Introducing DSPi | A powerful, user friendly and open source DSP for less than a cup of coffee

[MCH]

What frequency is 8 channels adat? I would be surprised if you don't run into trouble with Dupont connectors. Try at least to start with wires as short as possible and 2 channels first to see that everything is ok.

 

[Jumpybah]

Not typical but I made my first 6 channel version as you're describing with wire-wrap. It's very old tech but works fine for this stuff and is removable and remarkably stable. I ran my system for about 4 months before swapping for a real pc board. A wirewrapper for less than $30 and it works great with the typical pin-sockets.

View attachment 548712View attachment 548713

I used the wirewrap for prototypes in the 80s. It's a technique that works great, even if you need clogs with square feet and tulip connectors.
In the garage, somewhere, I still need to have the pen.
It certainly works much better than those horrible Duponts !!!

 

[john61ct]

Yes, those are DACs.

OK thanks, for when DACs are required.

But here, I'm asking about DDC, ADAT 8ch in and out

or for fewer pairs, AES in and out.

Which would imply ADAT one side and AES on the other, ideally bidirectionally

I assume AES3 Type I (or AES59, CAT5e as the shielded twisted pair) is going to be easier than the BNC Coax flavor, altbough for VERY long runs the choice would be ideal

 

[alekzander]

Hi Troy,
I am super impressed with the project and the speed of your progress. I think the project can really give even professional tools for room correction e.g. IK Multimedia's ARC Studio (stereo balanced in/out) or Audient Oria Mini (hardware Sonarworks, balanced/spdif input, 2+1 balanced output) a run for their money.

I am comfortable soldering or putting modules together. However, finding a high-quality DAC with balanced outputs at a good price, with simple power requirements, often +/-15V and +5V is needed, and a nice enclosure is a bit difficult. The SMSL SU-2 Desktop DAC (SPDIF in, stereo balanced out, about 100 EUR/$) is a nice compact package including a power-supply. Of course, adding a second small enclosure with the Pi Pico and TOSLink In/out connectors and 5V input would be one solution ending up at half the cost of an ARC Studio.

I am curious if there is a neater solution: does anyone have any pointers for either DACs with balanced out which have sane power requirements ideally in a suitable enclosure? Maybe there is a hackable alternative to the SMSL SU-2. Even for the SMSL SU-2 it seems that the enclosure should be large enough to mount the Pi Pico inside, grabbing power from the SU-2's PCB and rerouting one of the SPDIF inputs to the Pi Pico.

Anyways, looking forward to have a hardware always-on solution for room correction with DSPi. Thanks again for your work.

Best,
Alex

 

[jrosser]

I am curious if there is a neater solution: does anyone have any pointers for either DACs with balanced out which have sane power requirements ideally in a suitable enclosure? Maybe there is a hackable alternative to the SMSL SU-2. Even for the SMSL SU-2 it seems that the enclosure should be large enough to mount the Pi Pico inside, grabbing power from the SU-2's PCB and rerouting one of the SPDIF inputs to the Pi Pico.

You can use one stereo PCM5102 dac per balanced output by setting one of the output channels to be an inverted polarity version of the other. There is an "INV" button in the DSPi matrix mixer to do the inversion for you. Currently, you need make sure that any EQ or crossovers are applied identically to the two channels used to create a balanced output like this.

The DSPi can make 4 channel balanced output like this - the cheap purple PCM5102 boards are fine, and all runs off just +5v.

 

[CatNinja]

Even for the SMSL SU-2 it seems that the enclosure should be large enough to mount the Pi Pico inside, grabbing power from the SU-2's PCB and rerouting one of the SPDIF inputs to the Pi Pico.

The SMSL SU-2 is almost completely empty inside. Use something like this to mount the pi pico inside https://www.adafruit.com/product/4056

Then solder the DSPi SPDIF output circuit to the inside of the SU-2's SPDIF input RCA panel connector. No power is needed, since the Pico is powered by USB.

It's a very neat solution. All you see is an extra USB-C connection in the front panel of the SU-2.

You can also add another RCA panel connector to the front, and hook up either the Sub circuit, or a PCM5102 DAC. It's the cheapest balanced DAC with Sub Out I know of.

