Blue Yeti MIcrophone Repair

Attempt to repair a Blue Yeti USB Microphone.

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My Sister dropped off a Blue Yeti mic belonging to her son that apparently just didn't work one day.

The Blue Yeti Mic is a USB desk mic aimed at streamers apparently. Seems to get mixed reviews but that's not what Im worried about only that it no longer works.

Reported Fault

  • Just didn't work one day


  • According to the specs it is a stereo mic with headphone out
  • It has settings for
    • Mic Pattern
    • Mic Gain
    • Headphone Volume
    • Mute
  • Testing the mic
  • Would connect and register with Win10 WinXP and OSX
  • No Audio from mic to computer
  • Audio playback worked in 1 channel
  • Audio monitor function worked in 1 channel
  • Mute function worked on Audio monitor
  • Audio monitor works by routing the Analog Audio from the mic to the headphone Amplifier. This is an internal function of the CM6400 USB Audio chip. Mic in Pins 25 and 26 connect to HP out Pins 45 and 48 via an internal analog mixer

Scope showed Audio at both the Mic input L and R pins and THe HP out Pins. The HP audio then goes via a dual gang pot to the headphone amplifier. Only one channel made it through the Headphone pot. Resistance check of the pot confirmed one gang was inoperative - wiper open circuit. Needs a new pot to rectify the headphone audio but not a show stopper at this stage.

The Blue Yeti mikes are well known for broken USB connectors but this does not appear to be the case as physical inspection loks good and the unit does connect to the Computer and driver loads ok.


Timer ic used for mic muting status LED ( blinking)

Adobe Portable Document Format - 1.23 MB - 02/09/2023 at 14:31



Dual inverter gate - used in mic muting circuit

Adobe Portable Document Format - 915.82 kB - 02/09/2023 at 01:30



Single Schmitt-trigger inverter gate - used in mic muting circuit

Adobe Portable Document Format - 1008.20 kB - 02/09/2023 at 01:27




Adobe Portable Document Format - 337.98 kB - 02/09/2023 at 01:25



OP-Amp Mic pre-amp

Adobe Portable Document Format - 627.79 kB - 02/09/2023 at 01:23


View all 9 files

  • 1 × U1 analog board Rev8 MC33178 op-amp for mic pre-amp on analog board Rev8
  • 1 × U1 digital board Rev8C NE555 precision timer IC for mic muting status LED on digital board Rev8c
  • 1 × U2 CM6400 USB integrated audio single chip MCU
  • 2 × U4, U6 SN74LVC1G3157 SPDT Analog Switch for mic pattern switching and mic muting status LED
  • 1 × U5 24LC02B serial I2C eeprom used in conjuction with U2

View all 10 components

  • Firmware

    Saabman02/12/2023 at 10:43 0 comments

    Comparison between Bin Files.

    I was curious that the blue sherpa program detected that there was a firmware update available but what was the difference?

    I happened to take a copy of the firmware before I ran the update using the CM6400 tool so i took another copy using the CM6400 config tool and had a look at the two files.

    The only difference between them was the E in the Revision was changed to a 3

    R3V8 as opposed to REV8

  • EEPROM Contents

    Saabman01/27/2023 at 11:55 1 comment

    Just for interest I had a look at the contents of the EEPROM which holds the config for the CM6400. Using an Arduino UNO and a small sketch from Adafruit to read the EEPROM and send to the PC via Serial. The result looks like this. 

    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 4d
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 4d
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 4d
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 4d
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 4d
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 4d
    ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
    ff ff ff 

     I was expecting more. Maybe my code for reading the EEPROM is not right Ive never read an EEPROM before so possible issues in the Arduino sketch may be to blame. I might come back to this later.

    In order to read the EEPROM I lifted the SDA AND SCL lines of the EEPROM and noted when trying the mic out it still connected happily to the PC and audio out worked fine but noted that the mic through to headphones with in the Blue Yeti no longer worked. The Mic shows up as a generic USB Audio device rather than a blue Yeti as expected and the PID is also different.

  • Data sheet woes

    Saabman01/25/2023 at 20:34 0 comments

    In looking through the data sheet I just felt something was missing and while contemplating the data stored on the EEPROM I noticed that chapters 5 and 6 are missing from the datasheet available from the Manufacturer :(

    All the good stuff is missing....

    Ok The Data sheet on CMedia website is missing the good stuff but the one here

    has it all

  • USB Capture

    Saabman01/24/2023 at 11:01 0 comments

    I thought it would be interesting to have a look at what the data stream looked like between the Yeti and the PC.

