Classic Audio MC Pro Phonostage Review

[AudioSceptic]

I did like the upside down printing on the back so you can read it bent over from the front Seems rather expensive

Not expensive for hand-made top quality. You can pay vastly more for things that might *look* more high end, but perform worse or no better.

 

[Thomas_A]

??? meaningless???
That recorded "ambiance" is just noise pollution form fans. It should not be there! Ventilation systems with very low noise are available quite some time ago. But, if that noise is already recorded, than I want to filter it out! Why you would like to listen to fan noise and to watch how your woofers are bouncing like crazy reproducing fan farts? Implemented high-pass filter with -0.7dB@30Hz and -3dB@23Hz is just the right compromise.

Still it is the recording. Hifi is reproducing what is recorded on the medium. So meaningless discussion.

 

[DSJR]

Sure, I have no problem with that. I just say that I prefer a bit lower cut-off. With the DUT there is no way to choose a different f.

I swear that there's nothing on any commercial vinyl record below 40hz or so (certainly Decca and general 'Polygram' pressings of old) and one chap here mentioned 30Hz cut off too. Remaining bass is mono'd to stop the stylus jumping and this is a routine thing done as much as anything else. I had this verbatim from a cutting engineer!!! I also believe that DMM cuts which were popular, were filtered off below 60Hz as 'mod noise' resulted in the cut otherwise, the trade-off being superior high frequency cuts.

Good grief, you lot are complaining about -0.5dB or so at 30Hz. I remember popular well reviewed amps in the 80's (the height of vinyl in the UK) where the roll-offs started at 80 - 100Hz (Arcam, Cyrus, Linn LK1, Myst, Naim and many others too) and many a far eastern amp including quite expensive ones below 40Hz and these rolloffs were deemed highly acceptable in the HiFi Choice books I've just flicked through. The little NAD 3020 series we all loved back then suffered a 1dB bump at 30Hz before the rolloff below.

So guys, I'd suggest this little box does it RIGHT! It'd be interesting to discover how many of this filter's critics actually have any lengthy experience of the vinyl format at all, let alone of uncontrolled floppy bass cones banging on their end stops with a 'ripply' record

 

[AudioSceptic]

Is this spectrum from the vinyl ? Then I suspect everything below 30-40Hz is the kind of problems this filter will suppress and not actual content put there by the band . The 7hz peak looks like a resonance to me ?
I migth be wrong sold my vinyl 20 years ago , but I did remeber the speakers cones flapping around when playing vinyl due to that my equipment missed this feature .

The 7 Hz peak will be the arm-cartridge resonance and is on the low side. 10-12 Hz used to be considered ideal as it was more-or-less halfway between warp frequency and the supposed 20 Hz lower limit of any musical content.

 

[DSJR]

No, since MORSE code is a thing of the past and so is PHONO for me since October 1982.

We say a DAC or an AMP are bad when not
offering 96 dB but we accept and dance in happiness around a source offering 71.352 dB ...?

Unacceptable.

DACs and AMPs offering North of 120 dB so far, so...?

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We're talking audio output levels at 2V upwards as regards dacs and amps, the spectacular results with Class D amps 'helped' by less sensitive inputs needing less gain I understand. Input sensitivities of old were in the hundreds of millivolts back in the day (and Hegel and others still abide by that to a degree, hence the higher noise figures from memory due to the gain structure)

In a phono stage, we're talking a measurement average level in the groove of 5cm/s, where most 'MM' types give 3 - 5mv output and where MC types are around a tenth of that and sometimes lower, so extra noise is inevitable, especially when the inverse RIAA curve is applied, boosting lower frequencies and reducing higher ones. This is a MOVING COIL phono stage and for such a type, this one is excellent! The 'sinad' of a vinyl record (*estimated* at various frequencies) could be as high as 65 - 70dB at high frequencies with a new top quality highly profiled stylus and a spotless new record played but once and as low as 10dB or worse down at sub 50hz levels, the midrange somewhere between 20 and 40dB depending on all manner of factors from stylus to the player itself... I'm not able to give chapter and verse let alone proper technical evaluation, but do hope Mr Fidler and others with proper test gear can properly expand definitively on this.

 

[AudioSceptic]

I am being pedantic here but strictly it isn't noise, it is inaccurate out-of-transducer-band output.

From an engineering perspective the correct thing to do is analyse what the actual out of band frequency range is and filter it out.

To be super pedantic, isn't "noise" any unwanted signal other than distortion?

 

[Michael Fidler]

We're talking audio output levels at 2V upwards as regards dacs and amps, the spectacular results with Class D amps 'helped' by less sensitive inputs needing less gain I understand. Input sensitivities of old were in the hundreds of millivolts back in the day (and Hegel and others still abide by that to a degree, hence the higher noise figures from memory due to the gain structure)

In a phono stage, we're talking a measurement average level in the groove of 5cm/s, where most 'MM' types give 3 - 5mv output and where MC types are around a tenth of that and sometimes lower, so extra noise is inevitable, especially when the inverse RIAA curve is applied, boosting lower frequencies and reducing higher ones. This is a MOVING COIL phono stage and for such a type, this one is excellent! The 'sinad' of a vinyl record (*estimated* at various frequencies) could be as high as 65 - 70dB at high frequencies with a new top quality highly profiled stylus and a spotless new record played but once and as low as 10dB or worse down at sub 50hz levels, the midrange somewhere between 20 and 40dB depending on all manner of factors from stylus to the player itself... I'm not able to give chapter and verse let alone proper technical evaluation, but do hope Mr Fidler and others with proper test gear can properly expand definitively on this.

