©2018 by Signal Art Electronics. Proudly created with Wix.com

Just to be clear, this is a modification service where you send out the Alctron MK47 to me (at least the microphone itself and the power supply) and I return it to you once the work is complete (return shipping to you included in the price).  The mic must be in basic working order.

 

The Alctron MK47 is an Asian tube microphone that has been in production for some years now, which occasionally gets mentioned on the forums and discussed, as being a decent value for the money.  It appears occasionally on Alibaba or ebay, though it does not have much distribution outside of Asia; but of course was the basis for a well known American branded imported tube microphone.  Some folks who have discovered this model over the years have picked it up in an effort to 'cut out the middle man' and save some bucks; and sometimes it can be picked up relatively cheap.  However, it does need quite a bit of work in order to achieve respectable standards; hence the high price of this upgrade.  I have a long history with this mic, and I do know what needs to be done to bring it up to a quality level.  I would also stress that I do not endorse this mic or recommend that people rush out to buy one just to get it modded... I obviously would rather see people pick up an actual U47 reproduction (like ours!) than this thing; BUT... if you happen to already have one, or find one for a price so low it is too good to pass up, then this is for you.

 

Suffice it to say, the transformer, tube, capsule, and electrolytic capacitors in this microphone are nothing worth writing home about, particularly the capsule.  The asian contract manufacturer who puts this together, by their own admission in fact, are no good at making K47 capsules (and IMO, aren't good at making much of anything else either... and certainly not capsules, at least none that I've evaluated were worth being spared from the trash bin).  

 

This microphone circuit is a hodge-podge of ideas and shares more in common with the C12 (sans decent output capacitors, polystyrenes, and other parts) than any kind of U47, and not too dissimilar to many other Asian 12AX7-based mics.  I stress that it's not a U47 in any way or form, because not only does the circuit have nothing in common with a U47 design; it does a number of things that would be 'heresy' on any reproduction of a U47.  One is the variable pattern switch, which is additional circuitry that a U47 doesn't have.   It's capsule is directly polarized, and in Omni mode the polarization voltage is split across both diaphragms.  It's that simple.  The additional circuitry wouldn't be added.  The other is that this mic employs some level of active feedback to reduce its noise and THD to acceptable levels; and again this would never be done on a real U47 clone.  The U47 employs no feedback, therefore it has the full harmonic richness produced by the tube and transformer... that's part of the sound.  and humorously enough, even with the feedback design; this mic has far more THD and noise than our own baseline edition 47, sounds muffled and hissy and hollow by comparison, to be quite honest.

 

Getting on to specifics....

 

The poor K47 capsule is discarded and replaced with my own custom imported K47.  I have to use an alternate version of my K47 which is tuned for an 80v polarization voltage instead of the traditional 63v, give or take, that a U47 calls for... because, well, the MK47 mic is not a U47 and does things differently.  but that's OK.  The new capsule makes a world of difference... less over-sensitivity/microphony, less over-presence and sibilance, and fuller, more balanced sound.

 

The generic Chinese tube is replaced with a TAD Germany 12AX7WA HIGHGRADE, which is among the quietest 12AX7 in the business (essential to help tame the noise of this mic), and also has just the slightest touch of midrange forwardness to act as a proxy to Neumann's mid-forward capsule sound.  It's a trick, but the trick works.  Subtle, but nice.  I also add a set of Sandy Levy tube damper rings which eliminate any microphonics from the tube.  

 

The generic T14 output transformer is replaced with a Cinemag T14 style transformer.  This opens up the mic and adds clarity, openness, detail, and hugeness.  Gone is the smeared, pinched, plastic sound of the cheap magnetics.  


Literally all electrolytic capacitors are replaced with high performance Nichicon and Panasonic parts rated for long life and low ESR.  This helps with noise, sound, and longevity.  The generic film capacitor in the high-z section is replaced with a NOS polystyrene with appropriate dampening to prevent microphonics.  The generic polypropylene output capacitor is replaced with a network of NOS paper-in-oil capacitors to smooth out the top end and help deliver a more balanced, smooth, vintage sound.  Generic film filter capacitors in the microphone's audio output section are removed.  The upgraded components eliminates the need for them.

 

Lastly, the generic and poor quality 7 pin XLR cable is replaced with a Gotham 6 meter cable, wired appropriately for the configuration of the Alktron MK47's heater and B+ delivery rails and other considerations.  Yes, this makes a difference.  Most of the Chinese cables I've tested are complete garbage; particularly 7 pin cables seem to have such poor insulation quality that you can measure crosstalk between conductors and between conductors and ground.  This means attenuation, DC, leakage, and robbing of sound.  It's audible.  hum, buzz, and loss of bottom end and top end.  I've done the listening tests.  Additionally, the Chinese cables generally don't offer the 2 heavy gauge leads for tube voltages as the higher quality cables do.  forcing B+ voltage down a 28 gauge wire stresses the power supply, and just isn't good practice.  This is fixed with my cable.  I basically remove the ends from the existing cable and transplant them onto the Gotham wire, and discard the old cable.  Waste not, want not.  

 

After all is said and done, you will have a mic that, while maybe not the finest mic in the world, is now quite respectable and can do a great job in the studion on a large variety of tasks.

Alctron MK47 mic upgrade

$400.00Price
add 3 pin Gotham XLR for $40