    So I fired up Wireshark and selected the USB port and well if you've never looked at wire shark before its a bit confronting

    I know that audio out works so I set some music playing and selected the Yeti as an output. just watching the Wireshark screen it became fairly obvious what was what.

    A stream of Data like in the above image would show up. The highlighted line is the PC sending a data string 1216 Bytes long to the Yeti. The Highlighted block towards the bottom of the image is the Audio string. With some music playing (Tiffany of Course) its hard to see what is what. So I set Audacity to output a 1 Khz tone firstly to both channels and then just to the left and then just to right. Having a consistent output made it easier to have a closer look at what was going on.

    The Audio string with the tone to one channel looked like this

    Now knowing what the signal is and knowing that it only goes to one channel, in this case the Left it can be easily seen that the signal is interleaved 2 bytes to the left then 2 bytes to the right (as there is no output to the right its value is 00).

    Changing the signal to the Right Channel the order is reversed 00 first and sending the same signal to both channels the the first 2 bytes are the same as the next 2 bytes.

    Now Ive identified what the data string looks like for a given input I set audacity to record from the Yeti and captured the USB data again. Which looks like this.

    The incoming data is just toggling between FF FF and 00 00 at the sample rate for each channel. Next step is to find out a bit more about how the ADC works and determine what conditions would cause such an output - I Think I might be making some guesses as the Data sheet is garbage, there must be a different data sheet provided to purchasers of the CM6400 then is publicly available on their website.

  • Audio format

    Saabman01/22/2023 at 11:00 0 comments

    I ran wireshark while playing with the mic and captured the resulting Data stream. (Ill post the capture later) but that led me down the path of what is the format of the data.

    From the

    Universal Serial Bus
    Device Class Definition
    Audio Data Formats

    it appears that that most likely format is PCM PCM Format
    The PCM (Pulse Coded Modulation) format is the most commonly used audio format to represent audio
    data streams. The audio data is not compressed and uses a signed two’s-complement fixed point format. It
    is left-justified (the sign bit is the Msb) and data is padded with trailing zeros to fill the remaining unused
    bits of the subframe. The binary point is located to the right of the sign bit so that all values lie within the
    range [-1,+1).

  • board and schematic

    Saabman01/18/2023 at 11:09 0 comments

    After poking around on the board for a while tracing out where things go - YES it does use a 555 to flash the mute LED. and muting is done by latching a 4066 QUAD bilaterall switch to disconnect the mic - its not just a bit of code in the controller.

    I noticed on the board "Yeti digital rev8C" hmm I wonder - punch Yeti digital REV8C schematic into duck duck go and find what looks like someone has started to reproduce the board but allas they dont appear to have gotten far .

    Oh well back to grind stone.

  • Blue Sherpa

    Saabman01/17/2023 at 11:44 0 comments

    Blue provide a tool for controlling the Yeti called Blue sherpa

    This allows you to connect to the microphone and adjust the gain and volume settings. While I could connect and adjust the levels from the mic to headphones there was still no audio reaching the PC. So far apart from the Faulty HP Pot the ananlog audio chain appears to be working and the USB connection appears to be good.

    There is some reports that the Blue Yeti does not work well with USB3 ports.  So I tried it on a MACbook pro osx and win 10 and win XP via Parallels VM. a Dell Tablet and a HP windows 10 machine - a mix of USB 2 and 3 ports with no change. I get Audio out but no audio in.

    This is starting to look like the ADC of CM6400 may be faulty or some other internal fault in the chip. But dmage to the chip seems unusual as all the other functions so far appear to work.

  • Firmware update

    Saabman01/17/2023 at 11:16 0 comments

    A great quick video by Mike the Tech shows how to reload the firmware for the mic.

    I gave this a go.

    • download the utilities as described in the video below
    • connect to the mic
    • copy the Firmware
    • upload a default firmware provided by Mike
    • While the process worked flawlessly on windows 10 the mic still wouldn't work

View all 8 project logs

Enjoy this project?



johnny90k wrote 02/04/2024 at 16:03 point

Ive picked up a few Yeti Mics cheap on ebay that have been sold for non working to see if I can fix them up.   Most had USB port issues so easy fixes, but I have one, which seems to work fine, except for the mic.

It recognizes fine in windows, but when using the mic, notta.

Audio does work out of the Headphone jack, however, when the mic is un-muted, has some terrible noise in the right channel.   I checked all the connections to see if could be a bad wire, but everything seems solid.   After coming across this post, i now believe it could be the CM6400 IC

I attempted to "reflash" the firmware on it, but that had no effect on the symptoms.   I went ahead and placed an order on aliexpress for some CM6400 IC's, so when they come in ill do a chip swap to see if this fixes  (Naturally the other 2 mics i do have dont have this chip, but seem to be an older revision which uses a realtek chip)

I will post back to see if this fixes.   Finally an excused to fire up the hot air station!

