The FCC exempts test equipment from emissions concerns. See 15.103.c of Part 15. The reasoning is that when you are using test equipment, often the devices you are probing/testing are completely disassembled (cover removed) and thus those devices aren't meeting emissions either.
UL (and CE, somewhat) considers 75V DC (or 50V AC) the starting point for voltage worry, and so devices that have all the inputs/outputs under ~60V DC are below the limit (60 to 75V is a gray area depending on your location in the world). There are still a lot of other areas they are concerned about (power, heat, current, burns, shorting, etc). But if something is 60V DC in and/or out, it's not viewed as overly dangerous from a voltage perspective. Remember, you can find 48V batteries with exposed terminals on shelves in stores....And yes, they give you a tickle if you touch.
Many products today will include a 120V AC to 12V or 5V DC adapter that is UL/CE approved. As long as the adapter is approved, then the product can skip much of the regulatory issues that comes with being "off line" powered. If the product has a built-in AC to DC converter, then the product needs UL. Depending on the module or circuit that does the conversion, it could be simple (if pre-approved) or it could be quite involved (fully custom and discrete)
UL (and CE, somewhat) considers 75V DC (or 50V AC) the starting point for voltage worry, and so devices that have all the inputs/outputs under ~60V DC are below the limit (60 to 75V is a gray area depending on your location in the world). There are still a lot of other areas they are concerned about (power, heat, current, burns, shorting, etc). But if something is 60V DC in and/or out, it's not viewed as overly dangerous from a voltage perspective. Remember, you can find 48V batteries with exposed terminals on shelves in stores....And yes, they give you a tickle if you touch.
Many products today will include a 120V AC to 12V or 5V DC adapter that is UL/CE approved. As long as the adapter is approved, then the product can skip much of the regulatory issues that comes with being "off line" powered. If the product has a built-in AC to DC converter, then the product needs UL. Depending on the module or circuit that does the conversion, it could be simple (if pre-approved) or it could be quite involved (fully custom and discrete)
It's been a while since I posted here, so I thought it might be time for an update.
In the meantime some of you have done your best to scare anyone away from selling stuff, mentioning UL, CE, FCC, ENxxxx, etc. 😱
And pointing towards other product, which has a similar functionality 😡 😛
But that doesn't stop me at this point in time 🙂
Since my last post I have been busy doing the layouts for the new version. These are now done. I still need to do a review, but everything is included and has been routed.
The design now consists of:
1. A main board with the power supply, output drivers and attenuators, input amplifier and attenuators, I/O connectors and crystal oscillators.
2. An ADC board with an AK5394A, ADC driver and a few things more. The board size will allow a 2 x AK5394A + driver design at a later point in time.
3. A DAC board with an AK4490 + post-DAC filter. Also in this case a dual DAC design will be possible.
The modules can be replaced later if better ADC/DAC solutions become available. Or if additional functions become necessary, e.g. notch/band-pass/low-pass filters if extremely low levels of distortion are needed.
The QA401 definitely looks like a better product than the QA400. But the performance and flexibility of my design is still at a higher level than the QA401. It looks like my design will be available later than the QA401 though. I have tried to compare them in the attached document.
The CMRR changes with the input level setting. The 90 dB typical is for the 10 dBV setting, which is "straight through", with the lowest gain in the input amplifier and no attenuation. At higher gains the CMRR becomes better because the input stage works as an instrumentation amplifier, where the higher gain only affects the differential signals, not the common mode signals. When the attenuator is used, the CMRR drops due to the tolerances of the resistors in the attenuators (0.1%).
In the meantime some of you have done your best to scare anyone away from selling stuff, mentioning UL, CE, FCC, ENxxxx, etc. 😱
And pointing towards other product, which has a similar functionality 😡 😛
But that doesn't stop me at this point in time 🙂
Since my last post I have been busy doing the layouts for the new version. These are now done. I still need to do a review, but everything is included and has been routed.
The design now consists of:
1. A main board with the power supply, output drivers and attenuators, input amplifier and attenuators, I/O connectors and crystal oscillators.
2. An ADC board with an AK5394A, ADC driver and a few things more. The board size will allow a 2 x AK5394A + driver design at a later point in time.
3. A DAC board with an AK4490 + post-DAC filter. Also in this case a dual DAC design will be possible.
The modules can be replaced later if better ADC/DAC solutions become available. Or if additional functions become necessary, e.g. notch/band-pass/low-pass filters if extremely low levels of distortion are needed.
The QA401 definitely looks like a better product than the QA400. But the performance and flexibility of my design is still at a higher level than the QA401. It looks like my design will be available later than the QA401 though. I have tried to compare them in the attached document.
The CMRR changes with the input level setting. The 90 dB typical is for the 10 dBV setting, which is "straight through", with the lowest gain in the input amplifier and no attenuation. At higher gains the CMRR becomes better because the input stage works as an instrumentation amplifier, where the higher gain only affects the differential signals, not the common mode signals. When the attenuator is used, the CMRR drops due to the tolerances of the resistors in the attenuators (0.1%).
Well, I am not quite there yet.
Apart from working on the layout I am in the initial stages of looking at the options of how to eventually manufacture and sell the analyzer. There are a few options that I need to look at.
Apart from working on the layout I am in the initial stages of looking at the options of how to eventually manufacture and sell the analyzer. There are a few options that I need to look at.
Thanks JensH for the update.
