USB/SD/FM Digital Player Review
The advent of eBay and online buying
in general has led to a myriad of
cheap stuff available for sale from countless sellers in places like
Hong Kong, China and Taiwan. Some of this stuff is quite good and some
of it is total crap. Knowing the difference can be hard, and it's
disappointing to say the least when you wait for weeks to receive
something and then find it is complete junk. Most of these sellers do
accept returns, and seem keen on customer satisfaction, but it's a lot
of bother for cheap stuff like this. Paying the return shipping may not
be worth it.
One way to figure out what
constitutes a good buy would be to look at
what others are buying. (Well, it sounded better than saying "spying on
someone else's eBay purchases". And yes, that's exactly what I did.)
That's how I came to have this thing.
(picture shamelessly stolen from the
original eBay listing and sloppily edited by yours truly)
This thing, specifically, is the Kinter A5 USB/SD/FM Digital Player,
yours for about US $13 or so. With your purchase you get the player
itself and a remote control. No memory devices or power supplies are
provided. (More on the power supply later.) In theory at least, any old
9-12 volt, 500mA, center positive or
better power supply will probably do just fine. If you need such a
power supply, chances are good that your local thrift store has dozens.
You can also buy appropriate power supplies online for very little
money. If you're feeling handy, a few minutes with a soldering iron and
some other parts would get this thing up and running from battery power.
As with many other random low cost
Chinese goods, you may find this unit offered under other brand names.
I've seen a large number of different devices that use the same (or a
very similar) remote control to what came with this unit. I'm not sure who actually made the thing, though Chaozhou Tongheng Electronics Co. Limited seems like a decent guess.
FM in this case refers to an FM radio
receiver. Though it would have
been nice, there is no FM transmitter built into this unit.
One the front panel are a series of
controls to govern the basic
operations. A simple reddish-orange LED display shows what the player
is currently doing. The roughly credit card sized remote provides more
functionality and actually does include a battery. This is a
surprisingly nice touch.
Located on the bottom of the unit are
two color changing LEDs. These
turn to random colors whenever the unit is powered on. You may or may
not like them, but if you don't, it wouldn't be rocket science to
Getting started is simple. You need a
USB memory device or an SD card
with music in MP3 format and the previously mentioned power adapter. If
you don't yet have a USB memory device or SD card, you can listen to FM
radio. You'll also
need something into which the unit may be played. Off to the side is
the example I got, in a not-at-all ironic photo showing a Sony ES
stereo receiver (to which it was connected) in the background. Most
stereo headphones will work
fine as well. Connection to a stereo receiver or other outboard
amplifier is easy, requiring only a cable that usually has a stereo
miniplug (TRS plug) at one end and two RCA ("phono") plugs at the other.
You can't hope for fancy instructions
with something like this, and it
is a rare case that the instructions you do get are anything
comprehensible. Fortunately, this is an MP3 player and not brain
surgery. Power is turned on by a "hard" power button at the rear of the
unit. Once power is on, the unit will search for and start playing MP3
files from a memory card or USB device if one is present. If not, it
will play the FM radio, using the last station tuned in.
While the four front panel buttons
are better than nothing at all, you
really want to keep the remote handy. Otherwise, you have to work with
a slightly arcane set of front panel buttons whose functions change
when held down for a period of time. The remote has buttons for each
major function and that makes life a lot easier. As with most consumer
electronics, keep the remote handy and you'll be a lot happier.
"Mode" lets you choose between three
modes of operation...FM radio, MP3 (only if a USB or SD card is
inserted), and the curious "LINE". When you're in the radio mode,
tuning can be accomplished by pressing and releasing the two |<<
or >>| buttons on the unit's front panel or the remote. If you
hold the |<< or >>| buttons on the remote, seek tuning to
the next broadcasting station will occur. You will know when seek
tuning has been activated as the audio will go silent. Seek tuning
starts when you release the button.
Volume control is most easily
accomplished from the remote control
using the volume control buttons, though it may also be done by holding
down the |<< or >>| buttons on the front panel of the unit
itself in any mode.
Number buttons on the remote allow
you to directly enter the "track
number" that represents any MP3 file on the currently inserted memory
device. As track titles cannot be displayed and files can be ordered
arbitrarily on your storage device, this isn't really convenient. I
didn't find much of a rule set as concerns file ordering. If anything,
the most recent files to be added to the device are played last. Yet if
you go back and delete some files "in the middle", results are less
A couple of equalizer profiles are
provided, though none of them are
particularly exciting. It's probably best to leave the equalizer off
(set to E0). The equalizer functions only when playing MP3 files.
The back panel isn't too exciting to
look at. At the back you have the
FM antenna, audio output minijack, power switch and a DC power
connector intended for use with 9-12 volt DC power adapters. Slightly
more or less input voltage should work fine as long as your power
supply can deliver enough current to keep this thing happy.
This whole product would be pretty
pointless if it didn't sound good when playing.
