Sound system build progress thread (warning: will be slooooow)

[Spart]

The Arc Audio ecosystem uses relatively low impedance volume controls (500 ohms in this case) which is an intentional design choice for reasons I won't get into here, suffice it to say they know what they are doing. The problem arises from the fact that there are no 500 ohm digipots (the closest is 1 kohm) because they will be susceptible to ripple and noise.

...two channel digipot and wire it in parallel?

It's always something with these projects.

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[ashmostro]

I'm not certain that would work, and at any rate, the DAC version is simpler and more reliable. I should have gone this route in the first place. But I'm just a hobbyist, not an EE!

 

[ashmostro]

For those who want to build the volume control device themselves, here's the schematic I created on the path to getting PCBs made.

 

[ashmostro]

Was quite busy this weekend:

Automotive-grade connector (the same brand Honda uses):

 

[ashmostro]

Update: I have further modified the board and it's ready for PCB prototype production. I have design the board fit inside the smallest version of Lansing's "D" style enclosure seen here. They do custom features like flange mounts for surface mounting, and can pre mill the end cap to accommodate the single connector seen in the picture above. The footprint is pretty small: about 3"x2.75" by 0.75".

Even better news, I am working with a member in CivicXI to integrate to his Helix DSP and I have confirmed that Helix uses standard potentiometers in its remote control strategy, so we will be able to control Helix DSP/amplifier volume with this device (so factory integration is possible).

Here's the latest 3D model for fun while you wait..

 

[ashmostro]

Major Update 3/21/26

I am adding two features to the device to make it more broadly useable. Well, technically, one feature and one option.

1. Most modern DSPs use a 3.3V architecture for their accessory remote volume controls, while older ones may use 5V (even some newer lower-end brands can use 5V). I built this device to be compatible with 3.3V because that's what my DSP uses. I've migrated to a new architecture that allows you to switch between 3.3V and 5V depending on your application, via firmware update. I'll be building Windows software to go along with this device that you or your installer can run to make easy compatibility adjustments.
2. I had the thought of doubling up the DAC control submodule from one DAC to two DACs as an option. Why? For subwoofer level control! If you want the optional feature, you can tie in your bass EQ setting on your head unit into your DSP's subwoofer level control, if it has the additional capability. That, or if you use a separate amp for your subwoofer(s) and it comes with its own level remote, you can tie this second output into that. This would interface with the car in exactly the same way as the Single-DAC model, just with one extra output wire for your sub.

I'm quite curious to hear how interested folks will be in Item 2 above. I'm leaning towards offering this as an option rather than one SKU, because A) not everyone wants a subwoofer level control and B) it's more complex and therefore costs more to implement.

I'm starting to think this device might be more of an installer-focused device than a consumer-level one, because it will take a slightly deeper than typical understanding of wiring and configuration to make this work in your particular system. I'm curious about that, too - would you DIY this into your system, or rely on an installer to do it for you?

 

[ashmostro]

v1.0 of firmware updater has been written!

 

[bicycle_wreck]

The amount of engineering that went into this cannot be overstated. Truly cool hacking/RE.

Are you planning on making the code open source?

Thank you for sharing your progress!

 

[Spart]

I'm starting to think this device might be more of an installer-focused device than a consumer-level one, because it will take a slightly deeper than typical understanding of wiring and configuration to make this work in your particular system. I'm curious about that, too - would you DIY this into your system, or rely on an installer to do it for you?

This is going to be highly variable.

The spectrum of capability when it comes to this sort of thing goes:

Filthy Casual -> Most Shops -> Home Gamer -> Specialty/Premier Shops -> The Obsessed Hacker

Notice that you don't find people doing it professionally at either end of the spectrum.

On the low end, because most people are truly not as capable as someone who has f'ed up someone else's ride a few dozen times, and learned the hard way.

On the high end, because it's simply not profitable/possible to know any one vehicle as well as someone who spends an inordinate amount of time with that vehicle.

 

[ashmostro]

The amount of engineering that went into this cannot be overstated. Truly cool hacking/RE.

Are you planning on making the code open source?

Thank you for sharing your progress!

Appreciate the kind words!

This started out as a personal need, and then became something I could share with others with sufficient skills, and now I'm working on making this into a truly consumer-grade product that someone can buy and hand to their installer with appropriate documentation to integrate into their install.

My original intent: provide source code for the most basic design using off-the-shelf components, for the DIYers. This still holds.

Now that I'm committing significantly more time and R&D expense into building a robust consumer-grade solution, I haven't decided how open-source I want the higher-grade version to be. I'm still thinking about it, to be honest.

 

[bicycle_wreck]

Understood. I also echo the earlier point about the usual vendors (e.g., Metra, Scosche, iDataLink, NAV-TV) ignoring Honda/Acura in terms of aftermarket amp/DSP integration.

A homegrown solution is seemingly inevitable, historically speaking, once a truly hands-on person becomes interested.

Anyway, thanks again for posting your progress.

I think DiyMobileAudio.com would be another good place to document your project if you feel comfortable.

 

[ashmostro]

In fact I do have a thread on DIYMA! here it is.

 

[ashmostro]

Quick update: I found a better PCB manufacturer to work with as well as settled on a different brand of enclosure which I have purchase a sample of. Parts should start coming in next week and i will begin assembling the production prototype.

I also am thinking it might make sense to embed the conversion of the proprietary CE2 connector to RCA for the SPDIF source line, into this PCB and enclosure. It wouldn't be part of the volume control circuit, but would be a cleaner solution for the end user because everything related to the car's digital path would flow in and out of the same small piece of hardware.

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