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Classic Audio MC Pro Phonostage Review
- Thread starter amirm
- Start date
I think the system was designed by a competent engineer, you don't need to roll op-amps, better listen to your vinyl collection.
As seen on the pictures the OP-amps are from JRC. Whether these are same as NE5532 may be Amir can tell? Rolling OP-amps can be done as far as the max. ratings are kept. But there may arise issues like oscillation or different input/output impedances.
That's why many times great has been tested again with a sample from the market. However if they can produce a product why would they not sell it?
Looks like it would be worth it, if you're doing vinyl and using an MC cartridge. All phono stages need a switchable rumble filter b/c a warped record, of which any vinyl collector will have many, will cause your woofers to pump-- something not good for either your sound or your woofer's long term health.
DSJR
Major Contributor
The lf filter looks vicious, but that's really the expanded scale Amir used. -1dB at 30Hz and -5dB at 20Hz is absolutely perfect really, bearing in mind the general lack of *music* cut into commercial grooves generally below 30 - 40Hz.
Far better not to bother a line or power amp stage, let alone speaker drive units with all that distortion and noise down there. When I finally get round to restoring my Garrard 401, I'm going to need this kind of stage as Garrard tuned almost all the noise (when the deck was new at least) to below 50Hz where broadcast phono stages would blend and filter it out.
I'd seen the MM versions a while ago and didn't think the prices were bad at all (no dealer margins of course which would all but double the price once VAT is added as well)
P.S. If the maker sees this, any way an MM version could be sent for third party testing please?
Far better not to bother a line or power amp stage, let alone speaker drive units with all that distortion and noise down there. When I finally get round to restoring my Garrard 401, I'm going to need this kind of stage as Garrard tuned almost all the noise (when the deck was new at least) to below 50Hz where broadcast phono stages would blend and filter it out.
I'd seen the MM versions a while ago and didn't think the prices were bad at all (no dealer margins of course which would all but double the price once VAT is added as well)
P.S. If the maker sees this, any way an MM version could be sent for third party testing please?
dtaylo1066
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Quality is evident in spades. No exterior award winner for looks, but A+ for getting the job done, and with balanced outputs!
DSJR
Major Contributor
Bearing in mind what I know from a few sources now regarding how vinyl is cut, with bass-monoing and lf filtering below 30 - 40Hz done before the record is actually played, I now firmly believe that said lf filter should be fixed in place, as removing it puts so much nastiness into the rest of the system and this wastes power, even if subjectively, it adds 'charm' to some systems (which was never there in the first place!).
It isn’t rumble it is because the way seismic transducers (ie pickup cartridges) work all output below around 2x the sensor natural frequency is spurious and should be removed.
This was well understood (the physics of how the transducers work) when I worked in the business in the mid 1970s but is often ignored nowadays mainly by non-technically knowledgeable enthusiasts who don’t know how stuff works and want a CD like FR.
If the sensor resonance is 15 Hz its output needs filtering below 30Hz which is the frequency at which the headshell becomes a close approximation to stationary relative to the record.
Nango
Major Contributor
Pls sell the license to Topping so they can make it for 99€ ..... why not??
No it shouldn’t - from an engineering POV anyway.
One could debate (and make adjustable accepting some performance loss) the turnover frequency but, for proper engineering of the system it should always be there.
I just happen to recently come across this unit.
https://dandagostino.com/products/momentum-phonostage-preamplifier
Around $30,000?
To be fair the Dagasitino provides for multiple equalization curves, but still.......
My head just explodes when I see the $ needed to purchase this equipment.
https://dandagostino.com/products/momentum-phonostage-preamplifier
Around $30,000?
To be fair the Dagasitino provides for multiple equalization curves, but still.......
My head just explodes when I see the $ needed to purchase this equipment.
Well you can have tonearms with vertical resonance frequencies in the 15-30 Hz range and vacuum tables, effectively reducing LF warp noise. A linear response of the horiozontal movement down to 20 Hz is quite achievable. In this one, it is not achieved.
It has nothing to do with rumble, or anything else on the record or from the turntable.
It is entirely to do with the physics.
Seismic transducers are inaccurate up to around 2x their natural frequency by the nature of how they produce an output. This has always been the case. The exact frequency depends on the damping - more damping reduces spurious output at resonance but raises the frequency at which the cartridge body can be reasonably considered a stator. Until this frequency the output of any cartridge is wrong. This is simple transducer engineering.
The 1976 update of the RIAA equalisation did include an improvement in this area but still better to just filter it out in the phono stage and have done with it- like this one does.
This manufacturer understands how record players work, bravo for good engineering.
AudioSceptic
Major Contributor
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.
AudioSceptic
Major Contributor
His Krell stuff seemed reasonably priced in comparison. When you take into account the gross imperfections of vinyl it seems even more absurd to pay that sort on money.
AudioSceptic
Major Contributor
He also makes MM phono preamps, and I'd expect them to be equally good. <https://michaelfidler.com/products/spartan/>
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