Go Back   AnandTech Forums > Hardware and Technology > Peripherals

Forums
· Hardware and Technology
· CPUs and Overclocking
· Motherboards
· Video Cards and Graphics
· Memory and Storage
· Power Supplies
· Cases & Cooling
· SFF, Notebooks, Pre-Built/Barebones PCs
· Networking
· Peripherals
· General Hardware
· Highly Technical
· Computer Help
· Home Theater PCs
· Consumer Electronics
· Digital and Video Cameras
· Mobile Devices & Gadgets
· Audio/Video & Home Theater
· Software
· Software for Windows
· All Things Apple
· *nix Software
· Operating Systems
· Programming
· PC Gaming
· Console Gaming
· Distributed Computing
· Security
· Social
· Off Topic
· Politics and News
· Discussion Club
· Love and Relationships
· The Garage
· Health and Fitness
· Merchandise and Shopping
· For Sale/Trade
· Hot Deals with Free Stuff/Contests
· Black Friday 2013
· Forum Issues
· Technical Forum Issues
· Personal Forum Issues
· Suggestion Box
· Moderator Resources
· Moderator Discussions
   

Reply
 
Thread Tools
Old 10-17-2011, 02:31 PM   #1
repoman0
Senior Member
 
repoman0's Avatar
 
Join Date: Jun 2010
Posts: 665
Default Need a solution for connecting multiple microphones to PC

For my electrical engineering capstone project. We're testing an ultrasound positioning system using six cheap electret microphones and a simple biasing/power circuit - the whole system will eventually be implemented on some sort of microcontroller.

But, in the meantime, we need some way to have at least four, preferably six analog audio inputs to a PC for testing our algorithms in MATLAB. 192kHz sampling of all inputs would be best (for good ultrasound reproduction). Does anyone have a solution? We can spend up to $300ish, less is better.

We will not be using XLR cables but regular 3.5mm jacks.

Thanks!
repoman0 is offline   Reply With Quote
Old 10-17-2011, 04:28 PM   #2
videogames101
Diamond Member
 
videogames101's Avatar
 
Join Date: Aug 2005
Location: 52375
Posts: 6,124
Default

http://www.amazon.com/M-Audio-Delta-.../dp/B000085ZKX

you might need some adapters, but 10 inputs will be hard to find in one solution anywhere else.

edit:although it seems it's limited to 96khz recording, not sure if thats a dealbreaker
__________________
3570K
HD7870 (Tahiti LE)

Last edited by videogames101; 10-17-2011 at 04:34 PM.
videogames101 is offline   Reply With Quote
Old 10-17-2011, 07:01 PM   #3
repoman0
Senior Member
 
repoman0's Avatar
 
Join Date: Jun 2010
Posts: 665
Default

Certainly looks good - 96kHz will probably limit us to under 40kHz when the final result should be narrowband at 45kHz but looks fine for testing. Thanks, I'll update if we get it and test!
repoman0 is offline   Reply With Quote
Old 10-18-2011, 10:31 AM   #4
corkyg
Moderator
Peripherals
 
corkyg's Avatar
 
Join Date: Mar 2000
Location: Tucson, Arizona
Posts: 23,845
Default

Sounds like a mixer board for the mikes - and one connection from it to the PC.
__________________
CorkyG - Tucson, AZ

In my view you cannot claim to have seen something until you have photographed it.... Emile Zola
corkyg is offline   Reply With Quote
Old 10-18-2011, 10:41 AM   #5
Modelworks
Lifer
 
Modelworks's Avatar
 
Join Date: Feb 2007
Location: North Carolina
Posts: 16,237
Default

You will need to amp those electret mics for most cards to be able to accept the signal. Not many cards have 6 mic inputs, usually they are line level.

I would put a jfet opamp like the lm358 connected to the mics then output that to line level on the sound cards. I also use this setup for input to a dsp chip for sampling so it is something you can use on the final project too.

Circuit I use for the mics
http://circuitsfun.blogspot.com/2011...amplifier.html
Modelworks is offline   Reply With Quote
Old 10-18-2011, 03:33 PM   #6
repoman0
Senior Member
 
repoman0's Avatar
 
Join Date: Jun 2010
Posts: 665
Default

Right, I realize that the power circuit I built already will need to be revised so that it can bring the little mics up to line level. The Delta 1010 linked above has exactly 6 RCA line inputs.. perfect! I'd found this earlier - http://www.epanorama.net/circuits/micamp.html - not sure if the LM358 that you linked or the BJT amp will have better quality. We'll have to try both!

Mixer was my first thought as well but they are very expensive even for 2 inputs, and use XLR / 48V inputs which we don't want to deal with.. line in is way easier, and better transfers to DSP and microcontroller later.

Last edited by repoman0; 10-18-2011 at 03:53 PM.
repoman0 is offline   Reply With Quote
Old 10-18-2011, 05:13 PM   #7
vbuggy
Golden Member
 
vbuggy's Avatar
 
Join Date: Nov 2005
Posts: 1,594
Default

RME Octamic II will do what you need. A reasonably priced multi-mic 192Khz ADC.

EDIT: Oops, scratch the reco - I didn't see the $300 limit.
vbuggy is offline   Reply With Quote
Old 10-18-2011, 06:27 PM   #8
Modelworks
Lifer
 
Modelworks's Avatar
 
Join Date: Feb 2007
Location: North Carolina
Posts: 16,237
Default

Quote:
Originally Posted by repoman0 View Post
I'd found this earlier - http://www.epanorama.net/circuits/micamp.html - not sure if the LM358 that you linked or the BJT amp will have better quality.

Use the LM358 or even better the same circuit as the LM358 but use a TL064 opamp . It has quad inputs and very low noise. Both are Jfet based so quality is good. Using BJT the problem you will have is the noise floor is much higher. I can connect a single mic to the opamp and change out the pot for a 1.2M resistor, giving it 100,000 gain. The mic is so sensitive that I can hear a whisper at 10 feet from the mic. Paper tearing sounds like sand paper at the same distance. Not sure you want that high a gain but opamp is the way to go.
Price is also cheap, just 68 cents
http://search.digikey.com/us/en/prod...73-5-ND/277419

I feed that into a dsp chip and process it with filters to lock onto voices in the distance.
Modelworks is offline   Reply With Quote
Old 10-19-2011, 02:45 PM   #9
repoman0
Senior Member
 
repoman0's Avatar
 
Join Date: Jun 2010
Posts: 665
Default

Awesome, I really appreciate the suggestions. Will definitely buy some of the TL064, I'm about to place an order with digikey for the parts to build a bunch of those amplifier circuits that you linked.

We don't need a super high gain; the ultrasound noise will come from PWM power regulation of BLDC motors using switching freq above 20kHz and it seems pretty "loud" .. not that we can hear it!
repoman0 is offline   Reply With Quote
Old 10-22-2011, 05:13 PM   #10
repoman0
Senior Member
 
repoman0's Avatar
 
Join Date: Jun 2010
Posts: 665
Default

All electronics and the Delta1010 are in, now to get to work on real time hardware access with matlab
repoman0 is offline   Reply With Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 11:20 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.