Kinter A5 USB/SD/FM Digital Player Review

Rating: Four Star Rating

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.

Kinter A5 USB/SD/FM Digital Player

(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.Kinter A5 Front Panel View, with remote 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 remove them.

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 predictable.

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.

Back Panel

Kinter A5 Back Panel

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.

Audio Quality

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 radios 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 prodigious setting.

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 this.)

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 silent.

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 very aggressive.

I have had one report that the FM tuner worked extremely poorly in another example of this unit.

Tinkering

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 antenna, 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.

Kinter A5 CPU/Display/Card Reader Board

Kinter A5 Audio/Power Board

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 bus controller. 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 caused 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 Curiosities 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 level inputs.

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 output.

Audio quality through headphones with the FM radio was marginally better than the MP3 playback.

Overall

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 radio.)

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.)


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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 terms are met: attribution to this page and its author must be 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.