# DIY Custom Audio DSP (like miniDSP)



## 24th-Alchemist

New to this forum.

Built an audio signal processing device that I use in my car.

Not sure if the details are of interest here, but I think the end result might be -- a good deal of audio DSP capability for crossovers and EQ.

Some pics and then a brief description.

*ADAU1442 audio signal processor chassis:*









*Four Wolfson WM8524 DACs (2 Vrms ground-centered output, -89 dB THD+N, 106 dB dynamic range)*









*The computing core: Analog Devices ADAU1442 audio signal processor (easy to use with their SigmaStudio graphical user interface software).*










*ADAU1442 board top*









*ADAU1442 board bottom*









*Testing ADAU1442 and WM8524 analog outputs (DACs are "upside down" under the ADAU1442, protected by the two ground planes in the boards)*









*Final prototype, box open*









*Final ADAU1442 prototype audio signal processor*









Features:
*Analog outputs:* Four independent WM8524 24-bit stereo DACs (e.g. sub, midbass, midrange, tweets). 2 Vrms ground-centered output (no DC blocking caps).
*Digital Outputs:* Four independent optical S/PDIF outputs (CS8406 to TOTX147). (Future plans are to use these instead of analog).
*Inputs:*
_Digital:_ Two S/PDIF optical -- one from H/U, one direct from CD changer (TORX147 to CS8416 S/PDIF receiver to CS8421 ASRC).
_Analog:_ one "AUX" analog input (e.g. for handheld device) using CS5351.
_Optional:_ a third S/PDIF input if needed in the future.

*Power:* "12 volt" from car with remote turn-on/off.
*Control:* Digital volume up/down and digital source select. (Possibly more in the future if needed).
*ADAU1442 Computing Highlights:*
3584 instructions per sample at 48 kHz.
56-bit processing.
8k data RAM (up to 170 ms delay at 48 kHz).
IIR and FIR filters, EQ and more; easy implementation with GUI software (see below).

*ADAU1442 Usability:*
Self-boot from EEPROM (no microcontroller required).
Analog Devices SigmaStudio drag-n-drop graphical user interface is so nice to use.
Analog sampled a ADAU1401 evaluation board which allows for real-time EQ and A/B testing with a laptop.


After I spent some time reading about various ICs that are available, it only took about four partial weekends to build and debug the box. Then another couple hours here and there to fashion the GUI in Analog's SigmaStudio software that implements my current crossover scheme.

Many of the parts are free samples; others aren't very expensive.

I'm presently using the box for active crossovers. But now that I have some processing power I'm interested in learning about how to really EQ a car audio system.


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## 24th-Alchemist

. . .Oh, and can't forget Schmartboard, without which it might be almost impossible to use a lot of the small surface mount IC packages such as the TSSOP for the WM8524 DACs or TQFP for the ADAU1442 audio processor.


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## ErinH

Dude, that's badass! Congrats! 
Can we get screenshots?


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## rexroadj

bikinpunk said:


> Dude, that's badass! Congrats!
> Can we get screenshots?


X2
Well played sir! Well played!

I am VERY intrigued by this (not to build, but certainly to buy
Does it get warm? Looks kinda cramped in there? 
Regardless, good for you! I think thats awesome!


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## BowDown

Wow that is a pretty cool setup. Looking forward to hearing more about it.


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## azngotskills

Very interesting, way above my head component wise but definitely useful. Good work

Got any screen shots of the interface?

Building to sell or just personal use?


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## bassfromspace

We're in need of more processor options.


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## nubz69

Nice work, interested in building an SMPS for me?


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## armykyle1

thats freakin amazing 

good job man


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## pmang

Very nice indeed! What was the total cost of the parts if you don't mind me asking.


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## bmiller1

bassfromspace said:


> We're in need of more processor options.


x2 I don't know a whole lot but, I can tell you that I've been reading all the posts about processors for the past few days and rarely are people satisfied. Well, except those that use 1 or more Mini DSPs. Nice looking work, 24th.


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## Mic10is

interesting.veeeeeeeeeeeeeeeerrrrrrrrrrrrry interesting


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## highly

Mic10is said:


> interesting.veeeeeeeeeeeeeeeerrrrrrrrrrrrry interesting


Agreed!
Very interested in learning more about this. I stayed away from this option due to a severe lack of knowledge on coding DSPs. It looks like you have created a very elegant solution to a problem experienced by many. There could very well be a market there...


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## ashman5

HARDCORE DIY!!!

Nice Job


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## 24th-Alchemist

Thank you for the responses.

I think this project is good for DIY car audio applications. There are however at least three drawbacks: 
Time to solder circuits;
Learning to use ADI's SigmaStudio software;
Cost.

