I need a new oscilloscope - 300€?

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Gold

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I have it installed on a Surface Pro 3 tablet. The touch screen works pretty well but I found I liked having a keyboard. The keyboard cover that magnetically snaps into place is too large to keep hooked up. I was also having trouble connecting the keyboard because the strong magnets suck up resistor leads and random bits of metal and short out the connection. I got a mini bluetooth keyboard and trackpad for $20 from the bay. I figure if I destroy one or two a year it's no big deal.
 

Bo Deadly

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Gold said:
Because they are using the 14 bit AD2 interface. The software will display any level and frequency range you set it up for. I just tried measuring a tone at -110dBfs with the Konnect2 and it worked and displayed fine.
I'm not sure I understand. You cannot measure 110dBFS with 14 bits. I assume you mean you played a tone at -40dBFS and then scaled the display. AFAIK you cannot make meaningful THD or SNR measurements doing that. The software must use probably 32 bit float to take measurements that would be useful for pro audio. So again, it seems using WaveForms with a conventional USB audio interface is apparently not useful for anything but low resolution, low frequency AC-only visualization.
 

Gold

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squarewave said:
I'm not sure I understand.

We are talking about two different front ends connecting to the Waveforms software.  The Analog Discovery 2 is the front end from Digalent that is meant to interface with the Waveforms software. The AD2 is 14 bit. The AD2 is a measurement front end controlled from the software. It has built in attenuators and the software can directly control oscilloscope functions like time base. It is also a logic analyzer and has a bandwidth like an oscilloscope.

Waveforms will also recognize a USB interface. This can be anything you want. Low level noise and distortion measurements could use that interface.

The reason i like it is that all the measurements can be displayed together. The level from the soundcard can be referenced against the calibrated AD2. Not trusting  the setup of the soundcard is the main reason i want a dedicated calibrated front end.
 

Bo Deadly

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Gold said:
Waveforms will also recognize a USB interface. This can be anything you want. Low level noise and distortion measurements could use that interface.
Sorry but this is still not clear. I am only asking about using the WaveForms software with a USB audio interface.

So again, when you said before "I just tried measuring a tone at -110dBfs with the Konnect2 and it worked and displayed fine." can you please be more precise? Specifically, can you do a loopback test with a tone at or near 0dBFS and post a screen shot? So it should look like a floor around -110 and then a giant very narrow peak at 1kHz or whatever frequency you choose all the way up to 0dBFS.

Although in reality it should really be at least 130dBFS down (depends on the output impedance of the Konnect2).
 

Gold

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squarewave said:
Sorry but this is still not clear. I am only asking about using the WaveForms software with a USB audio interface.

Waveforms behaves like any of the other usual suspects like REW or Audio Tester with a USB interface. Waveforms supports ASIO drivers. The Spectrum Analyzer displays like you would expect it to. You can set the Y axis to be any range you want.
-144dBu is no problem.

I find Waveforms easier to navigate than REW. The software is only part of the advantage though. The main advantage for me is that the AD2 is a dedicated front end designed for measurement. I mostly need it for the Spectrum Analyzer. The AD2 noise floor is fine for most frequency response measurements. For noise and distortion below the AD2 noise floor I’d switch over to the USB interface.

 

Bo Deadly

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Gold said:
The Spectrum Analyzer displays like you would expect it to. You can set the Y axis to be any range you want.
-144dBu is no problem.
-144dBu! Wow. That's incredible. I've never seen a noise floor anywhere near that low. Awesome.
 

Gold

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squarewave said:
-144dBu! Wow. That's incredible. I've never seen a noise floor anywhere near that low. Awesome.

I’m not talking about any hardware. You can set the Y axis of the software to be any range you want.  The software will cover whatever range the attached hardware can handle. If the question is “can i use a 24 bit usb interface and measure over the whole dynamic range” the answer is yes.
 

jacomart

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This is what i get using my old Presonus USB (un)fortunately my new interface is an UAD thunderbolt and I can't use it with WaveForms. No input signal, only noise floor. 24bit/96kHz
 

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Bo Deadly

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jacomart said:
This is what i get using my old Presonus USB (un)fortunately my new interface is an UAD thunderbolt and I can't use it with WaveForms. No input signal, only noise floor. 24bit/96kHz
Thanks jacomart. That's sort of what I was looking for. It looks like it is using 24 bits.
 

Tubetec

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I  tried a beta version I found here ,

https://forum.digilentinc.com/topic/8908-waveforms-beta-download/

I found I could get it to work reliably upto 192khz with my interface when single channel mode is selected for input and output on Waveforms device manager panel . Even though Ive tried saving the project ,each time the program is opened a set of default sample frequency and bit rate values are loaded up that dont work , I couldnt find any way of getting it to remember my audio card setup, although maybe thats an inbuilt limitation of the demo version .
There doesnt seem to be any way of doing a loop back test/cal on the audio path like in REW unless you have the hardware .

 

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Tubetec said:
There doesnt seem to be any way of doing a loop back test/cal on the audio path like in REW unless you have the hardware .

I'm able to get Wavegen output at the Konnect2 USB interface and feed it via cable to the interface input. Is that what you are talking about? 
 

Tubetec

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What I meant was that you cant calibrate your audio interface unless you have the Digilent hardware unit, I guess its a fair limitation for free software .
I like all the audio specific stuff that comes with REW , the Waveforms is much more an instrumentation approach. As I mentioned I have issues running the software , it automatically selects an incompatible sample/bit rate that puts a supersonic squeal through my monitors until I can select the correct mode , thats getting a bit long in the tooth now  :mad:  . In general though the software does have a nice feel to it .
 


 

Gold

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You can calibrate the interface. Just measure the Wavegen output, feed it to the measurement input and match the level.

One of the reasons i like a dedicated front end is that the cheap interfaces always seem to have fiddly level adjusters in the signal path. I don’t trust the knobs not to get bumped.

I got an email this morning saying there is now a Transistor Curve Tracer attachment for the AD2
 

jacomart

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abbey road d enfer said:
What about performance? What are the bit depth, the sample rate and the converter quality on a tablet?

I'm really sorry but I don't know anything more than what is written in the page that I linked in the msg.
However, I can say that personally I don't have much confidence with this product but I would be happy to be proven wrong.

Cheers
JM
 

jacomart

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abbey road d enfer said:
The "Pro" reference in the name is a dead ringer that it's a toy.  ;D
there is no external hardware, which means that it uses the microphone input of the tablet and that says a lot  ;)
 

Gold

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jacomart said:
there is no external hardware, which means that it uses the microphone input of the tablet and that says a lot  ;)


There is a bunch of software that can do the basic functions we need. It's the front end that's the issue. The AD2 obviously isn't ideal because it's only 14 bit. The reason people use it for audio is that it has a dedicated and calibrated front end. This is crucial especially for beginners. Calibrating test equipment isn't something a beginner should be doing.

I think it's only a matter of time before there is an affordable dedicated test set. The new DScope is $3500. I could see something for half that in a few years.
 
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