Topic: DIY flash recorder?

[Gutbucket]

Are there any DIY chip development kits that could be used to build a very, very simple purpose-built but high-quality DIY audio recorder?

I'm talking a purpose-built bare-bones recording machine- Turn it on and let it fill a card and that's about all it does.  No need for any fancy display, no playback, no switching, no mic powering.  No need to adjust input gain once set initially via trimpots.

Was beyond the realm of possibilty 10 years ago, but perhaps now within the realm of the reasonably imaginable for a competent DIY project builder, certainly within the capability of someone like Jon as long as the necessary chips and support tools are available from the chip manufacturers. Are the capabilities of off-the-shelf chipsets now integrated enough to minimalize the support circuitry required to even consider the possibility of something like this?

With no obvious replacement appearing for the DR-2d's 4-channel mode in an easily pocketable recorder, I'm left wondering about this possibility.  I'd like  5 channels at minimum but I really can't see TascaSonyRolaZoom offering anything like that except in larger unpocketable machines which include XLR inputs.

Outside-
A small box with a power on/off switch and Record/Stop switch, power LED, cliping indicator LED, card slot, battery holder, and mulitple unbalanced inputs. 

Inside-
Inputs > input buffers with level trimmer pots > ADC hip > control chip, formating data for writing > SDHC card.  24/48 only is fine.   
 

Most would be content with 2 channels.  I need at least 5, but 6 or 7 would be welcome and I think appropriate 6 and 8 channel all-in-one ADC chips are available so make it 6 or 8 channels.

KISS- Keeping It Simple and Small with reliable operation are the keys here.  Not really interested in an interface to a recording app on a phone.

Crazy or possible?

[Gutbucket]

Thanks for the input Jon.

That's a simpler path and may end up being the defacto answer.   I just far prefer a single function, dedicated device for things like this when possible.  The dream is something like your tinybox with an SD card-slot, two switches and a mulitpin connector carrying 6chs of singled-ended low-power inputs.  USB>smartphone seems to me a more compact version of going back to the 24bit laptop taping done over a decade ago with cardbus interfaces, which most tapers were quite happy to abandon once decent flash/HDD recorders arrived, not just because of the reduction in size and interconnected devices but the increase in reliability and ease of use of one or two dedicated devices.  Time marches on and I'm sure it won't be that problematic, but I think you can see where I'm coming from.

Any thoughts on why adoption of USB audio device class 2.0 has been so painfully slow?  The specification has been in place for what? more than 6 years or so now?  I'm still holding out for a simple USB powered external soundcard with 6 output chs at 24/48 for use with a laptop.   Just line-outs, no preamps or fancy inputs.  Looked around and the inexpensive offerings are all about the same as 3 or 4 years ago, none can do it. 

[kleiner Rainer]

Seen this?

http://www.vlsi.fi/en/products/vs1005.html

They even sell a development kit:

http://verkkokauppa.planeetta.net/epages/Planeetta.sf/en_GB/?ObjectPath=/Shops/vlsi/Products/VS1005_DEV_BOARD

Maybe an approach...


Greetings,

Rainer

[Gutbucket]

That's interesting, thanks.  SD card I/O on-chip.  Only 3 ADCs though, it would need an additional converters.

[anode]

This is not my area of expertise, but maybe you could hook up several of them and somehow sync them.

[H₂O]

There are Quad ADC Dev kits w/ I2S support out there as well - but they run about $200 as well - still no Pre

[Gutbucket]

Seems that the highest ADC channel count of the chips I see on a cursory search of TI and the like is 4 per chip (most are 2ch), any more than that and I'd think one would need multiple ADC chips to get 6 or more analog input channels.   

Does the chip in Tinybox DSP incorporate its own ADC or do you use a seperate ADC chip for analog input?  Your posts on development of that a while back got me thinking about all this then.  I tend to do so in waves, and another set is currently rolling in.  The Tinybox DSP + smartphone is pretty close to a practical way to do this, except for the 2 input channel count limitation.