I'll put it simply. When it came to
listening through headphones, I've
heard better output from any MP3 player and most of the portable
that I've had over the years. The sound was not unlike that of a cheap
shirt pocket transistor radio. Yet it did not lack for output power, as
the output stayed clean even when I wound the volume level to a rather
Connecting things to an external
amplifier gave much better results.
The sound was still a bit bright, and none of the equalizer settings
were helpful when listening through headphones or speakers.
What really helped things out was the
placement of a simple equalizer
between this player and the amplifier. With a little bass boost around
the 32 and 62 Hz bands and some treble reduction at 8 and 16 kHz, the
sound was improved considerably. (Adjustment around the 12 kHz band
probably would have helped more, though my equalizer didn't allow for
The audio output stage is centered
around an LF353 operational
amplifier chip, provided by STMicroelectronics in this unit. I believe
it would be possible to achieve better audio quality with a different
op-amp IC or by changing the surrounding components. I may experiment
with this. (See also the "Tinkering" section, further below.)
I would recommend choosing a power
supply with a quiet output. I
noticed an occasional "siren" or "wailing" sound from this unit and
finally traced it down to find that it was in time with the color
changing LEDs. Regulated switchmode power supplies are cheap and
common, but the one I used was too noisy. A simpler transformer based
supply with regulation might be a better choice, though it is likely to
be more expensive. Battery power would also work, and should be totally
FM radio performance may be quite
variable. You'd never confuse this
thing with even a low end component tuner. I had fair reception results with mine. While no
station was truly quiet (some of which may have been the fault of my
randomly selected power supply), I was able to pick up fairly weak
stations from about forty miles out with usable results. I never noticed much if any FM stereo separation and don't know if FM stereo reception is forced off in
the design or if the blending/hi-cut process used by the tuner is just
I have had one
report that the FM tuner worked extremely poorly in another example of
or a look at the Design, testing it for Stability, searching for Curious or Unimplemented features and other interesting things that
happened to cross my mind.
It's no secret that I can't leave
anything alone, and this unit was no
exception. No sooner had I unpacked it, than I had pulled my Golden
Screwdriver out and set in to find out what was inside.
Four screws hold the unit together
and all four must be removed to take
out both the front logic/display board and rear audio/power board. A
wire ribbon cable links the two boards, but be careful of the FM
which is soldered to the logic/display board while being mounted to the
rear cover. Once you get the screws out, you might need to gently rap
the unit on a table or shake it to get the ends loose. You can unplug
the ribbon cable to give the boards more separation. This makes them
easier to inspect. It's possible with some finesse to carefully move
the antenna board through the case shell, allowing for better
inspection of the two boards that make this unit up.
If you choose to unplug the ribbon
cable, make a note of where the
connectors were plugged in. I don't think it's possible to mess them
up in such a way that you'd actually damage anything. Still, an ounce
of prevention is worth a pound of cure.
What you'll find on the logic board
is pretty simple. In addition to
the display, USB port and SD card slot, there is an anonymous
system-on-chip that almost certainly contains the MP3 decoder, system
CPU, control program, display driver and I2C
I could find nothing on this chip, which is marked only as "JM AC1220 H
77237". I would imagine it to be a product of some no-name Chinese IC
foundry. I would guess that it is the typical 8032 microcontroller core
with a dedicated MP3 decoding circuit and USB/SD communications
hardware on board. While I don't expect to ever know for sure, I would
appreciate any information that might exist on this part. A data sheet
would be nice.
Also on the logic board is a small
EEPROM along with a Quintic QN8075
FM tuner. Information about the QN8075 is thin on the ground and it
doesn't even show up at the Quintic site. I was able to find out
(through a Chinese page on the Baidu search engine) that this part is
controlled through the I2C bus.
I would guess that the EEPROM is used for nonvolatile storage, since
the unit does remember what FM station it was tuned to when power is
lost. A 32.768 kHz crystal is used for clock generation for the FM
tuner (and probably the microcontroller as well).
Update: I finally found a copy of the
Quintic QN8075 datasheet and it reveals some interesting features. In
particular, FM and FM stereo decoding is handled in the digital domain
by a DSP integrated into the QN8075. Audio is then converted to analog
form and output to its ultimate destination. I'm really not sure if the
Kinter A5's design makes use of the FM stereo tuner in the QN8075.
Nothing I listened to on the FM band had much stereo separation. (I
have an FM stereo modulator and could test this at some point in the
future. If I do, this review will be updated accordingly.)
I started writing this in November of 2012 and only published it
after finding the QN8075 datasheet in early 2013. This should serve as
adequate proof that procrastinating isn't always a bad thing!
Back on the audio board, the major
components are a 7805 voltage
regulator and the previously mentioned STMicroelectronics LF353 op-amp.
Looking at the connectors reveals the
purpose of the mysterious "LINE" setting. There is an unused line level
audio input. You could easily connect something to this and make use of
it. There are also certain variants of this unit produced with a built
in audio power amplifier that make use of the line input.
