory "subwoofer"
included in most computer speaker kits will be disappointed that a subwoofer
is not supported. Avid music listeners, however, should be thrilled: This small,
inexpensive amplifier allows a much wider range of speakers to be used
without the hassle of hooking the system up to a large component-based audio
system. With such selection, it should be easy to find speakers that more than
make up for the loss of multiple channels and a subwoofer. And, if you really
can't live without them, you can always use multiple Kama Bay Amps (three for
a 5.1 system).
The audio quality isn't perfect, but it's probably good enough
to satisfy the compact hi-fi market that it targets. 10W per channel doesn't
go that far for pure volume, but with most speakers it should be enough. As
long as it's fed clean power (the Molex adapter was hopeless), we had no issues
with the audio quality.
The interference issue was more serious. While not everyone uses
wireless peripherals, there are enough wireless devices around that nearly everybody
has at least one. Wireless phones, wireless networks, some remote controls,
and even cell phones are potential candidates for interference. Then there's
radio, broadcast television, and even medical equipment that could be affected.
The obvious fix is better shielding, but our experiments with aluminum foil
showed that this isn't as simple as it sounds, especially since both the power
brick and the amp itself appear to cause the radiation.
Like just about every other product we review, our opinion of
the Kama Bay Amp comes down to noise. Except, this time, the audible noise is
fine it sounds as good as we ever thought a $50 amp could sound. The
problem this time is electrical noise. Electrical interference is an engineering
problem that should have been solved before the product ever shipped, but it's
hard to say whether it's a deal-breaker or just a minor inconvenience. Ultimately,
the answer is probably subjective: If your household is wireless-crazy, avoid
the Kama Bay Amp. If not who knows? It might be worth buying just to
drive the neighbors crazy when their phone drops out...
Many thanks to Scythe
USA for the sample.
by Steve Hayashi
I would say that the Kama Bay is for an extremely niche market. It's specifically for people who want a cheap higher quality amplifier with a small footprint. For the same amount of money, you can go on e-Bay, and get a used stereo amplifier/receiver that will blow this product away in terms of power and possibly sound quality (though it'll take up more space). Receivers/amplifiers aren't exactly new technology (excepting high quality class D) so it's not unreasonable to suggest looking on the used market for quality. Those who want something new could spend around $100 for a new receiver or $200 for a higher quality receiver.
Even if it was fully functional without the interference, I would find it difficult to recommend this to anyone. Those that are happy with their current amp aren't likely going to be spending money, and those who aren't happy with their current amp are likely willing to spend the additional money (or go used) to purchase a superior amp. This is more of an in-between step for those who want to spend more of their money on nicer speakers.
by Russ Kinder
I think the real competitor to this is something like the Sonic Impact T-amp. Same concept, except for not being drive bay mountable and it being a class T instead of a D. Its cheaper too, like $35 at Amazon or Target. [Editor's Note: The price seems to have climbed a lot since Russ last looked; BuyItNow prices at eBay are >$65.] The other big difference is that the Sonic T sounds amazingly good. I've been using one for a couple of years now in my workshop system, and it consistently impresses people. Jeff Day did a nice write-up of it over at 6moons a while back.
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this article in the SPCR Forums.
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