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Classic Audio MC Pro Phonostage Review

Rate this phono stage:

  • 1. Poor (headless panther)

    Votes: 7 3.1%
  • 2. Not terrible (postman panther)

    Votes: 7 3.1%
  • 3. Fine (happy panther)

    Votes: 55 24.1%
  • 4. Great (golfing panther)

    Votes: 159 69.7%

  • Total voters
    228
If I ever get into vinyl again . The mm version of this product is what I’ll buy .


It seems to have other mm specific features that also novel and all the features this mc version has , would like to se this tested .
 
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 30 Hz peak is the recorded ambient noise from the fans in the church. The 7 Hz peak is warp-related/tonearm res noise. I mono my two subs below 100 Hz so any out-of-phase/warp-related noise is reduced.
 
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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.
The 30 Hz peak is the recorded ambient noise from the fans in the church. The 7 Hz peak is warp-related noise.

So no musical content at 30 Hz and below. Than, -0.7dB@30Hz and -3dB@23Hz high-pass filter in Classic Audio MC Pro is fully justified.
 
So no musical content at 30 Hz and below. Than, -0.7dB@30Hz and -3dB@23Hz high-pass filter in Classic Audio MC Pro is fully justified.
It's the recorded ambiance of the church at the time. Discussing whether it should be there or not as "musical" content or not is quite meaningless, IMO.
 
Would the Q have a bearing on this, or is it always 2x the resonant frequency? Also, 15 was a guess probably on the high side. I seem to remember that Shure published some research on this a *long* time ago when they launched the V15III. I think they found that compliances tended to be very high in an effort to track at the magic 1.0 g, resulting in resonance well below 10 Hz. Later on MC cartridges with much lower compliance became more popular, increasing effective mass requirements, but I don't recall seeing anything like Shure's research after the MC "takeover" of the high end.
Yes the damping, hence Q of the resonance, does effect the frequency at which the headshell is sufficiently stationary to be a stator as far as the transducer is concerned.

More damping gives less amplitude of the headshell bounce - the output is more due to the headshell bouncing about rather than stylus movement in this frequency band which is why it should be removed - but also raises the frequency at which the headshell can be considered to have become stationary (enough).

It does depend on the type of damping but a lot of damping just makes the cartridge inaccurate to a higher frequency - so further into the audible range.

Shure knew how cartridges worked, of course. Their information about resonant frequency mismatch was to try to stop people mismatching arm and cartridge.

The whole thing is a minefield actually since for good transducer engineering the arm and cartridge should be designed together.
 
The 30 Hz peak is the recorded ambient noise from the fans in the church. The 7 Hz peak is warp-related/tonearm res noise. I mono my two subs below 100 Hz so any out-of-phase/warp-related noise is reduced.
The point here is actually not whether it should be there but whether a record playing device is capable of accurately reproducing it.

I am quite sure the 30Hz sound is there. It is unlikely your record player is accurately reproducing its amplitude.

ALL the output on this plot below around 20Hz or so is spurious output due to the headshell bouncing about - ie not being a stator - more than due to stylus movement, and your plot shows what a high amplitude this dross has. Which is why it is best removed.
 
To be fair Frank, have you forgotten the array of LPFs we had on preamplifiers and integrated amplifiers back in the day? We had defeatable low (and high) filters for at least three reasons:
Not at all John.

I am not referring to any requirement to reduce noise in HiFi equipment in general, just the inevitable inaccuracy of a record player output in the region before a cartridge starts working.

That bit is best removed because it can be high amplitude and it is mostly spurious rubbish.

Filtering noise is a different thing altogether.
 
The point here is actually not whether it should be there but whether a record playing device is capable of accurately reproducing it.

I am quite sure the 30Hz sound is there. It is unlikely your record player is accurately reproducing its amplitude.

ALL the output on this plot below around 20Hz or so is spurious output due to the headshell bouncing about - ie not being a stator - more than due to stylus movement, and your plot shows what a high amplitude this dross has. Which is why it is best removed.
So how much does it bounce at 30 Hz with the Shure brush, would you say?
 
So how much does it bounce at 30 Hz would you say with the Shure brush?
No idea, hopefully nothing by 30Hz.

How accurate depends on the complete dynamic system at that frequency and will be influenced by both the arm and cartridge.

The most accurate in-band reproduction would be with zero damping, but this is obviously impractical. What the shure brush does is reduce the magnitude of out-of-band rubbish, not make improvements in-band.

It is still basic good transducer engineering to filter out out-of-band signal. 0.5dB down at 30Hz is a good choice IMO.
 
No idea, hopefully nothing by 30Hz.

How accurate depends on the complete dynamic system at that frequency and will be influenced by both the arm and cartridge.

The most accurate in-band reproduction would be with zero damping, but this is obviously impractical. What the shure brush does is reduce the magnitude of out-of-band rubbish, not make improvements in-band.

It is still basic good transducer engineering to filter out out-of-band signal.
So this was the result with my previous tonearm:

Resonance_vert_V15_JICO.jpg
Resonance_lateral_V15_JICO.jpg


Currently I don't have this arm but a 4 g damped Unipivot, lowering LF noise by 5-7 dB.