If you measure the SNR with a 10 ohm cartridge load from 220Hz (to exclude flicker noise which is made significant below 50Hz due to the RIAA curve) you get 81dB or more on tests relative to 500uV.

Testing with an audio generator tends to create a small loop that picks up mains hum (not present with a floating load) which is inevitable given something like 80dB of gain at 50Hz/60Hz.

If you measure the SNR down to 22Hz with a cartridge load it's something like 76dB although I prefer not to do this as noise below 220Hz isn't particularly audible (at least as long as it's below 70dB or so!) and it tends to mask the differences above that point where our hearing is more sensitive. A-weighting works well too here (82dB) but I prefer to simply exclude blow 100-250Hz as it gets rid of any small mains harmonics that can seriously skew the measurement.

As far as groove SINAD (EDIT: should be SNR!) goes, I'd tend to agree with you there, something in the region of 64-72dB.

 

[AudioSceptic]

Still it is the recording. Hifi is reproducing what is recorded on the medium. So meaningless discussion.

I agree. It is what was heard at the time, and nothing to do with any limitations of the playback medium.

 

[Thomas_A]

I swear that there's nothing on any commercial vinyl record below 40hz or so (certainly Decca and general 'Polygram' pressings of old) and one chap here mentioned 30Hz cut off too. Remaining bass is mono'd to stop the stylus jumping and this is a routine thing done as much as anything else. I had this verbatim from a cutting engineer!!! I also believe that DMM cuts which were popular, were filtered off below 60Hz as 'mod noise' resulted in the cut otherwise, the trade-off being superior high frequency cuts.

Good grief, you lot are complaining about -0.5dB or so at 30Hz. I remember popular well reviewed amps in the 80's (the height of vinyl in the UK) where the roll-offs started at 80 - 100Hz (Arcam, Cyrus, Linn LK1, Myst, Naim and many others too) and many a far eastern amp including quite expensive ones below 40Hz and these rolloffs were deemed highly acceptable in the HiFi Choice books I've just flicked through. The little NAD 3020 series we all loved back then suffered a 1dB bump at 30Hz before the rolloff below.

So guys, I'd suggest this little box does it RIGHT! It'd be interesting to discover how many of this filter's critics actually have any lengthy experience of the vinyl format at all, let alone of uncontrolled floppy bass cones banging on their end stops with a 'ripply' record

I am not sure what you are after. This is the digital Spotify version of the same song. 30 Hz not there? Please...

 

[Robbo99999]

You don't have to tell me that the medium is flawed and dated. Yet more vinyl products keep coming and are reviewed and here we are. Whether there are audible or rather tactile differences of the filter that is seen here - yes there is. And 30 Hz content in vinyl and even lower do exist, here is Cowboy Junkies Trinity sessions.

View attachment 305673

Although we've been told by experts in the field (both manufacturers & experienced users) that anything below 30Hz cannot be relied on to be actual content, instead it's noise that comes from a few different sources due to unavoidable technical limitations of the technology.

 

[Thomas_A]

Nonsense! Your definition of hi-fi is wrong! Hi-fi is reproducing music (and vocals) as faithfully to the original as it can be.
Noise fans, coughing and burping and farting from audience, noises from nearby metro station, lorries and trucks are not hi-fi! I do not want to listen to them in all their hi-fi glory! They a re just noises and have to be filtered out (if possible). What do you think - why all good studios and venues invest in very expensive sound insulation and very expensive noiseless ventilation systems?

I disagree. Whether it is live and audience clapping hands, it is still on the medium and needs to be reproduced with High Fidelity.

 

[AudioSceptic]

I am not sure what you are after. This is the digital Spotify version of the same song. 30 Hz not there? Please...

View attachment 305697

You beat me to it. I was about to do that with my ripped CD. The 30 Hz peak is part of what was heard and *should* be there, regardless of whether it is part of the music itself.

 

[Robbo99999]

I am not sure what you are after. This is the digital Spotify version of the same song. 30 Hz not there? Please...

View attachment 305697

This phono stage starts cutting off from 30Hz so that's fine with this content, and also fine when viewed in the limitiations of "vinyl tech".

 

[Thomas_A]

This phono stage starts cutting off from 30Hz so that's fine with this content, and also fine when viewed in the limitiations of "vinyl tech".

Splitting hairs, but I would prefer the Cambridge cut-off.

 

[AudioSceptic]

You beat me to it. I was about to do that with my ripped CD. The 30 Hz peak is part of what was heard and *should* be there, regardless of whether it is part of the music itself.

Here's 'Sweet Jane' from the ALAC rip of the CD. Same peak around 30 Hz, but different at the very bottom end.

 

[Thomas_A]

Here's 'Sweet Jane' from the ALAC rip of the CD. Same peak around 30 Hz, but different at the very bottom end.
View attachment 305708

So confirmed that the 30 Hz signal is not a flaw from the LP medium, but actually there.Ventilation noise.

 

[AudioSceptic]

Splitting hairs, but I would prefer the Cambridge cut-off.

Actually, that is too low considering the arm-cartridge mechanics.

 

[Frank Dernie]

To be super pedantic, isn't "noise" any unwanted signal other than distortion?

It can be interpreted as such.

 

[Thomas_A]

Actually, that is too low considering the arm-cartridge mechanics.

Arm-cartridge resonances can be all over the place depending on arm construction, see e.g.

Moerch.dk - High End Hi-Fi Playback Equipment - Finest Craftsmanship

 

[AudioSceptic]

Arm-cartridge resonances can be all over the place depending on arm construction, see e.g.

Moerch.dk - High End Hi-Fi Playback Equipment - Finest Craftsmanship

Yes, they can, but there is an ideal where the total effective mass is matched to the cartridge suspension compliance.