^ yup pwede sis. check lang sa limitations nung sound card like sampling rate. sa mga AV forums, meron silang common na ginagamit na USB Sound Card. 'yun ding mga ginagamit sa analysis ng amp at speaker merong loopback test para i-compensate sa output na graph 'yung mga parts na may rolloff, etc.'yung Virtins ata, test instrument talaga ang target. meron ding ibang analysis software na pang-audio talaga like TrueRTA. ginagamit ko 'yung TrueRTA na free version for quick evaluation ng speaker response using Pink Noise source (at kinuhang Electret Mic sa headset ). Speaker Workshop 'yung isa ko pang gamit. pero ngayon, gawa muna ng preamp ng ECM8000.
Meron na akong buffer para sa tutorial na to. Iyan po yung schematic para sa gustong gumawa din at ng mareview na din kung ok it .
quite interesting, sinubukan kong i-check ang levels nung output ng sound card ng laptop ko at mukha siyang may maliliit na notches (around 6dB) sa odd multiples ng 90Hz, pero pag-abot ng 1kHz above, ok naman na siya.
In a related thread, I was chided by one member for suggesting a power amplifier measurement procedure that requires the use of a distortion analyzer. Rightly so, because this piece of equipment is not cheap; it is unreasonable to assume that hobbyists will ever have access to this equipment to do the tests. You may not know it, but already on your desk is a piece of equipment capable of doing these measurements- your PC! Yes, PC has all the necessary hardwares to do these measurements with reasonable accuracy (albeit to a limited extent). With the right software, you can convert and use your PC to measure audio amplifier figure of merits, such as THD, S/N, Output Power and so on.PC Audio AnalyzerUsing the PC sound circuitry as digitizer to display sampled waveform (i.e. as digital oscilloscope) is not a new idea. It has been with us for years. But only few took interest because it suffers a few but important shortcomings that severely limit its usefulness: Bandwidth – it works only with audio frequencies Input Coupling- it work with AC inputs onlyAnd then a few talented individuals came up with an idea. Realizing that current PC processors now have enough processing surplus to do a lot of other things other than displaying those pretty desktop graphics, they worked and successfully add a real time FFT (Fast Fourier Transform) function to the PC soundcard oscilloscope suite. In other words, your PC now can perform the function of an audio spectrum analyzer! This wonderful development may completely changed the way you look upon these PC oscilloscope applications. The powerful FFT function enables you to directly measure (not just imagine) THD, noise, output power, and score of other parameters of audio circuits. Your newfound capability to measure these parameters will enable you further to take your audio related work to the next level and do some real engineering work. For instance, you can now study, measure, and fully appreciate the effect of “ground loop” or “star grounding” technique that is often mentioned by the analog gurus in this forum, which I suspect most of you simply regard as just one of our deranged fantasy.Who should read and participate in this threadThis thread is not just for audio enthusiast, it is for everyone who would like to venture into the analog realm and gain deeper understanding into this discipline. Audio circuit is just one of the many branches of the analog tree. The knowledge and skill you earn working with audio circuits will apply as well to other analog application circuits.Download PC Oscilloscope Software ToolsGoogling “PC FFT Analyzer” will yield a number of sites offering soundcard based PC oscilloscope suite. Most of them are shareware, they will allow you free use of the software for a limited period, after which you have to buy the software. The PC oscilloscope software I downloaded for evaluation is Virtins Technology Multi-Instruments 3.1:http://www.virtins.com/The evaluation version expires in 21 days after installation. The lite version costs USD49.95 - sounds reasonable. But I know that cash strapped third world creatures like us may still find this unaffordable. If you find a freeware equivalent, please let me know, perhaps we can base our future discussion on your find.What will I do in this threadUsing the Virtins software, I will do some quick verification tests, compare measurement results with real instruments, and report the result here. The purpose is to determine whether the PC analyzer measurement results are close enough to the real analyzer equipment readings to be trustworthy.What I will do next and hope we will accomplishI will build an experimental power amp and perform some experiments that you can duplicate using this PC software tool. By this time, I hope we will be joined by our analog gurus and get their precious views and inputs. At the conclusion of this project, I hope this effort will result in all of us broadening our knowledge that will make us even better engineers. *****Be patient though. Since I can only to this at home, it may take some few days between updates. I will try my best to make at least three updates a week. The truth is, early this evening, I already started performing a number of tests even as I started writing this intro, but at this point, I am now too tired to write a report. Expect some results in the next couple of days.