I recently posted a thread on here about what an audio interface really is, and what manufacturers of them put into them to make their prices range from $300 - $10,000 for similarly spec'd devices. ("similar" is slightly hyperbolic, but you get my point). I learned a lot from that thread, and now I would really like to try my hand at building a very simple audio interface that just does the following...
Is it incredibly bold and probably arrogant for me, a total novice, to even hint at wanting to try this? Sure! And I am sure I will get a lot of... <cough> constructive feedback from you guys about how foolish I am to even entertain such a thing at my level, when audio interface companies employee highly experienced senior engineers to design these things. But... even if I have to track down schematics online and "steal" designs, or even open up my own interface Focusrite Interface to have a look at what I can find out... I cannot help but think this is possible. I have removed anything "esoteric" from the above interface. I do not plan to include any pre-amps, which is often where audio companies focus on the "magic sauce" for their design. I will use really high end Rupert Neve audio pre-amps that I already own to boost the incoming signal up to an appropriate level before the signal even reaches my interface. There are tons of DIY headphone amp kits and schematics on the internet, for when the digital signal returns from the DAC and needs to be heard as audio again. Also, I used to work for Texas Instruments in their DSP dept. and know their products well. Have a look at this section of their www.ti.com website. They publish all kinds of pro audio design reference material and examples. Also, have a look at the TI TLV320ADC5140 ADC chip. TI even sells a $200 4-channel ADC evaluation board with this chip on it. Hell, it looks like this eval board might be exactly the design I am trying to create. I have not had a chance to really dig into the documentation, but I know the schematic for that board comes with it. I know that there is a lot more to these types of devices and just buying an ADC, a DAC, a thunderbolt chipset, and using the data sheets from these chips to build power supply circuits to power it all, and just soldering it all to a perf board. I hear the term "Clock" used a TON around this type of design and I even know there are whole companies that specialize in nothing but clocks that sync all this kind of stuff so that this system and interface with this and that. My goal, however, is not to take this thing to market, or try to design some universal tool that will set the pro audio world on fire. I literally simply want to build my own DIY audio interface that is very bare-bones and purpose built for just me and my digital home recording. I do not care about S/PDIF, ADAT, PCI card, SCSI, or any kind of "interface" other than thunderbolt. I do not care about trying to power things from the thunderbolt; I'm fine with it having it's own wall wart Power Supply.
So... I am willing to spend some cash for evaluation boards, samples, and breadboarding components. And I am certainly willing to spend the time... but... I am not really sure where to look for resources on how to learn about this area of electronics, other than the aforementioned resources from the chip companies like Analog Devices, Texas Instruments, and AKM? I checked on Amazon, and there are no books that come even close to something as specialized as this application. I know that companies like Apogee, Focusrite, MOTU, Universal Audio, RME, and Avid all have experienced and senior electrical engineers on staff to design stuff like this. But unless they all graduated from college within the past 10-15 years, I doubt they learned about all this stuff in school. So, let's say an electrical engineer who has been working in the automotive industry all of the sudden is asked to shift into designing a pro Audio Interface... what would be the first resource he/she would turn to trying to get up to speed on what goes into these things?
- Accept up to 2 simultaneous incoming audio signals
- Feed those signals into an ADC which converts them to digital data
- Send that digital data to a Mac computer running the Digital Audio Workstation (DAW) software Logic Pro X over the thunderbolt data protocol
- Accept a digital stereo (2x mono signals) signal back from the computer into a DAC for conversion back into analog and sent to a headphones output and two main audio XLR outputs (L & R)
Is it incredibly bold and probably arrogant for me, a total novice, to even hint at wanting to try this? Sure! And I am sure I will get a lot of... <cough> constructive feedback from you guys about how foolish I am to even entertain such a thing at my level, when audio interface companies employee highly experienced senior engineers to design these things. But... even if I have to track down schematics online and "steal" designs, or even open up my own interface Focusrite Interface to have a look at what I can find out... I cannot help but think this is possible. I have removed anything "esoteric" from the above interface. I do not plan to include any pre-amps, which is often where audio companies focus on the "magic sauce" for their design. I will use really high end Rupert Neve audio pre-amps that I already own to boost the incoming signal up to an appropriate level before the signal even reaches my interface. There are tons of DIY headphone amp kits and schematics on the internet, for when the digital signal returns from the DAC and needs to be heard as audio again. Also, I used to work for Texas Instruments in their DSP dept. and know their products well. Have a look at this section of their www.ti.com website. They publish all kinds of pro audio design reference material and examples. Also, have a look at the TI TLV320ADC5140 ADC chip. TI even sells a $200 4-channel ADC evaluation board with this chip on it. Hell, it looks like this eval board might be exactly the design I am trying to create. I have not had a chance to really dig into the documentation, but I know the schematic for that board comes with it. I know that there is a lot more to these types of devices and just buying an ADC, a DAC, a thunderbolt chipset, and using the data sheets from these chips to build power supply circuits to power it all, and just soldering it all to a perf board. I hear the term "Clock" used a TON around this type of design and I even know there are whole companies that specialize in nothing but clocks that sync all this kind of stuff so that this system and interface with this and that. My goal, however, is not to take this thing to market, or try to design some universal tool that will set the pro audio world on fire. I literally simply want to build my own DIY audio interface that is very bare-bones and purpose built for just me and my digital home recording. I do not care about S/PDIF, ADAT, PCI card, SCSI, or any kind of "interface" other than thunderbolt. I do not care about trying to power things from the thunderbolt; I'm fine with it having it's own wall wart Power Supply.
So... I am willing to spend some cash for evaluation boards, samples, and breadboarding components. And I am certainly willing to spend the time... but... I am not really sure where to look for resources on how to learn about this area of electronics, other than the aforementioned resources from the chip companies like Analog Devices, Texas Instruments, and AKM? I checked on Amazon, and there are no books that come even close to something as specialized as this application. I know that companies like Apogee, Focusrite, MOTU, Universal Audio, RME, and Avid all have experienced and senior electrical engineers on staff to design stuff like this. But unless they all graduated from college within the past 10-15 years, I doubt they learned about all this stuff in school. So, let's say an electrical engineer who has been working in the automotive industry all of the sudden is asked to shift into designing a pro Audio Interface... what would be the first resource he/she would turn to trying to get up to speed on what goes into these things?