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Old 1st December 2015
  #1582
Gear Maniac
 

Cm87/cm414

Hello, thanks for your comments. To quote, "The Greatful Dead".

What a long strange, trip it has been. I have loved every minute of it!!!

I have got to work with or meet quite a few of my heroes along the way.

I have been a professional audio engineer since 1965 and a mix/recording engineer since 1968. I built and wired several recording studio in the 70's and 80's.

I have re-built or serviced most types of the major recording consoles. I have designed lots of "proprietary" custom recording gear but I have never worked in a microphone factory even though I have repaired many different models and types.

In the 80's we ripped out all transformers because of "phase" issues and by the turn of the Century folks were putting transformers back in to help smooth out the "audio" before it went digital. Transformers are governed by the law of hysteresis as is recording tape. This can create "compression" of the high frequencies and more even order harmonics are generated". Which is "nice" sounding distortion.

One of the things David Royer and I discuss is there are no "proprietary" circuits.

All are variations of discrete, IC or tube circuit topographies that have been long discovered but there is still room to implement some if these more elegantly.

There are several ways to "skin a cat" and get the same result at the end.

You can apply slight variations and build a hybrid circuit like our CM28 which has a FET as the front end connected to the capsule and this Fet is placed across the cathode of the tube and the tubes grid is grounded. You get the detail of a fet circuit and the warmth of a tube circuit.

Components need to be selected for their location through the audio path we have found that polystyrene capacitors work best betwen the capsule and the fet or tube. So, using all WIMA capacitors throughout is not always the best design strategy but using them in strategic places as you would other components like Dale or Vishay precision resistors.

Some earlier versions of our microphones have metal film WIMA caps in that location. However, I see there are polystyrene in the front end of the Warbler circuit board pictured, which is good. My friend Tom Graefe who designed the Sony MXP3036 console turned me onto the polystyrene caps for coupling the capsule.

BTW, those "mustard blob" capacitors you talk about are tantalum capacitors costing nearly $3 each. This is what Neumann used in the audio path of the U87 as did AKG in the 414eb.

The Zen Pro Audio mod for the GA73 clone involves replacing 7 electrolytic capacitors and replacing them with tantalum capacitors as Rupert Neve used.

If you are going to replace them with Nichon electrolytics use 63v non polarized ones and bypass them with a .01 WIMA. The tantalums do add some vintage "colour" to the sound BUT if you put them in backward they are quickly destroyed and will cause horrible distortion.

All our tube microphone use a WIMA SMD-pet 2.2ufd output capacitors with a polystyrene input capacitor.

You could send the CM87 back and exchange it for our CM48. The CM48 is less brash at 10khz having a nice K47 upper midrange and the 2.25:1 transformer.

Which Warbler do you have the K67 capsule version or the CK12 version?

I basically designed the CM87 for voice/over work and spot miking.

My guess is you like the more open sound of the edge fed capsule but with a LP filter switched in to reduce the rise at 10khz about 3db.

The only thing we could offer is to modify our CM414 which has the edge fed capsule and 3 patterns so the LP filter becomes a HP filter pulling 10khz down 3db.

Now, I am not unhappy that there is a another microphone maker producing quality offerings and with alternative options in our price range. Especially, using the same body as our CM87, CM48 and THE TUBE CM48 is brilliant. It means the metalwork factory will keep producing these bodies, head grills and sleeves for the forseeable future. We all benefit from this as it keep the metalwork price low.

The body is very egornomic and easy to dissasemble for serving. Another adavantage is that we offer replacement HD shock-mounts that will fit that body.

I just finished "designing" a U48 type tube circuit that fits into the CM48/CM87 Warbler body and head grills. Its based on a miniature 6aK5-7 pin tube which has incredibly similar spec to the VF14 but requires a 6 volt filament supply. We are very excited about the prototype with our AK47 capsule fitted. It will have a BV8 transformer but with a custom turns ratio to match the 6AK5 which has a plate resistance about 20% higher than the venerable old VF14 tube. It will have 3 patterns plus a hp filter and pad.

We are going to layout the circuit board over the next few days and then send it out for printing. We have the bodies and head grills on hand in Shanghai to build up CM87 and CM48 microphones. We believe THE TUBE CM48 will be in production and ready to ship by late winter/ early spring 2016 for $595.00.

At the moment Scotty and Mike are down in the studio testing the prototype.

How old is your CM87? After the first two runs we increased the gain and headroom by 3db and the last run has an upgraded transformer much like the Warbler transformer but with a 2.25:1 ratio to match the emitter follower.

It is a bit more "HiFi" and open with the 2.25:1 larger transformer and the resistor change. R10 should be a 2.4K resistor not a 4.7K.