I've recently came across a functioning Shibasoku AM51B at a very good price, but I decided to let it pass and save up for your analyzer. Looking forward to it's release 🙂
I've recently came across a functioning Shibasoku AM51B at a very good price, but I decided to let it pass and save up for your analyzer. Looking forward to it's release 🙂
This comparison is convincing, I certainly prefer your design from the hardware specs and features alone (variable gain and stuff is super!).
I recently asked the QA people about software compatibility of the QA401/405. As far as I understood, they expect it to work as an "external soundcard" via ASIO, but they seemed to be unsure about this. It seems the QA thingies work well with the QA software only. Not good.
For me (and everyone else, I guess) the hardware must work as a standard USB audio device without a special driver in order to avoid software lock-in or limit it's use to a specific operating system. I want to use the hardware with Linux or Mac OS using MATAA or any other audio analysis software. Others prefer other software, and there is a gazillion of different options.
Will your design work as a standard USB audio device?
If yes: I WANT ONE!!!
If no: please fix this to a "yes"...
Thanks for your phantastic work!
Hi.
It is possible with Linux/Mac/Android, because these OS has USB UAC-II driver built-in.
But, for Windows users it is not possible - no USB UAC-II driver inside, just USB UAC-I, which is limited to 96/24. Higher sample rates required the driver, dedicated to the hardware.
Yes, for Windows a driver is needed. I use the driver provided with the MiniDSP USBStreamer. With this driver there is ASIO support, so you are not locked to a specific analyzer software. Any audio analyzer software package with ASIO support is supported up to 192 kHz.
This project looks really promising, awsome work so far!
I am also quite interested in getting one, however, depending on how much it will cost. Are there any price estimations?
I am also quite interested in getting one, however, depending on how much it will cost. Are there any price estimations?
Just to be sure: are you saying that it works with the USB interface in JensH's design (which would be super cool!), or are you just saying that USB Audio Class II is supported by Mac OS X, Linux and Android out of the box (unrelated to JensH's design)?
Interesting project!! I've been lurking on the thread for a bit now, and am very interested in the finished product and pricing! I currently use the e-Mu 0404 (also have a 1212m lying in storage for when I need to pull out the big(ger) guns. It is sufficient for basic amp measurements, with the main issue being ground loops in unbalanced gear. The 1212 would fix most of that, but the DAC is not so great compared to the ADC (the same 5394A being used here). This sounds like what I need.
Just FYI the UAC driver is now available on Windows Update if the system is enabled to look for drivers online. It recently picked up a CM6631 and installed the driver all by itself, but no ASIO was available (if that matters).
Just FYI the UAC driver is now available on Windows Update if the system is enabled to look for drivers online. It recently picked up a CM6631 and installed the driver all by itself, but no ASIO was available (if that matters).
I have mean the second - just that UAC-2 is supported by Linux/MacOS/Android, but what the difference? If JensH use USB interface with higher then 96/24, he use UAC-2.
Doesn't matter which interface - he use CM6631, I use XMOS for the similar design, some peoples use Amanero, but all of them uses UAC-2 and required drivers for Win only.
@altor
No, I don't use the CM6631. I use an XMOS based interface as stated in the first post of this thread.
I will probably update the first post soon to reflect the changes that have been made since then, but it will not change regarding the USB interface.
The USBStreamer supports MAC and windows according to the manual. https://www.minidsp.com/images/documents/USBStreamer%20Manual.pdf
I have only used it with Windows. Linux is not mentioned in the manual, but it seems like some people have been able to get it working with Linux, see
https://www.minidsp.com/forum/usbstreamer/10128-multi-channel-recording-linux?start=6
Concerning approximate delivery time, price and with or without casing, I need to get a bit further regarding the production setup. As soon as I know more I will get back with the details.
No, I don't use the CM6631. I use an XMOS based interface as stated in the first post of this thread.
I will probably update the first post soon to reflect the changes that have been made since then, but it will not change regarding the USB interface.
The USBStreamer supports MAC and windows according to the manual. https://www.minidsp.com/images/documents/USBStreamer%20Manual.pdf
I have only used it with Windows. Linux is not mentioned in the manual, but it seems like some people have been able to get it working with Linux, see
https://www.minidsp.com/forum/usbstreamer/10128-multi-channel-recording-linux?start=6
Concerning approximate delivery time, price and with or without casing, I need to get a bit further regarding the production setup. As soon as I know more I will get back with the details.
I know, I mean "he" not as you, just abstract people 🙂
Yes, yes, all XMOS interfaces works under Lin/Mac/Android. I have my own 2.2 and 8.2 interfaces with XMOS that I use in ADC/DAC.
The difference is that not all USB devices are AUDIO devices. For instance, a scanner or a keyboard with USB port is not an audio device. The same seems to be true for the QA400 analyzer, which does do seem to work as an USB AUDIO device. It just exchanges data with the vendor software using the USB port. Such devices are useless with common audio testing software, which just have access to the AUDIO devices recognized by the operating system.
Really? I can't find anything about this. But if you already have the XMOS interface, the analyzer will work with most operating systems out of the box (and without special drivers). COOL!
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The device connected to windows has to teli it is an audio device and what it is capable of. To bad that windows doesn't have drivers it can natively connect for UAC-2 capable audio devices. Hence the need for products without drivers to advertize themselves as something else that is compatible.
Regards
Regards