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S.M.S.L PO100, PO100 PRO & PO100 AK - Measurements (Digital Interfaces & DAC)

I'm returning my SMSL PO100 (2024 edition) because something is not ok. I get very low digital output level - I can barely hear the music when amplifier is cranked up to 100%. Tried with different sources (Macbook Pro and Google Pixel 8 Pro), also different outputs (Optical and Coax). Has anyone else experienced this?
 
I'm returning my SMSL PO100 (2024 edition) because something is not ok. I get very low digital output level - I can barely hear the music when amplifier is cranked up to 100%. Tried with different sources (Macbook Pro and Google Pixel 8 Pro), also different outputs (Optical and Coax). Has anyone else experienced this?
Have you checked the software volume control? The volume for my PO100 is reduced right down low each time I changed it to a different USB port (both in Windows and Linux).
 
Have you checked the software volume control? The volume for my PO100 is reduced right down low each time I changed it to a different USB port (both in Windows and Linux).

Yes, I did check - changing the volume on the MacBook Pro or the phone does not have any impact on the output
 
Weird. PO100 and MacBook Plus volume works fine here with my JDS Labs Atom 2 DAC (connected to Atom 2 amp).
 
Yes, I did check - changing the volume on the MacBook Pro or the phone does not have any impact on the output
This is actually strange.
You have to check the volume setting of both the system and the software you are using to play the music.
 
This is actually strange.
You have to check the volume setting of both the system and the software you are using to play the music.
The sound is very low on both the phone and fiio m11 plus Qobuz and apple music.
 
I recently discovered that a firmware update (V3.84) is available for the PO100. According to the changelog, it addresses the low volume issue:

Unfortunately, I encountered problems trying to update using the "XMOSUSBDACfu" tool. It throws errors about a missing driver DLL.

Has anyone successfully updated the firmware for the PO100?
 
I recently discovered that a firmware update (V3.84) is available for the PO100. According to the changelog, it addresses the low volume issue:

Unfortunately, I encountered problems trying to update using the "XMOSUSBDACfu" tool. It throws errors about a missing driver DLL.

Has anyone successfully updated the firmware for the PO100?
just ask them? They got even amazon support
 
The sound is very low on both the phone and fiio m11 plus Qobuz and apple music.
same behaviour on any device I test with Tidal and Spotify
At the moment I am assuming that the PO100 of your two is not defective, but has a fixable problem. It seems that a reduced low volume setting is not being reset.
There are several very similar reports, e.g. from WiiM Ultras with the same problem (solved).
That would also explain the new firmware.
Bildschirmfoto 2025-01-01 um 16.01.50.png


@alfaowner
The text files including the error codes are in the subfolder XMOSUSBDACDfu.strings. Maybe you will find something useful in them.

 
Okay, I finally figured out how to update the firmware, and I can now confirm that the update resolves the low volume issue. Here are the instructions:

Prerequisites:
  • PC running Windows 10 or later
Step-by-Step Firmware Update Instructions:
  1. Connect your SMSL PO100 2024 to the PC using the provided USB-C cable.
  2. Open Device Manager on your PC, locate the SMSL PO100 device, and uninstall any previously installed drivers by right-clicking the device and selecting "Uninstall Device."
  3. Download the latest Windows driver for SMSL PO100 2024 from the SMSL website:
    https://www.smsl-audio.com/upload/portal/undefined/SMSLUSBAudioDriver.zip
  4. Extract the ZIP file and install the driver "XMOS_USBAudio_v5.70.0_2024-11-08_setup"
  5. Download the latest firmware (v3.84) and update tools for SMSL PO100 2024 from this link:
    https://www.smsl-audio.com/upload/portal/undefined/PO100FW384.rar
  6. Unzip the downloaded file
  7. Open the firmware update tool named "XMOSUSBDACDfu" from the "XmosUSB" folder inside the extracted archive.
  8. In the update tool, select the firmware binary file named "PO100_MQA_3.84.bin" that is included in the extracted files.
  9. Click "Start" in the tool and wait for the update process to complete. Do not disconnect the SMSL PO100 2024 during this step.
  10. Once the update is finished, click "Exit" to close the firmware update tool.
Now you can connect the SMSL PO100 to your phone or any device you want to test it with. Make sure the volume is all the way up on your phone or computer to get the full output. Hope this helps!


