• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

New Fosi MC351 amp/DAC received and hooked up

ZA3, SK02, LC30 I bought them as soon as available. MC351, I just can't force myself to buy it though I really like the aesthetic of it.
 
It was close to being great. I noticed a slight manufacturing defect. There is some type of glue on the front below the VU meter.

It isn't going to let me simplify my office setup like I was hoping. I've decided to return it and go back to the ZA3. I will say it sounded good and could go louder than the ZA3.

Fosi: To make the next version great, I recommend the following changes:

1. XLR inputs
2. The VU meter looks great, but there should be two for left/right
3. Include a 1/4" headphone jack and cut off the speaker output when a headphone is connected
4. Make the case bigger, the same footprint as an Eversolo DMP-A6 and include some vents like the ZA3. It gets pretty hot.
5. Lose the passive sub woofer output and replace it with a coax output for active subs
6. Add a remote control for volume and input selection
7. Easier to read indicators for the selected input. Instead of a light next to the tiny letters for the selection, put the light behind the selection so it is readable
8. Add an additional optical or coax input
9. Add a couple of mid range knobs in addition to the bass and treble, something like the Schiit Loki
10. The dac chip sounded fine to me, but others seem to be objecting to the one you used

The current version is priced at about $185. Make the changes listed above and I would be glad to pay quite a bit more.
By the time they release the new version as recommended by users, Wiim Amp Pro is out already so as others same products from Aiyima, Nobsound, Douk, BRZhifi, etc.....
Yes, I really like the form factor of Eversolo, I owned Z6 and it performs well.
 
By the time they release the new version as recommended by users, Wiim Amp Pro is out already so as others same products from Aiyima, Nobsound, Douk, BRZhifi, etc.....
Yes, I really like the form factor of Eversolo, I owned Z6 and it performs well.
After three weeks using the MC351, i confirm the sound is great with Bookshelves (Tamise BC acoustique) spotify output USB C or BT from Mac pro or Hiby R6 III.
But it's not yet the perfect "all days" amps for my expectations... an upgrade with :
- 1. Headphone output
- 2. Easier to read indicators for the selected input. Instead of a light next to the tiny letters for the selection. Rotate button should be better.
- 3. A balance is missing maybe Volume knob with an Triple function... (On/off- Volume Level- Balance) or Volume and Balance together and On/off like BT20A
- 4. Smaller button like Fosi BT 20A ( more space for headphone output)
- 5. Air cooling output, (the box is too warm after an hour)
A level price 150-170 Us (The Loxjie A40 should be a great configuration, but he had less power and an infineon chip).
 
- 5. Air cooling output, (the box is too warm after an hour)

I was surprised by hot it got compared to the ZA3. It was hot enough that I would not be comfortable stacking any component on top of it.

They need to go back to the drawing board with this device. For several reasons, not just the heat.
 
This one is probably the most strange product (amplifier) I have seen in last few months.
Strange as in “not good”.
 
Hi, Bad news...
- Have a look to these reviews :

And i have tested Usb c output from my macbook pro and MC351 input Usb c, with diffrent flac files, and compare with Jack 3,5 output from Hiby R6 Gen III Dac and MC351 Rca input ...
Days and nights ! The MC351 Usb c input is really poor . Confuse middle and bass definition, and too much sybilance ...
I have repeat the test with Usb c Hiby output to Usb c Mc351 input...
I think the MC351 has also a poor quality Dac...
 
I've been living with the MC351 for a couple of weeks:
The first impression is that the amplifier is larger and more solidly built than most other Class D amplifiers available now. It arrived well-packaged, up to Fosi Audio’s usual standards, and included a 32V/5A power supply, an optical cable, and a USB B to C cable. According to the included user manual, the twin amp chips are the venerable TI 3255 and RMS power is 165 W X 2 @ 4ohms. The passive subwoofer circuit is rated at 350W @ 4ohms. The single volume control works for all output circuits. The sampling rate from USB is 24/bit/96kHz and via Optical/COA is 32bit/192kHz. The unit is powered on by turning the volume knob. There is no remote control function.

All my listening tests were conducted at the same decibel levels, measured by a phone app sound meter.

