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USB Audio Recorder Review

This page online since 29 Feb 2012

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Dates on this site are usually in this format: YYMMDD

#1 USB voice recorder with US nickel
#3 #3 USB audio recorder

Review summary - This is a combination of a rechargable battery operated audio recorder and a USB flash memory drive.  Each time you turn it on it creates a new audio file, then records audio until you turn it off.  Properties - small, light weight, portable, internal rechargeable battery, microphone, on/off switch, LED indicator, no internal speaker.  You play the audio files on another device. Many versions, so the outward appearance is not an indication of features or audio quality.

190709 Setting the Date Time
The recorders I have reviewed have this behavior:  When reset, the recorder date time is not valid or is set to a default like 2008 January 1.  When switched off, the recorder keeps the date time clock runing using a little power from the battery.  If the battery is fully discharged the date time is unknown.
     If the recorder is on and you want to correctly set the date time, you can plug the recorder into the USB of a computer and run a program on the computer to set the date time.  I don't host these set-date-time programs but they do exist. USE THESE PROGRAMS AT YOUR OWN RISK.  I don't know if these programs work with your USB audio recorder or are malicious or a virus threat.
     W.R. in Madison WI reports this:  "... There is software (SetDigitRecorderTm.exe or "SET DISK TIME.exe") to set the time.  ...  If the battery completely dies you will lose the time."  Is this program safe?  See this analysis.
     Also, this downloadable program SetTime.exe is for a USB audio recorder.  Some eBay sellers of USB audio recorders provide links to these programs:  SetUDiskTime.exe, SetUDiskTime(9x).exe.

150512 - Often sold as a "150 hour recorder", that is usually misinformation.  The battery charge life is typically 5 to 10 hours of recording.  An 8GB recorder at 128Kbps audio would typically hold almost 150 hours of audio files.

Of the different versions that I own and have tested, version #1 seems to be the best because it works reliably, records for about10 hours (a long time) on one battery charge and has very good audio quality.  The audio format is usually WAV -ADPCM.

150420 iTunes does not play WAV-ADPCM file format but does play WAV- PCM.  You can convert WAV-ADPCM to other file formats.  VLC and Audacity will convert audio files to MP3, WAV-PCM, AAC, FLAC and other file formats.

The features and quality of the versions vary as follows:
Audio bit rate ranges from 32 to 384Kbps.  Audio quality from poor to very good.  Have either internal flash memory or uses a micro SD card.  Recording time on one battery charge can vary from about 3 to 10 hours.  Some are audio activated.  Reliability varies from OK to terrible.

Many versions -
There are many versions of this audio recorder.  I have enumerated the versions that I have tested, but there might be many more versions.  The #1, #2 and #4 use the same plastic case that comes in these colors: black and silver, white and blue, white and orange, white and green.  So the case color is no indication of what is in the recorder.

Common features -
Rechargeable internal LiPo battery is charged from the USB.  ADPCM WAV audio file format.  No speaker.  No audio jack.  No external memory card.  No display.  FAT32 file system.

Version Specific Features
  Version #1 Version #2 Version #3 Version #4
Overview Internal flash memory.  Long battery life and record time.  Very good audio quality. Internal flash memory.  Voice activated.  Like the #1 but 1/2 the record time.  External flash card is required.  Low quality audio and short record time. Seems to be like #1 but with a 3X bit rate that only wastes memory.
Approximate hours of recording on one battery charge. 10 hours 5 hours 3.3 hours
6 hours ? (see below)
Approximate hours of WAV files per memory. 70 hours on 4GB 47 hours on 4GB 278 hours on 4GB.  You supply a micro SD or SDHC card. 46 hours on 8GB
Megabytes per hour, approximate. 57 MBph 85 MBph 14 MBph 174 MBph
Audio bit rate 128 Kbps 192 Kbps 32 Kbps 384 Kbps
Audio quality Very good Very good Poor. 
Low fidelity and a periodic noise.
Very Good.
Audio activated?
(sound starts and silence stops recording)
No. Yes.
Whenever the audio is above a threshold it opens a WAV file and records.  When the audio is below a threshold it closes any open file and does not record.  Audio level has no effect on battery time. Threshold is not configurable.
LEDs Flashing red LED indicates battery charging.  Blue LED indicates recording. Flashing red LED indicates battery charging. 
Flashing blue LED indicates recording.
Red LED.  When USB connected, LED is on. No LED indication when battery is charged.  Recording - momentary flashing LED when starting and ending. No LED while recording. TBD
Flash memory internal external micro (SD or SDHC) card. internal
Processor ATJ3315 BR3166 TBD
FAT32 date time stamp Sequential WAV files seem to increment the date time correctly.  There is no way to set the date time.  Seem that the date time is reset by the recorder reset button. The date time stamp never changes.  Always is 2009 Aug 1 12AM. TBD
File name format REC001.WAV VOICE001.WAV TBD
Reset button yes no yes
KMPlayer Info Format : Wave
Overall bit rate mode : Constant
Overall bit rate : 128 Kbps
Audio Format : ADPCM
Codec ID : 11
Codec ID/Hint : Intel
Bit rate mode : Constant
Bit rate : 128 Kbps
Channel(s) : 2 channels
Sampling rate : 16.0 KHz
Bit depth : 4 bits
    Format : Wave
Overall bit rate mode : Constant
Overall bit rate : 384 Kbps
Audio Format : ADPCM
Codec ID : 11
Codec ID/Hint : Intel
Bit rate mode : Constant
Bit rate : 384 Kbps
Channel(s) : 2 channels
Sampling rate : 48.0 KHz
Bit depth : 4 bits