It's worth the time & money IMO though. The only limitations are a person's imagination and the power of the IC -- there are almost none of the usual limitations with finished signal processors.



> I am VERY intrigued by this (not to build, but certainly to buy)





> Building to sell or just personal use?


Initially I did not intend to build this box for sale. Nonetheless I looked into it. But alas the answer is no, because without the flexibility afforded by software, the box doesn't seem very useful, and according to Analog Devices, their software is not licensed for use outside of design. (And I have no intention of learning how to write software to use the box; moreover I think a major strength of the box is the SigmaStudio software it uses -- I wouldn't want to change that!) A thread about ADI's software licensing is here. (And perhaps of interest, in the thread they mention programmable car audio amps that use their SigmaDSP products (like a miniDSP embedded in an amp); here's the link). 



> I can tell you that I've been reading all the posts about processors for the past few days and rarely are people satisfied. Well, except those that use 1 or more Mini DSPs


One of the main things miniDSP provides is software that allows us to use the ADAU1701. But IMO their software takes away from the full potential of the IC. Nothing against miniDSP, it's just a necessary trade-off. Actually, their prices seem very competitive, and they bring value in that their device does not require assembly. Furthermore they appear to offer easy-to-use software for operating the IC. A good product IMO.

Nonetheless I wanted to take a different approach. I was interested, like others might be, in a more powerful IC (e.g. the SigmaDSP ADAU1442 instead of the ADAU1701). I wanted something that could perform some basic FIR filtering and which could be used for longer delays (I ran out of delay with the ADAU1701). In addition I wanted to take full advantage of ADI's SigmaStudio software (in particular the "wide-open" possibilities it affords along with its quick & easy, yet nonetheless full, IC control). But in order to buy something that does not require DIY construction and which is comparable to the box described here, a person would have to purchase the evaluation board for the ADAU1442 for $699.00 (as of June 2011). But IMO that evaluation board isn't as good as the box described here, so the DIY approach seems a worthwhile option.



> Can we get screenshots?





> Got any screen shots of the interface


I'll provide a screenshot, but it doesn't do much justice. To see just the "tip of the iceberg" of what this stuff can do, *check out these two ADI videos with the girl in the pink shirt here*. 

Below is a screen shot of my crossovers in ADI's SigmaStudio software (subwoofer section is off the screen). Crossover components are added by dragging and dropping various software functional blocks into the schematic. From there parameters for a wide range of selectable crossover types can be specified. (E.g. low-pass Butterworth or parametric EQ to name a few -- custom coefficient biquads are also avaialable).










In my case (above) I'm using four main components: 
Delays;
Linkwitz compensators to modify speaker box characteristics;
Low- and high-pass 2nd-order Butterworth filters with specifiable crossover frequencies (to make LR-4 crossovers);
Theoretically "perfect-reconstruction" FIR filters between midrange and tweets. (Speakers are mounted in a nearly coax geometry -- CDT audio's braxial configuration).

But the crossovers are boring. To get a better flavor of all that is possible (e.g. super easy multi-band parametric EQ), check out this link (if you haven't already) to the pseudo-screen shot of the SigmaStudio software.




> Does it get warm? Looks kinda cramped in there?


It gets warm but not hot. I chose linear IC voltage regulators, so with the car at 13.3-14.4 V and the ADAU1442 core running at 1.8V, there is over 10V to burn at ~300 mA -- not including other components. I just stuffed some resistors in there so the regulators wouldn't get too hot. Heat was a concern initially but it hasn't become an issue. Nevertheless, just in case there were heat problems I had a switching power supply available: a 8-42V DC input, 3.3 or 5V DC output breakout by Sparkfun. (The breakout was cheaper than I could get the part (LMZ14203) when I bought it).

As for the cramping, that was part of the fun! There's a lot of functionality in a box measuring 2-1/8 x 3-1/4 x 1-5/8 inches. It forces compact circuit construction which I find relaxing. (It seems like building a ship in a bottle, which I've never done).




> What was the total cost of the parts if you don't mind me asking.