  Are you sure? yes | no

insanity213 wrote 06/03/2023 at 05:43 point

I have a mic with similar issue to @Justin, heavily distorted audio through USB but the audio sounds fine coming out of the onboard headphone jack.  At least I know the analog board is ok.  I wonder if my CM6400 is half dead, meaning the outputs it routes to the headphone jack are fine but whatever it's putting on the USB data lines is junk?  Any thoughts on the topic would be appreciated!

  Are you sure? yes | no

io nut wrote 09/16/2023 at 12:15 point

Hi and sorry for the late response, but I stopped getting notifications for some reason. If you have already checked the connections on the header as I advised Justin, then your best bet is a faulty CM6400. Just curious if you have tried reflashing the firmware first? There is a guide  for that:

  Are you sure? yes | no

io nut wrote 03/23/2023 at 23:59 point


Just picked up another faulty Yeti, identical to the first one (rev 8), but with a different set of issues: recording only on R channel while L channel completely dead and no sound output through PC via USB or headphone jack.

The analog headphone amp and the mic(s) pre-amp circuits checked out just fine, but the signal stopped at the CM6400 ic. The firmware was NOT corrupted and the mic identified itself correctly to the computer (reflashed it anyway, just in case, but made no difference).

I replaced the CM6400 with a new one and now the Yeti works amazing, just like new !

Saabman, I am curious about your progress and maybe we can brainstorm a little bit to (hopefully) find the root cause of these CM6400 failures ( below grade USB hubs or the missing filtering on the 3.3V rail).

Cheers !

  Are you sure? yes | no

decker9000 wrote 08/02/2023 at 05:31 point

Just out of curiosity, how did you manage to replace the cm6400 IC on the board, it looks a bit intimidating with so many pins

  Are you sure? yes | no

io nut wrote 09/16/2023 at 12:21 point

Yes I agree it might look intimidating if you have no experience with smd rework and the proper tools for the job: rework soldering station + microscope. It is definitely not an entry level of difficulty.

  Are you sure? yes | no

io nut wrote 03/02/2023 at 19:29 point


I can now confirm (my) issues were caused by a faulty CM6400 chip. I have just received a new replacement chip ordered on aliexpress, installed it and the Yeti came back to life as new. No other intervention necessary.

Waiting for Saabman's progress report on his Yeti.

  Are you sure? yes | no

Saabman wrote 03/02/2023 at 21:33 point

Awesome - Im still waiting for my chip to arrive .

  Are you sure? yes | no

mini wrote 01/04/2024 at 22:33 point

Hey can you give some more info on the chip you received? What did you have to do to get it working? How did you flash it?

I received a chip from Aliexpress and soldered it to my Yeti board, but it doesn't show up on my PC. Do I need to take any further steps to get it recognized?

  Are you sure? yes | no

Justin wrote 02/28/2023 at 02:05 point

This is strange, my friend brought me the same mic, his also "stopped working one day" which was yesterday, I hooked it up and have no input detection when setting windows to "listen" mode, but with the gain turned up the mic will pickup a heavy distortion if I yell into the mic and I can hear myself talk but very distorted, the mute is working, intermittently will only pick up 1 channel, sometimes stereo but unless I'm yelling at it it doesn't pickup anything, is this the same issue your having? If you come to a resolution I would love to know. Thank you

  Are you sure? yes | no

io nut wrote 03/01/2023 at 22:54 point

Hey Justin. Saabman and I have different issue(s) and we went through a lot a debugging just to conclude the main IC CM6400 being faulty. We ordered replacements and we're waiting to be delivered. I might have an update tomorrow- fingers crossed.

Yours sounds different (LOL no pun intended :)). First, you should have a close look at the connector header, I have read reports of cold joints creating similar issues with yours.

The header connects the digital board to the analog. Look at it under the microscope, you should be able to spot any bad joints there.

  Are you sure? yes | no

io nut wrote 01/31/2023 at 23:07 point

I find it amazing that 3 different people started tackling the same issue within days of each other: you, myself and hellomacos on ifixit ( I have commented to his original post):

Thanks to google's cr@$ppy search results, I have just found your project page about an hour ago. To my amusement, I have read here about the SPDT right after spending the whole morning trying to identify it based on the muting circuit tied to the 555 timer :)

Anyhoo, I am ready to share my findings along with the diagnostics on my rev 8c board and the experiments I've done with the firmware, hoping we can get to the bottom of the problem.

  Are you sure? yes | no

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