What version will you get? - Since the electronics of any version could be sold in a case of any color, if you order a recorder which one will you get?  I don't know.  My #1 was delivered in a white/blue case.  My #2 was delivered in a black/silver case.  Try asking the vendor which version they sell, but they probably will not know.

171127 - Simple Instructions
Physical description -
•  Holes - There should be a hole for an LED, a hole to reset the recorder (lightly push a paper clip end into the hole to press the internal switch) and a hole for the internal microphone. 
•  ON/OFF Button - Used to begin recording and stop recording.
•  Speaker - none.
•  LED - can indicate various things you will learn by trial and error including: battery is charging, battery charging is done, audio recording, or audio recording is done.  LED can also indicates device malfunction such as missing micro SD flash card, card full, card not formatted, card not FAT32, battery low, etc.
•  Flash Memory - There will be either internal flash memory or you must supply a micro SD card formatted FAT32.  The slot for the card is either next to the USB connector, or on the side on the recorder.

How to charge the internal battery - Plug the USB connector into a type-A USB port on a computer or USB power bank.  The LED should indicate charging.

What is the operating procedure -
•  Turn the switch on then audio is recorded from the microphone to to a file on the flash memory.  
•  Turn the switch off then recording stops and the file is closed. 
Each time the switch is turned on, another recording file is created. 
The LED should indicate recording or not recording.
NOTE - After the switch is turned on it can take up to 8 seconds before recording really starts.
NOTE - Some recorders will record only when the sound is more than a threshold.  Threshold is not configurable.

How to play the audio file - Plug the voice recorder into a computer USB port. The computer will show the voice recorder as a disk drive with files on it.  The files contain the audio you recorded.  Click on the file to play it through the computer speaker. The file format could be PCM, ADPCM, MP3 or something else.

How to know if the internal battery is charged -  Trial and error.  When connected to a USB port the LED should indicate if the voice recorder is charging or fully charged.  Or dissassemble the recorder and measure the LiPo batter voltage, charged is about 4.2V.

While recording, what happens to the audio file when the battery charge become zero or the flash memory becomes full? -  Many of these devices are not robust (bad engineering).  Learn by trial and error.  Each recorder type is different.  Worst case (bad engineering) you will loose everything you just recorded, the file will disapear or be empty or be so corrupt it won't play.  Best case (good engineering), the recorder will gracefull close the audio file and gracefully stop recording.

150929 - How to Recover a Failed Recorder
Try these things.

1.  Press the reset button.  If there is a momentary reset switch it is usually in a small hole in the case.  Insert the end of a paper clip through the hole to press the reset switch.

2.  Reformat the flash memory.  CAUTION - Any audio files on the flash memory will be deleted.  Connect the USB recorder to a computer and if it installs as a flash drive, reformat it in FAT32 format.

3.  Open the case and inspect and repair.  Look for hand soldered components that might be broken.  Common solder problems are the battery wires and the crystal (small can with two wires).

150311 - Putting the Audio on a CD.
USB audio recorders make WAV ADPCM files.  They are playable on Windows computers, but might not be playable on other platforms.

