Musical Fidelity MX-VYNL Phono Amplifier Review

Overview

The MX-VYNL is a fully balanced, high performance phono stage, able to operate with many moving coil or moving magnet cartridges. With both traditional RCA inputs and XLR fully balanced connections it can be connected to 2 turntables simultaneously.

The MX-VNYL offers a wide range of input impedance settings for moving coil cartridges as well as several capacitance settings for moving magnet units. Unlike many other pre-amplifiers it allows easy adjustment of these settings while playing. This allows easy experimentation and tuning to find the optimum setting for all your equipment.

The MX-VYNL also includes Musical Fidelity’s renowned RIAA correction that offers extremely accurate results to beyond 80kHz. That may sound extreme, but there is a good deal of information above 20 kHz that needs correction. If it isn’t corrected, it will show itself as ringing and overshoot.

With both excellent low noise and a very good overload margin the MX-VYNL can comfortably handle even the most demanding of cartridges.

MX-VYNL in brief

• Fully balanced XLR and traditional RCA inputs
• Fully balanced XLR and traditional RCA outputs
• Fully isolated inputs allow for switching between two turntables at once
• Adjustable input impedance on MC whilst it is playing
• Adjustable capacitance on MM whilst it is playing
• Very wide overload margin
• Accurate RIAA to beyond 80kHz
• Incredible noise ratio
• Low impedance output
• State of the art SMD technology
• Beautiful aesthetics and build quality

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Musical Fidelity MX-VYNL Phono Amplifier Review

SMD Technology. Bottom LH corner is the DC to DC converter.

Knowing I was about to upgrade my cartridge I decide that my Lentek head amplifier needed to be replaced as the phono stage in my Denon AVP A1 HDCI was less than stellar by modern day technical standards. I wanted a preamplifier with very accurate RIAA equalization, that could support both moving coil and moving magnet cartridges and provided a good range of loading options and gains to support a wide range of cartridges. My Denon AVP-A1 when running in all analog mode is fully balanced from input to output and to all speakers, so I also wanted a pre-amplifier that could provide that level of signal support, but did not require me to give up an entire months salary to purchase it.  The MX-VYNL fitted that technical and financial bill.

I purchased both the MX-VYNL and my new Hana SL MC cartridge in the same package from Hi-Fi Heaven. I decide that I would see how the MX-VYNL compared to my battery powered Lentek head amp and Denon AVP-A1 RIAA pre-amp before upgrading my Lentek Entre 1 cartridge to the Hana SL.

MX-VYNL Connectivity

I had previously modified my turntable and re-wired my arm to support a fully balanced connection to my cartridge by adding two 3 pin male XLR connectors to the rear of my Thorens TD1060S turntable. So I quickly assembled a ‘Y’ split cable that had two 3 pin female XLR’s connected to one female 5pin mini XLR that connected to the MX-VYNL pre-amp.

Balanced Phono Input ‘Y’ Cable

The balanced line level XLR output from the MX-VYNL was then connected to my Denon AVP-A1 balanced CD XLR line level inputs.

After selecting balanced input using the rear switch, which is indicated on the front panel, the required 100 ohm MC load, RIAA equalization and gain to +6dB I sat down to listen to my favorite Big Band D2D disc, Harry James and His Big Band – SL3 and my latest two female jazz albums by Shelby Lynne and Lyn Stanley.

The Comparison – To my Lentek Head Amp plus Denon Pre-amp

The Good

• Very low noise even with +6dB gain. (see later comments on this issue)
• Beautifully made and finished.
• Very solid.
• Very flexible.
• Great balanced I/O performance – zero hum and low noise. (see later comment on hum pickup)
• Excellent overall sound.

The Bad

• The maximum MC gain of 63dB is barely sufficient for very low output MC cartridges of 0.2mV like my Lentek Entre. The additional 6dB provided by the balanced output is not relevant to most systems as many inputs will drop the balanced level by -6dB in order to match other unbalanced inputs.
• Low end cheap external switched mode power supply (12VDC @ 500mA).
• The single rail input voltage from the switched mode power supply is converted internally to dual rail using a DC to DC converter – basically another switched mode supply. The good news here is that it is so well designed it creates little to no noise. This one feature almost caused me to not buy this pre-amp as I intensley dislike all forms of switch mode power supplies, particularly when used in low level signal amplifiers. (Linear power supplies rule the roost here)

The Gain

• MM Gain – 42dB or x125 – max gain 48dB or x250
• MC Gain – 57dB or x707 – max gain 63dB or x1414

The MM figure is quiet acceptable, but the MC figure is too low for very low output (0.2mV) MC cartridges – see comments.

Noise

At all times, and for all I/O configurations and gains the electrical noise was minimal and often not audible in normal use. I did compare the noise of the MX-VYNL in MC mode with a gain of 63dB to using my Lentek head amp (+28dB) driving the MX-VYNL in MM mode (+42dB) for a total gain of 28dB+42 db = 70dB. In order to compare the two arrangements at the same listening level, the MC MX-VYNL required 6-7dB additional volume gain from my AVP-A1 to get the same sound level as the Lentek combination.