My first application was in my office, using a WiiM Mini streaming Spotify, either directly to the MC351 via optical or with a Topping E50 DAC Optical in, RCA out to the MC351. Speakers used were Sony SS-CS5 with a powered Yamaha YST-FSW150 subwoofer, with the latter connected via the pre-out. I’ve been using this setup for some time, with the only difference being a similarly power-rated Class D Douk Audio ST01 integrated amplifier.

In a like-for-like comparison, I was surprised at the improvement in sound. The MC351 offered better separation, a deeper, wider sound field, and more ‘air’. It’s a more detailed, yet pleasant sound, with the improved definition of drum hits, symbols, and any other short, sharp sounds at the top of the list.

I tested the MC351 with and without the Topping E50 DAC. The Topping takes credit for providing more authority, depth, and clarity, plus providing a pre-amp function with a remote control. While the MC351 is not necessarily too large to use as a desktop amp an arm’s length away, I can see this benefitting greatly from a remote control.

The one issue is a significant, squint-inducing boom from the pre-out circuit through the subwoofer when turning the unit on – and again when turning it off. This boom doesn’t occur when not using the pre-out.

My second test was nearfield on my desk at home, using a WiiM Mini streamer either directly to the MC351 via optical or with an SMSL M300SE DAC/headphone amp to a pair of JAMO 801 speakers with no subwoofer and then with a passive substitute. The previous amplifier was a Fosi Audio V3. In this case, the mediocre speakers masked any difference between the DACs in the MC351 and the SMSL. The sound quality was comparable to the result achieved when using the V3 amplifier. This is a good indicator that it’s time to get better speakers.

To test the passive subwoofer connections, I added a vintage Altec Lansing Challenger 1 cabinet speaker, rated at 4ohms / 90dB@1W. This was interesting for three reasons: 1) the amp’s tone controls only affect the two main speakers, 2) you cannot change the sub’s volume relative to the two main speakers, and 3) you can’t set the step filter. Therefore, finding and matching a passive sub that compliments the two main speakers is important. In my case, the efficient sub was too forward.

My last test was in my workshop, where the MC351 replaced another Fosi Audio V3, this time using an Echo Link streamer tested with and without an SMSL SU1 DAC feeding Mission 700 speakers and a 250W-powered Polk PSW650 subwoofer. As in the first test, the MC351 showed off its downstream audio section by improving the definition, clarity, soundstage, and air to the better-quality speakers.

Conclusion: The MC351 offers interesting performance in an attractive package. Although the venerable TI 3255 amp chip is common in comparable Class D amplifiers, it’s apparent that the downstream audio circuitry shows improvement. It was easy to reach 85dB and more without issues. The VU meter moves much more than others I have at the same sound levels and spends much of its time in the upper registers. In fact, it isn’t useful due to its lack of accuracy and being alone in a stereo amp. It should be improved or deleted. Using the pre-out to a powered sub resulted in significant ‘thumps’ when turning the unit on and off, which is concerning. For those few with passive subwoofers, there’s no level control to dial them in. I prefer using these amps with external DACs with remote controls as ‘pre-amps’, but the DAC in the MC351 performed well enough on its own. The MC351 offers better sound than expected and is designed to accommodate other quality components. Lastly, as an integrated amplifier with multiple inputs, and an acceptable DAC, this would be a good starting point for many if it had a subwoofer high-pass filter, probably dropping the passive subwoofer circuit, and a remote control.
 

Attachments

  • videoframe_10320.png
    videoframe_10320.png
    1.6 MB · Views: 37
  • PXL_20240615_195827235.jpg
    PXL_20240615_195827235.jpg
    339.3 KB · Views: 24
  • PXL_20240610_211021451.jpg
    PXL_20240610_211021451.jpg
    266.5 KB · Views: 27
  • PXL_20240611_141738174.jpg
    PXL_20240611_141738174.jpg
    190.1 KB · Views: 30
I wonder how @Fosi Audio intends a user to match the level of their passive subwoofer to their passive mains.

With an active sub plugged in via RCA Sub out, one can just use the volume knob on the back of the sub to match levels.

But with a passive sub, there is no such volume control.

Is that not a major design fail?

Basically, either you win the lottery by having a sub and main speakers with identical sensitivity, or you just live with whatever unbalanced sub<->mains sound comes out of the MC351?