A WAV file codec can be either PCM and ADPCM.  See

If you burn the WAV ADPCM file to a CD-R, will it be playable?  Maybe.  You have two CD-R options: UDF or CDA.

- this is a file system that many CD players understand.  But many CD players won't play WAV ADPCM files.  Convert the WAV file to MP3 for best playback compatibility.  Audacity will convert WAV to MP3.
•  CDA - this file format is used on mass-produced (store bought) CDs. The sample rate is 44.1 kHz and a sample size of 16 bits.  When burned to CD-R, the WAV files are converted to CDA format by the burning software.

140522 - Update
It has been more than 2 years since I did these reviews on 4 different USB recorders.  I have these comments.

I have not reviewed any newer recorders and don't plan to.

As a group the USB recorders I reviewed are cheap and I can't recommend them to everyone.  They are inexpensive, small and light weight and the audio is sometimes OK and the price is tempting but there are too many problems for the buyer.   No matter what the seller says, you often don't know what you will get.  And once you get a recorder you have to experiment to see how it actually works because the instructions are often wrong or incomplete.  Also, the date time stamp on the recorder file is not correct and nobody has a way to correct that.

Olympus VN 702 PC USB recorder - I have this recorder and I recommend it as it is a world better than the cheap recorders.  It's has been about $40, but now costs more.  Copy recorded files to your computer using USB.  Battery life of about 72 hours on two AAA batteries. Records mono on the internal microphone, and stereo on an external stereo microphone.  2GB of internal flash memory, expandable with your micro SD card.  With external headphones you can listen to the microphone as it is recording.  Here is my Amazon review -

121013 - Where can I buy a #1?
I don't know for sure where to buy a real #1.   Make sure the seller is listing a 128Kbps recorder.  The buying risk is yours, but I would try this eBay search.  

Make sure you note this on the eBay order:  "This must be a 128Kbps audio recorder, as described. If not 128Kbps, the seller agrees to replace it or give me a full refund."

I received my #1 from eBay yallstore  Then they tripled the price and then that listing ended.

120909 - Comments about the #4 and external USB battery
Daniel emailed me that he ordered a 128Kbps audio recorder and received a 384Kbps (#4), not what he wanted.  He says he can increase the record time by using an external USB battery charger, sometimes called an emergency charger.  I will try that with my other recorders.  He has these comments.

Now, a couple of days ago i bought a 4GB USB audio recorder, and i believe it's a #4. In the eBay page and in the instructions it's mentioned the bitrate is 128Kbps, but it really is 384 Kbps.

In some informal tests, the battery lasted about 14 - 15 hours, but i connected it to a Duracell battery charger that has a USB output and it records and charges at the same time.

It records almost 23 hours (22:57) filling the 4GB, but the bitrate is really a waste. I saw at least a seller that has this type of items and he offers an utility to set the date correctly to the files. So, there's a bit of customization that could be done, but what i believe that may have happened with this crazy bitrate is that it was chosen just to fill a bit more the internal flash so it wouldn't leave so much space in blank.

If it could be reverted to 128 Kbps, and as it can be connected to an external USB battery bank and keep recording, that would (i think) 70 hours of recording. Is there any kind of utility like there is for the keychain recorders to re-flash to other bit rates these USB audio recorders?

I noticed something when using the recorder with the Duracell USB power pack: With the recorder in the off position and connected to the USB power pack and then turning on the recorder, it records the 23 hours.

If it is already on the on position, and then connected to the power bank, it stops the recording, and then starts recording once again. I believe it hung once (the blue light stopped blinking and the red stayed on).

120827 - Report about the #3
Chris sent me these comments about his #3.  He likes the #3 because of the low bit rate and long recording times.

I think yours might be goofy. I have gotten in excess of 6 hours record time with all my #3

I bought them SPECIFICALLY BECAUSE they recorded at 32kb.
Uploading 3 hours video of an evening engagement is hard and or impossible depending on the hotel Wi-Fi and extracting the audio and compressing is a PAIN.
I like 32kbps because even HOURS of video result in a tiny file yet more than good enough to listen too.
So with these no editing no compressing nothing insert stick upload audio file done :-)
So it depends on what your doing.
The other units you posted are unusable to me because the bitrate is too high !!

120820 - "You don't always get what you want" or what you ordered.  Version #4.
BUYER BEWARE - When ordering on eBay be sure to specify that you will expect a full refund if the product is not as described.

