micparts T-47: A fantastic DIY microphone

Discussion in 'DIY' started by purr1n, Sep 4, 2021.

  1. purr1n

    purr1n Super Friend

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    I'm posting this because a few people asked. First of all, if you are an objectivist, go away. This project employs a microphone capsule that doesn't have a flat response. It's also a transformer coupled (NOT transformerless) design with a single active component, a JFET, where I intentionally chose a resistor to bias the JFET for higher second and even order distortion.

    I had been looking for a large diaphragm transformer coupled microphone, particularly a vintagey sounding one, for some time now. The problem is that they don't make 'em anymore. Well, they actually do. But the problem is that we would have to cough up around $4000 for Neumann U47 FET. That's bullshit. I know Neumann is a respected name in microphones; but I f'ing hate them. Over the decades, they've cheapened their microphones while keeping their prices astronomical. It's for the mystique, the brand name. @Psalmanazar and I talk about studio gear every now and then and we joked about recording studios may have a Neumann on hand just for the cachet, but in reality probably use other microphones.

    For this project, I pretty much used the parts from the micparts T-47 kit (https://microphone-parts.com/collections/microphone-kits/products/t47-microphone-kit) with the exception of the capsule which came from @Soliloqueen. I can't down turn playing with creations from fellow members, encouraging them to make good shit. This capsule is intended to be similar to the K47 capsule of the U47 which has a bump in the presence region (it's intentional) and is still under development.

    PXL_20210703_002900066.jpg
    Note Sonicap boutique part and good WIMAs that would make Dannie Ritchie proud.

    Anyway, I feel like I've scored a fantastic deal with a little bit of elbow grease. I know that my current gear (MOTU Ultralite mk4) is not anywhere good enough to capture the resolution, texture, and nuance that this microphone is capable. It's the nature of the design: a single transistor (JFET) followed by a transformer. The downsides are higher distortion, especially at higher SPL, which limits max SPL. This is a different approach from more modern designs with tons of transistors and super low distortion. Many modern microphones even employ opamps - yuck - which is even another step backwards in terms of capturing the immediacy and nuance of recording.

    The first question I often got was this: was this easy to build?

    My answer is that is was brain-dead easy. It's million times easier to build this than to repair most Modius DACs. I do have a decent amount of experience with soldering irons and had only gotten better because of necessity. However, I still think it's an easy first time project. I will cover some bases first.
     
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    Last edited: Sep 4, 2021
  2. Azimuth

    Azimuth FKA rtaylor76, Friend

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    The only way to get a real U-47 sound is not through gold sputtered may, but with PVC. Yes, PVC, gold sputtered PVC. It is kind of like making ribbon microphones. Only a handful of capsules make it through.

    Neumann was bought by Sennheiser years ago and basterdized the line. Blame them, not Neumann.

    If you want a real Neumann, then get a Microtech Geffell. If you want a U-47 FET, then get a Geffell UMT 70S. Gaffell is what became of the original Georg Neumann factory in East Berlin.

    The copies do a really good job of the original circuitry and preamp design. The capsules are still Chinese capsules that are similar and will sound pretty great on axis, but off-axis some will be more colored than most. The PVC does not have this issue - super wide clean pattern.

    It's much easier to pick up a Rhode NT-1 or NT-1A which gets almost as close without the DIY.

    These are fun projects. As there are also kits and some upgrades you can do to MXL mics to better specs, lower noise, etc.
     
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  3. purr1n

    purr1n Super Friend

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    I will not purport to be a master of soldering. I will also not tell you that DIY is always cheaper. DIY requires considerable upfront costs with good tools. Even a first timer will benefit from good tools. Micparts makes this build super easy though. All the wires and leads are pre-tinned with solder (from what I can remember). They provide an excellent instruction manual with step by step procedures (of which I didn't bother to read most).