The two configurations were virtually indistinguishable in terms of overall sound quality, from bass to mid-range to top end. The ONLY difference being that the noise from the MC MX-VYNL was about 6dB lower. More importantly the spectrum of the noise from the Lentek/MM MX-VYNL combination was slightly more intrusive as it contained more mid band energy. The MC MX-VYNL by itself producing a slightly softer and less intrusive noise spectrum.

Hum

With no phono inputs connected and set to +6dB, MC 100ohm, the MX-VYNL was totally hum free with any levels being below that of the amplifiers very low noise floor. This was even with my Denon set to an additional +18dB volume gain, its maximum.

Despite the fully balanced and ground isolated connections from my phono cartridge to the balanced MX-VYNL inputs a very low level hum persisted on the left hand channel (the RH channel was totally silent despite identical cables and cable paths). Cable swaps and ground reconfigurations changed nothing. The only way to remove the 60Hz hum was to pass the two phono cables (see above Y cable) between the bottom of the MX-VYNL chassis and the metal shelf that it sat upon. This provided significantly more electrostatic and magnetic shielding than leaving the cables “in the air”. This removed most traces of hum in the LH channel.

I have yet to determine why this hum problem occurred and why the MX-VYNL exhibits it in just one channel, despite the cables and cable paths being identical – cartridge to MX-VYNL input and MX-VYNL output to AVP-A1 balanced inputs. The latter using 1192A quad cable, the same as all my balanced connections. I have too assume for now that the MX-VYNL internal layout makes the left hand channel more susceptible to hum pickup and doesn’t provide the same level of common mode rejection as the RH channel (or mine is faulty).

(I will be purchasing some miniature heavily screened star quad cable to replace the existing phono cable just in case the screening or some electrical aspect of the cable I used is at fault. I shall also contact Musical Fidelity to see what they have to say about this issue and report their response here.)

Hum Update

1. It turned out that the ‘hum’ I was hearing was created by switched mode noise from the MX-VYNL switched mode power supply. It was very significantly reduced by adding two large ferrite beads to the DC power supply cable as shown below.
2. Replacing the original phono cables with miniature silver plated star quad cable, Belden 1804A, made RF/switched mode power supply noise pickup worse. This is highly unusual as star quad cabling is designed to improve common mode rejection. I did not attempt to ascertain the reason as the original ‘Y’ cable was now virtually free from hum/noise after the addition of the ferrite beads to the DC power supply cable .
3. I did not contact Musical Fidelity as the problem has now been found.

MX-VYNL With Power Supply Cable Ferrite Bead Added

MX-VYNL Power Supply With Ferrite Bead Added

This goes to show that my original concern as to the use of switch mode power supplies in low level circuitry were totally justified. I suspect that changing the inexpensive switched mode supply to a good quality analog supply may further improve the MX-VYNL sound quality. See this link.

Sound

Besides the improvement in noise floor, the most notable difference compared to my Lentek Head Amp plus Denon RIAA pre-amp was that the MX-VYNL mid-range was so much smoother. Something I was really looking for. Bass extension, heft and punch were virtually identical, as was top end detail, stereo imaging and depth of image. Remember that the Lentek head-amp is just a pair of transistors running in Class A push-pull, DC connected input to output, not some complex multi-transistor op-amp design like the MX-VYNL. See here for the lentek schematic.

The disappointing issue was that the MX-VYNL just doesn’t have enough gain for very low output MC cartridges like the Entre, and I had to raise the volume on my Denon by +6 to +7dB to obtain the same listening level as the Lentek (+28dB) plus Denon (+42dB) pre-amp. This is NOT a good way to achieve the correct listening level. Using increased gain further down the chain raises all levels of noise. Most gain should be applied at the front end of a system not later down the chain.

In my forthcoming review of the Hana SL I comment on the gain/noise performance of the MX-VYNL and how it handles the Hana’s 0.5mV output level that is more than twice twice (+8dB) that of my Entre at 0.2mV.

Other Issues

I have noted some negative comments regrading the MX-VYNL EQ. It offers two alternatives:

1. RIAA
2. IEC

RIAA is the basic equalization curve used to correct for the most common recording equalization characteristic. IEC was implemented to help reduce turntable rumble at very low frequencies, typically below 15Hz. Both equalization curves are correctly implemented – see below.  IEC should not be required with a modern turntable due to their very low rumble output and the fact that IEC cuts 20Hz output by -3dB due to the inclusion of an additional filter pole at 20.02 Hz (7590uS). Some records however may benefit from its use depending upon their production and mastering and your arm/cartridge resonance.

Theoretical (red ) and ideal (blue) RIAA EQ Curves

IEC LF Rumble Roll-Off (red)

Expanded View Of Theoretical IEC LF Roll-Off

MX-VYNL Inverse equalized RIAA Frequency Response with IEC Equalization engaged.

Clearly the channel matching is excellent and the RIAA and IEC equalization is accurate down to 20Hz. I also checked each channels phase response and both were found to be a perfect match from 20Hz to 100KHz.