Mofi StudioPhono Stage Review

[amirm]

This is a review and detailed measurements of the Mofi Studiophono MM/MC phono preamplifier. It is on kind loan from a member and costs US $349.

The packaging has a retro feel to it and I don't mean that as a positive. When a device has the word "studio" in it, I expect solid metal enclosure, not plastic. There is selectable subsonic filtering but oddly, you have to press the button in to defeat it! There is also a mono switch which I understand to be very useful for playing vintage mono LPs.

The thing I really dislike about the StudioPhono is the seemingly endless number of DIP switches underneath:

Not only the plurality is a problem, but so is the stiff switches. I was worried I was going to break the tiny tabs in trying to move them. Worse yet, you can't really tell their positions as they don't slide all the way to each end. Not wanting to damage the switches, I left the unit with all switches off which means a gain of "40 dB" and cartridge loading of 47K Ohm.

Mofi StudioPhono Measurements
I had to mess a fair bit to get the least amount of mains noise for our dashboard (5 mv input):

I see no distortion spikes which is good. SINAD therefore is dominated by power supply noise and lands the unit slightly below average:

Most important test for a phono stage is the accuracy of RIAA equalization so let's measure the frequency response:

Well, this is not very good. We have a rise in gain with frequency so likely the unit will add a bit of brightness. Good news is the sharp subsonic filter so gets rid of most rumble without messing with musical content at low frequencies.

There is decent amount of headroom but short of what I like to see:

It does however stay frequency independent which is very good:

Finally, level of distortion is respectably low:

Conclusions
You already know my feeling about the packaging so I won't belabor that point. Technically, performance is about average with RIAA equalization being a bit worse than average. A bit more focus on accuracy would have lifted the unit up a notch in my opinion.

As it is, I can't recommend the Mofi PhonoStudio.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

 

[tmtomh]

Nice to see reviews resuming - thanks!

 

[amirm]

It has been hard to get back in the saddle. With garden season fully upon us, it is doubly hard.

 

[tmtomh]

It has been hard to get back in the saddle. With garden season fully upon us, it is doubly hard.

Indeed. Equipment can be tested anytime. But good-weather gardening days are precious.

 

[DWPress]

Ugly little goober indeed but most of the phono preamps I've had were just been hidden away behind other gear so cosmetics maybe not so important. Very retro packaging though.

Yup, spent my day replacing some deck boards and other house odd jobs. Little early for much garden stuff here yet.

 

[JSmith]

Good to see some device testing, resuming normal programming. Thanks for the measurements @amirm.

So these pics are from a model purchased 2018, board shows 2016 rev. and there are no dip switches is no instruction sticker on the underside. I suppose there could have since been a slight revision to this model since.

JSmith

 

[amirm]

Those are the switches in the last picture.

 

[JSmith]

Those are the switches in the last picture.

Indeed they are... I should get my eyes checked, that is just a sticker in your picture I see now, I thought there were more.


JSmith

 

[Jas0_0]

Will a phono pre ever beat the Cambridge Audio for SINAD? Bet Topping or SMSL could do it, but perhaps they don’t see a worthwhile market.

Then again, considering the medium, is there any point?

 

[DualTriode]

Looking at the FFT on the dashboard with the dBrA scale it is confusing. The test output is always at 0dBrA no matter the Gain; 36dB's for mm or 70dB's for mc.

It is hard telling what the noise floor level is or try to determine what level the noise will be if you put your ear in the speaker.

The APX500 software will label the output level in "Amplitude Spectral Density".

FFT Spectrum and Spectral Densities – Same Data, Different Scaling

www.ap.com

 

[amirm]

Looking at the FFT on the dashboard with the dBrA scale it is confusing. The test output is always at 0dBrA no matter the Gain; 36dB's for mm or 70dB's for mc.

