I’m researching active crossovers for a possible future build. What I’m looking for is,
It seems doable, but my searching hasn’t provided anything. I’m just looking for ideas on cases, layout, and positioning of components. Trying to fit three Hypex amps and two power supplies while providing enough space for cooling and separation for the DSP seems tricky without getting a large case. Maybe I should befriend some engineers from Denon 😆
edit
I found this earlier in the week which got me looking for similar designs with more powerful amps.
https://www.audiosciencereview.com/...to-the-smartcross-project.47976/#post-1721601
- Raspberry Pi
- Six+ channel DAC
- 6x200w amps
It seems doable, but my searching hasn’t provided anything. I’m just looking for ideas on cases, layout, and positioning of components. Trying to fit three Hypex amps and two power supplies while providing enough space for cooling and separation for the DSP seems tricky without getting a large case. Maybe I should befriend some engineers from Denon 😆
edit
I found this earlier in the week which got me looking for similar designs with more powerful amps.
https://www.audiosciencereview.com/...to-the-smartcross-project.47976/#post-1721601
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RPi is a serious source of conducted and radiated EMI/RFI relative to the sensitivity of a dac. If put in the same case with something like a dac, its likely to couple radiated EMI/RFI noise into the dac causing some reduction in SQ. Perhaps grainy or veiled sound. Use of proper shielding between RPi, Dac, and power amp modules may be needed. Internal shield walls could affect heat transport out of the unit however.
Do folks with a DAC HAT attached to the RPi suffer worse noise since it’s located on the RPi?
IME, yes. Some initial experiments I did on that, I think eventually influenced Iancanada to develop products like Shield_Pi and Station_Pi to help deal with the problem.
Without any mods or shielding, the RPi+DAC HAT combo is pretty good.
https://www.audiosciencereview.com/forum/index.php?threads/allo-boss2-review-stereo-streamer.22916/
I was thinking of using a better DAC, the Topping DM7. How much improvement can be had with shielding if the DAC is located in close proximity?
https://www.audiosciencereview.com/forum/index.php?threads/allo-boss2-review-stereo-streamer.22916/
I was thinking of using a better DAC, the Topping DM7. How much improvement can be had with shielding if the DAC is located in close proximity?
Allo made/makes some the most noise immune dacs for RPi. They use layer(s) of copper as shielding. Also, Allo Katana dac had an optional isolator board that could go between RPi and the rest of the dac stack. It audibly helped some.
Also, that was back when RPi was at version 3, which was less of a noise emitter than RPi v4. Another thing Allo did was design USBridge Sig, with low power RPi compute module on it. That replaced RPi with an lower noise device and helped even more with the noise problems.
Some people tried replacing all RPi power supplies with linear regulators and reported some improvement with noise problems.
Also, that was back when RPi was at version 3, which was less of a noise emitter than RPi v4. Another thing Allo did was design USBridge Sig, with low power RPi compute module on it. That replaced RPi with an lower noise device and helped even more with the noise problems.
Some people tried replacing all RPi power supplies with linear regulators and reported some improvement with noise problems.
Yes it is quite tricky, I might even say 'frustrating'. Heat of course, plus shielding/separation and decent cable routing, to avoid noise. Also it would be quite cramped to work on and so harder to assemble, debug or mend. Then if you later change your mind, or if requirements change, a singe combined unit is far less flexible than separate boxes.
In the past I've done many 'very compact' electronics projects, and they can be neat. But with the hindsight of experience I hadn't weighted the above types of inconveniences highly enough. But if you really do need to do it all in one largish unit then IMO yes, it might well be possible with class-D amps and a lot of patience and care. For a crossover scenario I would agree with using a single multi-way DAC (or single audio interface), as coherence from drivers within the same speaker is important; 'maybe' separate DACs would work sufficiently well over toslink, but I wouldn't trust separate USB DACs.
Anyway, I shall watch this thread with great interest, since I'm also just starting to take my first steps with a linux-based crossover (initially using camilladsp), teamed with a DM7. Though there are other hardware options like the Behringer UMC1820 and Motu Ultralite mk5.
No, unfortunately. In general lower processor clock frequencies and lower power should help. Avoidance of SMPS (another noise source) may help too.
Otherwise I would suggest to experiment. Get an RPI GPIO bus extender cable, hook up the dac and RPi, and move the dac closer and further away from the RPi. Hear any difference?
us
That said, I usually recommend to use RPi as a USB host for a USB dac, and use a USB board for the dac that includes galvanic isolation (such as I2SoverUSB from JL Sounds, at least it works for stereo). The USB cable can be used to provide some physical separation. Also I2SoverUSB sounds best with two isolated 5v linear power supplies. Bottom line IMHO is that is a lot of work to make good sounding compact all-in-one unit. A lot engineering effort to get right.
Well I won’t be contributing much worth. I’m researching and won’t have time to build anything till next summer. I suffer greatly from analysis paralysis - I sweat the small things endlessly too. Hopefully after a few months of researching, I can come up with a great solution for my needs.
IMO for such a multichannel project with integrated amps would it make sense to consider one of the SBCs with multiple I2S lines (e.g. Radxa has a decent SW support) hooked directly to multiple poweramp chips with I2S input (TI PurePath etc.), avoiding USB and DA conversion in the chain.
I would rather use measurement equipment since it’s so much easier to see changes, but I no longer have access to a lab or lab equipment. Although, what ultimately matters is what my (our) ears say.
I have very little experience with SBCs to know all the pros/cons between each. My tinkering mostly involved Arduinos back in my university days…I’m an electrical engineer and am willing to learn.
You have a DVM? Scope? Sound card? You probably need a little bit of test gear to realistically play in this space, but it doesn't have to be a lot of stuff or too expensive.
True. Have to be very careful with human biases though. Easier said than done.
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Nope. I have a Fluke 77 that I just wore the rotary selector switch out, so I need a new one. I’d like to get a scope, signal generator, and AC/DC power supply like I had at school, but as infrequently as I’d use it, the purchase doesn’t make sense for me.
Well, that would be a major project both hw- (electronics, PCB design, SMD work) and sw-wise (linux, linux kernel device tree).
Oh absolutely, that’s why I want to see what open-source info is out there for me to use. Reinventing the wheel is not high in my priority list and I’m also a weak coder/developer.
Lot of work, need test gear, that's more or less the type of feedback you're getting. Don't want it to be true?
I didn’t want to hear that I would be pioneering things. If I had all the equipment and workspace it sounds like a fun (and frustrating) DIY project, but I was not looking to spend that much time/effort…and I definitely don’t trust my coding abilities.