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Old 6th March 2013, 05:16 PM   #31
davada is offline davada  Canada
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Quote:
Originally Posted by soundchaser001 View Post
Does this mod invert absolite phase for this channel? It looks like it would.
It does invert the signal. This shouldn't be a problem unless the two channel are summed physically. The emu would be useless for music applications at this point.
An alternative is to leave the input op amp in the non inverting mode, ground the added resistor and adjust the R value for this mode.

I prefer the inverting amp.

Cheers,
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Old 7th March 2013, 07:52 AM   #32
1audio is offline 1audio  United States
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I got the EMU 0404 working. It starts with a reformatting of the hard disk and complete re-install of Win 7 with no Dell drivers, and ended with the laptop's battery self destructing. . . I'll grab a quick shot of its performance in the morning as is. I think the gain structure is limiting the noise floor. I'll know more soon. It seems the residual distortions are in the -115 dB to -120 dB in loopback. If the software works then its worth making an effort to get the analog performance optimized.
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Old 7th March 2013, 02:21 PM   #33
davada is offline davada  Canada
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I haven't looked at the left channel. It resembles what the 0404 looks like from the outside.
I bet they're the same input circuit. Whatever EMU used for a balance input.

EMU likes to direct couple each stage of there inputs. This make it difficult to minimize the number of op amps required. The driver bias voltage appears at the non inverting input.
This forces the preceding stage to operate a bit in class A. The output bias voltage is dependent on having the source resistor of the driver tied to a low Z ground reference source. Other wise we would not get the 2.5V bias required at the inputs of the ADC.
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Old 7th March 2013, 03:26 PM   #34
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I wish I knew how to design my own ADC. It seems like all of these issues could be avoided that way.
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Old 7th March 2013, 03:58 PM   #35
1audio is offline 1audio  United States
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The datasheet for the AKD5384a has most everything you need on it. The bigger challenge is programming the settings for the chip for different sample rates. It can be done with a multipole switch or a micro if you have the skills. Or you can use the hardware here: Open-source USB interface: Audio Widget which already has support for the AK53954A. The ADC code is already done so its just a PCB. The analog side does not need to be complex. I could be up for contributing if someone else is ready to do the bulk of the work.
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Old 7th March 2013, 04:33 PM   #36
iko is offline iko  Canada
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There was a great project a little while ago, here:

DIY Analog-to-Digital Converter project.Audio measurements tool

And, of course, for those who don't want the complications, there's the pcm4222evm, which, for $150 gives you some amazing performance; see post 4 here:

DIY Analog-to-Digital Converter project.Audio measurements tool
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Old 7th March 2013, 05:26 PM   #37
davada is offline davada  Canada
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Quote:
Originally Posted by 1audio View Post
The datasheet for the AKD5384a has most everything you need on it. The bigger challenge is programming the settings for the chip for different sample rates. It can be done with a multipole switch or a micro if you have the skills. Or you can use the hardware here: Open-source USB interface: Audio Widget which already has support for the AK53954A. The ADC code is already done so its just a PCB. The analog side does not need to be complex. I could be up for contributing if someone else is ready to do the bulk of the work.
Hi Demian,

Put it up I'll do it.

I've been looking into this anyway.

I do want try the parallel ADC technique. The summing can be done with serial adders and the division by a shift padded with a zero in a serial shift register. Doing this with discrete logic would be a real chore and DSP would be over kill. There must be a happy medium???
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Old 7th March 2013, 05:38 PM   #38
davada is offline davada  Canada
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Quote:
Originally Posted by 1audio View Post
The datasheet for the AKD5384a has most everything you need on it. The bigger challenge is programming the settings for the chip for different sample rates. It can be done with a multipole switch or a micro if you have the skills. Or you can use the hardware here: Open-source USB interface: Audio Widget which already has support for the AK53954A. The ADC code is already done so its just a PCB. The analog side does not need to be complex. I could be up for contributing if someone else is ready to do the bulk of the work.
I've done this with other codecs. It can be done with a header and shunt jumpers.
This way it's expandable to uP by replacing the shunts with a header connector and jumping to a different board.

The simpler the analog end is the better. I don't like long chains of op amp in the signal chain. I think the ADC should be integrated with the front end design and this is very doable.

We just need someone here who's really good at programming software. It's not my area of expertise. I can pull off the imbedded stuff okay but the windows programming not so well.

I don't know how well Visual Studio ports to Win7 when compiled in XP. The drivers are not the same.

Does anyone here know how to write drivers for Windows?
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Last edited by davada; 7th March 2013 at 05:44 PM.
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Old 7th March 2013, 07:53 PM   #39
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Quote:
Originally Posted by ikoflexer View Post
There was a great project a little while ago, here:

DIY Analog-to-Digital Converter project.Audio measurements tool

And, of course, for those who don't want the complications, there's the pcm4222evm, which, for $150 gives you some amazing performance; see post 4 here:

DIY Analog-to-Digital Converter project.Audio measurements tool
Thanks.

That DIY ADC does not have USB or other computer interface.

Yeah, I have the pcm4222evm, but it is a real hassle to install in a box. One set of connectors is not designed to be mounted in a box because they are recessed too far on the board. Unsoldering the connectors lead me to damage the board. So, while it may perform admirably, it's a hassle, and the board could be much smaller also. It also does not have holes in it for standoffs, but rubber feet instead. So, I either have to drill the board myself (scary) or use hot melt glue to hold it in place. I'm just not that excited about the latter and the former would make me worry that I'm further damaging the board. I don't want to rig up some kind of clamp that others have done to hold the board in place. The board has a lot of options that are probably not needed for audio ADC use (why two clocks?), and seems spread out, like it was designed by an amateur (though I doubt that). Obviously, I'm annoyed by this board....

Basically, what I'm looking for is a high performance ADC with balanced/unbalanced inputs, and a computer interface output (USB, etc.). It's not complicated, but sure is a pain to find as a DIY kit or board. I've got an I2S->USB interface board, so no problem there interfacing the TI evaluation board with a computer, but I'd obviously prefer a more integrated solution.

I don't mean to hijack this thread... sorry!

Last edited by dirkwright; 7th March 2013 at 08:03 PM.
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Old 7th March 2013, 08:05 PM   #40
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Quote:
Originally Posted by davada View Post
Hi Demian,

Put it up I'll do it.

I've been looking into this anyway.

I do want try the parallel ADC technique. The summing can be done with serial adders and the division by a shift padded with a zero in a serial shift register. Doing this with discrete logic would be a real chore and DSP would be over kill. There must be a happy medium???
I'm certainly willing to buy what ever board you make, as long as it has the interfaces I need. I've gotten a lot better at soldering SMD's now... they take forever though.
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