I received a USB audio recorder that does not match the sellers eBay description.  The seller said that the factory drop-shipped the wrong recorder directly to me.  The seller agreed to refund me US$6 (I paid US$12.50), and I keep the recorder.  I have enumerated this recorder the version #4.

I ordered an 8GB 128Kbps USB audio recorder from eBay seller el-craft who described it as a 8GB 128Kpbs 150 hour recorder.  My intent was to modify it with a large external battery to record more hours.

I received an 8GB (47 hour) 384Kbps USB audio recorder.  Deliver time was 11 days.  Because of the high bit rate the 8GB will only hold about 47 hours.  So this #4 is useless to my modification project.  It can still be used as an 8GB USB flash drive.

120712 - Version #2 Threshold Test.  #2 is Not Recommended.
Shaun in the UK requested some threshold information about the #2 so I did some tests.  Here is my reply.

I did some sensitivity tests for the USB audio recorder version #2 (the device) and here are my results.  The #2 records audio only when the volume is above a threshold.

CONCLUSION - The test condition was a quiet room and a normal voice at 10 feet (I don't have a decibel meter).  When the switch is turned on and the blue light blinks the device begins recording.  In a quiet room the device stops recording almost instantly.  Ten minutes later, the device will start recording a voice at 10 feet within about 0.1 second ("one two three" is recorded as "ne two three").   The device will stop recording almost instantly when the audio stops.

COMMENTS - The #2 USB recorder is inconsistent and unreliable.
Sometimes it works as expected, recording when there is sound and not recording when there is silence.  
Sometimes it just starts spontaneously recording white noise in a silent room and then when there is a sound it records the sound in the white noise.
Sometimes it starts a new WAV file after a silence.
Sometimes it records multiple sound sessions, with the silence removed, in one WAV file only.

Because of this unpredictable unreliable operation I can't recommend #2.

120415 - #1 Modification. 70 hours on one battery charge.  Large external battery replaces internal battery.
Do not attempt this modification unless you know how to safely work with LiPo batteries.  Do a full bench test to verify everything is safe.  LiPo batteries can explode, cause a file, and cause personal injury.

This modification increases the record time of the 4GB audio recorder to about 70 hours on one battery charge.  The original record time was about 10 hours on one charge.  The internal battery is removed and replaced with a larger external battery.

My #1 USB audio recorder has been reliable.  It records about 10 hours on a battery charge.

If 10 hours is not enough, the recorder can be modified (requires micro soldering skills) 
to replace the internal LiPo battery with a large external LiPo battery.  Then one battery charge will last until the 4GB is full, about 70 hours.  The larger battery takes much longer to charge via the USB.

Many different larger LiPo batteries could be used, but they will not fit inside the plastic case.  An external battery needs to be mounted on the outside with double foam tape or Velcro.  Any replacement battery must have a protection circuit. 

There are two LiPo batteries that I have found to be about the right size.  On one battery charge they will record for about 2 or 3 days depending on the battery size.  They are widely available and are less than US$5 on eBay.  They are a replacement battery for the "iPod video".  The external battery does not obstruct the USB connector or the microphone or the on/off switch. The external battery covers the hole for the reset switch.   To reset, either move the external battery or open the plastic case and press the reset button.
iPod 60GB 80GB video battery - This larger battery (about 8X larger the original recorder battery, 8.9 mm thick) is about 850 mAh.  This battery charge will record more than 70 hours.  70 hours is about 4 GB.
iPod 30GB video battery  - This smaller battery is similar but thinner (6.4 mm).  This battery will record about 49 hours which is less than 4GB.

Large battery characteristics
46 x 20 x 8.9 mm approx. battery size.  A convenient size to mount on the side of the recorder . 
7.7 mA - Battery mA while recording.
70.2 hours - Recording time until 4GB was recorded.
540 mAh - The battery discharged from 4.13V to 3.78V over 70.2 hours at about 7.7 mA, or about 540 mAh.  This did not completely discharge the battery.
The battery comes with a flat cable that must be removed (unsoldered).  The battery has 3 terminals.  The center terminal (internal thermistor) is unused.  Fully charge the battery before use.  Mind the polarity.
USB Audio Recorder #1 Modified with Large Battery
External 850 mAh battery.  #1 Recorder wires are soldered to the protection circuit on the battery.  The center battery terminal is unused.  Internal battery is removed.
850mAh LiPo protection circuit
850 mAh battery protection circuit.  Center battery terminal is unused.  Note chips on the battery side of the protection circuit.
USB Audio Recorder #1 Modified with Large Battery

USB Audio Recorder #1 Modified with Large Battery
850 mAh battery attached to #1 recorder with double sided foam tape.  Hole cut for wires to enter the recorder plastic case.  Black electrical tape for insulation.

