For a while now, I have been looking at updating to a computer-based electrical signal analyzer. This would mostly be for analyzing frequency response, noise floor, and distortion content of electronics. It would also be nice if it would serve as an oscilloscope, too. There seems to be many freeware programs available and more for sale, but much less information is given on the actual hardware. My concern is that the noise and distortion of the soundcard may be too high. Along with frequency response and scope functions, I am looking to take noise and distortion measurements into the -120dB regions if possible. With this on the table, what I am wondering is if there are low noise stand-alone usb modules built for this purpose that the test probes connect to?
If you want to use VA make sure you sign up to the Forum and to get the latest Beta Version.
It is much more stable than the ones you get on the main download page.
FWIW
jer
Thanks I did not know that, I am using 2011
Does the software work with a TI 4222 based ADC (plus USB interface)? Like those from Ross Martin?
If you are inputting the data via USB, then the software just needs to know which driver you're using for it, based on what I've used before.
To get performance you woud ned USB UAC2 hardware and drivers. Thats built into OSX and Linux but not Windows. Whomever you get the interface from needs to provide drivers. it can quickly become a black hole if you are assembling it DIY.
If you are using a desktop system a PCI card may be the cleanest choice. There are several choices for under $200 that will get you pretty near state of the art performance.
If you are using a desktop system a PCI card may be the cleanest choice. There are several choices for under $200 that will get you pretty near state of the art performance.
Well, if you are using the WDM driver interface with MS Vista & newer OS, you will have the MS Windows mixer running (in the MS Windows XP days this was not present). This will reduce your THD & THD+N & SFDR or use the ASIO or WASAPI driver interface...
HpW
I have never quite understood that, but I know it is the case. One would think that a PC environment would be worse for getting clean signals than a stand-alone USB (or Firewire) box. Also, why would the type of interface, PCI or USB, make a difference for the cleanliness of the ADC and DAC parts?
What is behind this?
Jan
It's RF noise & hum from source to sink over power ground's (PC & sound card & cable)... it's that simple and hard to get rid off!
Also the poor power regulator rises the noise floor below the 200 Hz region.
IMHO I would not say that a PCI is always better then a USB/Firewire, while finally it really depends on the RF flow (also simple hum) and introduced in the ADC/DAC measurement chain.
An example is the PCI RME HDSP and the better performing RME Babyface...
Hp
But it seems to me that a good local regulator in stand-alone sound card is a no-brainer.
The power supply within a PC must also be quite bad - going all over the board with multiple digital switching loads, instead of just one ADC and DAC and some glue logic.
Still doesn't make sense to me.
jan
The power supply within a PC must also be quite bad - going all over the board with multiple digital switching loads, instead of just one ADC and DAC and some glue logic.
Still doesn't make sense to me.
jan
Just look at #203
as an example...http://www.diyaudio.com/forums/digital-source/236028-xmos-dsd-384-khz-32bit-usb-21.html#post3813967
Hp
Yeah, I use the ASIO driver with a USB 3.0 card in my laptop on audt30d software. I have XP on this laptop. I want different hardware though. I'm hoping to get a PCM42222 ADC with a USB interface for input from a low distortion oscillator. I'm still trying to figure out exactly how to do all this though. I've used a simple and cheap Behringer ADC/DAC before but I want something better now.
Just look at #203
http://www.diyaudio.com/forums/digital-source/236028-xmos-dsd-384-khz-32bit-usb-21.html#post3813967
Hp
OK, so you're suggesting that the noise from the USB cable interferes with measurements, or what?
I agree with Jan. It should be better to have a separate ADC/DAC connected to the PC via USB or firewire, but I'm still a neophyte at this.
When I said clean I meant easiest to implement well with lowest overhead. The best performance I have had comes from transformer isolated spdif, Next best is the differential out/differential in on a PCI card. After much fiddling I can get about 10 dB better from a modified EMU 1212/1010card than a Juli@ card. Both are better than I have managed from an EMU 0404, The best and cleanest is the AKM AKD5394 with an spdif transformer upgrade.
After all of that I would use the ESI Juli@ and move on. Its not enough worse to be an issue. I would use an external interface for balanced to unbalanced I/O.
The big isue is common mode noise between the chassis of any of these boxes. USB seems to make the issue worse. It may be the high data rate signalling over the USB cable that is not perfectly balanced.
USB 3 may be an improvement but the only one I have seen is from RME and expensive..
After all of that I would use the ESI Juli@ and move on. Its not enough worse to be an issue. I would use an external interface for balanced to unbalanced I/O.
The big isue is common mode noise between the chassis of any of these boxes. USB seems to make the issue worse. It may be the high data rate signalling over the USB cable that is not perfectly balanced.
USB 3 may be an improvement but the only one I have seen is from RME and expensive..
Sound Card comparisons
Here are measurements made with two soundcards and an external interface. The two cards are a Juli@ in balanced interface, an EMU 1212M in +4 balanced and an external AKM5394A ADC demo board connected via SPDIF. The EMU has had its opamps upgraded to LME49880's. The AKM5394A has LME49710's and the Juli@ has its stock JRC's. The biggest difference is the noise floor. The Blue is the Juli, about 15 dB higher. It also has a stronger third harmonic, which seems to be a signature of the JRC opamps.
Not easily visible is that the distortion is pretty similar between the three cards.
I find the Juli@ the simpler of the three to use. There are fewer options than the EMU but it just works and is straightforward.
I have an RME Hammerfall 9652 but its analog input is identical in performance to the Juli@ so no need to measure it.
Here are measurements made with two soundcards and an external interface. The two cards are a Juli@ in balanced interface, an EMU 1212M in +4 balanced and an external AKM5394A ADC demo board connected via SPDIF. The EMU has had its opamps upgraded to LME49880's. The AKM5394A has LME49710's and the Juli@ has its stock JRC's. The biggest difference is the noise floor. The Blue is the Juli, about 15 dB higher. It also has a stronger third harmonic, which seems to be a signature of the JRC opamps.
Not easily visible is that the distortion is pretty similar between the three cards.
I find the Juli@ the simpler of the three to use. There are fewer options than the EMU but it just works and is straightforward.
I have an RME Hammerfall 9652 but its analog input is identical in performance to the Juli@ so no need to measure it.
Attachments
The EMU 1212M appears to be NLA.
The Juli@ seems reasonably priced, but I have a laptop.
What would you recommend for use with a laptop that has firewire and USB inputs?
I was planning on getting a stand alone PCM4222 ADC (and a S/PDIF to USB interface box) to use with my low distortion SVO.
The Juli@ seems reasonably priced, but I have a laptop.
What would you recommend for use with a laptop that has firewire and USB inputs?
I was planning on getting a stand alone PCM4222 ADC (and a S/PDIF to USB interface box) to use with my low distortion SVO.
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