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  • chaddavidkelly

always improving...


(image: main board of WA-47 as 'ultimate upgrade' is in progress)


It's been a while since I posted a blog so I figured I would just mention what is new in mic mod signal art land. So, things are still busy as heck and no signs yet of slowing down. It's been this way for the past year and a half. Coffee and no days off, full speed ahead...


I'm always trying to find ways to do what we do better, to take things to a new level. To that end, I discovered an American brand of resistors called PRP (Precision Resistive Products) who make an audiophile line of resistors which are supposed to sport the lowest noise and greatest accuracy in the business. It also just excited me to find that some resistors were still being made in the United States, and I always try to buy US whenever I can, for my builds and my mods. Their range of products and resistor values is limited; but we have started bringing in this line of resistors where we feel they make a difference and will continue to bring in more of them as time goes on. Obviously I despise waste, so if I have a good stock of a particular resistor value that works fine, I won't throw that out... but we will slowly start moving over to these as we need to replenish stock. We are already using a number of them on the SAE tube 47 and 48.


We came up with a way of adding some layers of shielding and anti-static tape to some polystyrenes, to improve their RF performance (always a concern with polystyrenes). We're not doing this mod to every polystyrene, but we are doing it in some places, particularly in the SAE tube 47/48/baseline edition and in the WA-47 modification.


The modification to the WA-251 has been improved to where we are now literally replacing every component in the microphone PCB sans the relays, output transformer, and capsule. I had discovered quite by happenstance that by replacing the generic tantalum capacitor in the tube driver section with a name brand part, it improved the sound and cleanliness ever slightly; so we began doing that on all of them. Then, I decided that since I'm already replacing one of the three generic polystyrene capacitors with an NOS mil spec part (because I change its value), that I might as well replace all three of them with better, NOS mil spec parts that are more resistant to microphonics and more rugged, and we found an additional benefit to doing that as well. So now, we basically change almost everything in the 251 from end to end. It might as well be considered an 'ultimate upgrade' at this point, because its darn close to it. These improvements really make me a lot happier with the WA-251, and I feel now that the stock capsule (which I never really liked) actually begins to sit well within the design once all these things are upgraded. It seems more clean, open, less harsh or hyped than before. While the stock capsule is still not a true CK-12, its now at least shown in its most flattering light and I feel a lot better about it. The reason I never just listed the mod as including a new 'true/chambered' CK12 capsule is the same reason I never listed the WA-47 mod with a new capsule upgrade...(even though I've done both many times on request), is just because I want to keep these mods in the realm of affordability... and making a $700 mod just starts to become silly. For that, you can put toward a nicer mic.


Why I stopped using NOS tubes alltogether...

So, this deserves a bit of explanation. In the past 2 years, I have really lost A LOT of money on NOS tubes that have gone south in both the WA-47 and WA-251 mods (and for some personal builds as well, to be fair). I've thrown away enough VERY EXPENSIVE NOS Sylvania and GE 5751's and NOS 12AY7s that either went noisy, failed, or sounded poor, that I'm almost glad I don't know the dollar total. :( Both of these mics have a tendency to sort of 'eat tubes' sometimes, and fixing that issue (if it is fixable) is going to require a complete board re-design of the mic and PSU so that I can do fine adjustments for B+, H+ and bias voltages in order to try to optimize and safeguard the tube as much as possible. That's a long term that project we are considering; but for right now we just have to do what everyone else does... find the tube that 'talks' to the board well enough rather than getting the board to 'talk' to the tube. For these 2 popular mods, this means using a new production EH or TAD valve that has been tested by a third party for lowest noise and microphonics. We currently are working with Tube Depot to do this; but may work with another company soon also. It is a shame, because I do still believe that the VERY best sounding tube for the WA-47 is the JAN Sylvania 5751, when that tube is flawless; but considering we are still stinging from having to throw the last four of those that we bought into the trash, it's just become a financial death trap that we can no longer expose ourselves to. Just as an example, because our margins are so thin, when I have to mail out just one of these tubes as a replacement 30 days later, I would essentially lose everything made on the mod service. They are that expensive, as is shipping. I just can't do it anymore. Likewise, my favorite tube (all things being equal) for the 251 is still the JAN GE 6072; but I've unfortunately thrown away far too many of these expensive little things as well. I've come to accept that the golden age of NOS valves is coming to an end. The best ones have been bought up, and what is left is getting far too expensive and also now just existing beyond their theorized operational lifecycle. I have to make do with what's new; considering that ruggedization and reliability is an important part of what I sell, not just sound. New production tubes are not immune from failure either, sadly; but it at least is something more manageable for a small operation such as ours. The best new valves available for these mods, as I see it now, are the TAD 5751 (Highgrade) and the EH 6072 (low noise/low microphonics), for the WA-47 and WA-251, respectively. EveAnna Manley recommended to me that I actually give new EH tubes a try and vouched for them, and I want to give credit where it is due for this hot tip. This is what I will use going forward on any mod that I do, unless a different tube is specifically indicated and provided by the customer.


Anwyay, that's all for now, back to the lab!

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