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Classic Audio MC Pro Phonostage Review
- Thread starter amirm
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Seeing what MF did with the Spartan series, I’d bet the next version will be better than the first.
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Or at least more scale-able! I'll post a picture of the new board once it's up and running.
I have nothing in the MC fight but I like that you are doing this.
It's going to take a fair few hours to do the layout justice. All the blocks in the schematic are done and dusted. 235 components on the board!
The original had 135, so almost a 75% increase in parts count, although no more incoming capacitor QC required. Hopefully, the smaller footprints of the 3216 caps and 0204 resistors will help fit it onto the same board size, so I can stick the prototype in the same enclosure.
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Blimey! Will you be able to make a profit?
If it can be automated, it should be OK. No time sifting through film caps matching them up!
The subsonic filter deals with cutting out tone-arm resonances/record warps/surface effects below 20Hz, while the LF XFEED function reduces stereo field noise below 100Hz or so. They both do different things: one operates outside the audio band, the other within it.
"Super-bombproof"!!
TVS + polyfuse on the input side, shunt diodes across first caps in the voltage-doubler "but how does my 24V AC Rega power adaptor SOUND with this unit". Usually I can "best of luck with your next choice" those guys before it comes to payment, but occasionally one will get through, or some predatory little reptile (almost always in the UK) will try and foist some dubious 'upgrade' upon them that results in destruction + it's still remotely possible to connect the wrong power adaptor by accident."Super-bombproof"!!
Also, strong RF filters on input and output. I designed the original to withstand about 5 times what you might expect from marginal EMC-passing equipment in the near vicinity, but it's still not quite enough for about 3% of cases, especially using exotic cartridges of the very low output type. In close enough proximity (60cm or so), dodgy LED lights from Aliexpress and ethernet-over-power adapters can yield enough RF at the input to provoke detection, especially if exotic cables are being used. Having a massively high gain doesn't help much, either. This does also affect the vast majority of contemporary preamps, but it would be good to make it much more resilient.
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Can you give an example of where there the LF XFEED helps, what sort of album or recording issue it addresses, that the subsonic doesn't?
I guess I'm not familiar with issues between 20 and 100Hz is what I'm saying.
Thank you @Michael Fidler, that was very informative.
Sadly it's virtually impossible to get custom connectors made that would be cost-efficient while precluding misconnection of dodgy PSUs.
I think it's probably better to just add the internal components to deal with it - that way you also have protection against severe power surges of catastrophic proportions.
ban25
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Jeez. I even forgot that there's no grounding lug on Rega TTs and you have to (presumably?) use their pre-amps in order to ground the tonearm. Ridiculous!
I wish! Then I'd be left alone... Regrettably, they hum equally well with all brands, depending on which power strip they're plugged into, the length of a piece of string, and which position the moon is in.
It's such a simple fix - just use a conductive coating on the glass platter to shield the motor and add the ground wire. Total cost: less than a cup of coffee!
Rega actually has a good reason for doing this as they put the ground on the left channel audio cable*. They believe doing it this way sounds better** and it is hard to argue with their decades of experience***.
*Cost-cutting measure
**Unfalsifiable claim
***Appeal to authority/chronology
Forgive me if I don't interpret this charitably
. The internet is littered with furious forum users and people who've tried the product and have given ample feedback that the company needs to change its ways. Personally, when I've dealt with clients who have Rega setups, it causes an issue half of the time, all for a tiny little wire...Rega: Just say anything, make anything up, say you've changed the electrical alignment of the design or some other BS, but fit the ground wire!
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Affirms why I don’t work on ‘tables for others anymore. Not enough money in the world.
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