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Musical Fidelity M6 PRX Power Amplifier
Musical Fidelity M6 PRX
Power Amplifier
Experience Review

Musical Fidelity M6 PRX Power Amplifier & Musical Fidelity M8 PRE preamplifier

Click an image to enlarge.

To say the last year and a half has been a testing time with regards to hi-fi component reliability is an understatement. When music is your sanctuary and your hi-fi components are failing all around you, or music being played through your system just does not sound right and you don’t know why, life becomes much harder!

After suffering various documented panel failures to my MartinLogan Scenario ESL speakers, it is only natural to keep a suspicious finger pointed directly at these very sensitive speakers. Instead of enjoying my record collection, I have spent many months swapping various components, interconnects, mains cables and even going all the way back to the electricity consumer unit to test the dedicated hi-fi circuit breaker, desperately trying to isolate the cause of sound degradation.

I can now confirm that issues such as distortion, smearing, loss of dynamics have been caused by multiple failures in the component chain. To make matters worse in respect of identifying and isolating the issues, these multiple component failures were slow to reveal themselves due to their intermittent nature. The above issues have been caused by speaker panel failures at various points (but now resolved with panel replacements) as well as a slow and intermittent amplifier issues.

Cambridge Audio Edge W Stereo Power Amplifier

The above confirmed diagnosis was finalised after several months of head scratching (I am nearly bald now). After receiving dozens of comments and suggestions on the back of existing write-ups, it took a helpful brief comment from a particular member of the Facebook MartinLogan Owner Experience Group which led me to point a very tired finger back at my Musical Fidelity M8 500s power amplifier.

Cambridge Audio Edge W Power Amplifier

I was fortunate to be able to swap out my Musical Fidelity M8 500s power amplifier with a loan Cambridge Audio Edge W power amplifier (utilising my existing balanced XLR cables from my Musical Fidelity M8PRE preamplifier). After doing so, all sound quality issues mentioned above immediately disappeared!

My Musical Fidelity M8 500s amplifier is now with the Audio Venue dealership in Ealing ready to be shipped to Henley Audio (Musical Fidelity UK Distributor) for a final fault diagnosis and fix.

Ironically, my M8 500s amplifier was returned to Musical Fidelity (Hounslow London) a couple of years ago after initial suspicions regarding reliability, annoyingly, it was turned around with a ‘no fault found’ diagnosis.

A few months later I returned it to Audio Venue in Ealing dealership, who again sent it back to me after a two week in shop ‘no fault found’ diagnosis. Though I was (and have been continuously) frustrated by the lack of fault finding with this amplifier, I also respect it was extremely difficult even for me to identify a marked degradation in sound quality when using traditional cone speakers for some unknown reason? Using two different models of MartinLogan ESL (Scenario & brand new ES11a models) instantly highlighted obvious sound degradation issues.

After using the Cambridge Audio Edge W power amplifier for nearly two weeks (sporadically) I was eager to box it up and return to its owner. Of course I was thankful for the loan, however, though I found the Cambridge Audio Edge W to be a solid punchy performer, it lacked the control, grace and musical elegance of any Musical Fidelity power amplifier I have ever owned or loaned (stand alone or integrated). The Cambridge Audio Edge W also performed at its best at high volume levels. I often have very late night – early morning listening sessions, so need to be able to enjoy music at low volume levels during these times. Unlike my Musical Fidelity M8 500s (which delivers great musical performance at all volume levels) the Cambridge Audio Edge W lacked detail and soundstage precision at low volume levels, so I chose to just watch television instead (a first for me)!

Musical Fidelity M6 PRX Stereo Power Amplifier (M6s PRX)*

Musical Fidelity M6 PRX Power Amplifier

I was over the moon to be offered the Musical Fidelity M6 PRX as a loan. As soon as it powered up and music began to flow, I found myself being drawn into the open, warm and deeply musical landscape offered by this extremely capable amplifier. (Again, I simply utilised my existing balanced XLR cables from my Musical Fidelity M8PRE preamplifier). The M6PRX definitely has a similar effortless signature to the M8 500s and it did not sound or feel out of place by any measure. Of course, to me there were obvious differences in performance between the M6 PRX and M8 500s (which I would expect) from amplifiers with a cost difference of around £1000 between them. Slotted into my system I found highs delivered via the M6 PRX slightly softer, lower octaves to be deeper, and more rounded (but slightly less defined). These noted differences are not a criticism of the M6 PRX. If I owned the M6 PRX and did not have previous experience with the M8 500s (or Musical Fidelity Nuvista 800) I would probably be dancing on the ceiling by now in complete joy. (Perhaps not as that would mean I would be outside my MartinLogan electrostatic speakers’ sweet spot)!