120227 Version #1 USB Audio Recorder
USB Audio Recorder Package
USB audio recorder package  - Note that the packaging is for a generic thumb drive, not a battery powered audio recorder.

Olympus audio recorders are great (see this table), but if you want something much simpler, smaller, lighter and cheaper then consider this recorder.  This small 1/2 oz product successfully hides a 10 hour audio recorder in a functioning 4GB USB thumb drive.  With one battery charge, a person could record most of their working day with this in a shirt pocket, or a student could record a week of classes.  The plastic construction is weak and might come apart if dropped on the floor, the USB performance is not the best but the audio quality is surprisingly good.

Here is a 23 second (380KB) sample audio file from this recorder.

Recorder - There is a simple elegance to the on off switch control of the recorder.  It has none of these extras: speaker, headphone jack, LCD, playback buttons, memory card or external batteries.  Switch it on anytime you want to record, and off when you don't.  Record up to 10 hours on one charge.  Charge it again and record another 10 hours, up to about 70 hours of audio storage. 

Thumb drive - The internal flash memory holds the recorded audio WAV files and any other files you want to store.  The class 4 performance is not the fastest but adequate for many purposes.

Operation when not USB connected - start a recording by moving the switch to on.  After a few seconds a blue LED indicates recording.  Stop a recording by moving the switch to off.  Each recording creates one to many WAV files.  If the blue LED flashes, that means the battery needs to be charged, or the 4GB memory is full.

Operation when USB connected - the red LED means the battery is fully charged and a flashing red LED means the battery is charging.  The device installs as a disk drive.  The audio WAV files are in the RECORD folder.

The recording blue LED is barely noticeable in a bright indoor room.  However, in an unlit room, the blue LED light fills the room like a nightlight.  To reduce the LED brightness you can open the case and cover the LED, or cover the outside of the case where the LED is.

Note - If the switch is in the on position while disconnecting the USB, recording starts, and this could unintentionally run down the battery.

HOW TO BUY - After I posted this review the seller I bought from raised the delivered price from US$16.79 to US$48.79.  Ridiculous.  Other sellers still have reasonable prices.  I don't know if every USB audio recorder that looks like this device has the same recording capacity or electronics.  You can't always trust the descriptions on eBay.  This recorder does not have a brand name or model number, so you need to buy it by description from a seller who will accept returns if it does not work like as advertised, or like the device described here.

WHO SELLS IT - It is sold by many online retailers, and the case comes in different colors and shapes.  Here are some search links to eBay sellers:
4GB recorder 70USB audio voice recorder4GB USB audio recorder
I don't recommend any seller or sellers.  The buying risk is totally yours.  The 4GB device I bought is priced from US$14 to US$150!.  Also available in 8GB.  I  ordered my USB 4GB audio recorder from a US eBay seller.  Delivery from US to US was 6 days for about US$18.  Can be purchased from a China eBay seller for about 20% less, but expect a longer delivery time.


Because of the misinformation and missing information in the eBay listing it is difficult to understand what this product is and what it does.  That is why I wrote this review.
Misinformation Truth
70 hours The fully charged rechargeable battery will record for about 10 hours (9.8 hours empirically) and the memory will store about 70 hours of audio (69 hours empirically).
digital Mp3 voice recorder. 
Record and Music Formats WMA.
Records in WAV format, not MP3, not WMA.
Telephone recording function Does not exist
This voice recorder contains a speaker, also work good for you.
Loudspeaker Yes.
No speaker


If the battery has a full or partial charge, the on off switch can be used to record audio.  If the battery is discharged, the on off switch does nothing.  When not connected there is no way to list, delete or listen to recorded audio files.

A RECORD folder is created in the root.  Filenames are of the format REC001.WAV, REC002.WAV, etc.  The file date time stamp is not settable, and not very usable or accurate.  For example the first file date time stamp is 2000 Jan 01 12:01:02 (created) to 2000 Jan 01 03:23:06 (modified) but the actual playback time is 239:10.