 

[jareinertson]

While it’s quiet, I thought I’d share my second standalone system build. I don’t need all the outputs, but I’ve future-proofed it since PCM5102 DACs are so cheap. DACs are on header sockets and can be removed if they fail.

Main system: WiiM Pro → TOSLINK DSPi DAC → Power amplifier and Sub

Setup
DAC 1: stereo right
DAC 2: stereo left
DAC 3: summed LFE/sub
DAC 4: spare (possibly future centre channel)

Running the latest firmware with my custom code for rotary encoder control and an RF remote with LED status feedback (e.g. double blink for loudness on). Remote has three functions: volume, loudness toggle, and source select — with very serious range from any room in my house.
Power side: 10,000 µF capacitor and Schottky diode on the 5 V DAC rail, completely eliminating power-down and USB disconnect pops.

Nicely done!

 

[DenonMate]

OK thanks, for when DACs are required.

But here, I'm asking about DDC, ADAT 8ch in and out

or for fewer pairs, AES in and out.

Which would imply ADAT one side and AES on the other, ideally bidirectionally

I assume AES3 Type I (or AES59, CAT5e as the shielded twisted pair) is going to be easier than the BNC Coax flavor, altbough for VERY long runs the choice would be ideal

Sorry for my naiv question, but why not i2s in to AES67 out (with possibility to bypass the DAC)?

 

[mike_008]

RP2350-Tiny-Kit - RP2350A miniature development board with USB adapter and FPC cable - Waveshare 29394​

This could also be used when external USB is required.

 

[Rastofer]

Hello!!

First of all, many thanks to Weeb Labs for their spectacular and altruistic project, it's truly commendable!!.

It has sparked a lot of interest, and I plan to tackle it at some point, although I have a question. My audio system consists of a mini PC, two Yamaha monitors, and an SMSL DAC. On my SMSL DAC, I have both the coaxial input and the I2S HDMI input free.

If I wanted to use the DAC's I2S HDMI input with a DSPi, would I need a simple connector with solder pins, or would I need a board like the purple one?

Thank you very much!

 

[Bamboszek]

I highly recommend using a coaxial or optical SPDIF instead of an external I2S connection over an HDMI cable.
The I2S was not designed to be used as a communications protocol between separate devices.

There is simply no point in dealing with high frequency signals, much more expensive cabling and non-standard connectors when SPDIF is perfectly adequate.

 

[DenonMate]

If you want to grab the 4+3 stereo (FFC) i2s signals from you digital section of your AVR to go full digital to your external amps I see no other way as using the i2s path (it has to be very short) to a little board. Or I’m wrong?

 

[Rastofer]

I highly recommend using a coaxial or optical SPDIF instead of an external I2S connection over an HDMI cable.
The I2S was not designed to be used as a communications protocol between separate devices.

There is simply no point in dealing with high frequency signals, much more expensive cabling and non-standard connectors when SPDIF is perfectly adequate.

That makes sense.
Perhaps I should rethink all the inputs and outputs and only use SPDIF...

 

[somebodyelse]

Hello!!

First of all, many thanks to Weeb Labs for their spectacular and altruistic project, it's truly commendable!!.

It has sparked a lot of interest, and I plan to tackle it at some point, although I have a question. My audio system consists of a mini PC, two Yamaha monitors, and an SMSL DAC. On my SMSL DAC, I have both the coaxial input and the I2S HDMI input free.

If I wanted to use the DAC's I2S HDMI input with a DSPi, would I need a simple connector with solder pins, or would I need a board like the purple one?

Thank you very much!
View attachment 548948View attachment 548949

Check SMSL's documentation of their I2S input as I2S over HDMI isn't entirely standardised. Usually they use LVDS to make the signal robust enough to send over more than the few cm of cable I2S was designed for, hence the driver chip on the purple board. There are variations in the pinout to check too.

Having said that I'd suggest you don't use it. It's very unlikely to perform better than coax or optical, and offers more opportunity to implement badly, resulting in worse performance. For details with measurements see https://www.audiosciencereview.com/...face-better-for-dacs-than-s-pdif-or-usb.7105/

 

[Rastofer]

Check SMSL's documentation of their I2S input as I2S over HDMI isn't entirely standardised. Usually they use LVDS to make the signal robust enough to send over more than the few cm of cable I2S was designed for, hence the driver chip on the purple board. There are variations in the pinout to check too.