When it comes to reducing subsonic downstream cartridge, I do have some options and have used it, even though it is not currently in system. So I have no issues with using subsonic filters.

IMG_3690.jpg
 
Yes, plus the unavoidable effective mass-cartridge compliance LF resonance, generally between 5 and 15 Hz. I agree that the response rolls off too high; it should be flat to 20 Hz.

("Rumble" used to refer to poor main bearing quality; it now seems to refer to any LF noise, such as ripples in the vinyl.)
Should be flat to 20 Hz (YES)
Is the rumble problem an issue (no mention of it in the specs) on this (my Technics SL-M3), a linier tracking TT? Or is it only about non-flat records?
I noticed that the signal to noise ratio is bettered by my turntable (by only .5 DB):
TypeQuartz DD full auto player system
<Turntable portion>
Drive systemDirect drive
Control systemQuartz control
Number of revolutions33 1/3, 45 rpm
Wow flutter0.022%W.R.M.S(JIS C5521)
0.008% W. R. M. S (Rotating Part Only)
Signal-to-noise ratio82 dB (DIN-B, IEC98A weighted)
Cartridge Section
TypePlug-in connector MM type stereo cartridge
Exchange needleEPS-P205ED4(¥15,000)
<General>
Pwer100 VAC, 50Hz/60Hz
Power consumption22W
External dimensionsWidth 526x Height 202x Depth 426 mm
Weight13.5kg
 
Currently I don't have this arm but a 4 g damped Unipivot, lowering LF noise by 5-7 dB.
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.
 
Should be flat to 20 Hz (YES)
Is the rumble problem an issue (no mention of it in the specs) on this (my Technics SL-M3), a linier tracking TT? Or is it only about non-flat records?
I noticed that the signal to noise ratio is bettered by my turntable (by only .5 DB):
This is not about classic "rumble" (i.e. noise from suboptimal bearings, poor motor isolation etc.) A million dollar turntable bearing and totally silent motor would not fix what is being discussed here. The limitation is simply that accurate sound can not be reliable be extracted from an LP much below 30Hz.

Perhaps if the centre hole is correct to a few micrometers and the record is flat to a similar level, and the arm, cartridge and suspension are perfectly matched and suitably damped, there may be a case for information retrieval at such low frequencies...
 
I would say that even for a record with significant content at 30Hz then losing about 0.8dB at this level is a very small price to pay for attenuating all that nastiness kicking up from about 15Hz to 5Hz.

Of course from a purist perspective (not likely to retain sanity when dealing with vinyl records!) you're right that this isn't ideal, but in reality it's not likely to be audible, whereas if we let the subsonic energy through it would almost certainly cause audible ill-effects. I've yet to come across such a disc myself, having quite a few DECCAs that were recorded in cathedrals and various other 'rumbly' venues and it seems the engineers applied some sort of strong filtering to do away with this below 50/40Hz or so. Either that or simply a matter of course to prevent over-excursion...

In my view given the constant presence of subsonic disturbances in need of attenuation makes the filter mandatory but everyone has their own approach. I think the most important thing is to consider all factors and think holistically.
 
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.
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.
 
Should be flat to 20 Hz (YES)
Is the rumble problem an issue (no mention of it in the specs) on this (my Technics SL-M3), a linier tracking TT? Or is it only about non-flat records?
I noticed that the signal to noise ratio is bettered by my turntable (by only .5 DB):
TypeQuartz DD full auto player system
<Turntable portion>
Drive systemDirect drive
Control systemQuartz control
Number of revolutions33 1/3, 45 rpm
Wow flutter0.022%W.R.M.S(JIS C5521)
0.008% W. R. M. S (Rotating Part Only)
Signal-to-noise ratio82 dB (DIN-B, IEC98A weighted)
Cartridge Section
TypePlug-in connector MM type stereo cartridge
Exchange needleEPS-P205ED4(¥15,000)
<General>
Pwer100 VAC, 50Hz/60Hz
Power consumption22W
External dimensionsWidth 526x Height 202x Depth 426 mm
Weight13.5kg
Having been reminded by Frank Dernie and others about the physics, I realise that "flat to 20 Hz" is actually not what we want (that is based on human hearing being ~20 Hz to ~20 kHz, at least when we are young). 30+ Hz is not only more realistic given the limitations of vinyl but also pretty much demanded by the arm-cartridge mechanics.

It's not really about "rumble" at all, however you define it, and I doubt that the Technics has audible LF noise in any case.
 
Have you seen better measured performance, especially at this price? Maker, model, price and, of course, competent test with all measurements, please!
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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There will unit to unit variations based on component tolerances. Some will test better than others, although the differences will be small if low tolerance components are used. If I were the manufacturer and had several units on the shelf, I would be tempted to review their test data and send the best one to the reviewer.
From what we know about the design and quality of manufacture, I'd bet that components are selected in order to meet the spec in every example. (I fear I might be a fanboy even though I can't find an excuse to buy one!)
 
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