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Old 30th April 2008, 08:13 PM   #1
cpemma is offline cpemma  United Kingdom
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Default Scythe Kama Bay amp

http://www.scythe-eu.com/en/products...ma-bayamp.html

Power IC: YAMAHA YDA138(D-3) Digital Power Amplifier

Runs off 12V DC, designed to replace the invariably nasty PC active speaker system using "proper" speakers. Looks decent hardware.

Anybody heard one of these, or come across the IC anywhere else?
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Old 30th April 2008, 08:20 PM   #2
djQUAN is offline djQUAN  Philippines
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I can't see output inductors in the picture.
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Old 30th April 2008, 10:36 PM   #3
cpemma is offline cpemma  United Kingdom
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Quote:
Originally posted by djQUAN
I can't see output inductors in the picture.
Apparently the circuit will work without output inductors, relying on the speaker inductance (though results may be better with them).
Quote:
YDA138 has a “Pure Pulse Direct Speaker Drive Circuit” which directly drives speakers while reducing distortion of pulse output signal and reducing noise on the signal, and realizes the highest standard low distortion rate characteristics and low noise characteristics as 10W-class of output digital amplifier IC.
In addition, circuit design with fewer external parts can be made depend on the condition of use because corresponds to filter less.
Datasheet
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Old 28th August 2008, 04:47 AM   #4
Pano is offline Pano  United States
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Old topic, but today I got the listen to the Scythe amp.
(Some of you will have gotten the same message from me via email.)


Played the Scythe on a pair of Planet 10 Fonken speakers. (Citypulse DAC as source - Holly Cole CD)
Well... all I can say is that a stock Kingrex T-amp walked all over it. In every way. Power, soundstage, detail, texture, channel balance, tonal balance and just pure pleasure.

That may not be fair to the Yamaha chip, the Scythe amp isn't built with the greatest parts - even though the layout and chassis build are not bad. Seems to be sensitive to power quality, too. A linear PSU sounded much better than SMPS.

It does use 2 inductors per output channel, just like other BTL amps - but they are tiny. Doubt they can take much current. Also has tiny electrolytic caps in the output filter - not the best choice. Residual RFI is not too high and seems up in about the same switching freq range as Tripath. Waveform is more sawtooth than sine - probably due to bad filtering.


If I ever get the chance I'll mod it and give another listen. Would be fun to hear if better parts will improve it.
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Old 20th September 2008, 01:07 PM   #5
cpemma is offline cpemma  United Kingdom
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A review at SPCR in the context of a $50 PC-mounted amplifier wasn't too critical of the audio quality but picked up another fault
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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.
And they do find PSU effects
Quote:
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.
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Old 21st September 2008, 04:39 PM   #6
Pano is offline Pano  United States
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Yeah, pretty much what I found,

If I ever get the chance, I'll upgrade the amp. Would be nice to know what the Yamaha chip can really do.
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Old 11th May 2009, 11:59 PM   #7
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maybe not anymore to the interest of anyone.
a serious review by tnt-audio after a generous burn-in of 50 hours:

http://www.tnt-audio.com/ampli/scythe_sda1000_e.html

seems pretty good, i'm definitely having a try for the price. maybe it can drive a pair of chr-70...
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Old 3rd April 2014, 06:09 PM   #8
pinobot is offline pinobot  Netherlands
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Found one board with 2 yda138-e on ebay, i think they are bridged.
Ordered one.
Click the image to open in full size.
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Old 19th August 2014, 02:10 AM   #9
phase is offline phase  United States
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So, how does it sound?
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Old 21st August 2014, 10:21 AM   #10
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Electrolytic-cap coupled output-stages "can't" sound good, it's always a tradeoff. O.o
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