In this article I take a look at TU04 USB audio mixer, also known with many other names names like Teyun A4. This mixer can be found on many discount sites like AliExpress, Banggood, DHgate and Wish.com at low price ($30-50).
For the price this audio mixer seems to offer quite a lot of features: two microphone channels, effect processor, USB connectivity to PC. MP3 playback from USB stick and Bluetooth connectivity. Teyun A4 is amazing for this price! Of course, there are a few limitations that you’ll encounter with this mixer.
Basic mixer operation is straightforward in use. The build-in Bluetooth and phantom power are good features. And all this in a portable form factor: small and light. I believe that this mixer is a great grab if you can find it at the right price and are prepared to accept the limitations. For the money it work great as an interface and OK as a mixer.
For your inputs you have an XLR & 1/4 inch mono plug combo jack on both inputs 1 and 2. Those are mono inputs. Those mic inputs support 48V phantom power, so they can be used with microphones that need phantom power to work.
Inputs 3 and 4 are actually a single stereo input that has RCA and 6.3 mm jacks. The 6.3 mm jacks are unbalanced.
The main audio output is 6.3 mm jacks that give out unbalanced signal. There are also RCA output for connection to recording device.
The mixer can take two mono microphones and one stereo sound source (line, MP3, USB or Bluetooth) which it can mix together to one stereo output.
Teyun A4 can act as a Bluetooth receiver. This allows you to to have a wireless audio connection from your smart phone or tablet to this mixer. You can for example play back music with your smart phone, and get the audio to the mixer without connecting any wires.
The mixer has an USB connector for you to plug an USB memory stick to your mixer. This USB stick connector is designed mainly to allow you to play back MP3 files from your USB memory sticks. That MP3 playback worked well wit some random MP3 files I tried for testing. The playback promised so support file formats MP3, WMA, WAV and FLAC (though I have only tested MP3).
In addition to the playback, this mixer also allows you to record audio directly to a USB flash drive. In my tests first the recorded audio was stored to JL_REC directory on the USB stick with filename FILE0000.MP3. The created file was mono audio sampled at 48 kHz sample rate and encoded to MP3 format (MPEG Audio layer 1/2) at bit rate of 128 kbit/s. At least in theory you use this mixer with a power bank and flash drive together as a cheap field recorder.
This mixer has quite flexible powering options because it is powered through USB connector. You can power it from computer USB port, practically any USB AC adapter like phone charger or with a rechargeable USB power bank. On my tests the mixer took around 350-400 mA current from 5V USB power when powered on and not doing anything special. When I added USB drive for MP3 playback, the mixer took around 450 mA of current. When I added one phantom powered microphone and shouted to it, the mixer took up to around 820 mA from 5V USB power.
This mixer lacks proper manual. The supplied manual is just a small 2-page flyer telling you what every buttons function is, but it doesn’t really explain well how to use different advanced functions and what are the limitations in using them. Fortunately I found some extra documentation on-line.
I should note that while the XLR inputs claim to have phantom power, it’s not true 48V. One review said that phantom voltage was between 38V and 40.5V. In my own testing I measured only 30-31V phantom voltage on the mic connectors with no microphone connected. Even though the voltage is a bit low, though that is more than enough juice to drive most condenser mics.
There are a few audio signal input limitations that you’ll encounter with this mixer. First, channels 1 and 2 are center pan mono, so you can’t isolate the mics for editing in post. Second, every analog input other than XLR is incredibly quiet so that your signal source should have strong signal coming toward the mixer. There is just a single stereo input that handles both analog (using left and right RCA plugs or 1/4 jacks 3 and 4) as well as your digital inputs (Bluetooth, PC audio, and audio playback from a USB thumb drive).
The digital functionality is pretty much either-or-game with available options. From the digital options (Bluetooth, PC audio, and audio playback from a USB thumb drive) you can only use one of them at one time. So whatever you do, you need to choose which of the following functionality you choose to use (you can pick only one at one time): Bluetooth, MP3 playback, recording to USB stick or USB connection to PC.
The audio processing options are pretty basic. There are basic high and low frequency boost/cut controls for inputs, but that’s all (lacking the ability to tweak the mid tones). The effect processor (EFX) is pretty limited.
USB drive limitations: You will need to create several files on a clean usb drive before it will play music or record your audio. Things worked OK after I copied few MP3 files to the USB drive before attempting to record to an old 8 GB flash stick. It might not record to all currently sold USB drives and won’t connect to an external hard drive.
Bluetooth connectivity is only for playback from smart phone to the mixer. You can’t use Bluetooth to get your mix to your smart phone.
The USB stick can be used at one time only for playback or recording (not both at once). You can’t use USB stick at the same time with PC connection.