Now, I admit I have fallen a bit out of touch with the average project and small town studio guy of which I was once a card carrying member.

After, sampling the rare air up at top and getting my 15 minutes of fame with my super-heros; I realized that I should now set about to built a classic sounding vintage tube microphone based on the U48 that would be worthy of being used in a major studio but well within the budget of most project and grass root studios.

Once the circuit boards go off to print I will be heading to Mexico for vacation and to record some live latin and jazz music in Los Cabos.

All the best to everyone for the Holiday and the New Year and thanks for supporting and talking about our microphones.

Cheers, Dave Thomas
aamicrophones.com













Quote:
Originally Posted by MYN View Post
Dave,
You crazy mad genius. You know that old saying about how "you can't polish a turd"? Well, kudos to you for showing that you can. You are able to take an inferior microphone someone else designed and mass manufactured, identify what could be done better and, gosh darn it, you or your man Scotty get in there with your soldering irons and modify the heck out of that thing until it sounds like something much better than what you started out with. Really, as a mic modder with a decent biz plan, you're aces. You've even written here about how your manufacturing sources are integrating your circuit changes and mods into their stuff. I only hope you're getting a royalty for that, but I probably wouldn't bet you are. Your story, your background, impressive. I even bought one of your microphones. But, unfortunately, to my ears that microphone still sounds sterile and lacks depth. I don't really like it and I never use it. Ironically, I've been thinking about modding it! Maybe taking out some of those ugly mustard blob caps and throwing a couple of Nichicon Muse caps in there to see if I can add more life to it.

And while 3U Audio may share some same metalwork sources for their mic bodies coming from that one square block in China where you say 90 percent of mic bodies come from, I'm of the belief that the comparison ends there. It appears that Guosheng designed his own proprietary mic circuits and capsules and then he builds them in his own factory. Look inside any 3u Audio Warbler or GZ series and you're going to see it's loaded with premium components, Wima caps, Dale resistors, etc. Open up an AA mic and... well, you don't. To me, that feels like a really big difference right there.

Plus, you can't deny that AA mics, are costlier than 3U Audio mics. Perhaps that's just a function of you being the middleman here and having to account for your bench time, import fees, etc. IMO, on a dollar for dollar basis, AA loses this contest, hands down. Because of the way 3U is set up as an all-inclusive system, it's not an even playing field, but then again, neither is life.

Here's the kicker though. Price-schmice--It's all about sound, right? You look at this ridiculously massive thread and all the comments to date and one thing is pretty clear: people are losing their minds over how these 3U Audio mics sound. My mics get used for work every day. I rely on them to make a living and one thing has been clear: the increased number of compliments I've been getting on my sound from my clients ever since I switched to using Warblers as my main mics. In my little world, that's enough empirical evidence to justify what my ears are already telling me. In a world of wanna-be's, 3U Audio mics are the real deal.

I will never profess to ever know as much about mics as you obviously do, or as much as Guosheng does. But I do know one thing: your CM87 doesn't hold a candle to the Warbler I. It's not even close. To my ear, next to the Warbler, the CM87 sounds cheap and thin. Put those two mics side by side (which I have) and you'd never guess your mic is the one that costs $100 more (not counting shipping). I guess you can only polish a turd so much. Going back to your Zappa paraphrase that was sadly deleted by the moderator for being OT, the CM87 is more of a Sears poncho.

Dave, as much as I've been amused by your puzzling screeds in this thread, I've found them educational to a point. Dude, you know so much about microphones but this thing you're doing here and telling us 10 thousand times that a mic of yours is on so and so's album, well, it's starting to get sad. And I think you're better than that. You are probably one of the top 5 mic modders in the world. Guosheng is a mic and capsule designer. We're talking apples and oranges. However, the ultimate difference may be the scalability of his business vs yours.

Sigh.... Perhaps what would be a better use of your down time, instead of trying to OT this thread, is to tap into that massive mic knowledge of yours and design your own proprietary circuits. That I'd love to hear. Or write a book or blog about them. That's something I'd buy/read in a heartbeat. You've been around forever and 3U is obviously an embryonic entity, one that's been selling mics for a fraction of the time you have, but one that is quickly developing a rabid following of early adopters. And as many threads as there are on GS about AA mics, I don't recall reading reactions like the ones we're seeing here, and how telling that is, well, is probably up to one's interpretation.

The fact that Guosheng has used this thread as a user feedback mechanism to improve his offerings in almost real-time is pretty incredible and maybe that's a strategy that could benefit more people in the mic biz. But when it all comes down to brass tacks, there's a "bang for your buck" factor with these amazing sounding 3U Audio mics that gives them an incredible edge... well that and there are no polished turds in the bunch.

Best,
M