    Before we begin, I suggest the following if one doesn't have any gear or much experience:
    1. A Metcal PS-900 Production Soldering station. I basically threw my Weller with temperature adjustment into the trash after using this. The soldering iron is ready 10 seconds after turning it on. You do not fuss with any temperature adjustment. It's set depending upon the tip. It's got some kind of high-tech deal where power delivery is adjusted via RF sensing. The specs say that the output frequency is 450kHz. Bottom line is that this iron feels significantly less hot than any ones I've used before with better capability to get the solder flowing. I have not destroyed anything because of excess heat using this iron. The downside, it's $250+. Good tools aren't cheap. I refuse to use any other kind of soldering iron. The Metcal spoils you.
    2. Superwick fine braid soldering wick. You will screw up or have a brain fart. When you do, add an extra blob of solder and then use this wick to wipe up the spot. Actually, remove the part first. Blob the pin near the hole to melt the solder to pull the part out. Then wick it up. A solder sucker can help too, but get a big one. The small suckers don't work. I don't think this project needs a solder sucker. It's pretty much small holes on the PCB.
    3. 60-40 tin lead solder. Don't be a retarded audiophile and use silver formulations. Just don't. Although the Metcal will save your ass if you fuck up.
    4. Magnifying glass with light on a clamp. Unless you have 16 year old eyes with better than normal vision. I'm over 50 now. My eyes suck. Even if you have good vision, it doesn't hurt to have one of these because it lessens eyestrain.
    5. Carburetor cleaner with Q-tips to clean the board. You are supposed to use alcohol. This works x50 better, but is arguably worse for the environment.
    6. Practice on a CMOY board: https://jdslabs.com/product/cmoybb-diy-kit-rechargeable/
    Here is the main PCB for the T-47 kit (the manual is in the background).
    PXL_20210702_144310132.jpg

    Note that the manual has decent-sized print with big photos. It's not like a Topping DAC instruction manual which requires a microscope to use.

    The process of stuffing the board was dead easy. I only have one suggestion. The instructions say to lift one leg of the JFET up from the board (it needs to be far away from the surface of the board). If I had to do it again, I would lift the leg up a few mm higher. The reason is is where four or five other connections terminate, including one from the capsule. Having this up a bit higher makes it easier to reach with the soldering iron.

    PXL_20210702_164207003.jpg

    Here is the same point, but from a different angle. Sorry, it a bit out of focus.
    PXL_20210703_002543594.jpg

    Note the switch on the bottom. This board will support cardioid and omni directional patterns. Keep in mind which is the front of the mic when you slide the board into the body! Changing the pattern requires opening up the microphone body. It takes less than minute to do this - it's just a matter of unscrewing the end cap that keeps everything in place.
     
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    Last edited: Sep 4, 2021
  4. purr1n

    purr1n Super Friend

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    This is the other PCB that houses the transformer. It's a house brand. There are at least two Cinemag transformers that will work - they have different distortion profiles.
    PXL_20210703_010023117.jpg

    Note that I did elect to bias the JFET for added second harmonic. Micparts provides two resistors. It's not a ton, just a bit more. I can elect to reduce this effect by turning on the pad switch which lowers the output. This is because the harmonic distortion isn't constant, it's only goes higher at higher levels. Now combined with different transformers (which have the same type of behavior, i.e. THD goes up with a hotter signal), this could be a tweaker's delight. As I like to say, roll transformers (or bias) rather than tubes. Yes, there's an art to using microphones. (OMG, how are audio "science" people going to deal with this? Audio is like cooking or painting? The horror!).
     
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  5. purr1n

    purr1n Super Friend

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    5F4A0027.JPG

    Here it is at my workstation. I use it for my cybersecurity consulting work in M&E. (Yeah, I got dragged back into it). Anyway, I found this project super rewarding considering how easy and fast it was to put together. There is an immense level of satisfaction and joy knowing that you are using something that you assembled from parts. (Again, I recommend that newbies put together a CMOY first).
     
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  6. purr1n

    purr1n Super Friend

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    Those are all transformerless designs and not exactly what I was looking for. I also wanted to highlight what some members are trying to do. Thanks for ruining the vibe.
     
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  7. Azimuth

    Azimuth FKA rtaylor76, Friend

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    If you want a real $4000 U47, you would want a tube one anyways. The later FETs have a slightly different sound.

