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Scythe SDA-1000 Kama Bay amp - class D integrated amplifier

I had a dream...

[Scythe Kama Bay amp in silver]
[Scythe Kama Bay amp in black]
[Italian version]

Product: Scythe SDA-1000 (kama bay amp) - integrated amplifier with Yamaha YDA 138 Class D chipset
Manufacturer: Scythe (Scythe USA website) - Japan
Approx. price: 50-60 € (54.80$ in the USA)
Reviewer: Lucio Cadeddu - TNT Italy
Reviewed: May 2009


Four years have already passed after our T-Amp review and, during this period, audiophiles have become familiar with small high-quality Class D amplifiers. Even the high-end market has started to pay attention to Class D amplification: from Rotel to Mark Levinson, from Bel Canto to Jeff Rowland we've seen many new amps using Class D operation. Of course we shouldn't forget NuForce, which played a major role in capturing audiophiles' interest, winning the title of "Best amplifier of the year" accordingly to The Absolute Sound mag.

In the lowest end of the market we've seen (and reviewed) many different Tripath-based amplifiers, both reasonably priced and ridiculously overpriced ones. In any case, nowadays it is hard to find the same incredibly high quality/price ratio of the original T-Amp. Overall quality has increased (e.g. Trends TA 10.1) and even power output (e.g. Virtue Audio Virtue.One) or flexibility (e.g. NuForce Icon, which includes three inputs and also works as USB DAC).
In any case, the stellar quality/price ratio of the original T-Amp is gone. For this reason I've started my search for something as inexpensive as the original T-Amp, possibly better sounding and with all the things one might need (power supply, cables, good connectors etc.). At the end of 2008 I discovered a chipset which could be the answer to my query: the Yamaha YDA138. And, luckily, I found an integrated amplifier with everything I was hoping for...plus some nice surprise. Introducing you the Scythe SDA-1000 (pronounce as in "skies", or so I've been told by Scythe EU), an integrated amplifier with the YDA138 chip that costs 50 € (YMMV) and offers all of the following:

Now try to ask for more if you can :-) Oh yes, I can hear you asking for 2 or 3 line level inputs but, hey!, all of the above costs you 1/4 of a Trends Audio TA 10.1!!! I would be surprised if this gadget could even sound decently...

Before I start describing it in detail, let me spend two words about the manufacturer. Scythe Inc. is a Japanese Company which specializes in heatsinks and liquid-cooled fans for "tweaked" PCs. Overclockers and PC tweakers know this Company and its products very well! Scythe Inc. plants are located in Akihabara (Japan) but there's also a Scythe USA and even a Scythe EU (kind suppliers of the test sample, thanks Stefan!).
The amp has been designed having the average "PC tweaker" in mind: for this reason the SDA-1000 is also called "kama bay amp". Actually it can be installed inside any standard 5.25" PC bay slot, like a disk drive, for example. It can be powered directly via the inboard PC power supply thanks to a supplied adapter. Nevertheless the unit works well (perhaps better!) as a stand-alone unit, powered via its external switching PSU.
The Scythe SDA-1000 is very small, measuring just 152 x 41 x 113 mm! (exactly like a NuForce Icon, see pics below).

The following paragraph is mostly technically-oriented so less skilled readers might want to skip it. It mostly explains how the Yamaha chipset works and why it is different from the rest of the other Class D chipsets in the market. Worth a reading anyway :-)

Description & tech specs

[Yamaha YDA138 chipset]

The hidden secret of the Scythe SDA-1000 is its heart, that is the Yamaha YDA138 Class D chipset. This makes use of a highish switching frequency (500 kHz!) and delivers 10 watts per channel @ 8 Ohms with 10% THD. In audiophile terms, these means the chip can deliver 7-8 watts of undistorted power on a standard 8 Ohm loudspeaker. More or less it is the same power of the Tripath TA2024. One first - and perhaps interesting - difference is that while the TA2024 couldn't be mono-bridged, the YDA138 can. This way it can deliver 20 watts @ 4 Ohm with 10% THD. More reasonably it can produce 15 undistorted watts in mono on a 4 Ohm load. Unfortunately this option can't be easily selected since you need to completely modify the way the chipset pins are connected. If you have a look at the chipset datasheet (see link below) all you need to do is connect terminal VREFR and REFA together and then INR to AVSS. Shorting the outputs OUTPL & OUTPR and OUTML & OUTMR you get the desired bridged mono configuration.
The datasheet suggests the minimum impedance, in standard stereo mode, should be no less than 7.5 Ohm. Actually, I've used the amp to drive difficult loudspeakers, where the minimum of impedance was around 4 Ohm with no problem at all.
As said, the chipset comes with a separate Class AB headphone amplifier and with a large number of protections against any kind of possible failure/damage: thermal, over-current, anti pop-noise, low voltage supply, fluctuacting voltage supply, internal clock failure etc. Being a chipset designed to work in any circumstance these protections are quite relieving.