Good question for a DIY setting. I'm glad the question was asked because I ended up learning something. But first, a components "recipe" with costs:
*One Audio DSP:* Analog Devices ADAU1442. Free samples from ADI (see bottom of link). (Otherwise at June 2011 $16.88 from Avnet).
*IC board for ADAU1442*: 0.5 mm pitch 100 pin LQFP from SchartBoard, $9.99 at June 2011.
*Four DACs:* Wolfson WM8524. At June 2011, $1.24 ea from Mouser. (2 Vrms ground-centered output; 24-bit -89 dB THD+N; $1.24? -- Wow!)
*IC board for DACs*: 0.65 mm pitch 72 pin TSSOP from SchmartBoard, $9.99 at June 2011.
*Four S/PDIF transmitter IC's:* Cirrus CS8406. At June 2011, $4.71 automotive qualified from Avnet, $3.76 commercial grade (I used automotive grades for fun).
*Four TOSLINK transmitters*: Toshiba TOTX147 or TOTX141 with shutter (see bottom of link). Getting hard to find. (Tsunami?) Should be $1 to $4. Check Avnet or Digikey.
*One 4-channel select S/PDIF receiver:* Cirrus CS8416. At June 2001 $6.79 automotive qualified from Avnet, $5.16 for commercial grade.
*Three TOSLINK receivers*: Toshiba TORX147 with shutter. At June 2011, $1.27 from Avnet. (I also use TORX142 192 kHz specified but no longer know if available).
*One ADC:* Cirrus CS5351. At June 2011, $6.74 from Avnet. (Note: CS5351 does not appear to be available in automotive grade in SOIC package).
*Six 28-pin SOIC mounts (S/PDIF trans & rec, ADC)*: At June 2011, $3.95 each from Sparkfun. (Other options also available on ebay).
*ADC signal conditioning:* Analog Devices ADA4841-2. Free samples from ADI (any number of op amps could be used).
*One 20-pin SOIC mount (for two op amps)*: at June 2011, $3.95 from Sparkfun. (Ebay options also available).
*One ASRC (sample rate converter):* Cirrus CS8421. At June 2011 $8.34 automotive qualified from Avnet, $6.68 commercial grade. (Note: ADAU1442 has 8 ASRCs so this component is actually not necessary.)
*One 20-pin TSSOP IC board*: At June 2011, $3.95 from Sparkfun. (Other options also available on ebay).
*Additional components*: Linear regulator IC's, ferrite beads, power supply bypass capacitors (ceramic and tantalum), 1/8-inch analog jacks, IC clocks -- up to builder, $30-50?
*Metal Box*: at June 2011 looks like $5.46 for Model #000 from LMB Heeger. (2-1/8 x 3-1/4 x 1-5/8 inches; _very_ tight fit). (I think I paid less when I bought mine).

So total cost of IC's and mounts is around $150 -- but a person could make different choices and substantially reduce the cost. Also, it's important to keep in mind that there are no less than _8_ independent outputs here (four TOSLINK, four analog), along with three TOSLINK and one analog inputs (with room on the ADAU1442 for more I/O -- but there's no more room on the small box).

As for circuit construction, I just wired the circuits as shown in the manufactures' data sheets and evaluation board schematics. The time it took to build circuits and learn ADI's software was less than, say, disassembling my car interior and applying dynamat and mass loaded vinyl.

One issue though is that in order for a DIY'er to use the ADAU1442 and program it, ADI's SigmaStudio software is required. And although ADI says the software is "free", it may only be "free" with purchase of an evaluation board. Several years ago when I first became interested in Analog's SigmaDSP platform they gave me both an evaluation board and software _for free_. But I suppose those days have passed. For $195 Analog sells a "mini" evaluation board for their ADAU1701, where the evaluation board has 1-ch analog line-level IN and 1-ch line-level analog OUT, among other things. That would get a person the Sigmastudio software along with some hardware that is something like a basic miniDSP board (but with much more versatile -- and somewhat more complicated -- software). Additionally, as is shown in the pic below, any evaluation board and software affords self-boot programming as well as real-time software control for any number of DIY boxes. (Where a DIY box can have many more high-quality I/O channels and, relative to miniDSP, much more customizable signal processing).










The real-time control seems invaluable for in car tuning. However, I am not doing real-time tuning in the car yet, because I'm waiting to receive an IC that electrically isolates my box from the evaluation board. My concern is that in the car the box connects to chassis ground, but the eval board runs off laptop USB power, and not knowing how a laptop USB ground is configured in a car (especially when the laptop might be running off a powerinverter), I don't want to risk blowing out a CMOS interface on the ADAU1442 in the box. The IC I'm waiting for is ADI's ADUM1250. It electrically isolates the I2C communication between the eval board and box. (The three wires in the pic above; the colored wires connect the I2C interface and the black wire establishes a common ground, the latter of which I'm worried about in a car). (I don't know much about I2C, I just wire it up and it works; some info about I2C and optical isolation is here, here and here).



> I stayed away from this option due to a severe lack of knowledge on coding DSPs. It looks like you have created a very elegant solution to a problem experienced by many.


Elegant yes, but credit Analog Devices. All I did was solder some IC's. For $699 a person could buy the evaluation board for the ADAU1442 (several years ago I received something comparable for the ADAU1701 for free; it's in the pic above). No assembly required and a lot of powerful software right out of the box -- and no DSP assembly programming needed. 