    You just have to realize that condenser microphones are the oldest design microphones and almost all of them are a copy of the old German designs in some way or another. So there are hardly any secrets anymore. They have even found a way to copy the elusive ELA M 251E with it's crazy solid state circuitry. So these designs have been copied to death and now by all kinds of boutique companies to many others. There is a U-47 type is almost every price range.

    The kit you have does have quality parts and I am sure sounds better than most mics in that price range. And some capsules are certainly better or can be tailored for a certain sound. There is a guy here in town that makes custom mics and repair, and even tensions his own capsules for whatever the customer wants.
     
  8. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    I personally subscribed to this thread so I can hear @purr1n sing.
     
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  9. Psalmanazar

    Psalmanazar Most improved member; A+

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    @Azimuth Gefell is great. It’s good bright in a way that the current Neumann ahem Sennheiser mics are not. It is full range. None of them sound like older Neumanns from the 40s-80s. @purr1n is right. Neumann doesn’t make bad mics, they’re just all tuned for a very bright diffuse field sound so that middle aged and older German guys can record screechy modern classical or bright modern rock and pop. They often like the peaky response to come across as louder without eq too.

    Rode is dogshit and brittle as glass. I’ve heard talk of good Rode mics but I’ve never found this to be the case in reality. They all sucked and needed to hit multiple de-essers and all other kinds of crap.

    U47 FET is known for being a kick drum mic.

    A lot of the current Neumann and Sennheiser mics are just poor value and there’s not enough money in this business.
     
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    Last edited: Sep 5, 2021
  10. batriq

    batriq Probably has made you smarter

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    @purr1n Do you this will be good for recording violin? Is the capsule that comes with it good?

    @Soliloqueen is it possible to still purchase one of your capsules?
     
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  11. Soliloqueen

    Soliloqueen Friend

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    Yeah! They're still on sale for $99 OBO. I didn't do the backplates myself, and they got the through hole sizes slightly wrong, so the FR is a little less stable through patterns than I'd like (omni is a little bright, figure 8 is a little dark). That's why I made sure to mark them clearly as prototype capsules. I'm moving the backplate production in-town and I will be personally supervising it for the next batch (which will hopefully be production spec). These existing prototype capsules are still equal to or a bit better than other capsules available on the DIY market in the $150-200 range though.
     
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  12. purr1n

    purr1n Super Friend

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    Yes, this is what large diaphragms are for, along with a lot of other stuff like vocals, guitar, bass drum, upright bass, cello. These kinds NOT good for high-hats, cymbals, triangles, etc - where a small condenser is better. You get the idea. The large condensers have a richer sound than the smaller ones. The smaller ones are "faster" and can keep up with higher frequencies.

    if you had to go with one mic on violin, without complex arrangements of multiple mics and mixed in (funny how the modern world can make stuff more complex), just use a large condenser. Put it on a stand and have the microphone up high to face the body. It's crucial that you hit the front of the body of the violin because that's where the lows come from. Two to three feet away is a good start. Closer will pick up details like the rubbing of the bow on the strings, fingers moving on the fingerboard. It depends what you want to do and what you want to pick up.

    With this capsule, you may want to EQ down the highs a few db. I am thinking 5.5kHz with a Q=1 as a starting point. Play with omni and cardioid patterns and distance. You should be able to get big sound with a good sense of the room. Unlike voice, you will not need to treat the room or have panels. Note that this approach is very different from a violin pick-up mic.

    You can get some spectacular recordings if you or anyone else plays in the house.
     
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    Last edited: Sep 5, 2021
  13. Psalmanazar

    Psalmanazar Most improved member; A+

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    And yeah the MOTU preamps and AD conversion are outclassed by decent condenser mics. They’re warmed over for cheap and nasty condensers. They use fuzzy JRC opamps and digitally controlled analog multichannel ics. The MOTU AD is noticeably worse on loopback than the DA. You’re just going to have a hard time finding a good ad for under a 1000 bucks. There’s no audiophile market to push the prices down.

