This is a review and detailed measurements of the Musical Fidelity M2si integrated stereo amplifier. It was kindly sent in by a member. I think the list price is US $999. However I see it selling for just US $599 from the outfit the owner purchased it. Other places have it as high as US $700.
From the pictures, the M2si looked very elegant and high-end. In person in black, it looks a bit less so and somewhat industrial:
Still, head and shoulders above DIY enclosures or budget products. To wit, it came wrapped in thick velvet and even came with white gloves!
The back panel shows what you would expect:
Sadly no balanced inputs. but we do get preamplifier out. I did not see that until this morning when I took pictures of it. So I put it back on the bench and took a quick snapshot of that too.
The unit is heavy being a class AB amplifier with toroidal transformer and such. In use the left side remains almost room temperature. The right side though gets warmer but nothing resembling hot.
I liked that the protection circuit was not latching in that when the overload conditions when away, it would reset itself and the amp was functional again. I see too many AVRs and amps these days that shut down and require power cycle to work again.
And oh, plastic remote comes with it which I did not use. But I don't see it listed on the MF website.
Anyway, overall impression is positive for an amplifier in this price range from brand name company sold through dealers.
Preamplifier Audio Measurements
As noted, I only got a chance to run the dashboard against the preamplifier section:
This is good performance with SINAD that is 100 dB and dominated by noise, not distortion (distortion is near -108 dB).
Integrated Amplifier Audio Measurements
It is a bit of a quandary how to measure integrated amplifiers. Do I feed it the full output of 2 volt and then bring the level down with volume control to measure 5 watts? Or do I set the gain high (e.g. common 29 dB) and feed it much lower level to simulate what we get in power amplifier testing? I ran both:
The difference fortunately is not much because as I showed earlier, the pre-amplifier is much cleaner than the power amplifier. I used an average SINAD (signal over noise and distortion) of 82 which places the M2si slightly above average:
Frequency response is flat in audible band and extends fair bit past that:
Here is our 32-tone input response:
Really like to see 16 bits here to clear the most common CD/download format.
Distortion rises with frequency which is typical.
Amplifier Power Measurements
There has been discussions recently about how to measure power output from amplifiers. First, let's start with our usual graphs starting with 4 ohm load:
I was surprised to see the protection circuit kick in and shut the amp down before anything clipped. Seems too aggressive to me. Regardless, this makes power measurement easy as there is only one max power level at 80 watts.
Switching to 8 ohm, we get our classic clipping response at max power:
As is typical we are shy of reaching manufacturer's 72 watt spec. Looking at the clipping portion of the graph you see that if I went to the right some, I would get more power -- as much as 100 watts.
Question is, how far do we want to go to the right if any? And how about different test frequencies? Above are all at 1 kHz which is common testing criteria but with music, most of energy is at lower frequencies. I grabbed a few tracks from my music library and analyzed their spectrum. Highest peaks were around 40 to 45 Hz so we are way off the mark with 1 kHz tone.
Let's run a sweep to measure power for the full audio band and change the criteria for amount of distortion we allow for 8 ohm load:
I have included the control panel so you can see all the parameters. The top line separated from the rest is at THD+N of 10%. The rest that are bunched up on top of each other are 1%, 0.5% and 0.1%. For this amplifier at least, it seems that it makes no difference what we pick between 0.1 and 1% THD. An amplifier that would soft-clip would be different.
With respect to frequency sensitivity, we do have some power droop at low frequencies. The reservoir capacitors cannot catch their breath due to slow rate of change at lower frequencies. So maybe we should change my THD+N versus power graph to use 45 Hz? We would lose the data we already have if we did that.
One thing that has been bothering me is that peak power is measured at 1% THD but my regular power specs have been at onset of clipping, making comparison of those two values hard. Alas, I could not do that for 4 ohm with this amp because it never clips. So I set the continuous power threshold to 0.1% to get the max power:
We see quite a bit of headroom as is typical of class AB amplifiers versus class D.
With 8 ohm I could use the same 1% THD+N for both:
Notice how our maximum power is around 75 watts which beats the spec and my graph measurements of 66 watts.
Like to see some feedback on what to measure in the future. While I could run all of these, in case of devices with multiple functionality (e.g. AVRs), it would increase my workload more than it already is. With simple amplifiers like this I could run them all.
Conclusions
The Musical Fidelity M2si is a well built and nice looking, branded integrated amplifier. Its preamplifier performance is very good but the power amp holds it back. The price is reasonable and inclusion of remote control is very nice in my book. I can't recommend it on pure performance but you have all the data to decide for yourself.
------------
As always, questions, comments, recommendations, etc. are welcome.
