Musical insrument to USB 2 ?

[Element_115]

Hi

I would like to make a simple instrument recorder that plugs in to the
USB 2 port of a computer. And ultimately I would like to interface with
software like CoolEdit .... or similar.

I was wondering if anyone has info that would get me started.

Any info is appreciated

 

[Buriedcode]

Hi there,

Nice name btw, apparently element 115 is 'green'

Anyway, if I understand what you want correctly its:

Analogue input (from mic, amp etc..) - > magic box -> USB2 -> PC ?

Well, I'll just tell you what I think, I'm not really an expert at anything...
Thankfully, there are some USB2 compliant chips about now days, so theoretically, it should just be a case of some analogue front end, ADC (16-24 bit, 48kHz?) a microcontroller/processor, and a USB comms chip. The only problem I can see is the driver/firmware for the PC.

Although USB it very versatile, many companies wanted to have complete control over any of their USB devices, so for the most part, you can't plug in USB from say, a micro development board and expect the PC to recognise it for what it is, without some form of driver/software. So you may end up plugging it in and windows/linux gives an error, or just assumes its a 'pendrive'.

As for interfacing with 'cooledit', although audio editing/sequencing software is pretty damn versatile these days, I'm not sure many are geared for 'digital recorders'. That said, there ARE external USB2 (or firewire) soundcards, which obviously have analogue inputs for records, as well as outputs - so if you could fool your software into thinking that its one of them, and simply omit the DACs, might work. After all, all you are doing is providing the data from an ADC directly to the software, instead of letting a soundcard do it.

I can't really say any more, since google is currently down (been so for about 30 minutes) but I am VERY interested in this, since I'd like to do some 'good quality' recordings on a laptop, without paying 400UKP on a USB soundcard, which, like nearly ALL soundcards, has terribly designed analogue layout for the ADC recording...meaning in 24bits, the last 4 are pure noise. (Sorry, rant.)

Let me know what you think,

Regards,

Buriedcode.

 

[Element_115]

Thanks for the reply Buriedcode.

So is it Florescent or Ever (Green)?

Yeah I knew that there would be a driver issue, and I've been looking in to that.
But I was looking for any "Typical" circuits that takes Audio and sends/formats
it in to USB format.

I know that it would be easier and cheaper just to buy one, but if I can find some
basic easy schematics and IC that can do the trick I think it would be fun to make
my own.

Cheers

 

[Buriedcode]

hello again.

So is it Florescent or Ever (Green)?

According to 'Bob Lazar' its a light green, and emits/amplifies gravity waves
....fruitloop

but if I can find some basic easy schematics and IC that can do the trick I think it would be fun to make my own.

Well, with any driver issue out the way.....and you're just after hardware, I'm not aware of any schematics that will do the job. But, thankfully a few IC's would do the job, probably quite well.

ADC: I can't recomment 'crystal/cirrus logic' ADC's enough. (www.cirrus.com). They're sigma delta (so they don't require any complicated filtering, just a few caps/resistors) and they're specifically designed for audio. Simple, small, and easy to use. Only thing, cirrus ignored two of my emails, and don't seem to give out samples.

Controller: PIC have some USB2 compliant IC's out. That would take care of most of the USB stuff, packeting, transmission, etc.. You may need to configure it to send certain information for config. Also, nearly all USB2 microcontrollers have an SPI port - considering the ADC's use I2S to transfer the audio samples, its remarkably similar. In fact, I've got a PIC that can take the samples from an ADC and send it over RF, sampling at 48Khz, 24-bits. Stereo.

I am only aware of one 'one-chip' solution. There are some 'audio codecs' about, and the newer ones are USB 2.0 Essentially, these chips are used in soundcards, doing pretty much all the work. They contain, ADC's, DAC's, SPDIF interfaces...and some USB. Unfortunately, a vast majority still use USB 1.1, which franky, should be fine for recording 2 channels (USB2.0 is backward compatable). Simultanous 8+ channel recording will need USB2.

USB1.1: http://focus.ti.com/docs/prod/folders/print/pcm2902.html
**broken link removed**

Texas Instruments are great, they've sent me many samples in the past.

I believe philips also do codecs, possibly USB2, since they're pretty far ahead with their chips. Also, Analog.com who made nearly all of the AC'97 compliant codecs (remember those on-board sound cards). And google unveiled many 'unknown' complanies, poping up with IC's for portable audio.


Some links for your interest:
**broken link removed**
http://www.extremetech.com/article2/0,1697,1473855,00.asp
**broken link removed** - one of my favourite sites
**broken link removed**


And finally, what ready-made products are like:
http://messe.harmony-central.com/Musikmesse03/Content/Edirol/PR/UA-1000.html
**broken link removed**

Well, thats what 10 minutes of research can do. I know you want nice easy schematics, but, soldering surface mount isn't that hard. And with a one-chip solution, these chips don't really require many external components, its a great selling point for companies. If I have any success (when I have spare time) I'll look into it more, and hopefully knock-up a prototype.

Regards,

BuriedCode.

 

[fobyellow]

if extrem low distortion needed , i suggest you to choose a professional ADC chip like PCM1804 etc, and use a digital transmitter connect to USB Audio chip(pcm29**).
And of course with good buffer

 

[borisz]

If you dont look for very high end, use PCM2902 from TI. For a figure, there is application on my page. You may see photograps an schematic.
http://po.labs.googlepages.com/usbaudiokartica

If you want more high end varian (= much more complicated), put a post.
best regards

Boris