Amplifier MC331 Low Volume cut-off.

[RobotX]

Hi,
I've recently purchased MC331 and wired it to my bookshelf Onkyo SKB-960 130W 8Ohms speakers.
It's connected to my LG TV via Bluetooth, in general it sounded great.
However I've encountered issues where if the source material has a low volume, it cuts of abruptly and create a cliff on the sound.
I've tried increasing the bluetooth volume to max and set the volume to be quite loud in the MC331 it doesn't help.

Here's an example of video clip that demonstrate the issue: (the first 20 seconds of the video where there's fireworks cuts in n out).

Is this a known issue? Is there any fix for it or it's time to move on to a different bluetooth Amp?
Thanks in advance.

 

[Fosiuser]

I have the same issue with my mc331 paired with B&W CM1 S2 bookshelf speakers. Very bad cut offs on especially classical music and anything with low volume parts. Fixed if volume is turned up, but it’s making low volume listening almost impossible. A firmware fix or ideas on how to resolve would be highly appreciated

 

[RobotX]

I'm sure Fosi knew about this issue, but unfortunately they probably already moved onto their newer product. They kept churning newer product one after another that have similar functionality. Highly doubt they'll go out of their way to support past product.

Because of this low volume issue, forget on using this product for desktop DAC, you'll go insane with the audio cut-off.

I've contacted their support, but there's no reply.
I'm past the return window of this product now.
It is very disappointing, but that's the reality.

Using MC331 as a headphones driver also introduce lots of noise, unlike FiiO USB DAC.

I've come to accept that this product has a defect on their design from the get go.
The price didn't break the bank and the audio quality is decent enough to drive the passive speakers.
I just use it to listen to music with stable audio volume and live with it, most likely not buying any more Fosi product in the future.

 

[Drchandru1971]

I have the same issue of low volume how to resolve this any one can help me with Fosi MC 331

 

[Ward000]

Just got one today and immediately found the same issue, wish I saw this thread before I bought it, but I only saw glowing reviews online. It's fine with louder music, but I'm using it as an amp for desktop speakers connected to my PC, so it has to work for quiet listening and other audio like games and video at low levels. For anything other than louder music, it doesn't work well, for example the cut off makes any video with quiet background music sound pretty bad. I thought I had a faulty unit, but seems to be a common issue and if there is no fix, I think I'll have to return it.

 

[RobotX]

Just got one today and immediately found the same issue, wish I saw this thread before I bought it, but I only saw glowing reviews online. It's fine with louder music, but I'm using it as an amp for desktop speakers connected to my PC, so it has to work for quiet listening and other audio like games and video at low levels. For anything other than louder music, it doesn't work well, for example the cut off makes any video with quiet background music sound pretty bad. I thought I had a faulty unit, but seems to common issue and if there is no fix, I think I'll have to return it.

I kind of wish it is a faulty unit, since there's a lot of glowing review about it. But I suggest return it if you still can.
I passed my return window.

 

[Ward000]

Yes, I returned it. I found a review on Amazon where the reviewer had been in touch with Fosi support who told him it’s intentional and part of the design due to the high noise floor of the amp. If so, that’s a massively flawed product.

Another interesting point is that in course of troubleshooting, I swapped the valves and at one point powered up the amp with them removed - it worked and sounded exactly the same with no valves, which suggests they are entirely for show on this model.

 

[RobotX]

Yes, I returned it. I found a review on Amazon where the reviewer had been in touch with Fosi support who told him it’s intentional and part of the design due to the high noise floor of the amp. If so, that’s a massively flawed product.

Another interesting point is that in course of troubleshooting, I swapped the valves and at one point powered up the amp with them removed - it worked and sounded exactly the same with no valves, which suggests they are entirely for show on this model.

I'm going to try that. That's hilarious if it's reproducible in my unit.
Hope you share your experience with new device that replace the MC331.

 

[RobotX]

Yes, I returned it. I found a review on Amazon where the reviewer had been in touch with Fosi support who told him it’s intentional and part of the design due to the high noise floor of the amp. If so, that’s a massively flawed product.

Another interesting point is that in course of troubleshooting, I swapped the valves and at one point powered up the amp with them removed - it worked and sounded exactly the same with no valves, which suggests they are entirely for show on this model.

I tried running the MC331 without the tubes, while it did work, the volume is low and muffled.
The tubes definitely make a difference in the audio output and quality.
That aside, since the volume output is small, I can crank up the volume to max and it helps with the low volume content despite not sounding good. Suffice to say, I'm not going to run this device without the tubes.
Just wanted to share my test results.

 

[doxygenthief]

The MC331 uses a DSP chip from MVSilicon. It is possible to communicate with this chip through the USBC port using ACP workbench. There is a tab for a noise suppressor (0x88) and a silence detector (0x89). It is possible to adjust settings and possibly improve low volume noise. I have not been able to save the changes made and each time the amp reboots the default settings are loaded. There is a 4db bass bump programmed into the amp as per the screen shot below. If any one has information on how to make the changes permanent then please post here.

 

[RobotX]

The MC331 uses a DSP chip from MVSilicon. It is possible to communicate with this chip through the USBC port using ACP workbench. There is a tab for a noise suppressor (0x88) and a silence detector (0x89). It is possible to adjust settings and possibly improve low volume noise. I have not been able to save the changes made and each time the amp reboots the default settings are loaded. There is a 4db bass bump programmed into the amp as per the screen shot below. If any one has information on how to make the changes permanent then please post here.

Whoa that's really cool, I didn't know there's a software to do that. If you adjust the noise suppressor temporarily, does it helps the low volume cut off?
Maybe FOSI can get their act together and release a firmware update to write the settings permanently.

 

[doxygenthief]

I use the following settings.


compared to the stock ones

This stops the jumping at low volumes and makes the sound more musical in my opinion, as the background gets darker. I mainly use the optical input so your milage may vary.

It seems that the stock threshold setting of -68 is too high and results in the silence detector cutting in and out too often.
There is still a little hiss present regardless of DSP settings but nothing too intrusive. If you run the amp of a battery it improves.

Wondom, Eiffelton and others bundle the ACP workbench tool. It is annoying to connect to the amp and make the changes each time so I am looking forward to Fosi letting us know how the make permanent changes.