It is the other way around. By always setting the test signal at 0 dB, you can easily determine the distortion/PS noise levels. Having it be different every time leads to total confusion as is the case in your measurement. People would just read the number on the left, not realizing the main tone is not at 0 dB. You have the gain in the dashboard so you can always compute actual level.

 

[restorer-john]

The RIAA deviation is disappointing for sure. The infrasonic/low filter appears to be pretty good and better than most.

I like the top down look of it- very reminiscent of late 1980s early 90s Alpine with flat black switches and that square lit LED.

@amirm A bamboo skewer/satay stick is perfect for those little DIP switches.

 

[restorer-john]

Looking at the FFT on the dashboard with the dBrA scale it is confusing. The test output is always at 0dBrA no matter the Gain; 36dB's for mm or 70dB's for mc.

It is hard telling what the noise floor level is or try to determine what level the noise will be if you put your ear in the speaker.

The APX500 software will label the output level in "Amplitude Spectral Density".

View attachment 365035

FFT Spectrum and Spectral Densities – Same Data, Different Scaling

www.ap.com

It depends if you are talking about absolute noise floor in uV, or noise in the presence of signal, which is a completely different metric.

You want noise floor, short the inputs and measure it.

 

[DualTriode]

The RIAA deviation is disappointing for sure. The infrasonic/low filter appears to be pretty good and better than most.

I like the top down look of it- very reminiscent of late 1980s eraly 90s Alpine with flat black switches and that square lit LED.

@amirm A bamboo skewer/satay stick is perfect for those little DIP switches.

I like to use these, there always a couple on my bench. https://www.amazon.com/Hedume-Funct...tional+cuticle+pusher+remover,,aps,149&sr=8-1

 

[DualTriode]

It depends if you are talking about absolute noise floor in uV, or noise in the presence of signal, which is a completly different metric.

You want noise floor, short the inputs and measure it.

That is not the metric you are looking for.

As far as the analyzer knows the signal is notched out and everything else is THD+N.

Yes we can short the input but that is not what the FFT shows and that is not the sound that comes out of the speakers before the needle drops.

 

[DualTriode]

You have the gain in the dashboard so you can always compute actual level.

Yes you can also see the output voltage on the dashboard. However there is nothing there to calculate noise floor voltage, you know all that bin size stuff that is included in "Amplitude Spectral Density" when the software does the calculation.

Thanks for the reply, had my say.
DT

 

[DSJR]

Mofi use AT based MM cartridges don't they? These are not hugely high in output so the overload may well be ample here. RIAA is poor by today's example and it seems a lot of money for something like that - the Mani 2 seems a lot better and undercuts it...

 

[AdamG]

Nice to see reviews resuming - thanks!

It’s the Weekend. For Amir his two extra work days of the week the rest of us Slackers waste! He is a Taskmaster and most certainly was a pure Joy to work for back in the day. What am I saying? He is still a Joy to work for! ..>.>……..

 

[restorer-john]

That is not the metric you are looking for.

As far as the analyzer knows the signal is notched out and everything else is THD+N.

Yes we can short the input but that is not what the FFT shows and that is not the sound that comes out of the speakers before the needle drops.

You're missing the point.

If the stimulus signal is not stopped AND the inputs are physically (electrically) shorted, the residual noise number is not 'real'. It become noise in the presence of signal, like the AP and many other analyzers perform.

And, a shorted (or even cartridge loaded) IS the sound that comes from the chain before the needle drops. What else are you imagining it is?

 

[French Meloman]

Good job from Amir as always.
It's a shame that this device has such poor ergonomics. Obviously, the brand wanted to save money to the point of making the setting changes perilous. This compromises the use of the device with an MC cell. The brand is expected to review the design of the device on this point, even if it means increasing the price a little. The other weak point is the RIAA EQ which should be better.
The brand should use the results of this test to improve its product, which is in fact unfinished. Still, it has some interesting qualities: an efficient subsonic filter, frequency-independent leeway (which is rarely the case), and good distortion management.