Before the update (in v3.83), the SMSL PO100 2024 had volume control in the control panel, and it was set to -40dB by default.

smsl_po_100_volume.png



After the update, the volume controls are now removed from the control panel, and I assume it is now fixed at 0dB.

smsl_po_100_after_update.png


Unfortunately, after the update, there is still an issue when streaming at 96kHz, from time to time, the soundtracks stutter with Pixel 8 Pro & Tidal. There is no stuttering when playing at 44.1kHz or 48kHz.
 
Last edited:
Okay, I finally figured out how to update the firmware, and I can now confirm that the update resolves the low volume issue. Here are the instructions:

Prerequisites:
  • PC running Windows 10 or later
Step-by-Step Firmware Update Instructions:
  1. Connect your SMSL PO100 2024 to the PC using the provided USB-C cable.
  2. Open Device Manager on your PC, locate the SMSL PO100 device, and uninstall any previously installed drivers by right-clicking the device and selecting "Uninstall Device."
  3. Download the latest Windows driver for SMSL PO100 2024 from the SMSL website:
    https://www.smsl-audio.com/upload/portal/undefined/SMSLUSBAudioDriver.zip
  4. Extract the ZIP file and install the driver "XMOS_USBAudio_v5.70.0_2024-11-08_setup"
  5. Download the latest firmware (v3.84) and update tools for SMSL PO100 2024 from this link:
    https://www.smsl-audio.com/upload/portal/undefined/PO100FW384.rar
  6. Unzip the downloaded file
  7. Open the firmware update tool named "XMOSUSBDACDfu" from the "XmosUSB" folder inside the extracted archive.
  8. In the update tool, select the firmware binary file named "PO100_MQA_3.84.bin" that is included in the extracted files.
  9. Click "Start" in the tool and wait for the update process to complete. Do not disconnect the SMSL PO100 2024 during this step.
  10. Once the update is finished, click "Exit" to close the firmware update tool.
Now you can connect the SMSL PO100 to your phone or any device you want to test it with. Make sure the volume is all the way up on your phone or computer to get the full output. Hope this helps!


Before the update (in v3.83), the SMSL PO100 2024 had volume control in the control panel, and it was set to -40dB by default.

View attachment 417847


After the update, the volume controls are now removed from the control panel, and I assume it is now fixed at 0dB.

View attachment 417848

Unfortunately, after the update, there is still an issue when streaming at 96kHz, from time to time, the soundtracks stutter with Pixel 8 Pro & Tidal. There is no stuttering when playing at 44.1kHz or 48kHz.
It's not that you would hear a difference switching to 96kHz, right?
 
It's not that you would hear a difference switching to 96kHz, right?
I'm sure everyone would hear a difference at 96kHz if it stutters.
 
Just for everything outside of what you can hear, it wouldn't be audible
 
you can replace that value with the threshold of your hearing, though and it still is true.
Just for everything outside of what you can hear, it wouldn't be audible
If the playback jerks or stutters, every hearing threshold and every value is irrelevant.
Perhaps you should read what it was about again. You quoted it.
Unfortunately, after the update, there is still an issue when streaming at 96kHz, from time to time, the soundtracks stutter with Pixel 8 Pro & Tidal. There is no stuttering when playing at 44.1kHz or 48kHz.
 
@Roland68 great. So we both agree that the comment about jerks or stutters is irrelevant to my comment.
There's for certainty no real need for a frequency above the standard 48kHz unless the extra headroom is required for engineering tasks.
 
