Just to be clear, this is a modification service where you send us your microphone and PSU and we ship them back to you, modified Shockmount and other things not required, however if you do send the 7 pin cable we will test and clean it for you. I use the same Gotham cable as this microphone, so there's nothing to upgrade there; however if you need a cable longer than their provided 5 meter cable, contact me about the length you require and I can sell you a custom made cable.
I go over some of the journey in developing this mod in my blog, so I will not repeat all of it here. Suffice it to say that this is a very thorough re-build where I go through it from end to end and make it as good as I believe it theoretically, realistically can be. Thankfully this is a decent sounding mic, has a decent capsule, and has a decent output transformer; so the raw ingredients are there and its not prohibitively expensive to take it to its full potential.
I have to begin this mod offering with a bit of a disclaimer; so bear with me. This 'is' a good sounding mic, and I do endeavor to make it sound a little better, a little more authentic, and significantly quieter in terms of noise; but it is not a U47. Nothing I do, short of gutting the entire mic and PSU (which I don't wish to do), will make it a '47'. It's circuit is closer to that of a C12 and based on an Asian 12AX7 design. It is a modern mic, and engineered to be a 'sound-alike' that captures some of the broadest strokes of what a 47 is expected to have; but if you want anything close to a real 47 for something in this price range, I highly urge you to buy my baseline edition U47 available on this site. This mod offering is not an endorsement to go out and buy this product; it is more intended for those who already have this mic, or who found one for such a good deal that it couldn't be passed up. This mod is for that person, and allowed me to finally 'complete the thought' and put a pin in something I worked years prior.
As mentioned above, unlike its Asian predecessor which requires considerably more work to be brought up to spec; this mic already has a fairly good capsule and a fairly good output transformer. Though the capsule is an 80v K47 and not a traditional 63v version, and the transfomrer is a double-wound T14 variety and not a BV8; it is what this particular design requires and it does not need to be upgraded. This is good, and allows me to focus on the rest.
I take a holistic approach to this upgrade, since noise comes in from many sources and self noise is one of the things I try desperately to bring down considerably in this microphone. To that end, I replace all electrolytic capacitors in the mic from head to toe (mic and PSU), and glue down the ones as needed to prevent them from coming loose. All the new caps are name brand, low ESR, high temp, and ultra long life. This not only improves the mic's sound and noise specs; it also fulfills one of the other things that make a U47 a real investment: that the mic will last for a lifetime of use. Generic capacitors do not guarantee this; but the ones I put in will.
Next I install the TAD (Germany) 12AX7WA-HIGHGRADE valve, along with a US-made tube damper ring made from aerospace silicon by Sandy Levy. While the retaining claim provided within the microphone body does a decent job of ensuring the mic does not fall loose, I do not feel it provides adequate vibration prevention; so the added damper ring ensures no microphonics or resonance will creep in through the valve circuitry. This particular tube was selected after carefully evaluating almost everything out there. This tube is not only one of the lowest noise 12AX7's in current production (if not the absolute quietest), it is also exceptionally clean, clear, and high headroom with low distortion. When it does saturate at very high SPL's, it tends to provide the very transparent and gentle rounding that a U47 was known for. This tube, by design, also has the very most subtle midrange-forward boost.... every slightly, but there. This is similar to the mid-forward punch that identifies Neumann's own capsule work; and while doing that subtle trick via the tube is not the same as doing it via the capsule, it does sort of give it that help it needs there. The stock capsule, while good, is a more scooped (smiley face) type of sound than the mid-forward sound that the German capsules were known for. This just ever so subtly helps bring things into balance. That's why I consider it the perfect tube. If that weren't enough, being a 12AX7 as the circuit originally calls for, the mic will not produce far less heat than it does driving the less efficient 5751 valve.
The output capacitor, while an excellent Solen part, is not really the best choice considering context, for a mic of this vintage. I replace this part with a network of vintage paper-in-oil NOS components that I've selected for giving it the right output sound... smoother, thicker, and richer bass. It fills in the cracks. I also calculate this set of 3 capacitors to provide the originally specified output value of just over 1.5uF. The 1.8uF Solen Fast-Cap was chosen in part to give a low end bump to help out with the slight shallowness in low end extension on this mic. However, in hindsight, I feel it is better to select the brand and type of capacitor to help sculpt this low end response rather than raising the value on the component, as unfortunately the latter technique merely adds a bit of a hump to the low end region that most consider the frequencies where 'mud' accumulates, and doesn't really do much in terms of extending actual bass response. When I mod this mic, it has rich, full bottom end; but is not boomy or muddy. And it is quieter, cleaner, and will last a lifetime.
Lastly, I add some adhesive to the polystyrene cap in the high z section to prevent resonance, and replace it if microphonic or thermally damaged; and generally check, tighten down, and rebuild any part of the mic where I feel that assembly QC was lacking (see my blog). I spray the open frame rotary switch for patterns on the PSU for lower contact resistance. It's a holistic process; I look at every part of it, remanufacture where needed, and address anything I find. The end result may not be a 47; but it brings this mic to a level that I think is highly respectable, sounding cleaner, clearer, lower noise, rich, warm, deep, and full... and able to last a lifetime of use.
At the end of the day, this mod will make the best possible scenario out of a situation, and give you a mic that, while not a true 47, is as good as it can be, as quiet as it can be, as rich and full as it can be, will last as long as possible, and ben an overall more pleasing souding and unique studio possession.
Some quotes from first pair of these that were modified:
"First impression is great! Your work really elevates the microphones. It's does something that other mics don't do. With the mic two to three feet away from an acoustic guitar it sounds 'like an acoustic guitar.' It has a nice full sound that 'lesser' mics do not reproduce....
I have one mic setup in the control room. My voice, and acoustic Guitar sound very nice, and no wind sound (noise) in the background."
- Stephen Schoenecker, freelance recording and mixing engineer, Bristol, TN
6 meter Gotham 7 pin XLR
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6 Meter Gotham mic cable
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