Stability seems to be quite
good. Nothing I could do to the player made it behave strangely. Not
even VBR MP3 files or suddenly removing the USB memory key or SD card
problems. In the latter case, playback just quietly stopped. Files from
64 to 320 kbps played just fine.
There isn't too much to report in the
department. Anyone playing with one of these will have undoubtedly
noticed the odd and seemingly not useful "LINE" input. This is actually
brought out on the front logic board and is put to use in a different
model with a built in power amplifier module and input jacks for line
There are no unused characters in the
display, outside of the "WMA"
(Windows Media Audio) notation. Other variations of this unit can
decode WMA format files, but this one does not. I have seen no evidence
that a model supporting AAC format playback exists. It will ignore WMA
files on your storage device and my attempt to rename a WMA file to an
MP3 (just to see if the capability was "hidden") met with confused
performance from the unit. Some of the previously mentioned variants
paired with an audio power amplifier do claim to have WMA playback
support. I'd love to know if they use a different decoder IC. I'm not
dedicated enough to purchase one and find out.
Interestingly, the Kinter A5 can play
uncompressed PCM wave files without any trouble at all. I only tested
files with a sampling rate of 44.1 kHz and a 16-bit sample depth, so I
don't know what it might do if you fed it a file with a lower sampling
rate. The only obvious defect is that the equalizer doesn't work.
Considering that it really doesn't work very well, I don't think this
matters. When the unit plays a WAV file, the display continues to
indicate "MP3". I take this to mean that the MP3 indicator is simply
forced on under the assumption that no one will ever try to play
anything other than an MP3.
While dreaming up strange things to
try and plug into this unit's USB port, I happened to try a USB hub. I
was moderately surprised to find that this did not work when a storage
device was in turn connected to the hub. Yet I never had any problem
with my stable of USB memory devices or SD cards when connected
directly to the USB port or SD card slot. SDHC cards up to 4GB (the
largest I have) seemed to work just fine.
The built in SD card slot has
priority over a USB device. Both can be plugged in at the same time, although the unit's
logic is not smart enough to let you choose between them.
MP3 (and/or WAV) playback loops back
to the beginning whenever the last file in line is played.
(More) FM Radio
As previously mentioned, the Kinter
A5 includes an FM radio tuner. While I can see this being useful in
some cases, I would have preferred a model without the FM radio
present. It performs about as well as any low budget FM tuner that was
(probably) tacked on as an afterthought possibly can. Local stations tend to
come in well and distant stations are hit or miss. Reception usually
either happens or it doesn't.
This unit falls back to the the FM
radio by default when you remove the memory device, resulting in a loud
burst of static if you don't have the tuner set to an active frequency.
If you don't want it, disabling the FM radio should not be difficult.
Should you be feeling bold, you could cut the traces for the I2C
data input and output lines going to the QN8075. A safer option would
be to cut the traces or lift the IC pins for the FM tuner's audio
quality through headphones with the FM radio was marginally better than
the MP3 playback.
If you're an audiophile who demands
the best in audio reproduction that you can get (or afford), you
probably won't like this unit. Its audio quality leaves something to be
desired on both FM and MP3/WAV playback. (It could be argued that if
you're an audiophile, you probably aren't listening to MP3s or perhaps even FM
There's a lot to like about this
thing. Its modest power requirements, small size and even the FM radio
are all handy features. You could pair it with something like a Class T
amplifier and put together a very credible portable system with high
power output while maintaining good energy efficiency. MP3 playback
seems to work flawlessly. WAV playback is a nice touch. It could also
be used where audio fidelity isn't as important--to provide a "hold
music" or advertising feed for telephone systems or even as a
music/message player for use with PA systems. You could even strip off
the cabinet and use this unit to quickly and easily add MP3/FM radio
playback to a project of your own. It's easy to forgive this unit's
less than perfect audio quality considering how well it works and the
great deal of flexibility in usage that it offers.
I have used mine to play back
pre-recorded pre-shows recorded by others for use on my live streaming
broadcasts. It's never given me a moment's trouble. No one, not even
the few really picky people I know, has complained about the audio
quality after "helping" it with the equalizer.
I'd have liked to have seen WMA or
AAC decoding made available. WMA decoding exists on similar devices and
I'm fairly sure that AAC decoding is just a matter of time. (I'm sure
you cannot upgrade the simplistic microcontroller in this unit to
support new formats.)
This unit really does what it says it
will do, and on that account alone it's worth buying. I'd recommend it.
Click here to buy one! (This is an eBay link. Please verify that
it opens the appropriate eBay site for your country.)
Copyright © 2013 William R. Walsh.
All Rights Reserved. Permission is granted to reproduce this material
or to use any part of it in other creations, so long as the following
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supplied, no part of this page may be displayed along advertising
content of any sort, no fee may be assessed to provide access to this
information (except as reasonably necessary to cover connection time or
printing supply expenses) and no part of this material may be used in
creations that are illegal, dangerous or derogatory. Created
11/15/2012, edited after much procrastination and posted 04/29/2013.