audio card as signal source - Page 1
Forum section: electronics / testgear

author: free_electron
author_rank: Super Contributor
timestamp: April 17, 2013, 11:16:23 pm
content: Has anyone ever tried to use a very good quality audio card ( like an X-fi) as a signal source. I am looking for a bit of software where i can enter things like :give me a 1khz sine with this amplitude.add a 2khz triangle with this amplitudemulitply the result with a square wave of 10khz with this amplitude.play that in an endless - click free loopSomething along those lines.the software needs to be able to use the true 24 bit of the dac in the audio card. software that calculates 16 bit and then upsamples is no-go.anyone any idea's ?

author: AndreasF
author_rank: Frequent Contributor
timestamp: April 18, 2013, 06:35:11 am
content: Audacityhas some simple built-in signal generation capabilities. I think the default internal sample format is 32-bit float, which then (presumably) gets converted to whatever your hardware/driver can handle. Amplitude itself is only given as a more abstract unit (0-1.0). Obviously the real amplitudes will depend on settings that are external to Audacity.

author: BravoV
author_rank: Super Contributor
timestamp: April 18, 2013, 06:38:55 am
content: How about using LTSpice ?I think its very capable to generate waveform that surpasses the playback capability of most high end sound card.Quote from LTSpice .wave directive :Quote

author: free_electron
author_rank: Super Contributor
timestamp: April 18, 2013, 02:35:54 pm
content: Hmm. Ltspice looks i teresting.But i was kinda hoping for something with a more graphical i terface..I know there is a program that can use the audio card as scope, generator, voltmeter, network analyser rlc meter and much more... Just can't seem to find it..

author: amyk
author_rank: Super Contributor
timestamp: April 18, 2013, 03:11:36 pm
content: Quote from: free_electron on April 18, 2013, 02:35:54 pmThis one?http://www.daqarta.com/index.htmOr this onehttp://www.trueaudio.com/rta_abt1.htm

author: grenert
author_rank: Frequent Contributor
timestamp: April 18, 2013, 05:45:26 pm
content: Quote from: free_electron on April 18, 2013, 02:35:54 pmSounds like Virtins Multi-Instrument:http://virtins.com/

author: Lightages
author_rank: Unknown
timestamp: April 18, 2013, 09:26:05 pm
content: This program is freeware and does some of what you want:http://www.infinitespectra.com/freeware/index.htmlIt is from this page of other freeware:http://www.infinitespectra.com/freeware/SGOne/index.html

author: Deckert
author_rank: Regular Contributor
timestamp: April 19, 2013, 01:12:37 am
content: Quote from: free_electron on April 18, 2013, 02:35:54 pmOr this one:http://www.zeitnitz.de/Christian/scope_en--deckert

author: BravoV
author_rank: Super Contributor
timestamp: April 19, 2013, 01:27:50 am
content: Visual Analyzer (freeware) ->http://www.sillanumsoft.org/prod01.htmImpressive piece of code I'd say, considering it's price.Features :- Oscilloscope (dual channel, xy, time division, trigger);- Spectrum Analyzer with amplitude and phase display (linear, log, lines, bar, octaves band analysis 1/3, 1/6, 1/9, 1/12, 1/24);-Wave-form generator with "custom functions", triangular, square, sinus, white noise and pulse generation (NO ALIASING);- Frequency meter (in time and frequency domain) and counter; in time domain by means of a real time zero crossing algorithm;- Volt meter with DC, true RMS, peak to peak and mean display;- Filtering (low pass, hi pass, band pass, band reject, notch, "diode", DC removal);- Memo windows (data log) for analysis and storage of time series, spectrum and phase with "triggering" events; possibility to save in various formats and display them with a viewer;- A TRUE software digital analog conversion (for complete signal reconstruction using Nyquist theorem) ;- Frequency compensation: one can create/edit a custom frequency response and add it to the spectrum analyzer spectrum ; added standard weighting curves A,B,C in parallel with custom frequency response;-Support for 8/16/24 bit soundcard by means of API calls;- Unlimited frequency sampling (depend from the capabilities of your soundcard);- Cepstrum analysis;- Cross Correlation;- Extended THD measurements, with automatic sweep and compensation.- ZRLC-meter with Vector scope, automatic sweep in time and frequency for automatic measurement.

author: Lightages
author_rank: Unknown
timestamp: April 19, 2013, 01:40:59 am
content: I was trying to remember that one BravoV!

author: BravoV
author_rank: Super Contributor
timestamp: April 19, 2013, 02:00:09 am
content: Quote from: Lightages on April 19, 2013, 01:40:59 amReally, that web site deserved a place in anyone's bookmark here.

author: ivan747
author_rank: Super Contributor
timestamp: April 19, 2013, 02:34:05 am
content: It would be interesting to design a custom sound card with a known output/input amplitude, frequency accuracy and bandwidth to use with these products. It shouldn't be hard if you get access to some of those USB sound card chipsets. Selectable AC/DC coupling would be interesting as well (insert rock band pun here). One of those chips must have some sort of discrete GPIO.

author: commongrounder
author_rank: Frequent Contributor
timestamp: April 19, 2013, 02:58:54 am
content: ivan747-I think something like this is similar to what you have in mind...http://www.quantasylum.com/content/Products/QA400.aspxThe whole setup costs $200.00

author: free_electron
author_rank: Super Contributor
timestamp: April 19, 2013, 04:52:00 am
content: right , looks like i have a bunch of things to pick from.my main focus is signal generation. the rest i really don't care about.here is what i want to do:generate two sine waves of different frequency and add them together. the resulting wave is scaled to use a full 24 bit control wordthis needs to be played back and sent into an a/d under test.This a/d samples at 136Khz and will be read out by an FPGA who will collect the samples and save them in memory. after that the collected data will be dumped and post processed in matlab to figure out the distortion and linearity of that a/d.So this is a setup to test A/D converters. This a/d is a 16 bit a/d with option of 18 bits.So i need a source that is 'cleaner than that , hence the idea of using a 24 bit audio dac...I may build a setup myself. i found some nice usb to i2s interface chips from silabs. Tacking on a good quality dac (wolfson) with differential outputs allows me to transport the signal to where i want it. A good opamp with very high cmrr then converts it locally into the single ended signal i need. I will use the audio profile 1.0 so i can use full speed usb as opposed to high speed mandated by audio 2.0 profile. The reason is i want to isolate the usb path galvanically (analog devices usb isolator) to avoid ground loops and noise coming from the PC side and injecting in the clean path. signal scaling will be done in analog domain as i always want to optimally use the 24 bits available from the DAC. ( it doesnt do any good to play a sound at 1/8 max amplitude .. you're only using 8 bits ... plus you let the computer do some rescaling that throws in uncertainties... i need to be sure that what is played is the exact binary value i specify.i just dont want to muck around with having to write code on the pc side to create the waveforms and play them ... off the shelf there will do nicely.so far the virtins thing looks the most interesting.