On the other hand, for $10 a person could put a free-sample of a ADAU1442 (or any other SigmaDSP) on a Schmartboard themselves, and also buy the ADAU1701 mini-evaluation board for $195. That board comes with the SigmaStudio software and also a "USBi" interface that could communicate with a DIY ADAU1442 similarly to what is shown in the pic above. It would provide self-boot programming as well as real-time operation for in car tuning and other experimentation. (How to do it is explained by ADI in application note AN-1006. There is also some background information in application note AN-923. Unfortunately I found it necessary to wade through such documentation to get these things to operate).


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## rexroadj

WOW! just WOW! 
THANK YOU for sharing your findings, and Thank you for the details. EXCELLENT DIY project (not for me though  Love the balls forward approach, it will interesting to see what can be built off of this as well?
Again, thank you for sharing, REALLY cool reading!


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## pmang

FANTASTIC WRITE UP! Wayyy out of my league, but VERY impressive


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## subwoofery

How's the noise rejection installed in your car? (it's for the car, right?)  

Kelvin


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## stereojnky

It appears that you can request a software key from them. If I order a ADAU1442, and get a software key, how much would you charge for plans to build my own? This seems like a cool project.


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## 24th-Alchemist

> looks like the evolutionary step for the Linkwitz Pluto's analog filtering replacement


Actually, when I first started using SigmaDSP ICs and SigmaStudio software (with an ADAU1701), I emailed Sir Siegfried to tell him about it. In addition to active crossovers for speakers, I think the real-time control capability would have been of interest to him; for example, it could be used to conveniently A/B test whether a person can hear distortions due to phase such as is discussed in his Group Delay and Transient Response section (see especially the last two plots in section F). He was polite and emailed me back, which I thought was nice, but he didn't seem overly interested in what the ADAU1701 and SigmStudio has to offer. An oversight by him IMO -- but I should say that his site is hands down, far and away, the best audio resource I've ever encountered on the internet.



> If I order a ADAU1442, and get a software key, how much would you charge for plans to build my own?


I'd be happy to charge a lot of money, but I made neither schematics nor even drawings for this project. The reason is that they're all already available online for free. Just about everything you would need to know is in the links in the bullet points of the "components recipe" I posted above. Take the ADAU1442 for example. The link to its data sheet (a PDF file) is here. Look at figure 64 on page 89, "_Self-Boot Application Schematic_". The ADAU1442 should work if wired as shown in that figure, except for two misprints that I'm aware of: (1) supposedly, there should be a 10k resistor between pin 21 (CLATCH) and ground (I haven't tried it without); and (2) on the "self-boot switch" at the bottom of the page, "DVDD" should actually read "IOVDD". If a person were unsure of whether I'm right, you could go straight to the source and post in the help section for SigmaDSP's in Analog Devices' help forum here. Now, suppose you didn't know what that three-lead symbol is next to "REGULATOR" in the schematic. Searching "regulator" in the PDF would lead to a nice explanation on page 25: Analog recommends the NJT4030P from ON semiconductor. Google NJT4030P and so on. This, along with looking at the evaluation board schematics for various ICs, has basically been my approach, and after googling a few things I didn't understand, it all ended up working. Another good resource if a person got stumped by something would probably be diyAudio. I don't really go there but I think they build a lot of IC's and would be happy to help. (Relatedly, they might be interested in a build such as this but I posted here b/c I use it for car audio).

There might be a problem with the plan though. If a person gets the SigmaStudio software, how is the software going to communicate with the ADAU1442? My understanding of what Analog Devices says (see application note AN-1006) is that the software talks to one of their USBi devices over usb, and then their device converts the usb communication to either I2C or SPI -- but without their USBi (part of evaluation boards), how to talk to ADAU1442? I believe their software does generate a self-boot file for an EEPROM, but then a person would need to get an EEPROM burner and there would not be real-time control of the ADAU1442 (although the ADAU1442 would work with programs pre-configured in SigmaStudio). It might be worthwhile to email Analog Devices and/or look / post on their help forum to get such questions answered.


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## envisionelec

24th-Alchemist said:


> I'm presently using the box for active crossovers. But now that I have some processing power I'm interested in learning about how to really EQ a car audio system.


Welcome!

I was excited when I saw this, but my excitement deflated when you said you didn't write the software interface (which is what I need) Drat.  

Nevertheless, it's a very ambitious DIY project! Congratulations!


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## piyush7243

thats a great write up.. Keep up the nice work


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## xxx_busa

Great job, I hate soldering fleas - smd's at my age, makes me crosseyed, looks very promising, Should start 60% finished piece like at pear audio, I bet it would go over well.