Move the switch to on.  After a a few seconds delay the red LED goes on for a few seconds.  Then red LED goes off and the blue LED goes on and audio recording begins.  While recording the blue LED stays on.  Because of this long startup time it might be impractical to use this as a memo recorder.

TO END RECORDING - There are 4 ways that a recording can gracefully end.

1) Switch off - Recording terminates when the switch is moved to off.  The blue LED goes off and the red LED goes on and recording terminates. After a few seconds the red LED goes off and the WAV file is closed.

2) The battery charge runs out - Recording terminates when the battery charge ends (empirically the battery drops to about 3.5V).   Exactly what happens with the red LED was not observed.  The blue LED goes off and the WAV file gets closed.

3) The flash memory free space runs out - Recording terminates just before the flash memory free space runs out.  The blue LED goes off and the red LED lights for a few seconds.  Then the red LED goes off and the blue LED flashes for about one minute then the blue LED goes off.  The WAV file is closed.

4) The recorder is plugged into a USB port - With the switch still on, the blue LED goes off and the recording terminates and the WAV file is closed.  The red LED goes on for a few seconds then goes off.  While USB connected the recorder does not record even if the switch is on.


Unconnected to connected - The USB audio recorder will install on any computer (MAC, Windows, Linux) as a mass storage device.

Connected -
While connected the on off switch is disabled and you can't record.  The thumb drive is a generic mass storage device that can read and write your files as well as the WAV audio files created by the recorder.  With the host computer (i.e. Windows, Apple, Linux) the WAV files can be listed, copied, moved, deleted or played with a media player.  The battery charges through the USB.  The red LED flashes while charging.  When fully charged the red LED stays on.  Unfortunately, the red LED stops flashing before the battery if fully charged.  Keep charging for [unknown] minutes until fully charged.

Connected to unconnected -
Keep the switch off.   If the switch is on when the USB is disconnected, recording will immediately start (probably unintentionally) and that will run the battery down.

Version #1 METRICS
Vbatt = battery voltage)
Audio file, format  WAV files in IMA ADPCM format. 128kbps.  16000 Hz sampling.  Mono but two channel.  No automatic volume control.

Other KMPlayer information for a 230,406,656 byte (240 minute) WAV file:  Endianness : Little, Codec ID : 11, Codec ID/Hint : Intel, Bit rate mode : Constant, Bit depth : 4 bits, Stream size : 220 MiB (100%)
Audio file, size limit The recorder limits the size of each WAV file to 4 hours.  Empirically 239 minutes 10 seconds.  About 230.4E6 bytes.  If a file reaches the limit it closes the WAV file and starts another WAV file. The time gap between files is [unknown].
Audio file, data rate 128000 bits per second.
16000 bytes per second.
960000 bytes per minute.
58 megabytes (57.6E6 bytes) per hour. 
4GB (3.99E9 bytes) per 69.4 hours.
Audio file, filenames Folder in the root: RECORD.  Filenames:  REC001.WAV, REC002.WAV, ...
Audio file, file count limit  999 WAV files.  REC001.WAV to REC999.WAV.
4GB mass storage device, capacity The Windows 7 formatted memory capacity is 3986644992 bytes, empirical.  YMMV.
Recorded used file size limit The recorder stopped recording at 3985113088 used bytes, empirical.  That is 99.96% of memory capacity.  YMMV.
Recording time on one battery charge 9 hours 51 minutes (9.85 hour) empirical when new.  YMMV. 
Vbatt release voltage. When the battery protection circuit releases  the LiPo. 4.31V
Vbatt while charging when the red LED changes from flashing to on. 4.24V
The battery module continues to charge until the Vbatt release voltage.  There is no indication to know that this release happens.  So, to fully charge the battery it must remain connected for [unknown] minutes after the red LED stops flashing.
Vbatt standby after USB disconnect and after the red LED stops flashing while charging. 4.13V
Vbatt at the end of one battery discharge and USB disconnected 3.51V
Many LiPo devices do not operate below 3.6V. LiPo voltage drops off rapidly below 3.5V. 
Battery charge current when Vbatt is 4.24V 65 mA
Battery current draw while audio recording 7.7 mA
When starting a recording, the red LED is briefly on and the current is briefly 20 mA.  This might be while the processor is accessing the flash memory chip to create a WAV file and opening it for write.  Also, periodically the current spikes briefly to about 15 mA, probably while writing the WAV file.
Battery current draw while standby (switch off, USB not connected) 21 µA
Battery charge life hours in standby About 6 months based on the battery mAh and the standby current.  To keep the battery healthy, best practice is to charge the battery every few months, if the recorder is unused.
Battery mAh 100 mAh (guess).  Unknown because it is not marked.  The battery seems similar to a 100 mAh Hyperion LG325-0100-1S-UM, 30.8x10.7x5.5, 3.22g, but the Hyperion might not fit.  See this list of polymer battery sizes  and  another list.
Battery size 4.1 x 14 x 32 mm
Battery weight 2.6 g
Dimensions 2.8x0.9x0.4 inch (71x22x10 mm) with cap.  2.7 inch (68 mm) without cap.
Weight 12.40 g with cap.  11.24 g without cap.  7.16 g internal electronics and battery.
Flash memory performance Measures about class 4 speed.  After a full re-format, Crystal Disk Mark benchmark:
Sequential Read :    16.192 MB/s
Sequential Write :    3.479 MB/s
Random Read 512KB :  16.100 MB/s        
Random Write 512KB :  0.822 MB/s