Seems like an incredible oversight to me..
Good observation. It is a lot of functionality for the price.

They could add one extra mode on the mode select, and an associated LED. It could be for "Sub Adjust."

In that mode, pressing and holding the mode button, the volume control would adjust the relative sub volume for the currently selected source mode. They might be able to do it by reprogramming the control microprocessor and the sub amp gain. Or maybe they could take over the bass knob in sub adjust mode.

Or if there is a BT remote app, it could be done there.
 
I've been living with the MC351 for a couple of weeks:
The first impression is that the amplifier is larger and more solidly built than most other Class D amplifiers available now. It arrived well-packaged, up to Fosi Audio’s usual standards, and included a 32V/5A power supply, an optical cable, and a USB B to C cable. According to the included user manual, the twin amp chips are the venerable TI 3255 and RMS power is 165 W X 2 @ 4ohms. The passive subwoofer circuit is rated at 350W @ 4ohms. The single volume control works for all output circuits. The sampling rate from USB is 24/bit/96kHz and via Optical/COA is 32bit/192kHz. The unit is powered on by turning the volume knob. There is no remote control function.

All my listening tests were conducted at the same decibel levels, measured by a phone app sound meter.

My first application was in my office, using a WiiM Mini streaming Spotify, either directly to the MC351 via optical or with a Topping E50 DAC Optical in, RCA out to the MC351. Speakers used were Sony SS-CS5 with a powered Yamaha YST-FSW150 subwoofer, with the latter connected via the pre-out. I’ve been using this setup for some time, with the only difference being a similarly power-rated Class D Douk Audio ST01 integrated amplifier.

In a like-for-like comparison, I was surprised at the improvement in sound. The MC351 offered better separation, a deeper, wider sound field, and more ‘air’. It’s a more detailed, yet pleasant sound, with the improved definition of drum hits, symbols, and any other short, sharp sounds at the top of the list.

I tested the MC351 with and without the Topping E50 DAC. The Topping takes credit for providing more authority, depth, and clarity, plus providing a pre-amp function with a remote control. While the MC351 is not necessarily too large to use as a desktop amp an arm’s length away, I can see this benefitting greatly from a remote control.

The one issue is a significant, squint-inducing boom from the pre-out circuit through the subwoofer when turning the unit on – and again when turning it off. This boom doesn’t occur when not using the pre-out.

My second test was nearfield on my desk at home, using a WiiM Mini streamer either directly to the MC351 via optical or with an SMSL M300SE DAC/headphone amp to a pair of JAMO 801 speakers with no subwoofer and then with a passive substitute. The previous amplifier was a Fosi Audio V3. In this case, the mediocre speakers masked any difference between the DACs in the MC351 and the SMSL. The sound quality was comparable to the result achieved when using the V3 amplifier. This is a good indicator that it’s time to get better speakers.

To test the passive subwoofer connections, I added a vintage Altec Lansing Challenger 1 cabinet speaker, rated at 4ohms / 90dB@1W. This was interesting for three reasons: 1) the amp’s tone controls only affect the two main speakers, 2) you cannot change the sub’s volume relative to the two main speakers, and 3) you can’t set the step filter. Therefore, finding and matching a passive sub that compliments the two main speakers is important. In my case, the efficient sub was too forward.

My last test was in my workshop, where the MC351 replaced another Fosi Audio V3, this time using an Echo Link streamer tested with and without an SMSL SU1 DAC feeding Mission 700 speakers and a 250W-powered Polk PSW650 subwoofer. As in the first test, the MC351 showed off its downstream audio section by improving the definition, clarity, soundstage, and air to the better-quality speakers.

Conclusion: The MC351 offers interesting performance in an attractive package. Although the venerable TI 3255 amp chip is common in comparable Class D amplifiers, it’s apparent that the downstream audio circuitry shows improvement. It was easy to reach 85dB and more without issues. The VU meter moves much more than others I have at the same sound levels and spends much of its time in the upper registers. In fact, it isn’t useful due to its lack of accuracy and being alone in a stereo amp. It should be improved or deleted. Using the pre-out to a powered sub resulted in significant ‘thumps’ when turning the unit on and off, which is concerning. For those few with passive subwoofers, there’s no level control to dial them in. I prefer using these amps with external DACs with remote controls as ‘pre-amps’, but the DAC in the MC351 performed well enough on its own. The MC351 offers better sound than expected and is designed to accommodate other quality components. Lastly, as an integrated amplifier with multiple inputs, and an acceptable DAC, this would be a good starting point for many if it had a subwoofer high-pass filter, probably dropping the passive subwoofer circuit, and a remote control.