24th-Alchemist said:


> New to this forum.
> 
> Built an audio signal processing device that I use in my car.
> 
> Not sure if the details are of interest here, but I think the end result might be -- a good deal of audio DSP capability for crossovers and EQ.
> 
> Some pics and then a brief description.
> 
> *ADAU1442 audio signal processor chassis:*
> 
> 
> 
> 
> 
> 
> 
> 
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> *Four Wolfson WM8524 DACs (2 Vrms ground-centered output, -89 dB THD+N, 106 dB dynamic range)*
> 
> 
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> *The computing core: Analog Devices ADAU1442 audio signal processor (easy to use with their SigmaStudio graphical user interface software).*
> 
> 
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> 
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> 
> *ADAU1442 board top*
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> *ADAU1442 board bottom*
> 
> 
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> *Testing ADAU1442 and WM8524 analog outputs (DACs are "upside down" under the ADAU1442, protected by the two ground planes in the boards)*
> 
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> 
> *Final prototype, box open*
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> 
> *Final ADAU1442 prototype audio signal processor*
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Features:
> *Analog outputs:* Four independent WM8524 24-bit stereo DACs (e.g. sub, midbass, midrange, tweets). 2 Vrms ground-centered output (no DC blocking caps).
> *Digital Outputs:* Four independent optical S/PDIF outputs (CS8406 to TOTX147). (Future plans are to use these instead of analog).
> *Inputs:*
> _Digital:_ Two S/PDIF optical -- one from H/U, one direct from CD changer (TORX147 to CS8416 S/PDIF receiver to CS8421 ASRC).
> _Analog:_ one "AUX" analog input (e.g. for handheld device) using CS5351.
> _Optional:_ a third S/PDIF input if needed in the future.
> 
> *Power:* "12 volt" from car with remote turn-on/off.
> *Control:* Digital volume up/down and digital source select. (Possibly more in the future if needed).
> *ADAU1442 Computing Highlights:*
> 3584 instructions per sample at 48 kHz.
> 56-bit processing.
> 8k data RAM (up to 170 ms delay at 48 kHz).
> IIR and FIR filters, EQ and more; easy implementation with GUI software (see below).
> 
> *ADAU1442 Usability:*
> Self-boot from EEPROM (no microcontroller required).
> Analog Devices SigmaStudio drag-n-drop graphical user interface is so nice to use.
> Analog sampled a ADAU1401 evaluation board which allows for real-time EQ and A/B testing with a laptop.
> 
> 
> After I spent some time reading about various ICs that are available, it only took about four partial weekends to build and debug the box. Then another couple hours here and there to fashion the GUI in Analog's SigmaStudio software that implements my current crossover scheme.
> 
> Many of the parts are free samples; others aren't very expensive.
> 
> I'm presently using the box for active crossovers. But now that I have some processing power I'm interested in learning about how to really EQ a car audio system.


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## quietfly

truely awesome leg work there. i hope something great is able to come out of it...


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## AccordUno

Interesting.. Very Interesting.. I do write software for a living, I would what the code looks like for that software, my guess would be C++, I wonder if could be extended using .Net and give it a very user friendly UI.


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## sonikaccord

Man I was just thinking about building my own audio processor. I'm doing some internship that is very similar (it involves ASICs and FPGAs).

Check this out though. I want to use a carPC for my source. Which means I could potentially just use a digital out directly to the DSPs input, and spare the cpu from processing the audio. The audio would remain in the digital domain until it hits the DACs. From what I'm imagining, building it is simple but like previously mentioned programming is going to be a pain. Also I could probably use some cad software and send it to a third party to be fabricated. I shall stay tuned for this though. 

Great work OP.


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## highly

sonikaccord said:


> Man I was just thinking about building my own audio processor. I'm doing some internship that is very similar (it involves ASICs and FPGAs).
> 
> Check this out though. I want to use a carPC for my source. Which means I could potentially just use a digital out directly to the DSPs input, and spare the cpu from processing the audio. The audio would remain in the digital domain until it hits the DACs. From what I'm imagining, building it is simple but like previously mentioned programming is going to be a pain. Also I could probably use some cad software and send it to a third party to be fabricated. I shall stay tuned for this though.
> 
> Great work OP.


Don't forget about volume control... the problem with a pure digital design.


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## sonikaccord

I haven't. I was on ti website looking at some of their IC's. They have a digitally controlled line driver chip with +/- 15v rails. It controls the volume in the analog domain, just digitally. I'm still looking into it. Plus it will look good on a resume lol.


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## highly

Be sure to use a zero crossing digital volume control. Without zero crossing detection you get the zipper noise found in the H701's volume circuit. Yuck. 