Of course my M6 PRX experience would change by various degrees using different interconnects and speaker cables etc. My system cable choice is set up around my M8 500s. I have owned my M8 500s for five years+ and when it is on song, the precise soundstage, depth, clarity and organic musical delivery offered with both vinyl and CD playback is outstanding. The M8 500s and other in-line components simply disappear from the mix. It is extremely difficult not to consciously (or subconsciously) critically judge all other power amplifiers (around this price bracket and above) against such a high musical bench mark!

Again, none of the differences noted between the M6 PRX and M8 500s are major criticisms due to the fact this amplifier (as with all Musical Fidelity amplifiers) offer a musical performance way above other hi-fi companies’ solid state offerings at this price point.
I have absolutely no reservations in recommending the M6 PRX.

All of the above listening tests were conducted mainly using vinyl playback via my AMG Viella V12 turntable. CD listening was minimal with similar results to vinyl playback.

Musical Fidelity M6 PRX Power Amplifier

One small aesthetic observational note: As previously mentioned, Musical Fidelity offer music lovers superb value for money with a range of high quality amplifiers at various price points. Understandably, decisions have to be made regarding manufacturing processes, build materials and overall design ‘performance against aesthetics’, to keep prices within a specific range. BUT how much extra cost would be added to the retail price for Musical Fidelity to use a top plate with countersunk holes to enable the use of flat headed hex nuts (instead of round headed hex nuts)? I respect in many set-ups, the top of the amplifier may be hidden and such a minute aesthetic blip may not register. This design feature is still not as bad as the infamous Musical Fidelity flimsy Christmas cracker prize remote controls I guess!

Visit company websites for power amplifier full specifications:

*Musical Fidelity M6 PRX Stereo Power Amplifier (rebadged M6s PRX in 2019) £2599
Power output: 230 Watts per channel into 8 Ohms (24 dBW)
THD(+ noise): <0.007% typical
"Signal to Noise Ratio: >120dB
Frequency Response: +0, -1dB, 10Hz to 100kHz

Musical Fidelity M8 500s Stereo Power Amplifier £3600
• Power output: 500 Watts per channel into 8 Ohms (27 dBW)
• THD(+ noise): <0.007% typical
• Signal to Noise Ratio: >120dB 'A' weighted
• Frequency Response: +0, –1dB, 10Hz to 80kHz

Cambridge Edge W Stereo Power Amplifier £2499
100W RMS into 8 Ohms; 200W RMS into 4 Ohms
<0.002% 1kHz at rated power (8 Ohms); <0.02% 20Hz – 20kHz at rated power (8 Ohms)
<3Hz – >80kHz +/-1dB
>93 dB
< -100dB
>113 dB
Input A1-A2 (unbalanced) 1.09V RMS
Input A3 (balanced) 47k Ohm; Input A1-A2 (unbalanced) 47k Ohm

Complete system details:

AMG Viella V12 turntable with AMG Teatro MC & AMG reference tonearm cable
Phono stage & interconnect cables. Whest PS.40RDT Special Edition phono stage with Kimber Hero & Kimber select KS-1116 XLR interconnect cables.

CD player
Musical Fidelity A3 CD player (internally upgraded). Van Den Hul The Second Analogue Interconnect cables.

Musical Fidelity M8-500S power amplifier & M6 PRX power amplifier with Musical Fidelity M8PRE preamplifier
Luminist Revision Poseidon XLR balanced cables.

MartinLogan Scenario hybrid electrostatic speakers
Russ Andrews 12TC speaker cable & Chord Legend speaker cable.
REL S3 SHO subwoofer (experience review conducted with & without subwoofer connected).

Quadraspire Q4 EVO turntable wall bracket. Quadraspire Q4 EVO 4 tier shelf.

Power & mains cables
Russ Andrews BMU 3000, Michael Valentine Studio Silver Gold Special Edition BMU for Rel S3 SHO subwoofer,
Powerkord 300 mains cables for BMU, amplifier, preamplifier & subwoofer.

Robin Francis
© Michael Valentine Studio
May – June 2020


Use the links below to read MartinLogan Owner Experience 2,
or The System Upgrade 2015...

MartinLogan Scenario Owner Experience 2 (click to go to this page) The System Upgrade 2015 (click to go to this page)

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