Welcome to ASR!

Your solution to connect your powered sub to the pre out is a good idea.
 
I ran into an annoying compatibility issue with Windows 11 - Per Fosi rep, it's fixed in newer models (although in a week-old product...)

The MC351 only support SBC and AAC and Windows 11 prefers AAC... and then fails (barely audible pop on sound stream starting, but otherwise silent).

It works fine with SBC once you disable AAC in Windows:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BthA2dp\Parameters]
"BluetoothAacEnable"=dword:00000000

(Note that BluetoothAptxEnable is also an option - windows will fall back to it, just not with the MC351)

What's interesting is that my Android device can connect to the MC351 with AAC just fine, so it's something about the Windows 11 AAC implementation.
 
Has anyone figured out what sort of DAC implementation this box has, or still a mystery after days of release?
 
Has anyone figured out what sort of DAC implementation this box has, or still a mystery after days of release?
As far as I can tell, no one has taken one apart yet. Therefore, the DAC chip remains a mystery.
 

 Complete EIAJ CP1201, IEC-60958, AES3,S/PDIF-Compatible Receiver

 +3.3 V or +5 V Power Supply

 4:1 S/PDIF Input MUX

 I²C Interface

 32 kHz to 192 kHz Sample Frequency Range

 Low-Jitter Clock Recovery

 Single-ended or differential input

 Multi-bit Delta-Sigma Modulator

 24-bit Conversion

 105 dB Dynamic Range

 -90 dB THD+N

 Low Clock-Jitter Sensitivity

 On-chip Digital De-emphasis


probably not quite even close to the SOTA universe
 
Received an email from Fosi yesterday about the MC351 being released. Ordered it from Amazon and received it today.

My intention is to use this to simplify my office setup and move the Fosi ZA3 and other components to another room.

Setup: MC351 output to Sony SSCS5 speakers. Inputs: CD player to coax. Wiim Pro Plus to RCA inputs. PC, Chromebox and Xbox Series X to optical (HDMI audio extractor).

First impression, very clean and clear. Much louder output than the ZA3 at the same clock position. 12:00 is loud. The MC351 has bass and treble controls. I added just a touch of bass. I love the VU meter. Not a digital display, an actual old fashioned moving needle.

First test, Sony 4k Blu-ray player using the coax input playing a CD to try out the DAC in the MC351. It sounds great. Not a blind test, but I don't hear any differences between this and the Eversolo DAC-Z8 I was using previously.

The speakers are totally silent with the CD paused. No hiss with the volume at max.

Second test, my Galaxy S23 ultra connected to the USB input, using the UPnP player Pro to play flacs (44.1/16 bit CD rips) from my server. Again using the DAC in the MC351. Played metal, country and classical tracks. All sounded perfect as expected.

Third test, Galaxy S23 ultra connected with Bluetooth. Played Spotify, Youtube Music and Tidal. All sounded great.

Fourth test, Hiby R6 Gen 3 DAP connected to USB. Played flac files (44.1/16 CD rips) stored on the DAP. Sounded great.

Fifth test, PC running Linux connected with optical. Played flac files from my server, Spotify, Youtube Music and Amazon. Sounded great.

Sixth test, Wiim Pro Plus connected to RCA jacks (using the Wiim's DAC). Played Tidal. Had to turn it down. Tidal always plays louder than any other service. Sounded great.

I like the MC351 so far. Great sound and seems to have a good DAC. More power than the ZA3.

Now I need to figure out what to do for a headphone amp. The MC351 has a preamp out (3.5mm). I hooked that up to my Schiit Midgard using a 3.5mm stereo to RCA connection. The pre out volume is controlled by the volume control. The headphone amp worked, but still had output going to the speakers which won't do. Any suggestions for this?

Fosi, if you are listening, this would have been the perfect DAC/amp if you had just included headphone amp functionality or a switch to cut off the speaker output.
An Other review ...
 
Back
Top Bottom