mic pre - a tiny line-level electret microphone preamp for Norns/modular/field recording and whatnot

Brett_Gershon · 2022-07-17T15:18:41.451Z

Ah! Do you have any more of these laying about Steve?

ramphands · 2022-07-17T16:22:27.782Z

If you order them from JLCPcb, there shouldn’t be any problem with the gerbers.

robbie · 2022-07-17T18:02:24.225Z

His shop listing says sold out.

okyeron · 2022-07-17T20:28:57.916Z

I don’t, but could add some more on my next prototypes order (maybe later this week).

FWIW - It’s likely OSHpark has a different minimum board size than JLCPCB (where I got those done)

@kasselvania you get any of those built yet?

Brett_Gershon · 2022-07-17T21:04:37.286Z

Oh shoot. I just ordered a batch of them from JLC. That being said. If anyone needs one I’ll have a few more than I need here soon.

Anyone know where to easily get the op-amp right now or is it a play the waiting game with mouser kind of situation?

robbie · 2022-07-17T21:26:43.498Z

Teenage Engineering TX-6 Equipment

actually, looking at octopart, the opamp for this mic preamp appears available directly through TI and from one other distributor.

kasselvania · 2022-07-17T21:33:00.030Z

I plan to on Monday. I’ve had a bit of a… week… with some family in town.

I also plan to get some good size shrink tube for all of this. Very excited.

Durdee · 2022-07-17T23:06:04.350Z

Sadly the opamp is available direct, but only in batches of 1000 to businesses. I found some on eBay and they’ll take awhile to get here but I’m hoping they’re good. If anyone figures out how to get them in smaller quantities in the USA I’d love to know! Once I get the ones from eBay and have a look I’ll report back as to whether they’re the real deal!

jaseknighter · 2022-07-17T23:35:54.657Z

@Durdee, yeah, i figured that out too but then discovered that LCSC has them in stock.

kasselvania · 2022-07-17T23:37:21.482Z

Wait, really? I bought 4 from TI directly

jaseknighter · 2022-07-17T23:49:31.320Z

i ~~think~~ thought they stopped selling individuals of this ic just a couple of weeks ago.

edit: but i was mistaken

ramphands · 2022-07-17T23:57:22.892Z

Edit - the link was for the wrong footprint. Make sure you get the SC70-5 footprint version!

Durdee · 2022-07-18T01:05:44.865Z

THAT’S what I must have been searching for. Well that’s awesome!

PedalsandChill · 2022-07-18T19:47:33.821Z

So, I’ve never purchased someone’s pcb design outside of a kit before. Could someone help me out and fill me in on how I can order the mini pre amp with the audio jacks??

ramphands · 2022-07-19T03:34:55.370Z

Hello!
The easiest process is this:

go here and click on the green “code” button and select “download ZIP”
GitHub - ramphands/mic-pre: battery-powered ultra-small electret microphone preamp for synth/Monome Norns/field recording
open the zip file and extract the contents.
navigate to the /gbr directory in the root of the folder (not the one in the /tiny mic pre/ folder)
find the file “mic pre.zip” - this is what you need for PCB fabrication.
open your browser and go to JLCpcb or one of the various PCB fab sites. For simplicity’s sake I’ll give the JLC instructions.
click on the “order now” option on the screen.
drag the “mic pre.zip” file onto the “add gerber file” section on the web page. This will upload the file to the site for you.
once uploaded, you’ll see an image of the board along with a whole slew of options which you can safely ignore. You might want to change the PCB colour if you wish - it’s free to do so. I generally choose the black option as the solder mask is non-reflective. You can check the different shipping estimates here, but you actually choose the shipping in a future page, so take note.
hit the “save to cart” button on the checkout, then go through the checkout process.
that’s it!

PS if you do order a bunch, please consider giving away the remainders to people in your general geographic location. The boards cost almost nothing, yet minimising landfill waste/the environmental impact of having the boards manufactured is something important to consider.

PedalsandChill · 2022-07-19T04:40:06.953Z

Awesome I’ll order some tonight! Thanks for helpin me out with it! Also, love the giving them away deal. Although I’m not sure anyone in my area would be into it. Small country town. I’ll happily mail the spares to any future reader on this thread free.

kasselvania · 2022-07-19T15:37:41.906Z

Quick question; how long do the 9v batteries last?

ramphands · 2022-07-19T17:27:39.603Z

Theoretically an alkaline 9v battery has a capacity of 500mAH.
The opamp in the circuit is extremely low draw, so about 250 hours conservatively.

kasselvania · 2022-07-19T17:37:40.738Z

Does that merely occur when you plug it in to a recording device? Like, does that complete the circuit? Or does it always draw?

ramphands · 2022-07-20T00:13:08.372Z

The “standard” version has a switch on it to break the connection.
The “tiny” version does not as it was designed to be encased in some kind of tubing/sleeving, so you’d need to either unplug the battery or add a switch at the power source.