The plastic case is made of two halves that press together, plus the end cap.  The on off switch is captive.

120227 - #1 Modification Ideas

Any modification should only be attempted by someone experienced with advanced electronics and the dangers of LiPo batteries.  Any modification must be fully bench tested for safety.  Any replacement LiPo MUST have a protection circuit.

Replace the internal LiPo battery with an external 700 mAh (or larger) LiPo battery mounted on the back of the thumb drive.  This should permit about 70 continuous hours (about 3 days) of audio recording.

Remove the plastic case, replace the battery with a 700 mAh (or larger) LiPo and mount it in an enclosure for about 70 continuous hours of audio recording.

To reduce the brightness of the LED, open the case and cover the LED with a piece paper.  Post-it-note paper works and holds in place.

120227 #1 Internal Photos
USB audio recorder cap off with ruller for size
Size without end cap.  

USB audio recorder internal
Version #1 USB audio recorder button side.
Label - PCB Labeled "USB RECORDING V1.2".  
Hynix H27UBG8TATR - Memory Flash NAND 32 Giga bits (4GB). 
Actions ATJ3315 - Multimedia SOC. 
Reset switch. 
Electret microphone. The 2R2 (2.2 ohm) resistor and two S4 diodes are probably part of the charging circuit.

USB audio recorder internal battery side
USB audio recorder battery side.
LiPo battery (not marked for size or mAh). 
Electret microphone. 
Crystal (can) is marked 24.000 (probably 24 MHz).
On off switch.

120709 #2 Internal Photos
USB audio recorder version 2
USB Audio Recorder #2 - button side.  Samsung K9GBG08U0A - Memory Flash NAND 32 Giga bits (4GB).   Actions ATJ3315 - Multimedia SOC.   Reset switch.  Electret microphone. The 2R2 (2.2 ohm) resistor and two S4 diodes are probably part of the charging circuit.
USB audio recorder version 2
USB Audio Recorder #2 - battery side.  Labeled DR - U1580-Board - V1.1 2011-11-21.  Double-sided sticky tape holds the battery to this side.  Removing the battery can and will lift the crystal so be prepared to re-solder the crystal (not an easy task).  Electret microphone.  Slide switch.  LiPo battery is not marked.

#1 Users manual , USB audio recorder, from the seller
USB audio recorder manual
Version #1 USB audio recorder manual Page 1
USB audio recorder manual
USB audio recorder manual Page 2

Modification, Larger Battery
CAUTION - Any modification should only be attempted by someone experienced with advanced electronics and the dangers of LiPo batteries.  Any modification must be fully bench tested for safety.  Any replacement LiPo must be bench tested to verify it has a working  protection circuit.
You must bench test any replacement battery to verify it has a protection circuit and it works to release the battery at high voltage (about 4.31V to 4.36V).  If a replacement battery does not have a protection circuit (many do not) you must supply a protection circuit or reuse the protection circuit from the original battery.  The protection circuit prevents over-charging the LiPo when USB connected.  Overcharging could result in a fire, explosion, injury or death.
USB audio recorder, larger battery702045 LiPo battery module with flat cable. White label removed.
This modification increases the record time on one battery charge to more than 49 hours.  It removes the original internal small LiPo battery module and replaces it with a external large (702045) LiPo battery module.