The best volume control you can get is a nice Alps analog audio taper pot. They have motorized ones if you need it. No noise, great wiper life, and no 1dB minimum attenuation 'step'. You know, if you are going that far.


-Todd


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## t3sn4f2

I think the best ones come free in jl hd amps 

Solid state potentiometers iirc


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## highly

t3sn4f2 said:


> I think the best ones come free in jl hd amps
> 
> Solid state potentiometers iirc


The JL HDs _do _allow you to chain one remote volume control to all amplifier channels. That's a very viable solution to the problem, though an expensive one considering even street prices on those babies.

Apologies to 24th-Alchemist for enabling the mistracking of your thread. I hate it when I do that.
Bad Highly!


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## AccordUno

24th-Alchemist, I write code for a living, is there any way you forward me that app or if I link to some software, would you run it and send me the results? Basically, not trying to circumvent their software, just wondering if you can build upon it or totally rewrite it for something more user friendly..


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## nfrazier

Looks good, how does it sound?


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## 24th-Alchemist

... An update and then some responses ...


UPDATE: Real-time in car tuning. (Electrically isolating "the box" from laptop controller power).

It is possible to make real-time, on the fly modifications to the code the audio DSP runs by using Analog Devices' SigmaStudio software and SigmaDSP Audio Processors such as the ADAU1442 used here. Such real-time capabilities are useful for real-time in-car EQ and tuning. The code changes are communicated to "the box" via I2C from an evaluation board (with the board connected via USB to a PC running the SigmaStudio software). A potential problem however is that the box runs off car power, while the board runs off laptop USB power, and different power-source ground levels could result in destruction of a CMOS interface on the ADAU1442 in the box. My work-around is to use Analog Devices' ADuM1250 I2C electrical isolator. (The I2C coupling with the ADuM1250 is magnetic).

Below are some pics of the electrical isolation.

The ADuM1250 (8 SOIC) that electrically isolates "the box" from the communication board.











Soldering it up.











Bottom side, the removable 24AA256 EEPROM (8 PDIP) for self-boot when there is no laptop software control.











Real-time software control of the box with I2C electrical isolation using a ADuM1250.











In the trunk with the board allowing real-time control of the box (electrically isolated).











Laptop in front passenger seat, running SigmaStudio software and controlling the audio DSP (the box) in real-time. (I was listening to effects of changing midbass HP crossover in real-time).










RESPONSES:



> ... and coming from an era that saw the switch from tubes to solid state I'd say that he's already reached critical mass.


Lol. (And I hardly ever write lol).



> I have high hopes for your project ...


Thanks, I do too. For me the next step is to get a mic and to start learning how to tune and EQ. I wish other people on this forum with more EQ experience would build and use a box like this. I realize it's a time investment, but I suspect many people have already invested way more time that it would take to solder up a box similar to the one described above.



> I want to use a carPC for my source. Which means I could potentially just use a digital out directly to the DSPs input, and spare the cpu from processing the audio. The audio would remain in the digital domain until it hits the DACs. From what I'm imagining, building it is simple but like previously mentioned programming is going to be a pain. Also I could probably use some cad software and send it to a third party to be fabricated. I shall stay tuned for this though.


Yes to everything except one thing: programming is super easy if you use Analog Devices SigmaStudio GUI software. What we were discussing above that might be more difficult is writing new software that is just as good as what ADI provides. We were discussing this b/c Analog does not allow their software to be used by people who use devices that ADI does not sell (for more from Analog see here). I use Analog Devices' software b/c my device is not for sale, and their GUI software is easy and a pleasure to use.



> Don't forget about volume control... the problem with a pure digital design


Digital volume control with the ADAU1442 and other SigmaDSP IC's is easy and I have not encountered any of the problems mentioned in this thread. The SigmaStudio software has drag-n-drop volume control blocks with clickless volume control, user definable slew-rate and the capability for volume step-sizes so small they'd be annoying to use.

The only volume issue I see is using a DAC with sufficient dynamic range (volume control here is accomplished by multiplying a line-level signal by a number between 0 ("silence"), 1 (full), or something >1 (gain)). It seems to me however that sufficient DNR is becoming a moot issue. For example, check out the new PCM510x DAC family TI. The PCM5102 has 2 Vrms ground centered output off a 3.3V supply (via integrated on chip charge pump), no need for DC blocking cap, and furthermore no need for active post-DAC filtering (a first order passive is all that is required); its THD+N approaches -100dB at around 10 dB down from full scale. (At 60 dB down THD+N is still -50 dB, see fig 4 on page 7 in this PDF). High-quality DACS are getting easier and easier for a DIY'er to solder up and use. (I have samples of the PCM5102 on the way.)



