PC Hi-Fi: Scythe's Kama Bay Amp

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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 audio chipset.

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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Squeezebox 3 Digital Music Box
Zalman ZM-RS6F Surround Sound Headphones

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