We're always keeping busy here at the lab and there's a few new things to go over. Firstly, we finally have developed an upgrade for the WA-67 tube microphone, after years of requests. I procrastinated about this particular model for a number of years because I just wasn't sure that I had anything to 'add' to this design, given certain immutable constraints that it has (Lundahl output stage, etc) and the limited real estate on the board, etc. It turns out, I do have something to say about this mic afterall and have come up with a best-case-scenario set of upgrades to make it, it my opinion, the best it can be within reason.
There are a few things they did right, and I do want to give credit where due. The mic circuit for the most part follows the 67 schematic, and the power supply is built correctly as well. It has the some of the telltale 67 characteristics that a 67 must have, including a negative heater voltage that can be calibrated. They did that right, and did a few things right. They used good polystyrenes and WIMA film caps. The included Electro-Harmonix EF86 is a decent choice as well, although we 'do' retrofit the tube to a selected new old stock pentode anyway.
The output capacitor is a generic film capacitor; but in their defense, there really isn't enough real estate to put something a lot nicer in that position. They didn't put their customary 'Solen Fastcap' there (ala 251 and WA47); but I never liked those anyway. I'd honestly put a generic film cap there in place of those in most mics. What we did to get around the real estate problem was to firstly move some WIMA caps around to the backside of the board to get them out of the way, then to split the larger value 4.7uF cap up into four smaller JB JFX Premium film caps that we can place around that position with even one on the backside, all in parallel to form a composite 4.7uF capacitor network. It was cumbersome; but it was the only way to upgrade that and make it fit. Also pretty expensive to do, considering each of these constitent JB film capacitors cost around five bucks!
I am puzzled over their choice of a custom Lundahl transformer for the output, as Lundahl have never made a conventional BV12 transformer (ala 67), and this certainly isn't one either (significantly smaller); but it is what it is. The part is PCB mounted and there is no room to do anythnig larger; therefore this is simply part of the baked in properties of this mic. This transformer, and the 10x larger value output cap needed to drive it, are deviations from a traditional 67 design and therefore will probably make this mic miss the mark a little bit in terms of sounding like a 67; but they are quality parts and the slight difference from authentic tonality just has to be accepted. I still feel that we can still work around this design decision and improve everything else that is possible so that in the end its affect on the final sound is minimal.
What I did take greater issue with is their choice of capsule on this design, as this capsule appears to be a more generic Asian K67 import, something along the lines of the Alctron/Xingde Trading K67 often seen in more generic/cheap products or that pop up sometimes as affordable 'capsule upgrades' by some other vendor sites... This is a very budget capsule, one that sells for only a fraction of the more decent Asian capsules they typically use in their products. It olmost certain accounts for some lack of realistic sound or lack of 'heft' or weight that some listeners may perceive. I have evaluated these very capsules in the past, and always found them to sound thin, harsh, un-lifelike, one dimensional. We never before replaced the capsule in our WA mic mods, hoping to keep things more budget consicous; but in this case we are making an exception. For not a completely unreasonable amount of money, we are able to put in a much better imported K67 capsule made to our specs. The better capsule is not cheap (runs us about $50); but unlike the other tube mic mods where we have to replace the regulator, in this case we do not, and so we save some money there and have simply decided to absorb the rest of the cost. The upgrade capsules gives it a slightly fuller and smoother sound.
Once again (as with the WA-CX12, WA-47, and WA-251), the cable is reconfigured to be optimal for this mic design, and we do our usual process of replacing all capacitors and wire in the PSU and rebuilding it more clean and tidy. On the mic, we replace the output capacitor, add a chassis ground wire, add more adhesive to the polystyrenes to reduce microphonics, replace the capsule with our own custom imported K67, and replace the stock tube with a selected New Old Stock EF86 pentode (typically 60's era Winged C or Tungsram, which is what we have the most of here). The stock tube makes a great spare, but I still find the vintage ones have better construction and a richer sound.
Little box news!
In other news, the final production run of Signal Art ReAmps and DI's is moving fast. I have less than 8 left of the ReAmp, AngReAmp, and Direct Box. Speak now or forever hold your peace! I am extremely grateful to the customers who have kept the lights on around here over the last 6 years with the ReAmp; and looking forward to our renewed focus on mic designs!
So, while the OPR historic K47 is and will continue to be our 'go to' and stock capsule on all our handcrafted 47 and 48 mics, it is undeniable that people love to have a choice in the ingredients that go into their mic. I have listened. I am working to start offering again the Heiserman K47 capsule on request as well as a high end historic M7 capsule option! Very very excited about this, and we've already had our first inquiries about getting a U47 made with an M7 capsule and with the HK-47 capsule, in addition to our stock version and baseline edition version. If anyone has been waiting for the day when there were other capsule options to choose from, please wait no longer and get in touch with me. The website will be updated very soon to reflect this but I will already be taking pre-orders for them.
That's it for now. Have a great weekend! Hard to believe NAMM is already just over 3 months away. time sure flies.