120322 Testing stopped -
Conclusion: The 702045 battery records for about 5 times a long (about 49 hours) as the original battery (about 10 hours).  The recorder stopped recording when the battery ran out.  Still free space on the flash memory.  Thirteen WAV files produced, (12 * 4 hours) + 1.426 hours.  Recorded for more than two days (49 hours, 25 minutes, 34 seconds = 49.426 hours).  Final battery voltage: 3.49V.

120320 Started testing - Charged the 702045 battery to 4.28V.  Started recording with the 702045 battery.  This will take a few days, then I will publish the results.

702045 battery module (usually means 7.0x20x45mm).  iPod video 5G 30GB/60GB battery module.  White label says Part 616-0229, 4265007XA 3,7V 580mAh.  Remove the white label and the battery is labeled NY702045BH 400mAh.  Empirical measurements 6.4 x 21 x 49mm, 11.22 grams (4.3 times heaver than the original battery).  My 702045 has a protection circuit and disconnects the battery at 4.36V, bench measured.  Link to sellers of this battery on eBay.  It has a flat cable, a protection circuit and a LiPo battery.  Here is a video about how this battery is installed in an iPod.

For this modification the battery flat cable was removed (un-soldered). There are three solder connections.  The middle connection is for the battery internal thermistor (nominal 10K to ground) and can be ignored.  Some sellers claim this larger battery is 900 mAh to 650 mAh (probably misinformation), the white label on my battery claims 580 mAh and under the white label my battery is stamped 400 mAh (based on weight it is probably about 550 mAh).   I evaluated hundreds of LiPo batteries and chose this one to test because it fits nicely on the outside of the case, is inexpensive (about US$5), is widely available and is much larger than the original.

The larger battery was at 4.28V when I stopped charging it.  That is charged enough to begin testing.  Based on the 2.2 ohm resistor and the S4 diodes on the recorder PWB, the charging circuit seems to be dumb (does not switch from constant current then constant voltage).  More research is required.

USB audio recorder original and larger battery
702045 battery with battery flat cable removed.
Original battery.
#1 USB audio recorder switch side with paper covering the LED to reduce brightness.
USB audio recorder test with larger battery
Testing 702045 battery mounted outside the #1 USB audio recorder.

Olympus Digital Audio Recorders Compared

120200 This table compares the longest recording on a single battery charge.  This table was constructed from information on the Olympus digital audio recorder page,  Some models might be obsolete.  All metrics are subject to change.

Olympus model MSRP
USB? Hours of recording on one battery charge,
VN-7200 $50 86  
VN-7100 $30 86  
DP-201 $35   80  
VN-702PC $60 USB 72 120629 - US$40 at Costco store, not website.
VN-701PC $50 USB 72
DP-10 $35 63  
VN-801PC $50 USB 51  
VN-8100PC $60 USB 51  
VN-8000PC $50 USB 51  
VN-7000 $40 39  
DP-2400 $300 USB 32  
WS-600S $80 USB 25  

120712 - Added threshold comments about #2.  Not recommended.
120709 - Add internals photos of #2
120629 - Costco price for VN-702PC $40
120414 - Documenting #1 and #2 differences.  Add Olympus DP-201 recorder.  Add version specific features table.
120412 - Testing #1 with large external battery.
120328 - There are multiple versions of this USB audio recorder.  I received another USB audio recorder which I will call version #2.  The original recorder will be version #1.  The shape of the plastic cases are identical but different color. More testing and photos will be posted. They both record WAV ADPCM.  Circuit boards are different.
#1 - White and blue case.  The PWB is labeled "USB-RECORDING-V1.2".   Records 128 Kbps 16000 Hz sampling.

#2 - Black and silver case. The PWB is labeled "DR-U1580-Board-V1.1  2011-11-21".  Records 192 Kbps, 48000 Hz sampling.

120326 - The battery charge indicator (red LED) is not accurate.  Documented the protection release voltage and charge current.

120325 - Verified 702045 battery has a protection circuit.  Measured standby current, recording current and calculated approximate standby battery life.

120320 - Adding Modification, Larger Battery.

120308 - Removing the name of the eBay seller who raised the price by 190% after I wrote this review.

120227 - This page online.



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