Topic: diy recorder

[weroflu]

Next project: try to stuff an odroid C0 running debian and any recording software such as audacity for example,
booting right into record mode, have not figured out how to get it to stop recording yet. maybe one button attached to gpio will stop recording and power down.

http://www.hardkernel.com/main/products/prdt_info.php?g_code=G145326484280

3000mah battery

and smaller version of my preamp with switching inverter lt1611 (1.6Mhz) for the -3.7V, hopefully with no ripple artifacts

into an altoids tin

used in conjunction with the miyo adc converter which has just  enough metering to not need a screen for the odroid

also just  learned about samsung artik boards

https://www.artik.io/

i think in the next year or two  people will come out with high quality adc, perhaps dsd, for these odroid/pi boards.

[Gutbucket]

Long dreaming of something like this with 6 or 8 channels of input via a D-sub connector, 9V mic power on each, simple trimmer pots to adjust input gain inside the box to match the output of the mics to that of the ADC (the miniature mics have a D/R approximately equal to the D/R of the ADC, so "set it and forget it", making metering unnecessary). Simple On/Off and Record/Stop control via two switches with LED indication of power on/off and record/stop.  Write to SD card.  Simple, small, compact, no-nonsense.

[weroflu]

Thanks Jon.

The miyo is a commercial product, usb powered, all enclosed so I can't get at any of the power rails and I wouldn't even attempt an adc at ths point.

I'm onto the ltc1983 now on your recommendation. Aside from fewer parts count is there any other advantage?

[udovdh]

Very interesting concept.
Probably more doable than ever at this point in time.
A decent stereo analog front-end with plug in power @ 9 volts would be very usable.

[Gutbucket]

Very interesting concept.
Probably more doable than ever at this point in time.
A decent stereo 6ch analog front-end with plug in power @ 9 volts would be very usable.

FTFY 

[weroflu]

Great help Jon, thanks.

Just getting all the bits together. Miyo on left, AA battery placed for size reference. Odroid fits easily but is not mounted yet. lipo battery can sit right on top of the odroid, slightly on top of th hdmi jack since it's too snug. USB connecter on odroid not soldered yet, after it is I'll cut the case so the connector protrudes out and then the whole board will sit further left giving more room for my preamp board (not that I  need it). I need to Y that molex connector on the battery to power my preamp - anyone know how to do that without cutting the connector off. Also if anyone has mounting ideas for the odroid and battery let me know, mechanics are not my strongpoint. I have a 32gb microsd and 16gb emcc card on the underside of the odroid - it's very compact. I don't even need that hdmi jack sitting middle top of the board.

There is an IR receiver not yet soldered. Deciding whether to use that or a simple button/switch right into the gpio to act as a 'new file' key and power off. A lot can go wrong before this gets off the ground. Testing usb power tomorrow to see if it will power the miyo, grounding will really suck and then getting all the software running on debian.

[Gutbucket]

You can probably find a pre-made molex Y cable for the battery. Or find the mating connector and solder/crimp your own.

Good old hot glue is an easy solution to secure the board (and battery if you like).  Or sealant/adhesive. Scuff the inside of the Altoid tin with sandpaper and wipe with solvent to make sure the glue areas are grease-free before blob application for a better bond to the case.  You don't want to electrically short the board on the steel case, so you might insulate using a piece of mylar tape, or clear polyester mailing label tape stuck to the tin under the board before gluing.  I'd not tape under the glue areas though.  There is always the old-school method of mechanical mounting with nuts and machine screws long enough to serve as standoff legs, but that's more of a PITA, requiring hole drilling and fastener heads on the outside of the box.

[udovdh]

Very interesting concept.
Probably more doable than ever at this point in time.
A decent stereo 6ch analog front-end with plug in power @ 9 volts would be very usable.

FTFY 

If it can do six channels in the same small box then yes, that is OK if we can have 9V PIP on these lines. Two channels for stereo, the rest is optionally active.
I don't know if the Odroid can handle 6 times 44.1 Khz 16+ bits PCM. (it is .5 MB/s, not much data but can the CPU cope?)

Is this the MIYO device you mean? https://gomiyo.com/

How does that perform? See https://gomiyo.com/pages/specifications

Analog frontend should be able to cope with some amplification but also a small bit of attenuation to remain under +12dBu.  How to do this simply, efficiently?
Impedance of Miyo is 4.76kΩ, how make 16+ KOhm impedance towards mics... ? Add PIP?

What about the software? Reliable, solid, accurate?

[weroflu]

I'm still testng the miyo, it looks really good so far.

Odroid booted up fine into lubuntu.

Also passed the usb 2.0 power spec and powered the miyo correctly.

The preamp part of this, power, and getting everything to work together is the challenge. 2 channel preamp is easy enough to fit into the remaining board space. 4 channels, probably doable, 6 is stretchng things a bit. And keep in mind this is stereo recording into a stereo adc, not multi channel adc.

Ultimately I'd like to have this footprint turn into a 6-8 channel stereo mixer but I don't think it's possible with my current iq. If preamp metering and serial control was done on a smartphone then it's possible but now it's 3 boxes: preamp, adc, and smartphone, all with room enough for a large enough battery. I'm drawing the line at 2 boxes.

[udovdh]

The preamp part of this, power, and getting everything to work together is the challenge. 2 channel preamp is easy enough to fit into the remaining board space. 4 channels, probably doable, 6 is stretchng things a bit. And keep in mind this is stereo recording into a stereo adc, not multi channel adc.

4 channels is to MIYO boards connected to the two USB inputs.
With a small USB hub one could do 6 or more channels, assuming the Odroid can cope.

Ultimately I'd like to have this footprint turn into a 6-8 channel stereo mixer but I don't think it's possible with my current iq. If preamp metering and serial control was done on a smartphone then it's possible but now it's 3 boxes: preamp, adc, and smartphone, all with room enough for a large enough battery. I'm drawing the line at 2 boxes.

For me two channels is plenty for now. Can double to four anytime later.
Two channels with ~8 dBu(?) of amplification and 6-10 dbU of attenuation is plenty for me, if we can have 9V PIP too.

Who could design a simple circuit that does this?
Or where can I find such a circuit?

[weroflu]

USB hub?

The whole idea is to make something smaller than what is available commercially.

The miyo is not a 'board' it's a product all enclosed in an aluminum case that doubles as a heatsink.

Two channels with pip is doable for you, I'll try to get to it when I finish getting it working as is.

[weroflu]

odroid c0 working well in arch and lubuntu console.
miyo adc and dac working
recorded test file today 192khz 24bit

one problem is the miyo adc metering craps out as soon as i connect it to usb port on my atom n550 or
the armv7 soc. dac metering works fine though.

i need to test it on an x86 machine, that will narrow it down perhaps to an arm/atom usb problem.