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Introduction to the SmartCross project

danstahl

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Jul 5, 2022
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I have not. I was considering using an Okto or Topping 8 channel to go along with a RPI, but I may end up just getting the Minidsp HTx. Unfortunately I've had a hard time testing the software since I don't have a USB DAC currently. It should work with HDMI out of a RPI but my processor isn't able to play anything over 4 channels from my RPI for some reason.

That said, my code should be basically useable if you want to fork it or tweak it. The UI is straightforward (at least IMO :) ) and generates camilla compliant configurations. The only potential gap I can think of is the need to map decoded channels to camilla input...right now I assume that a multichannel decoder magically knows that input 0 is the left speaker, for example. Up to 4 channels my RPI did map it correctly.
One other thing to keep in mind is that I boost the sub level 10db rather than decrease the other channels by 10db...I did this to retain highest quality for non-sub implementations, but it does mean that you need to use the digital volume control on your DACs to avoid clipping if you are using subs.
 

IAtaman

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Mar 29, 2021
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Very nice! This was my "dream" DIY project as well - wanted to build something similar with an ARM SBC with a custom kernel at the input, feeding multiple DACs driving multiple power and headphone amplifiers.

Kudos to you and best of luck!

SmartCross is powered by a generic 64-bit ARM CPU (up to 1.8GHz),
I strongly believe this is the right way to go about DSP. The amount of processing power and flexibility it gives is unmatched compared to a DSP chip and a seperate microcontroller.

I think software is gonna be key. Sooner you ship something we can play around and give feedback, the better in my opinion.
 

srrxr71

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What you can say is that AVRs don't measure good. As for sounding ... well, any ABX?
I mean really if anyone can hear the difference between SINAD 95 and 108 without blowing their ears up I’d really like to know.
 

Jukka

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Apr 24, 2019
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I'm a DIYer and all the speakers I currently use are DIY, so my needs are probably not as common as for many others.

My best speakers use Hypex plates, so digital inputs from preamp is a necessity. For that I use currently miniDSP SHD. I would not be trading these away easily, so anything I would acquire would need to play nicely with these. I do got multiple large (sub)woofers, that could benefit from having this kind of unit in addition to my current gear, if it had both analog low level and high level outputs.

For analog DAC+amp stage I have some strict requirements. High frequency drivers are usually very sensitive (currently 110 dB/W/m), so hf needs the best possible SNR. On some occasions I lend my system for PA purposes, so the woofers need multi-hundred Watts of clean power, so apparent solution is analog output for external amps. That's a hassle for every day life.

The digital side needs to offer a dedicated DSP channel for each speaker driver. It needs to be able to control all channels and their volume digitally. There is no signal alteration in analog domain. The preamp needs to be able to get signal from multiple sources, have adequate number of output channels, a display, (IR) remote control (some TV's use bluetooth remotes now) and analog output needs to be balanced. My TV, PC, BD-player and miniDSP all listen to one IR remote control, it's almost magical how one remote can rule them all. As a cherry on top, my current system has wake-on-signal, which contributes to ease of use, power save, component life and I couldn't live without it anymore. Trigger connector is one option for external wake-on-demand, but that also depends on the external device.

I'm constantly thinking of new designs and builds, and for that reason I need flexibility so that I can add or changes units. For example, I first built 2-way speakers, then I added powered subs. Then I upgraded the subs with passive woofers+power amps. For most of the time, the system runs with only the 2-way (TV and such) and the woofers come online on-demand by changing DSP preset. That preset changes also the crossover point. I consider this to be the perfect system for a family's living room. Now I want to add even larger subs for movie rumble. I'm not sure how I could implement this with my current gear without adding two more Hypex plates, but the fact is that only the lowest way needs much power...

For other projects, like computer speakers, I use passive crossovers and small miniamps. I could go all-active with them, you would need to compete with price. The demands are lesser than with the best system of course. Mostly a physical volume nob and USB-input.

That's what it would take to best my current system. Not easy, I spent years searching and waiting for appropriate products to emerge. For the actual DIYing I have other tools.
 

TabCam

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Feb 16, 2020
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I have active DIY front speakers, currently with MiniDSP and 3 separate amplifiers. One Box sounds better but...
1) I need to integrate with a HT setup so either all volume control in one box (preferred) or a HT bypass Is necessary.
2) All audio equipment need to be in a TV cabinet (PAF) and for convenience I consider a remote a must.
3) While making changes to the setup AB(X) testing is important so several slots for different setting and fast switching is a must.
4) Stable and usable software is far crucially important to be able to use a device. I consider glitches, pops, clicks etc. a deadly sin as it often showcases an immature development process and/or poor quality control.
5) Amplifier are the least important thing, Just have both balanced and unbalanced out and maybe make a stackable box. That would maybe make room for expansion into 10-12 channels possible.
6) The biggest MiniDSP limitation is 10 PEQ slots per channel. I would like to either use all pass filters for timing compensation for other drivers and/or use IIR/FIR to both linearize and adjust slope.
7) I would like to do more precise time alignment but that is sample rate limited. Maybe DSD or convert to high sample rate and back can help???

As far as I know Trinnov is maybe able to do most of these things but is a little too expensive. I watch the result of the progress with great interest
 
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