The most original feature of the chipset is the so-called Yamaha-proprietary Pure pulse direct speaker driver circuit. Summarizing, standard Class D chipsets need the interface of a LC circuit between them and the loudspeaker. This means the sound has to cross an intermediate stage before reaching the speakers. Yamaha claims to have introduced a scaled-down LC filter inside the chipset, so an additional circuit is no longer needed. This means lower costs and a shorter signal path. Anyway, for more technical details please refer to the complete YDA138 datasheet or, for a more verbose and less technical explaination, to the YDA138 features page on the official Yamaha website.

Yamaha makes also other Class D chipsets, both of lower and higher power output. Similar chipsets had been already used on the high-end Yamaha flagship power amplifier MX-D1, a 500 watts per channel monster.
The cost of a YDA138 chipset is 630 Yen, more or less 5 €.

The internal of the SDA-1000 amplifier is quite clean, with a decent layout. The only cables that run from the front to the rear panel are signal (input) and power (output) cables. Considering how small the amplifier is we're still talking of few centimeters of cabling!!!

[Scythe SDA-1000 - internal view]
Scythe SDA-1000 - internal view
These are the claimed tech specs:


Being a product intended for PC users/tweakers the Scythe SDA-1000 is quite easy to find. In the USA I've found it for as low as 51.50$ at Iguana Micro Stores and, of course, on various international Amazon sites and Ebay (Buy It Now formula) where prices can range from 37 to 62 €. Finally, any PC tuning components store can have it in stock or might order it on request. It is not impossible to find it sold as second-hand item on Ebay (prices around 20 €).

I had a dream...

I've extensively tested this amplifier again its natural competitors, that is the original T-Amp, the Super T-Amp, the Trends Audio TA 10.1 and the NuForce Icon, using different pairs of loudspeakers. Original T-Amp aside, the other competitors cost 3 or 4 times as much so I admit this isn't going to be a fair comparison test. It is like comparing a 1000 € amp to a 3000 or 4000 € one, not exactly what I'd call a reasonable match. Nevertheless, the inexpensive SDA-1000 proved to be up to the task!

[Scythe SDA-1000 + competitors]
[From bottom to top] Scythe SDA-1000, NuForce Icon, Trends Audio TA 10.1

When I started to compare these amps one thing appeared suddenly clear: both the T-Amp and the Super T-Amp weren't in the same league of the SDA-1000, the TA 10.1 and the Icon. The Super T-Amp was clearly worse than the TA 10.1 so I decided to keep the TA 10.1 as "reference" for a TA2024-based amplifier. Not that the Super T-Amp was all that bad, actually it was close to the TA 10.1...but this was overall better, especially in terms of bass performance. The original T-Amp, with its limitation in the area of deep bass, was clearly the worst of the group.

So here I am with just three similarly powered amplifiers, each one with its own chipset (Yamaha, Tripath, NuForce). Let's not forget the TA 10.1 and the Icon cost nearly 4 times as much. My scope is to prove that the SDA-1000 isn't clearly worse.

Its tonal balance is the brightest of the group and this adds sparkle and vividness to the reproduction. It may appear overbright on certain recordings but its strong bass and mid-bass counterbalance admirably this attitude. Perhaps "smooth" isn't the first adjective you might pronounce, "crisp" and "detailed" coming first to mind, indeed. The Scythe SDA-1000 is a brilliant performer, especially "at home" with lively and rhythmic pop and rock. Its performance on the tough track "Hollow" (Tricky - album "Vulnerable" Anti Inc. Records - 6648-2, 2003) is simply exciting and "electric". One feels the urge to turn the volume up ...and up. Both the Icon and the TA 10.1 appear more laid back and relaxed, even if perhaps a bit more correct.
The SDA-1000 reproduces also excellent pizzicatos, rich in harmonic content and very, very tactile. Even violas and cellos do possess their natural body and strings vibration. Furthermore, a very good performance can be experienced with the percussive sounds of the piano.
Voices, both male and female ones, have a very strong "presence" effect hence lesser recordings might be easily exposed with all their faults. The TA 10.1 voices seem to have more body and weight in the bass notes but appear less precise and open in the highest notes. The Icon reproduces voices correctly but sometimes with more sibilants than the SDA-1000. It's a tough match, indeed. Any of the three amps has pros and cons and it is difficult to decide which one offers less compromises in this particular area.