A kind member is building me a PC and I have to pay him soon. Alas, I looked in my paypal account and it is darn near empty given the use of funds for the last few wild parties we have had (had to drown out the sorrow after a few bad review results). So please donate as much money as you can using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
From the pictures, the M2si looked very elegant and high-end. In person in black, it looks a bit less so and somewhat industrial:
Still, head and shoulders above DIY enclosures or budget products. To wit, it came wrapped in thick velvet and even came with white gloves!
The back panel shows what you would expect:
Sadly no balanced inputs. but we do get preamplifier out. I did not see that until this morning when I took pictures of it. So I put it back on the bench and took a quick snapshot of that too.
The unit is heavy being a class AB amplifier with toroidal transformer and such. In use the left side remains almost room temperature. The right side though gets warmer but nothing resembling hot.
I liked that the protection circuit was not latching in that when the overload conditions when away, it would reset itself and the amp was functional again. I see too many AVRs and amps these days that shut down and require power cycle to work again.
And oh, plastic remote comes with it which I did not use. But I don't see it listed on the MF website.
Anyway, overall impression is positive for an amplifier in this price range from brand name company sold through dealers.
Preamplifier Audio Measurements
As noted, I only got a chance to run the dashboard against the preamplifier section:
This is good performance with SINAD that is 100 dB and dominated by noise, not distortion (distortion is near -108 dB).
Integrated Amplifier Audio Measurements
It is a bit of a quandary how to measure integrated amplifiers. Do I feed it the full output of 2 volt and then bring the level down with volume control to measure 5 watts? Or do I set the gain high (e.g. common 29 dB) and feed it much lower level to simulate what we get in power amplifier testing? I ran both:
The difference fortunately is not much because as I showed earlier, the pre-amplifier is much cleaner than the power amplifier. I used an average SINAD (signal over noise and distortion) of 82 which places the M2si slightly above average:
Frequency response is flat in audible band and extends fair bit past that:
Here is our 32-tone input response:
Really like to see 16 bits here to clear the most common CD/download format.
Distortion rises with frequency which is typical.
Amplifier Power Measurements
There has been discussions recently about how to measure power output from amplifiers. First, let's start with our usual graphs starting with 4 ohm load:
I was surprised to see the protection circuit kick in and shut the amp down before anything clipped. Seems too aggressive to me. Regardless, this makes power measurement easy as there is only one max power level at 80 watts.
Switching to 8 ohm, we get our classic clipping response at max power:
As is typical we are shy of reaching manufacturer's 72 watt spec. Looking at the clipping portion of the graph you see that if I went to the right some, I would get more power -- as much as 100 watts.
Question is, how far do we want to go to the right if any? And how about different test frequencies? Above are all at 1 kHz which is common testing criteria but with music, most of energy is at lower frequencies. I grabbed a few tracks from my music library and analyzed their spectrum. Highest peaks were around 40 to 45 Hz so we are way off the mark with 1 kHz tone.
Let's run a sweep to measure power for the full audio band and change the criteria for amount of distortion we allow for 8 ohm load:
I have included the control panel so you can see all the parameters. The top line separated from the rest is at THD+N of 10%. The rest that are bunched up on top of each other are 1%, 0.5% and 0.1%. For this amplifier at least, it seems that it makes no difference what we pick between 0.1 and 1% THD. An amplifier that would soft-clip would be different.
With respect to frequency sensitivity, we do have some power droop at low frequencies. The reservoir capacitors cannot catch their breath due to slow rate of change at lower frequencies. So maybe we should change my THD+N versus power graph to use 45 Hz? We would lose the data we already have if we did that.
One thing that has been bothering me is that peak power is measured at 1% THD but my regular power specs have been at onset of clipping, making comparison of those two values hard. Alas, I could not do that for 4 ohm with this amp because it never clips. So I set the continuous power threshold to 0.1% to get the max power:
We see quite a bit of headroom as is typical of class AB amplifiers versus class D.
With 8 ohm I could use the same 1% THD+N for both:
Notice how our maximum power is around 75 watts which beats the spec and my graph measurements of 66 watts.
Like to see some feedback on what to measure in the future. While I could run all of these, in case of devices with multiple functionality (e.g. AVRs), it would increase my workload more than it already is. With simple amplifiers like this I could run them all.
Conclusions
The Musical Fidelity M2si is a well built and nice looking, branded integrated amplifier. Its preamplifier performance is very good but the power amp holds it back. The price is reasonable and inclusion of remote control is very nice in my book. I can't recommend it on pure performance but you have all the data to decide for yourself.
------------
As always, questions, comments, recommendations, etc. are welcome.
A kind member is building me a PC and I have to pay him soon. Alas, I looked in my paypal account and it is darn near empty given the use of funds for the last few wild parties we have had (had to drown out the sorrow after a few bad review results). So please donate as much money as you can using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/