Yeah, I have tried a couple different usb sound cards at this point doing a loopback test, both of them measure pretty poorly. I am going to try some better cables and try again.
I also tried feeding the output of the turtle beach card into the creative input and got very similar results which is why I think my cables may be marginal. I am wondering if one of the cables might have some quieting measures in place (FCC?).
Ultimately I plan to use my M-audio 1010 which I hope measures better than what I have seen so far. I guess I should go ahead and test it. If it measures as badly, there is not much point.
I also tried feeding the output of the turtle beach card into the creative input and got very similar results which is why I think my cables may be marginal. I am wondering if one of the cables might have some quieting measures in place (FCC?).
Ultimately I plan to use my M-audio 1010 which I hope measures better than what I have seen so far. I guess I should go ahead and test it. If it measures as badly, there is not much point.
The M-audio tests much better than the USB cards I used before. I just am not ready to risk damaging the M-audio.
With a 6 foot cable between the in/outs I am getting freq resp down .07db at 20khz, -1db at 40khz. at 20hz down .1db.
Using RMAA's automated test it is showing noise -98.6dbA, range 98.4dbA, THD .0011%, IMD+N .0037%, IMD+N sweep .0037% frequency response +0.0, -0.0
With a 6 foot cable between the in/outs I am getting freq resp down .07db at 20khz, -1db at 40khz. at 20hz down .1db.
Using RMAA's automated test it is showing noise -98.6dbA, range 98.4dbA, THD .0011%, IMD+N .0037%, IMD+N sweep .0037% frequency response +0.0, -0.0
i think if the opamp is choosen wisely and an anttenuator added the distortion introduced by a circuit like this would be much less in magnitude than the amp under test, almost unmeasurable with this kinda kit, and the sound card used. it would be a basis for a very simple measuring set up.
a whole circuit? this is very simple and after all this is diy audio. i think it could be developed into a great piece of test gear. this i will do when time is on my side, i was hoping someone else would take up the challenge.
that clipper circuit uses the IC to convert the balanced input to single ended (unbalanced) output.
The Maudio has both balanced inputs and balanced outputs.
I think it was Syn that said for excellent performance the Maudio MUST be used balanced.
All you need is the high impedance attenuator and the clipping Zeners.
But accurately match the resistors/capacitors in both sides of the balanced attenuator.
The Maudio has both balanced inputs and balanced outputs.
I think it was Syn that said for excellent performance the Maudio MUST be used balanced.
All you need is the high impedance attenuator and the clipping Zeners.
But accurately match the resistors/capacitors in both sides of the balanced attenuator.
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That would be VERY interesting indeed! Sounds like a logical way to go, but do you think Spectrum Lab can do it? Keep us posted please!
jd
I think I could do a pretty good job based around the Allison buffer I've been experimenting with. But I still haven't tested the Allison enough to implement it in anything special yet. I need to build several prototypes.
I would be happy to try it, but if so it won't be anytime soon. Too many projects at the moment.
- keantoken
Thanks,
Has anyone here had any experience with Virtins Technology Multi-Instrument 3.1 (Standard)? www.virtins.com. It's not free.
I'm considering one of their USB oscilloscopes and it comes with that software, which can also be used with a sound card instead of their 8-bit USB oscilloscope hardware.
Cheers,
Bob
They have the 21 day fully functional trial version, which I did download a while ago and tried. I was more interested in the spectrum analyzer part. It was one of the many products of that kind that I tried, so I don't recall now why I didn't like it, but I remember feeling quite strongly about it. You should probably just download it and make your own impression about it.
Hello Bob
Yes, i have purchased the VirtinsMI 3.1 1,5 year ago. I use it with an EMU0404 usb or with an Asus Xonar Essence STX pci. When i asked Virtins for its usb oscilloscopes, they replied me that, for spectrall analysis it is better the use of a sound card because its bit depth of 24bit which gives a dynamic range of 6 X 24 = 144dB which is far better from the poor 8bit usb oscilloscope (D.R. = 8 X 6 = 48dB). Thus the oscilloscope it is only for measurements that requires a big bandwidth.
I have the full version of M.I. installed in a clear 64bit P.C. under WinXPx64. No one problem! The Virtins MI accepts ASIO drivers, under which the windows mixer is bypassed. The level is adjusted via the software, and this is very good especially in callibration of sound card. Remark: The EMU0404 ASIO driver is unstable and may installed again and again when the MI is launched. Instead the ASIO driver of Asus Xonar Essence it is very stable and it is matched very well with the MI Pro3.1. OTOH, Xonar Essence has very delicate input. If you inject a signal above 2Vrms, then the ADC is destroyed. As for the software, IMHO the MI Pro3.1 it is the closest costless software to Audio Precision. Virtins (Singapore) it is a very kind company, very helpfull and its software it is under continuous upgrades according to the demands of users. Its CEO is an extremelly experienced person in software development, and he knows almost everything about the needs of audio measurements.
Before you try to experimenting with MI Pro3.1, you must study the 240 pages instruction manual.
You can see some trial measurements that i did with the MI in my web page http://www.eal.gr in a microphone preamplifier, as well the performance of Asus Xonar Essence STX in hardwired loopback test.
I am available for any further information.
Fotios
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Hi Fotios,
Thanks very much for your detailed response! I'm glad to hear that you are getting good results with the Virtins software. One of the things I have found lacking in some of the free packages is clear documentation and examples that can get even a dummy like me going.
Best regards,
Bob
Best regards,
Bob
My pleasure!
Bob, i suggest you to study the chapter 3.3.2.8.3.1 THD, THD+N, SINAD, SNR, NL starting from page 149 to 151 and especially the page 150 in which you can read many interestings things about the correct frequency settings of signal generator, according to different FFT size / Sampling frequency settings. You will see very interesting things.
I forgot to reffer that the signal generator of MI Pro 3.1 it is its heavy weapon against other softwares. It is amazing flexible and very accurate. Try to measure it from the output of sound card with a trusty external DSO and make a comparison with the internal oscilloscope of MI Pro3.1.
Greetings
Fotios
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