Bass performance is quite different too: strong and almost irriverent that of the SDA-1000, more correct that of the Icon and sligthly softer that of the TA 10.1. For rock and pop I would perhaps choose the SDA-1000! Extension is paired with an irresistible punch. Overall, I think the bass range of the Icon is the closest to reality but, again, it's a tough decision to take :-)

Summarizing, considering the price, the SDA-1000 wins hands down, at least in terms of quality/price ratio. The Icon and the TA 10.1 sound slightly better overall, perhaps, as they appear more correct in the long run but there are areas where the SDA-1000 performs slightly better. And this is quite embarassing, in my opinion. The tonal balance of the SDA-1000 isn't perfect, perhaps, but it performs damn good in some areas so that one tends to forget certain compromises. For example, an area where both the TA 10.1 and the Icon are clearly better is the "details retrieval" department: hidden low level sounds are always brought to the listener with ease. With the SDA-1000 you tend to focus your attention on the "big picture", ignoring tiny details here and there.


Despite the fact we have always written very clear which are the limits of a low-powered amp (ANY low-powered amp!) there are readers who still complain because a sub-10 watter can't properly drive a low-efficiency loudspeaker inside a large listening room. Well, you can still believe in miracles, we don't. 8 watts are just 8 watts: more than enough for the average listener (maybe) inside a small listening room with medium-efficiency speakers, perhaps not enough to transform your listening room into a dance floor. This means that if you ask for too much the amp will clip and produce distortion, exactly like any other amplifier driven above its natural limits. Clipping is nearer when playing extra-low bass recordings, of course, because current draw is stronger.
Do not complain with us if the amp can't properly reproduce the cannon shots of Tchaikovsky's 1812 ouverture with standard speakers! If those are your expectations, perhaps you should better use 100 dB/w/m speakers!
Staying within the amp's natural limits overall dynamics can be considered good/very good. Its sound is crisp, fast and detailed, even in the bass range area. This means the power supply is adequate though I suspect, looking at the datasheet, that some extra power can be obtained using a 13.5V power supply instead (a worthwhile experiment?).
Anyway, with its standard 12V-3A power supply the amp is lively and even punchy when required, though one shouldn't forget its natural limits. As said, heavy and deep bass make clipping nearer. If that's the case, just turn the volume down!
Compared with the TA 10.1 and the Icon it appears a bit punchier in the bass and mid bass (as far as the power output allows it to be) and adds some extra "sparkle" to pop and rock music.

[Scythe SDA-1000 + competitors]
Rear view of the three Class D amplifiers. Note the easy-to-use high-quality connections of the SDA-1000 (bottom)

3D soundstage

The virtual image created by the SDA-1000 is rather large and deep, well extended even "above" the line of the speakers. In this particular aspect it does sligthly better than the TA 10.1. Perhaps the scene doesn't "surrounds" the listener like it happens with the TA 10.1 but it does extends a bit farer behind and in front of the speakers. The NuForce Icon is more convincing overall and the virtual stage has more "air" surrounding singers and players.
Once again, I'm surprised by the level of performance in this particular area. Inexpensive amplifiers normally can't "image" at all!

