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  • chaddavidkelly

are there things I do differently?


Yes, quite a few. One thing I know I do a bit differently is that I obsess about wire a bit more than most people do. the length and positioning of wires, which ones are twisted, which ones are shielded, their gauge, strand count, and quality (am a big fan of silver teflon wiring), what types of exterior cables I use and how long they are (Gotham, and 6 meters, FYI), etc. Wire alchemy is one of the ways I try to combat noise and hum, keeping them down to very very low levels. I'm probably the only one I know who makes his own IEC power cable from scratch (premium edition mics anyway, the baseline mics have a power cable that I selected and added a Ferrite clamp to).


Another thing I do more than most involves adhesives on capacitors. This is something you more often see with cheaper mass production mics and PSU's than boutique, oddly enough, because its not considered very photogenic or attractive (and I agree, its not, though I can minimize the visual distraction when I am making a photogenic board). On mass produced stuff, you usually see a bunch of hot glue and silicon RTV and a good bit of some red knock-off of Locktite I often refer to as 'candy coating'. I use real Locktite on many screws; and for adhesive I always use a special kind that is 100% removable and non chemically interactive with the glued surface (something most silicons are not).


The reasons that a factory will glue down, say, large electrolytic capacitors are for very different reasons than why you would want to glue down, say, a small polystyrene in the high-z section of a microphone. Polystyrenes are prone to microphony, and gluing them down with a small amount of adhesive generally fixes this issue well unless the capacitor is truly a bad apple and needs to be replaced (it can happen, esp with cheaper polys made in Asia.. I actually use old stock polystyrenes most of the time, military stock if possible).


The reason for gluing down (and in the case of larger power supplies, even zip-tying them as well) electrolytics is mostly to keep them from rattling or vibrating and causing a cold solder joint, or from using their own weight and inertia to pull loose from a board if the device is dropped. High voltage components can microscopically expand and contract when they pass current, and over time this can lead to cold solder joints as well. Keeping the components still helps with this.


Tubes are something I both screen and treat for microphonics as well. I usually use Sandy Levy tube damper rings as in the case with my U47's. In the case of say the upcoming 251 and C12 microphones, where there is literally not room for a tube damper ring; I will sort of manufacture something to take the place of it. I cut a strip from a sheet of high temp silicon (same material used to make the rings) and put it around one side of the tube, with another strip bracing the backside of the tube against the PCB, and tighten it on with a zip-tie. It would be bad to put a zip tie directly on the glass envelope of most tubes because it would a.) put a localized pressure on the glass, and b.) probably melt and snap; but with the high temp silicon under it, the tie never touches the tube. This is basically a 'low-profile' solution for dampening the tube in close quarters.


This is something that, oddly enough, I feel that mic manufacturers knew about more so in the past than many people building mics today. I've seen old German mics where the small capacitors were often laid on their side with an adhesive silicon pad underneath them. Tube sockets such as that for the venerable VF14 were suspended in a rubber saddle. They knew what was going on. Today, manufacturers may be more concerned with having a photogenic or easier to assemble (or disassemble) board than a board that will stand up to room vibrations and other less than idea conditions.


This is one of those things where, I feel like the experiences of ones life can't help but affect how you do things. I've had weird experiences with microphonics. I've been called out to a studio before to look at a tube preamp I'd worked on, that was 'pinging' every time the snare drum was hit. It was of course, in the same room with the drums, sitting on the floor; but... that's a real world situation that can happen, and it did. I fixed it by replacing the one offending tube and adding more tube damper rings, and decoupling the PCB from the chassis, and adding some dampening to the chassis.


I worked in mass production for most of my career. I managed repairs at one company and had to do all of them at another. I want to make things that don't come back. Making and developing is more fun than fixing. I want you to be able to use any of my mics as drum overheads on the loudest kit in the world, with the power supply sitting by the kick drum if that's where you want to put it, and not care. That's the goal. I hope you never drop the mic or PSU (I really do); but I'm going to always put effort into trying to make sure nothing can shift around much if that does happen, and that it will stand a good chance of surviving. So, you'll see more clear adhesive and zip ties in my stuff than in many others. Less da Vinci and more OCD. So far, everything I've put out over the last 2 years is still floating out there making records. :) So, that's one thing I do a little differently.

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