This is obviously an intellectual exercise at this point exploring the possibility, and I'm not as concerned about the preamp part of it since that's basically a solved problem.  I'm currently having a very compact/pocketable 4-channel low-voltage preamp built for use with the DR2d, which is sort of a practical next step along this multichannel-recording-system-in-a-pocket road.. 

But for the DIY recorder I have in mind, I'm not sure a true preamp would be needed, maybe just low-voltage mic-power and input buffers in the recorder would suffice.  I don't need much adjustment as I'd always use the same mics with this which are sensitive and probably output a signal level very close to what is required at the ADC input.

[2manyrocks]

Heathkit?

[Gutbucket]

Closer to reality than I expected.  Appears the VLSI chip has one I2S input, so in addition to it's 3 onboard ADC channels (which unfortunately have only a 90dB SNR as Jon noted), I'd need an additional 2ch ADC chip to get a total of 5 analog input channels, which is the minimum channel count I'd need.  It's unfortuante that the VLSI chip doesn't have 5 better quality converters onboard which would make it a bit more tempting to give it a go with the dev kit,  but I'm somewhat suprised it is as full featured as it is. 

Not a project I'm jumping into anytime soon, just exploring the possibilty.  Thanks everyone.

[illconditioned]

There are Quad ADC Dev kits w/ I2S support out there as well - but they run about $200 as well - still no Pre

This would be an *excellent* solution.

Is it possible to write a Linux generic usb driver, ie., "snd-usb-audio" that could connect to an ADC using I2C?

One thing I am trying to do is get an ADC that handles DC input.  The purpose of this is as a measurement instrument and/or scope.

  Richard

[illconditioned]

ADAU1701 has two internal ADCs and supports I think four more via I2S input.  You'd need external ADC chips to get six channels in.  I only need two channels.

If you are serious about the project then that VLSI chip is the way to go, buy the dev kit, tweak the software, then do a PCB design minus all the stuff in the dev kit you don't need (the dev kit is a larger footprint than you probably want, 4" x 10" I think, and doesn't have the analog front end you need) and have it fabbed.  There are shops that do very short-run PCB assembly at not too horrible cost.  Or if you can live with the dev kit footprint then just do a daughterboard with the analog functions, and breakout the dev kit switches (which would control recording) to chassis-mounted units.

Jon, I'm loving my AKG actives.

ADC: If you build it, they will come...

[udovdh]

Interesting thread.
If you could make it as small as an M10 with detachable battery and PIP at 5/7/9 volts for line in.
More than 16 bits of audio are very welcome.


Battery can be Liithium-whatever with a slightly higher energy density versus AA's to compensate for space.

[stevetoney]

What universe are you guys from and what language is this that you speak?  Take me to your leader.

[capnhook]

What universe are you guys from and what language is this that you speak?  Take me to your leader.

visitors from the planet DIY

[Len Moskowitz (Core Sound)]

We went through this exercise last year, the year before that, the year before that (and so on).

Around 6 years ago we designed our 4Pre four-channel mic pre, and then never went into production on it because the mass market was starting to offer products like the DR-680 at prices that were really difficult to beat if the projected sales was under around 10,000 units. 4Pre was a great product, but based even on optimistic sales projections it didn't make any sense to invest in its production.

Then we looked at offering a bare-bones, really low-cost two channel digital recorder. Again the large electronics manufacturers were offering products at prices that made it a no-brainer not to do it. Tascam, Edirol, Olympus and Sony have those markets sewed up. A small manufacturer can't compete there.

And even a DIY-er will have a very hard time matching what they can offer at a given price point.

[sic_tune]

I wonder if there are microcontrollers out there that talk AES42 right out of the box.
They would be really useful to create a simple, small bitbucket that just syncs AES42 from 2-x digital microphones and writes them to flash.
No need for ADCs, preamps and no worrying about gain or level settings. High quality assured.
Maybe a simple DAC for headphone monitoring.