Some advice

Not much to say here except the obvious. It is true that any amplifier performs better after a brief period of "break-in". For unknown reasons chip amps seem to need a longer break-in. For this reason AVOID to judge this amplifier before 50 hours or so: let it play for a long while then start evaluating its performance. It will get better day after day. Unfortunately there are many audiophiles who judge any component in few minutes, right out of the box. This is the worst way to evaluate HiFi components. First, break-in is always necessary, secondly a minimum amount of "warm-up" is crucial and third, our brain takes time to fully understand the sound of a component. Don't be fooled by first impressions! Actually, the first minutes of listening with the SDA-1000 have been unsatisfictory, to say the least.
Despite the fact I haven't encountered problems using it, at full power, with tough loads (speakers with impedance below 4 Ohm) I wouldn't recommend using 4-Ohm nominal impedance loudspeakers with it. The datasheet recommends anything ABOVE 7.5 Ohm but performance graphs seem to prove the contrary. Anyway, you've been warned :-)
DO NOT experiment with different power supplies UNLESS you know the difference between Volts and Amperes. Too many T-Amps died because "abused" and connected to wrong power supplies. Use the supplied PSU (which is good) and you'll be home and safe.
The Class AB headphone amplifier seems to accept 16 Ohm as minimum impedance, 32 Ohm being optimal. Higher impedance headphone might cause a decrease of the power output. Sound quality of the headphone output doesn't seem on a par with the speakers output.
I'd recommend using high sensitivity speakers if your system plays in a large room or if you like high pressure levels. I've tested this amp with 90 dB/w/m speakers inside a dedicated 18-20 sqm room: my SPL meter registered nearly 100 dB peaks at the listening seat. If you need more (100 dB _is_ LOUD!) use higher sensitivity speakers (or a more powerful amp!). That said, many readers confessed to use sub-10 watts amps with 87/88 dB speakers without feeling the need for extra sound pressure. Hence, the concept of "how loud" is strictly subjective!
As for system matching, I'd generally avoid bright sources and speakers. You need to use speakers with good bass extension in order to fully enjoy the good performance of this amp. Small bookshelf loudspeakers, with small woofers, might cut away one of the areas where the SDA-1000 performs at its best (bass and mid-bass). In my opinion, a small tower loudspeaker could be a good partner, especially if of good sensitivity.
Finally, I haven't tested the amp as a PC component, only as a stand-alone unit. Using a PC internal power supply might yield worse results and generate interference problems with other sections of the PC, such as wireless peripherals etc. Switching digital amps might cause problems to FM and AM radios, as well. I've used the SDA-1000 close to DAC, CD transports and CD players and experienced no problem at all.


Undoubtedly, someone will try to tweak and improve this small amplifier: better passive components, better volume pot, external rechargeable battery power supply, internal rewiring and so on. I prefer to keep it as it is: good sounding, inexpensive, easy to use. While tweaking a T-Amp was almost mandatory, this SDA-1000 can be used as any standard stereo amplifier, just hook up the cables and you're done. I don't want to discourage die-hard tweakers, just try to avoid them spending time and money when it isn't really needed.

[Scythe SDA-1000 + accessories]
Accessories: speaker cables, two interconnects (RCA-RCA & RCA-minijack), owner's manual, power supply etc.


Manufacturing & finish.
This is a nicely designed and finished amplifier: it makes use of good materials and offers a good level of craftsmanship and user-friendliness (thanks to the easy-to-use rear connections!).
The amp sits on three feet (metal with anti-splippery rubber). One of the things I don't like much is the finish of the front fascia which does have some sharp edge, while the rest of the cabinet has rounded, smooth corners. Also, I don't like the black/silver colour mix: a full black version would have been nicer. Actually the full silver option is cool, except for the (too many!) black screws here and there. The power on switch activates a white led which I've found to be excessively bright.
The speakers binding posts are of good quality and accept good section bare wire, besides forks and bananas. I've found the banana holes to be slightly larger than standard, though. The volume pot is micro-stepped and quite precise. I've found very useful the mute switch, for temporarily "muting" the amp without changing volume settings.
I'd love to see a full black version with 2-3 line inputs (possibly a minijack, also).
This amplifier isn't euphonic, nor warm or "soft". No, it is crisp and precise, instead, and very, very transparent. Its sounds reminds me that of the TA 10.1, tough it appears cleaner in the mid-highs (female voices in particular) and less forgiving. I wouldn't define it hyperdetailed - which isn't - or overbright but audiophiles used to smooth and warm amplifiers might define it bright. Overall, it is a matter of personal taste and right partnership.


Four years didn't pass in vain. I've seen many T-Amp clones and I've noticed that sound performance has grown up together with prices. From 20$ to 200$ (original T-Amp --> Trends TA-10.1) is a whooping 10X factor. This Scythe SDA-1000 brings us back to reality and explores new quality/price territories even the original T-Amp wasn't aware of! This little marvel costs like an original T-Amp + power supply and offers a lot more: better quality of construction, better sound, finally good "audiophile" connections, a headphone output and even two different faceplates!!! All of this at the price of two full-price CDs!

For 50 €, be it new or second-hand, no other amplifier comes close. This is an amp that, instantaneously, makes obsolete and ridiculously overpriced any other Tripath-style chip amp. This is the new "value for money" state of the art.
In terms of absolute sound quality it is very close to the TA 10.1 and the Icon (and does even better in some areas!) but if one takes into account the price, this amp is a hands-down winner.

We're living times of uncertainty, due to the financial crisis: it's good to know that with 50 €/$ you can still buy an amplifier that sounds this good. Astounding.

Update (October 2010): the SDA-1000 has been redesigned and is now available as SDA-1100. See our review of the new release!

Copyright © 2009 Lucio Cadeddu - www.tnt-audio.com

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