DIY Audio Analyzer with AK5397/AK5394A and AK4490

mkc

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Joined 2002
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Hi Jens,

These things just to take time. As long as there is progress.

I noticed your comment on new USB interface to reduce cost. I have been planning to try out the USB gadget feature in Linux, but have not got around to it yet. So you have to take what I say with a grain of salt. But, my idea have been to try using the Raspberry Pi Zero as an USB audio device. As far as I can tell the code already supports UAC1 and UAC2 and the RPI Zero has I2S interface and can be externally clocked. It's hard to find a cheaper (£4.25) and more powerful piece of hardware.

Besides this it of course give the flexibility to connect an USB ethernet adapter also if one wishes to run it a little differently. Running Linux does make it a powerful little piece of hardware giving all sorts of possibilities since it can easily be programmed. But, again. I haven't tried it out yet. There might be something that I have missed. :)

Cheers,
Mogens
 
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Joined 2009
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Thanks to everyone here for your kind interest in my project.

Unfortunately it is taking longer than I had hoped to work out the details around production, including the final cost. This is still in progress. I am determined by now to make sure that it will go into production somehow, and I definitely will do my best to hit a reasonable price point, to make it affordable. But I still don't have a delivery date or price. I will do my best, but I am dependent on feedback from other parties involved.

In the meantime I have also worked on the design side of things:

1. Yesterday I assembled the first prototypes of the new USB interface. This interface, mounted on a single PCB, provides a USB to I2S interface, a USB to I2C interface as well as isolators. The USB to I2S interface will be able to handle up to 384 kHz sample rate for future options. The audio data is now 32 bit versus 24 bit on the old solution based on the USBStreamer.

2. The PCB for the user interface (front PCB with switches, LED's and I2C I/O interface) is being designed at the moment. This goes along with working out the design of the enclosure.

3. I am looking into the option of using the AK4497 DAC as an alternative to the AK4490. I have seen some measurement results recently and there seems to be real improvements on both noise and distortion.
 
Can a signal greater than 2vrms be fed into the analyzer without attenuation?
Will this design output the distortion residual waveform on the screen?
Will it have it's own low distortion sine generator on board? If yes what are the specs?

Great work. I'm following this with a lot of interest.

Appologies if these questions have been asked a million times.
 
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Joined 2004
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Me too, I'm hitting the capabilities of my EMU 0404, need something better soon and the QA401 is simply too limited....

Jens, I assume you have looked at the new AK557x ADC series ? Looks pretty good, although it's not in full production yet.

I'm meeting with AKM next week and I'll check on the new parts. So far they have not been able to duplicate the distortion performance of the AK5394a.
 
Thanks to everyone here for your kind interest in my project.

Unfortunately it is taking longer than I had hoped to work out the details around production, including the final cost. This is still in progress. I am determined by now to make sure that it will go into production somehow, and I definitely will do my best to hit a reasonable price point, to make it affordable. But I still don't have a delivery date or price. I will do my best, but I am dependent on feedback from other parties involved.

In the meantime I have also worked on the design side of things:

1. Yesterday I assembled the first prototypes of the new USB interface. This interface, mounted on a single PCB, provides a USB to I2S interface, a USB to I2C interface as well as isolators. The USB to I2S interface will be able to handle up to 384 kHz sample rate for future options. The audio data is now 32 bit versus 24 bit on the old solution based on the USBStreamer.

2. The PCB for the user interface (front PCB with switches, LED's and I2C I/O interface) is being designed at the moment. This goes along with working out the design of the enclosure.

3. I am looking into the option of using the AK4497 DAC as an alternative to the AK4490. I have seen some measurement results recently and there seems to be real improvements on both noise and distortion.

The new USB interface also sounds interesting. Is it based on XMOS? Are you developing drivers? Can this interface support multiple channels over I2S? How is it clocked?

thanks
 
I'm meeting with AKM next week and I'll check on the new parts. So far they have not been able to duplicate the distortion performance of the AK5394a.

Within some month we will see soon some AK557x on the market!

The real pain or market is, that the AKM with 384/768kHz and its early freq. roll off & noise shape rising made this only suitable for "audio" ... just my 2 cents..

The point is, if you rise the SR, a higher measurement bandwidth is required to get oscillations & spurious on your DUT.

Anyway, the Jens board is on a modular design :cool:

Hp
 
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@WH Fusion
I am getting pretty close to starting a small prototype series, with mechanics included.

@soekris
I have looked at the AK557x series, but only data sheets and evaluation board manual. I have not done any tests on these ADC's.

@2 picoDumbs
Yes, the inputs can easily handle more than 2 Vrms. The highest level going straight to the input amplifiers is 3.16 V (10 dBV). If the levels are higher the built-in attenuators can be used to allow up to 100 Vrms. As stated in post #1 it supports full scale inputs from 100 mVrms (-20 dBV) to 100 Vrms (+40 dBV) in 10 dB steps.

@1audio
It will be very useful if you can check with AKM how the AK557x performs.

I expect to get my hands on an AK4497 evaluation board in the near future. The AK4497 could be interesting for the generator. I have seen some measurement results, which look very promising. If available in time, this could become the standard solution. Otherwise the AK4490 will be used initially, with the AK4497 as a upgrade option.

@jojip
I am working on a couple of solutions for the USB interface. Both a Savitech SA9227 based solution and an XMOS based solution.
If it ends up being an XMOS based solution I expect to use the stereo driver from XMOS.
In addition I have made an FTDI based design of a USB to I2C interface for control and switch readout.
The clock comes from low jitter crystal oscillators located close to the ADC and DAC.

@HpW
Yes, the latest design is modular. So who knows what will come down the road ? :)
 
I think this thingmabob will be a really nice tool, but to achieve real greatness as "THE ONE STOP SOLUTION", there have to be a way to use a microphone, or two of course, together with it.
Any suggestions for a mic preamp that would be a good companion to this one ???