Having said that I'd suggest you don't use it. It's very unlikely to perform better than coax or optical, and offers more opportunity to implement badly, resulting in worse performance. For details with measurements see https://www.audiosciencereview.com/forum/index.php?threads/study-is-i²s-interface-better-for-dacs-than-s-pdif-or-usb.7105/

I didn't know the I2S design was for internal use, I'll read the thread you attached.
I think I'll definitely rule out I2S.

What a great community ASR is!

Thank you so much!

 

[john61ct]

AES59 is just convenient physical wiring on the back end, CAT5e as the shielded twisted pair for the AES3 Type 1 flavour of AES/EBU.

Same can be used for balanced analog, but in my case talking about DSPi input & output without any ADC/DACs involved.

Sorry for my naiv question, but why not i2s in to AES67 out (with possibility to bypass the DAC)?

Wut? I mean sure, anything is POSSIBLE, but AoIP requires network infrastructures, plus a host board or PC connection, neither of which is part of what's being discussed here.

My question is about standalone usage, digital to digital,

with a focus on using ADAT for 8-channel I/O and AES/EBU wiring for lower counts or subsets, e.g. discrete pairs, ideally bidirectionally.

Just because you see "AES" in a standard's label name does not mean those connections have anything to do with each other.

 

[john61ct]

Totally off the wall sorry if OT but IF using an RPi host for more than just initial configuration, I just found the PI2AES HAT

I/O includes

all three S/PDIF types: TOSlink and Coax, both RCA and BNC

AES/EBU (Balanced XLR type "AES3")

and I2S-over-HDMI (not recommending)

...

I guess connect the RPi + HAT to DSPi over USB?

Which leaves the ADAT question - how to get ADAT physically in & out from the Pico RP2350 hardware?

...

I ultimately plan to connect multiple (4x) DSPi's to the one RPi host, each of the DSPi-attached external ADAT converters (32 channels total I/O) will be BNC Word Clocked, so no need for ASRC or other clocking within the RPi / DSPi cluster.

This would in effect act like an RME Digiface, but with a fair but of total DSP built in for DRC and crossovers, speaker-specific PEQ, overall bass management etc.

Any feedback welcome, especially correcting any noobish misconceptions.

 

[mike_008]

These are working nicely with ADAT here:

FCR6842031R
FCR684217T

 

[john61ct]

From Google, please anyone fact check

Reception (ADAT In)

PIO architecture lacks the asynchronous oversampling arrays, Phase-Locked Loops (PLLs), or delay-locked loops (DLLs) necessary to track and lock onto this incoming bit phase dynamically.

data bits will arrive at the Pico 2’s GPIO pin with an unpredictable phase offset relative to the Pico's internal clock cycles.

...

(I asked about the fact that my source device is part of BNC WC global network connecting all DDC and AD/DA converting devices, thinking that would obviate such issues)

No Sub-Clock Tracking: A standard Word Clock line only pulses once per audio frame (e.g., 48 kHz). It does not provide the high-frequency bit-rate clock (e.g., 11.2896 MHz or 12.288 MHz) needed to sample the center of each incoming NRZI bit.The Sampling Risk: Without phase alignment, the Pico 2's PIO sampler risks reading the digital pin exactly when the optical signal is transitioning between a 0 and a 1. This causes massive jitter, bit errors, and audible digital clicks.

...

Reco solutions

Dedicated ADAT Receiver IC (Highly Recommended)Route the output of your FCR6842031R optical jack directly into a dedicated hardware transceiver, such as a Coolaudio V1402 or an ALALES Alesis Semiconductor AL1402

or?

Implement a Tiny External CPLD / FPGAPlace a cheap, low-power CPLD (like a Lattice iCE40) between your FCR6842031R receiver and the Pico 2.The Mechanism: Feed both the BNC Word Clock and the optical data line into the CPLD. Use the CPLD to run a high-speed digital clock-data recovery (CDR) loop to deserialize the ADAT data, then feed it to the Pico 2 over a clean, synchronous SPI or TDM interface.

 

[john61ct]

I have a bunch of old Yamaha mini YGDAI boards, the MY8-AE version breaks out its 8 channels of balanced AES3 I/O to a standard DB-25 connector.

How hard would it be to figure out if the edge connector or pin headers are standard I²S or 24-bit Left-Justified?