> ...what the code looks like for that software, my guess would be C++, I wonder if could be extended using .Net and give it a very user friendly UI.


Check this FAQ from Analog here.



> if I link to some software, would you run it and send me the results? Basically, not trying to circumvent their software, just wondering if you can build upon it or totally rewrite it for something more user friendly.


Not sure what all this means. I'm happy to help but maybe these FAQs from Analog will help: A PDF slide show and related FAQ; another FAQ.


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## AccordUno

Thanks for those links. found my answers


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## soFat!

very nice work and thanks for sharing your process.


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## mr_smit

Please show converter circuit USB <-> SPI/I2S for SigmaStudio.


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## 94VG30DE

Excellent project. This has got to be one of the best technical write-ups I have ever seen. Obviously you have no shortage of attention to detail though...


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## dnvm84

Hello, everyone. I thought I would add some info that I hope will be helpful.

I am starting a new system build and I decided to research DSP and that brought me to this thread. This thread is very well done and has been very informative.

My update is to let you know I started looking into getting samples from Analog Devices. Plus I started researching how to obtain the SigmaStudio software. *You do not have to purchase anything!* What you need to do is send an email to [email protected] and request a download key. I emailed them last night at 12:47am and I had my key at 1:01am.

My quick disclaimer: It is specified by Analog Devices that: *“SigmaStudio is intended for use by SigmaDSP system designers. It should not be downloaded or used by end users of commercial products. System designers may not provide SigmaStudio to customers of their commercial products.”* I ask that you use my information to legally obtain and use SigmaStudio.

I also looked into the surface mount adaptor boards like SchmartBoard & Proto Advantage. I believe the advantage of the Schmartboards versus the others is the number of holes per pin. Most have one hole per pin around the edge while Schmartboards have two or three holes per pin plus a set number of specified grounded holes.

I am ordering my samples this morning. ADAU1442YSVZ-3A, ADA4841-2YRMZ, and ADUM1250WSRZ from Analog Devices. I hope later, with a lot of support, I will be able to add more to this thread.

Thank you to 24th-Alchemist for his work and write up.


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## flecom

anybody thought about doing a run of PCBs for this with proper ground planes etc?


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## 24th-Alchemist

> anybody thought about doing a run of PCBs for this with proper ground planes etc?


I have thought about it, but I don't know much about the PCB ordering process (especially low numbers). Do you know about PCBs _flecon_?

I'm actually in the process of making an updated version of this thing with three (or maybe four) ADAU1442's, with all but one ADAU1442 running at 8 kHz audio sample rate to allow for significant FIR filter capability for cabin acoustic correction in the lower frequencies.

_Neil_J_, the main author of this thread, looks like he knows what he's doing with PCBs (and enclosures too), but he seems busy preparing for a competition so I've been hesitant to pick his brain about PCBs right now.

His thread raises an interesting thought though: he's using a car PC, which is probably a better processing approach for most users.

And one last question for anyone to answer: is there a problem with ground planes here?

As is buried in the descriptions in the thread, there are two ground planes, one on each of the mounts from Schmartboard, with the ground planes facing each other and separating the four WM8524 DACs from the ADAU1442. I'm interested to learn what I can about PCB layout -- grounding etc -- but that said, I haven't noticed any problems with this device. In fact, a while ago I used Audacity as a crude way to look at the S/PDIF digital output from the CS5351 ADC, and IIRC it looked like the noise did not exceed two to three bits in maximum magnitude -- not bad for 24-bit resolution in my opinion.


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## req

very cool, interested on how it works in practical day to day use. too bad its not something that is marketable


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## optimaprime

wow just wow!! where does a guy learn how do this stuff!!! now you need your own soft ware .


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## Neil_J

There was a guy at IASCA Spring Break Nationals last year that did his own DSP with some Analog Devices parts, and placed very well for his class. No CarPC or anything. I believe he worked for Panasonic designing OEM radios for far manufacturers. If I could have done it cheaply and easily without a CarPC, I would have.

As for the PCBs, there's a bit of a learning curve and time investment, but the payoff is excellent. And mail-order pcb services haven't been cheaper lately. Mine are basically 1$ each in quantities of 10 or more, plus S&H.


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## 24th-Alchemist

> too bad its not something that is marketable


Not sure what is meant by the above but I think something similar to what is done here with Analog Devices ADAU1442 is marketed by miniDSP as their miniDSP 8x8. (Can anyone who owns an 8x8 verify whether the main IC is an ADAU1442 or 1445?)