Okay, I finally figured out how to update the firmware, and I can now confirm that the update resolves the low volume issue. Here are the instructions:

Prerequisites:
  • PC running Windows 10 or later
Step-by-Step Firmware Update Instructions:
  1. Connect your SMSL PO100 2024 to the PC using the provided USB-C cable.
  2. Open Device Manager on your PC, locate the SMSL PO100 device, and uninstall any previously installed drivers by right-clicking the device and selecting "Uninstall Device."
  3. Download the latest Windows driver for SMSL PO100 2024 from the SMSL website:
    https://www.smsl-audio.com/upload/portal/undefined/SMSLUSBAudioDriver.zip
  4. Extract the ZIP file and install the driver "XMOS_USBAudio_v5.70.0_2024-11-08_setup"
  5. Download the latest firmware (v3.84) and update tools for SMSL PO100 2024 from this link:
    https://www.smsl-audio.com/upload/portal/undefined/PO100FW384.rar
  6. Unzip the downloaded file
  7. Open the firmware update tool named "XMOSUSBDACDfu" from the "XmosUSB" folder inside the extracted archive.
  8. In the update tool, select the firmware binary file named "PO100_MQA_3.84.bin" that is included in the extracted files.
  9. Click "Start" in the tool and wait for the update process to complete. Do not disconnect the SMSL PO100 2024 during this step.
  10. Once the update is finished, click "Exit" to close the firmware update tool.
Now you can connect the SMSL PO100 to your phone or any device you want to test it with. Make sure the volume is all the way up on your phone or computer to get the full output. Hope this helps!


Before the update (in v3.83), the SMSL PO100 2024 had volume control in the control panel, and it was set to -40dB by default.

View attachment 417847


After the update, the volume controls are now removed from the control panel, and I assume it is now fixed at 0dB.

View attachment 417848

Unfortunately, after the update, there is still an issue when streaming at 96kHz, from time to time, the soundtracks stutter with Pixel 8 Pro & Tidal. There is no stuttering when playing at 44.1kHz or 48kHz.
Thanks, this helped - I have a minimal Windows 10 machine that didn't have appropriate app to handle rar files, so didn't know what to do with them initially :). Installing 7-zip helped.

I am using SMSL PO100 2024 with two bit-perfect players - JRiver Media Player and Tidal. For normal shared mode I use 16bit/44.1kHz setting. Initially I was confused why I am able to still use Windows volume control in exclusive mode (trying to play youtube video while Tidal was in exclusive mode didn't work, which told me that exclusive mode is still active). With the firmware update, this is no longer possible. When I use Windows volume control, it has no effect on exclusive mode sound - it stays at 100% (good!).

I am running an old mini-tower running Windows 10 as my 'under TV' HTPC. USB is converted to SPDIF and sent to Anthem MRX 700 AVR, driving Nautilus 805S speakers (and the matching center, surrounds and subwoofer). I use Audioquest Cinnamon 0.75m USB to PO100, and Audioquest Cinnamon 1.5m digital coax cable to Anthem SPDIF input. I am playing my ripped CDs using JRiver Media Player v31 in exclusive mode (using WASAPI driver).

One interesting thing: JRiver insisted on keeping a 50ms buffer which forced 2048 buffer setting for 44.1kHz (and x2 for 96kHz, x4 for 192kHz). Bigger buffer results in 'weightier' sound in my system - it should not affect the sound but it does somehow. I kept this setting when playing Tidal as well.

I am able to quickly compare HDMI audio (via NVidia RX1030 video card HDMI out via 1.5m Audioquest Pearl 48 HDMI cable) and SPDIF with PO100 2024. HDMI sounds beefier and highs are 'whiter' - signal path over USB -> PO100 -> SPDIF feels 'airier' and with more midrange bloom. Classical and jazz sound amazing, with some well recorded live performances having insanely lifelike instrument timbres. Both Cinnamon USB cable and PO100 are a few days new so I presume they will take more playing to 'break in' and settle into the final sound signature.

Side note: I know, bits are bits, but ears tell me they don't seem to be. Since I can flip from HDMI to USB/SPDIF signal path in less than a second, I can hear clear differences. It is the same exact signal flowing into the same AVR in both cases, so there should be NO difference, and yet...
 
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