There is no power on/off switch on this device. To power down the mixer, the user needs to disconnect the USB cable (or disconnect the external USB power supply from mains).
The device has somewhat cheap plastic feel.
On my first tests it seems that the audio connection from the mixer to the PC seems to be actually mono – the PC gets stereo signal, but it seems that both audio channels get exactly the same audio signal.
Here are some review videos:
Under $40 USB Mixer from Wish.com Review + Test | A4 Mixer Review | Budget Tubing Ep. 7
USB Mixer Under $40 from Banggood.com Review + Test | A4 Mixer Review |
Mixer Teyun A4
Best A4 Sound Mixing Console with Bluetooth Record 48V Phantom Power Monitor Review
A4 Multi purpose Audio Mixer with Bluetooth Record
Best A4 Sound Mixing Console with Bluetooth Record 48V Phantom Power Monitor Review
Unboxing cheap Chinese trusiner A4 4 channel line mixer with usb recording under 50 dollars
Product review pages:
Instructions for use:
The web page https://www.aliexpress.com/item/32848540712.html?af=1583447&cv=30712828&cn=43q54o9omw9v26pgw0kdvuqgagj83b1b&dp=v5_43q54o9omw9v26pgw0kdvuqgagj83b1b&afref=https%253A%252F%252Fwww.youtube.com&aff_request_id=416be80d52b1466b9769db9e9bdda9e4-1580736733165-02512-m2TOU8NK&aff_platform=api&cpt=1580736733165&sk=m2TOU8NK&aff_trace_key=416be80d52b1466b9769db9e9bdda9e4-1580736733165-02512-m2TOU8NK&terminal_id=a4bbc8d96cd144f890e0036f69e2522e includes good instructions how to use different advanced mixer functionality (MP3 playback, Bluetooth, USB recording, USB connection to computer). I managed to get a print-out of that. Here are pics of the most important parts of instructions with comments:
I got a phantom powered microphone working nicely as shown in the instructions. The instructions for MP3 playback works also OK. The MP3 controls allow adjustment of volume (which can also be done with channel controls), go back and forth between songs (but not fast forward within song), pause and continue playing. Features work as shown. The switch next to the micro-USB connector needs to be in the “MP3″ position.
The Bluetooth instructions worked pretty much as as shown but instead of “blue” text my mixer showed text “bt” on the display. My smart phone showed the mixer as “MIXING BT” Bluetooth device and connected to it nicely for audio playback. The switch next to the micro-USB connector should be in the “MP3″ position.
Connect to computer worked as shown. The mixer shows as USB sound card to the computer. For connection to work the switch next to the micro-USB connector needs to be in the “PC” position. The mixer shows as speaker “JieLi BR21″ and microphone “JieLi BR21″. My computer shows the microphone and speaker to be 2 channel 16 bit at 48 kHz sample rate.
The effect settings allow to add a pretty basic echo/delay type effect to the microphone channels. The EFX button needs to be pressed down for the effect to be turned on for a specific microphone channel.
This mixer also allows you to record audio directly to a USB flash drive. For the recording to work you need to have an USB stick that is supported by the device (I had old no name 8 GB stick) and the stick needs to have some data on it (I had some MP3 files in the USB stick root). When recording was activated, the recorded audio was stored to JL_REC directory on the USB stick with filename FILE0000.MP3. The created file was mono audio sampled at 48 kHz sample rate and encoded to MP3 format (MPEG Audio layer 1/2) at bit rate of 128 kbit/s.
Record to computer worked also nicely for me with Audacity software.
Home karaoke setup with recording using a line mixer
Recording Sound Mixing Console mixer with USB Digital Mixer Bluetooth
BM–800 Microphone and Teyun Bluetooth Mixer
I have decided not to do a full tear-down of my working mixer. Here is a video that I believe to be an accurate view on the electronics inside this mixer. It was pretty much what I expected it to be. NOTE: The end o the video seems to show a modification to the mixer (added extra USB power connector and power switch).
A4 inside view
I believe that this mixer is a great grab if you can find it at the right price and are prepared to accept the limitations it has. For the money it seems to be great as an interface and OK as a mixer.
Banggood.com sells similar mixer at the following addressed (affiliate links): https://www.banggood.com/4-Channels-USB-Portable-Mixer-Bluetooth-Record-Live-Studio-DJ-Audio-Mixing-Console-p-1403458.html?p=27131452996820140438 and https://www.banggood.com/Teyun-A4-4-Channel-bluetooth-4_0-Audio-Mixer-Mixing-Console-Sound-Card-48V-Phantom-Power-p-1553857.html?p=27131452996820140438