We've done a good few of these now and the verdict is in. The ultimate upgraded WA-47 is basically like having a 'high end' microphone build inside of your existing WA-47's enclosures. The noise levels drop down to nearly as low as they can go, everything becomes tighter, clearer, punchier.
The Ultimate mod includes all of the work of th standard mod (complete end to end rework and replacing all capacitors, correcting output capacitor value and style, etc) but takes things to a whole new level by upgrading the tube to a rare NOS JAN Sylvania or JAN GE 5751 valve, replacing stock wire with silver teflon wire, simplifying and re-working the mic's factory wiring scheme and replacing all the wire from the XLR plug all the way up to the top deck, bypassing the transformer deck (wiring transformer directly), and completely stripping clean the top PCB deck -discarding almost every part on it and desoldering it and cleaning it down bare with anhydrous alcohol, then rebuilding using only top shelf precision WIMA audio grade film capacitors, audio grade polystyrene capacitors, name brand multilayer ceramic capacitors, Nichicon electrolytic and mil spec tantalum capacitors, NOS paper-in-oil output capacitors, Belden silver-teflon hookup wire, 1/2 watt and 1 watt vintage style carbon composition resistors, and name brand axial precision metal film resistors for the high value resistors in the high-z section, and a gold pinned ceramic tube socket, all soldered with Cardas silver solder. Essentially the main PCB of the mic is completely wiped clean and then 'reborn', built again at our lab to the highest standards. The result is a cleaner, purer, more natural sound, less hash and noise, and even a bit more of an authentic vintage mic vibe once the mic has warmed up, thanks to the subtle interactions of old school carbon composition resistors.
This mod is 'over the top', and not for everyone. I actually recommend to most normal peeople to just get the standard mod. But over the years we have been asked if it is possible to dive even deeper into the WA-47 and make it a true centerpiece microphone... and this is what we've come up with.
WA-47 ULTIMATE tube microphone upgrade
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 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 better, more authentic, and 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, feedback-amplifier type tube 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 allows me to finally 'complete the thought process' of making this mic everything it is possible to be and put a pin in something I worked on years prior.
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. Every capacitor I install is a name brand (Nichicon or Panasonic) and rated for 10,000 hours or more.
Next I install a tested and cleaned (pins de-scaled and then sprayed with contact enhancer) NOS (new, old stock) JAN Sylvania or JAN GE 5751 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. After evaluating just about every possible tube that could be put in this microphone, I determined that the JAN Sylvania 5751 and JAN GE 5751 (they are interchangeable parts, sonically and cosmetically), have the biggest, warmest, fullest, and most vintage vibe of anything out there. It sonically 'fills in all the cracks' in the microphone's sound and image, doing what I loved about the 5751 (warmer, more 3D, larger than life sound) but doing it so much more convincingly than the stock JJ part did, which is more shrill and emptier in tone by comparison. These tubes are VERY expensive and VERY hard to find, particularly certified and tested tubes from a reputable vendor; but I am committed to keeping a few on hand at all times for this mod. I personally clean (de-scale) and test the tube, and put it through a burn in process in your microphone for a day before sending it out.
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.
Everything from end to end on the mic is tightened, locktite added where needed, adhesive added where needed, the cable is inspected and sometimes rebuilt, and even the chassis cutout for the 7 pin XLR is re-cut to allow for better latching of the connector. Factory wiring is shortened and tidied up. Internal contacts are lubricated, and the rotary switch contacts are treated with heavy silicon grease for silent operation. It is a very holistic approach.
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 sounding and unique studio possession.