I mention this because back in 2010 I had transitioned from a second iteration of an earlier project focused around Analog's ADAU1701 to the project described here (using the ADAU1442), and I asked miniDSP why they appeared to be using the ADAU1701 instead of the more powerful ADAU1442 (see last post on page 3, top posts on page 4, of thread on DIYaudio here). At that time miniDSP replied that the 172 MHz core clock of the ADAU1442 was prohibitively difficult to deal with, but apparently their contentions have changed since then. In fact, one of their more recent offerings circa 2013, the miniSHARC kit (reportedly centered around Analog's SHARC ADSP21369) easily surpasses the processing power of even the ADAU1442. Apparently the problem with the ADAU1442 and Sharc ADSP21369 for the typical car audio enthusiast is that the software that Analog provides for controlling the devices is too tedious and too time consuming to use -- a problem that miniDSP appears to solve by writing graphical user interfaces that, although less general than the software provided by Analog, are much quicker and easier to use while maintaining the majority of features desired for car audio. IMO miniDSP's miniSHARC kit seems to be a great product for people who want to have maximal ability to use FIR filters for processing audio signals, and it probably affords computational overkill if only IIR filtering is desired (i.e. overkill if digital implementation of analog filters is the aim).



> ... If I could have done it cheaply and easily without a CarPC, I would have.


FWIW I still think you should incorporate a miniSHARC kit into your design: toslinlk out from carPC (or whatever music media device you end up using) to miniSHARC kit to FrankenDAC seems like it would be straightforward and offer excellent opportunity for multi-channel sound and FIR correction too (if the latter is still of interest).



> As for the PCBs, there's a bit of a learning curve and time investment, but the payoff is excellent. And mail-order pcb services haven't been cheaper lately. Mine are basically 1$ each in quantities of 10 or more, plus S&H.


Duly noted -- 'preciate the info. But what about soldering small pinout ICs to the PCBs? Toaster-oven reflow?


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## tnbubba

subbed...


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## Neil_J

24th-Alchemist said:


> Duly noted -- 'preciate the info. But what about soldering small pinout ICs to the PCBs? Toaster-oven reflow?


A steady hand, a decent soldering iron, maybe a stereo microscope and/or webcam with macro focus. I can solder chips with 0.5mm pitch leads just fine, all day long. It doesn't even take much practice, once you get the hang of it, and youtube offers a ton of instructional videos. I'd stay away from reflow ovens until you have a few dozen or more smt boards to assemble in the same time span... you'll have to obtain a lot of other stuff to go this route (laser cut smt stencil, solder paste, alcohol wipes, at a minimum), and it's only worth it if you're assembling a lot of boards.


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## MinnesotaStateUniversity

Excellent work!

You hang around edaboard?


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## 24th-Alchemist

Neil_J said:


> A steady hand, a decent soldering iron, maybe a stereo microscope and/or webcam with macro focus. I can solder chips with 0.5mm pitch leads just fine, all day long. It doesn't even take much practice, once you get the hang of it, and youtube offers a ton of instructional videos. I'd stay away from reflow ovens until you have a few dozen or more smt boards to assemble in the same time span... you'll have to obtain a lot of other stuff to go this route (laser cut smt stencil, solder paste, alcohol wipes, at a minimum), and it's only worth it if you're assembling a lot of boards.


_Neil_J_ I know you're busy with not only your own work but also your thorough posts about your work (which we all learn from) so I am especially thankful for the information you've provided here. Thank you.



> You hang around edaboard?


Nope -- because I've been unaware of it until now, so thanks for pointing it out. It looks like the closest thing I've done to eda is Analog Device's engineer-zone and in particular their SigmaDSP section.


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## Cobranet

nubz69 said:


> Nice work, interested in building an SMPS for me?




Hello

My SMPS might be an intrest for someone

http://i39.servimg.com/u/f39/19/01/03/77/2014-012.jpg

Regards


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## steelbreeze

Neil_J said:


> A steady hand, a decent soldering iron, maybe a stereo microscope and/or webcam with macro focus. I can solder chips with 0.5mm pitch leads just fine, all day long. It doesn't even take much practice, once you get the hang of it, and youtube offers a ton of instructional videos. I'd stay away from reflow ovens until you have a few dozen or more smt boards to assemble in the same time span... you'll have to obtain a lot of other stuff to go this route (laser cut smt stencil, solder paste, alcohol wipes, at a minimum), and it's only worth it if you're assembling a lot of boards.


Great project!! I'm thinking about doing something similar once I get over the steep learning curve to design pcbs.

I have done SOT-23 regulators fine applying solder paste with a toothpick, then using hot air. Do you think it'd be possible to do a ADAU1442/45/46 using that method? I have seen videos where the paste is magically sucked up the leg of the IC, so it doesn't create shorts...


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