    The cheapest new mic pres that are good and clean without a lot of objectionable qualities is the FMR Really Nice Pre or 500 series diy kits or used scores. Expect to pay 200-300 a channel. Otherwise expect to pay 1000 a channel for something good and maybe 2000 for a channel strip. Most of the classic big name and number pre amps are just distorted in a cool way and building clean tube pre amps now is pretty much almost impossible now due to the available production tubes.
     
  14. purr1n

    purr1n Super Friend

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    More photos. Capsule and what comes in the box for the circuit board. As we can see, there's really not much work to do.

    DSC00771(1).JPG
    t84kit_1024x1024.jpg
     
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  15. purr1n

    purr1n Super Friend

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    Any decent microphone will be too much for the MOTU. Sure an AT 2000 or 4000 series into the MOTU will be better than a Blue Yeti USB; however once we get something better, the MOTU really shows it's limits. I've been looking for a Neve or Neve clone mic-preamp. @philipmorgan suggested the Daking Mic Pre One. Maybe this directly into the MOTU's line level in would yield better results. I don't know how good the MOTU is as a pure A to D. I'd be willing to bet Schiit's discontinued Jil line level A to D is much better.
     
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    Last edited: Sep 6, 2021
  16. Psalmanazar

    Psalmanazar Most improved member; A+

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    Objectivists can leave the hall. There just aren't audiophile style internet keyboard warrior objectivists producing engaging recordings in the pro world. Ethan Whiner's recordings sound worse than artists who recorded and mixed onto cassettes with Tascam Portastudios. There are psycho measurebaters modding everything for better specs and designing their own gear for more clarity but they would never, ever, be content with cheap Chinese crap; they would eviscerate it.

    I agree with you on that. These PGA2505 suck. Pretty much anything not a budget interface is better than the MOTU's AD.

    Daking is great. Clean but slightly colored at the same time. Everything sits well and little bit of zip helps it cut. It's based on the Trident A range circuit, not Neve.

    Do you have a 500 series rack? There's so much good cheap stuff available for them due to not having to spec out power supplies including great diy stuff. RND 511 is about 600 bucks. Good diy 500 series kits will run you about 300ish.
     
  17. Azimuth

    Azimuth FKA rtaylor76, Friend

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    I'd love to see a 500 series DAC and headphone amp. Separate units obviously.

    I've always loved RME A/D. Their newer D/A maybe not, but it is clean and deep. Otherwise get a megabuck Lavry, or Apogee, or some of the newer Lynx. Although the RME preamps are just okay.

    So nice to have a thread related to my actual college degree.

    The Jil too could only do unbalanced line in with no level control. Based an an AK input chip.
     
  18. atomicbob

    atomicbob dScope Yoda

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    @purr1n : I suggest you find the following:

    1) Great River MP-2 (original NOT the NV version)
    2) Symetrix 620

    Original MP-2 is a Jensen transformer input preamp that has served me well for years.
    The 620 is "only" a 20 bit converter that just happens to sound far better than many 24 bit converters and the so-called 32 marketing bit converters. It also has an extraordinarily useful metering system. You will need the MOTU to provide interface between 620 digital audio data output and computer USB input. The 620 must be the clock master.
     
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  19. philipmorgan

    philipmorgan Member of the month

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    I'm about 95% sure the MOTU m4 (I know you have a different MOTU but maybe this applies?) line input does *not* route through a pad resistor and into the mic pre like lots of the other interfaces in that price class. This is based on close listening to the m4's mic pre vs. Daking Mic Pre One into the line input on the m4. The Daking into the line input doesn't have that "inner warmth" that the m4 mic pre does.

    That said I can't promise even a solid pre like the Daking into the m4 line in will be as good as what you're looking for. :)
     
  20. Cspirou

    Cspirou They call me Sparky

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    Anyone familiar with FMR audio? It's a guy in Austin that builds cheapish recording gear that Steve Albini has praised, saying you need to spend 10x to get any better. His naming scheme is as unserious as Schiit. (RNP = Really Nice Preamp, RNC = Really Nice Compressor)

    http://www.fmraudio.com/rnp.html

    reading the description there's a lot of features that sound right. Class A, discrete output pair, etc
     
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