[Sticky] USB-C Microphone (official topic)

@marcdraco Okay so I have skimmed through this whole 35 pages thread. The only thing I have ordered thus far is a 25mm condenser capsule.

I am looking at your GitHub and wondering which version of the preamp you would suggest going with. I see the latest V2 being the Katie songbird. Is the V2 pro coming out soon so I should wait or do you have any other suggestion?

Also do the schematics include all the neccessary components?

Only show the spoiler if you want a peek behind the curtains and are prepared to risk making a V1.00 design.

Pretty much everything on GitHub has already passed QC. The 48V module looks to need a little work but I haven't actually used it "in anger" so to speak.

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@marcdraco Thanks for the quick reply. I plan to make my own stand and head and so forth so my only real concern is the electronics. Sadly I am not versed in circuit design so even if I got the kiCad project it would not clear up anything. If you plan to release Nightingale in the future I am happy to wait since I don't really have much time during June anyway and would not progress with the project. 

If you do not plan on making it public yet I might just go with the Bobbi starfire unless you would suggest a different one which maybe focuses on audio quality even if it needs a separate power supply.

We're kinda spoiled for choice at the moment. I'll have to pare it down somewhat so the production versions are clearer.

The gotcha with buying from China (i.e. JLCPCB in this case) is they charge extra for "special" components such as USB connectors, pinheaders and even electrolytic capacitors. These are the sorts of parts that can be sourced locally on eBay (or in your spares box if you have a collection). Hence it's a case of only factory fitting the stuff that's absolutely got to be SMD and limiting what JLC call "extended" components to a minimum.

The full board is almost entirely SMD with THT jumpers on a 2.54mm (100 mils) pitch standing in where we need to take a tap for something so it can be fitted in a case. 

@marcdraco Oh yeah I have no issues waiting 4-6 weeks. Will probably just go with the full version of nightingale once you release it. 

I have used JLCPCB before and I only ordered blank pcbs thus far. I even soldered some SMD stuff by hand just because it came out cheaper (it was just  a couple components I would not bother with a whole smd board). Do you perhaps have an idea of the aproximate cost that JLCPCB would charghe for the full version with SMD components?

Looks around $16 per board with DHL shipping plus taxes. I haven't suggested this to Matt, but they will be better crowd-sourced (the more we order the cheaper everything gets). You don't need to add much in the way of parts - you can even get away with a fixed gain resistor (which you get by trial until I've had a chance to calibrate a couple of different capsules). I hope we can get an eBay seller to carry them - as neither Matt nor I are geared up for stock management. You could always get two (the extra boards are pennies) and sell one for a profit people who don't want to wait.  Most of the cost is taken with the crystal and the TI chip. Almost everything else (save the output caps) are fairly everyday items. Some of the SMD parts are pretty small though as I've had to use a fair number of 0402 parts and they're tightly packed. 

So apart from the capsule and a headphone socket, they're pretty much ready to go. The cost managed one will be around 1/2 to 2/3 of that.

The others aren't deprecated, they fill a different niche, primarily for people who want to do a lower-cost upgrade, esp. Regan which is entirely through-hole. 

@marcdraco Oh cool to see that. I will be keeping my eye on this thread closely then.

@marcdraco also I have seen your message but cannot reply since I need 5 approved posts on the forum. Think this one might be the  5th.

You can reply now, you're out of the moderation queue. It's to stop spammers - and trust me, we get a fair number trying it on.

Im looking at recreating the V1 from the original video mostly due to the excellent instructions in the form of the video itself. Would I be missing out on much compared to attempting V2(or the in progress "pro" version)?

Yes and no. (Talk about hedging my bets...)

The published ones at GitHub (and there are plenty to choose from) do require further instructions but were mostly a bridge between what I'd promised Matt and the real V2 which is just being tuned in KiCAD now. The new one is a true successor with pretty much every useful metric tuned. Version like Michelle were developed for people who are unable to access chips such as the THAT1512 which can be hard to locate (if you want a genuine one that is). I've kept the real one very much under wraps because it's a complete, ground up re-design with all the best features of the original but broadly at lower cost overall for the basic setup with options for expansion. The first prototype has a few bits I need for testing but as soon as I've validated it all works correctly, I'll publish it to GitHub and everyone can have crack at it. It's been in development for months with a couple of hold ups like one of the parts going into short supply and the heatwave making it difficult for me to think, let alone solder! 🙂

You'll have noticed that I move at a glacial rate but that's largely due to my tendency for perfection (within reason) for a four layer PCB, it's easier with six or more but that gets rather expensive.

@marcdraco Does the new design still use the original capsule(JLI-2555BXZ3-GP)? Thats the only thing I actually ordered so far so I wouldnt mind waiting if I will be able to make use of that part still.

