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Muffsy phono preamplifier minireview (update)

Thomas_A

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This review was updated September 21, 2023. Main change was the use of the E1DA Scaler to fix the impedance issues that is evident when using the E1DA ADC alone.

This is an attempt to make a small review with measurements of the Muffsy MM phono preamplifier. It is a DIY kit so it is far from something that everyone can and will buy. What makes it interesting is that it is one of the few phono preamplifiers where you can modify both capacitance (C) and load (R). The version that is reviewed here is the PP3 rev A which is different from the the current one (PP4). The difference between them is a better layout of the PSU and main board of the PP4 to reduce noise further. Price with main board, PSU and back panel is 153 dollar. To that you need the box and an AC adapter.
1692212802202.jpeg


Measuring a phono pre was harder than I thought. The equipment was a Cosmos E1DA grade B, mono mode, together with two series-attached adjustable passive Monacor ILA-1020 dampers (- 20 dB, together or separate), and the E1DA Scaler (updated review). A D10s with an USB-isolator was generating signals and everything was hooked up to a Macbook on battery. The Muffsy had gain "high", about 44 dB in all tests.

The first two distortion measurements were made with ≈5 mV input signal, left and right channel:
Muffsy scaler left channel distortion.png
Muffsy scaler right channel distortion.png

In this setting the noise was -76 dB, but virtually no distorsion could be observed. Good result. (Note that the updated Muffsy should have less noise.)

Looking at headroom at 1 kHz, the Muffsy turned out to be excellent. Clipping above 120 mV. (Here I used the 43V input of the E1DA, so distortion is higher due to the impedance mismatch.)
Stepped THD level distortion.png

Distortion vs frequency was very low:

Stepped THD distortio vs frequency.png


Lastly, the RIAA curve accuracy. When you are a DIYer, you also have the option to buy a little extra capacitors and match them better to the ideal values. This unit I have does have better matched capacitors than would be expected from random choice. -1 dB was at 10 Hz and variations were within +/- 0.1 dB from 50 Hz- 20 kHz. Excellent result.


frequency response muffsy scaler.png


In conclusion, an excellent MM preamplifier with adjustable gain and load (R & C). However, it's DIY so not for everybody. Notably, the Cosmos ADC is not ideal for measurements without a buffer. This review was updated with E1DA Scaler to get better result. Distortion was generally lower with the Scaler and the frequency response was more linear in the bass region. I have kept the old figures as attachments.
 

Attachments

  • 5 mV in L ch sens 1.7 V.png
    5 mV in L ch sens 1.7 V.png
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  • 5 mV in R ch sens 1.7 V.png
    5 mV in R ch sens 1.7 V.png
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  • 5 mV in L ch sens 10 V.png
    5 mV in L ch sens 10 V.png
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  • Frequency response.png
    Frequency response.png
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  • Stepped THD distortion vs fr.png
    Stepped THD distortion vs fr.png
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JeffS7444

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It drops in the bass with -1.5 dB at 20 Hz though. I am not 100% convinced I got this measurement correct but anyway, it seems to be rather good for a phono preamp.
Considering the amount of low-frequency garbage that a record playback system can generate and pick up from the environment, -1 dB @ 30 Hz response seems logical to me.
 

GXAlan

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. I am not 100% convinced I got this measurement correct but anyway, it seems to be rather good for a phono preamp.

View attachment 306176
Great post!

The E1DA has no input buffer so the input impedance can matter for capacitor coupled outputs. One way to play with this is to run your sweep with the 1.7V versus the 43V input
 
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Thomas_A

Thomas_A

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Great post!

The E1DA has no input buffer so the input impedance can matter for capacitor coupled outputs. One way to play with this is to run your sweep with the 1.7V versus the 43V input
The Muffsy has a 1 uF on its output, so yes impedance of the E1DA will matter.
 
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Thomas_A

Thomas_A

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Considering the amount of low-frequency garbage that a record playback system can generate and pick up from the environment, -1 dB @ 30 Hz response seems logical to me.
I would think this will vary with input load. E1DA is not ideal for this kind of testing, I think.
 

GXAlan

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The Muffsy has a 1 uF on its output, so yes impedance of the E1DA will matter.

If you use the E1DA with the Schiit Freya, the bass roll off is pretty extreme, even though it’s the E1DA.

If it’s not tough, just run a few sweeps at the higher input sensitivity since you really don’t care about the noise. That will let you estimate how bad the bass roll off is.

There used to be an online calculator that let you punch in the capacitor and the input impedance and then get a graph of the roll off.
 

GXAlan

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Thomas_A

Thomas_A

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Thomas_A

Thomas_A

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Made an update with distortion vs frequency. Also a note that the Cosmos ADC needs a buffer to get correct results.

Yet another major update made September 2, 2023, using the E1DA Scaler together with the E1DA ADC.
 
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