Yeah, it's 100% compatible with the original head (even for those who have built and encapsulated it in brass). This was one change I've refused to make for the V2 but the rest of the signal chain has had a complete re-design from the ground up. It's not that there's anything wrong with the original per se, but I using an SMD PCB gives me access to parts that just aren't made on a 100mil (2.54mm) pitch.

You have a wider selection of JFETs for reasons not really worth discussing but the original JFET is an excellent part. Even the gain switch retains the same basic resistor set although sensitivity is predicted to be better. The JLI2555 is a perhaps the best GP "FETLess" back elecret capsule currently in production. To get better you have to go to a polarised capsule but those tend to run costly. I have a working example here but it's not ready for prime-time as yet.

I decided to write a post about the final result of V1 in Matt's design.
I should clarify that I am using the SSM2019 preamplifier while waiting for the THAT1512 to be delivered from the US. It has a very similar tadashite, and the result will surprise those who are not yet familiar with it.

At first, I tried using a perforated board, but even after assembly, there was still a little noise that wouldn't go away, even after changing many variables. In the end, I came to the conclusion that it was the board itself.

For the final version, I decided to use a printed circuit board from Electronoobs.

I used a 0.12 mm shielded wire from the capsule to the amplifier, 3 mm wide.

There were many different wire options because they had to pass through a brass tube. Many of the options caused noise, but with this wire option, I was able to eliminate it.

Below is an example of the sound quality without any processing, as well as a photo of the microphone itself.

Vero is not ideal when you have a HF floating around the place, the noise from the NMA0515 is the worst source but a fair bit can creep up from your laptop, seems less of a problem with desktops, but it can still happen. A properly designed PCB should always give better results because we can control the fields more accurately.

Very nice work there.

@marcdraco thats great to hear! Ill be eagerly awaiting your new design. Thanks for the time and effort you have put into this!

@cyphecx If you repeat V1, you won't regret it either.

Yup. @polaryeti is dead right. Even V1 is quite superb. It's a LOT easier to look at someone else's design and take inspiration from it (which is what I've done), analyse for mistakes (again, WAY simpler when someone else has done the grunt work) and fix them. I've pushed my own skills beyond my limits and walked into territory (>1GHz on the rails) that I've always avoided.

But wait, 1GHz - that's well outside the audio range, right? It is but when you've got a high-speed mixed mode design (and these will give you some clues about the real V2) the clock edges are switching from 0 to 3v3 and back again in times measured down in the nano-seconds or less. As Rick Hartley puts it - even if your board only switches once ever 24 hours, the actual edge is so sharp that it produces harmonics to moon! And that means (if you mess up) the board is infected with fast moving edges and your nice, high-impedance audio signals sound like there's a thunderstorm.

V1, despite being made on experimenter's board (stripbboard, often called Veroboard in much the same way we call Hook and Loop material, Velcro) is brilliant.

And that's why development of V2 - as a true successor to the king of Maker mics has had such a long development phase.

Phase one was to make a board with the same functions as V1 but with better noise suppression to get that noise floor down while putting less load on the USB supply. Over time I experimented with P48 (professional) phantom power but came to the conclusion that more electronics causes more noise. Not much but enough to give me pause. A P48 one is sat in "the lab" complete with a 5 to 48V boost converter and that might appear eventually, but it's only really useful for unbiased capsules which cost >$150 a piece and frankly the TSI/JLI-2555 is more than sufficient for a vocal mic. It's a little peaky in the higher registers but most people find that more pleasant than the flat response. Larger capsules (because of physics) tend to be more "boomy" and the 25mm size is a nice compromise between 10mm (about the smallest you can get with a cardioid response without resorting to MEMS units and the 34mm standard used in the "pro" capsules.

I can do a MEMs "head" if there is call for one but they require a more expensive production board due to the "breather" hole which has to be drilled underneath the mic - which itself it only a couple of milimeters square. These things are incredible with an ASIC chip on board to make more responsive to applications like very high-end headsets like this one: https://invensense.tdk.com/download-pdf/ics-40800-datasheet/  

It's very easy to lay out the board and they typically only require a couple of volts to drive them, much like a classic electret, although C0G capacitors are a MUST if anyone wants to take a crack at it. V2 has an extra input (assuming it makes the final cut, which it might not) to accept another mic.

For headset use you can use a small fixed board for the mouthpiece (perhaps made on a 3D printer) and either a flexy PCB or some jumpers to wire it to the remote electronics - which, naturally, go into the earpieces. I've done all the boards necessary for this but they aren't all in one at this stage. If there's any call for one, I'll do that after the V2 is complete as most of the schematics are ready, they just need laying out. I'll leave that one up to the community and Matt to decide.