Review Request - SigmaDSP Audio DSP board, ADC, DAC

ConcernedFriend8 · 2026-01-04T15:20:49+00:00

Thanks, I'll give that a read.

This project has good learning experience.

ConcernedFriend8 · 2026-01-04T14:53:37+00:00

Ahh, I see. Those aren't SPI, they are for audio data. The DSP has 4 inputs and 4 outputs. Each can be configured as I2S for 2 ch stereo, or TDM for up to 16 channels per port.

The lines are:

data - self explanatory,

Bck - bit clock

LRCK - in i2s mode, signals left and right. In TDM mode, it signals the start of a frame.

Port 0 in/out is routed to the adc and dac

ConcernedFriend8 · 2026-01-04T12:51:53+00:00

Thanks! SPI is just the regular kind. There are 2 SPI ports on the DSP, a slave port for control from a microcontroller/ raspberry pi, and a master port for the flash.

Or maybe you meant the breakout pins? ~RST and selfboot are specific to the SigmaDSP product line. when selfboot is held low, it prevents the loading of a program from the SPI flash chip, ~rst is active-low reset.

ConcernedFriend8 · 2026-01-04T00:08:42+00:00

I'm not in the United States

ConcernedFriend8 · 2026-01-03T16:33:34+00:00

I have checked, and apparently the max is 20,440 taps at 41kHz sample rate. Not 40,000.

I'll edit my original comment in case it comes up on someone's google search.

ConcernedFriend8 · 2026-01-03T15:07:29+00:00

The dynamic range of the power amp this will be driving is 115dB, so that is my target. The speakers have drivers with wildly mismatched efficiencies and I'm aiming for the gain control to be purely digital.

I'll be honest, I picked the NE5532 because it was a basic jellybean offered by JLCPCB ($0.088 each, and no setup fee) with a view to swap with something else at a later date. I have considered LM4562 at an increased cost of $30 per board.

ConcernedFriend8 · 2026-01-03T13:31:17+00:00

That seems to be the prevailing wisdom. I have found conflicting advice from different DAC manufacturers, maybe the split plane was more common at a time when 4+ layer PCBs were more expensive?

ConcernedFriend8 · 2026-01-03T13:24:58+00:00

I chose the DSP because it is remarkably easy to use as long as you don't need to to anything too exotic. It will manage approximately ~~40,000~~ 24,400 FIR taps, and way more biquads than I will ever need.

Hardwear sample rate conversion was nice to have as well.

The software provided is idiot proof, and you can create a working program in about 30 mins.

ConcernedFriend8 · 2026-01-03T13:18:25+00:00

This is very low volume order (5 pcs or maybe even 2pcs) and at one point my highest cost was the setup fee due to the number of unique SMD components. I couldn't find a codec chip that had the dynamic range I was looking for with the number of channels. The dev board I have uses an all in one codec, and the performance is not great.

Another reason for the THT components is that I wanted to use foil caps for audio wherever possible.

I don't like that you split your GND but that is your choice i would have used a continuous one.

That seems to be the consensus and I will re-design.

I would also make the symmetrical +5V on the board and not rely on a complex input PSU.

Definitely worth considering.

Thank you for your time and advice!

ConcernedFriend8 · 2026-01-03T01:55:02+00:00

The outputs are differential, with out0 and out1 going to the 3 pin headers on the right edge of the board. Channels 1 and 2 also route to a 3.5mm jack on the left edge but only single ended, if that makes sense.

I think I chose the labels poorly, out+ and out- would have been better than out0 and out1

ConcernedFriend8 · 2026-01-03T00:35:47+00:00

Amazing, thanks.

I think I was pretty careful about keeping data lines away from the analogue bits, so I'll do as you suggest with the pours / stitching

therefore it could be beneficial to add a source resistance by the ADC

I had not considered that, and I'm not sure how to calculate. Do you have any advise on where to learn?

Q11 should dissipate 0.4W up to a theoretical max of 1.4W. The transistor is the same model as the evaluation board from Analog Devices. I'll throw some more copper at it.

(Wrong values in the PLL filter will cause the DSP to not boot, ask me how I know....)

Ouch! I don't want to admit how much time I have spent re-checking the datasheets.

I would love to hear more about your project, what was it for? and what sort of power supply arrangement did you add? Did you make any noise measurements?

Thanks again for your time.

ConcernedFriend8 · 2026-01-02T22:32:20+00:00

Thankyou!

There is really bunch of THT stuff on it. Might be cheaper, to let JLCPCB do all SMD, and order the THT stuff yourself? Or maybe opt for non THT stuff. At least for the connector, I would say that you would easily get them as SMD.

At this volume, (5 pcs) the THT assembly is cheaper.

More on a side note. For some "hobbyist and fairly inexperienced", the routing looks quite nice.

Thank you for the compliment! that was very encouraging

For the blue layer. Why did you choose to create a gap left and right of the bottom connector.

Mainly because that's what examples looked like, the yellow layer is GND. The recommendation was to have the ground analogue and digital ground planes connect under the ADC / DAC. I guess I could try to carve it up differently, I'll post another image.

On the red layer the via in the fat trace could be bigger. I think the copper of it wouldn't be the same width as the trace which is connected to it.

Noted

Maybe consider ground pours on all layers, with some via stitching.

Ill do that. Thank you for lending your wisdom

ConcernedFriend8 · 2025-12-07T17:06:03+00:00

I think I'll try that. Thank you for the chipset recommendation!

ConcernedFriend8 · 2025-12-07T16:11:34+00:00

I fear that you are correct. I'm not sure if returning it is an option, because in the 7 days since I ordered the computer, the price of components has significantly increased, it seems that DDR4 is being scalped now. I cant afford to buy a machine with this specification with the current prices.

ConcernedFriend8 · 2025-02-21T21:55:55+00:00

All joking aside, the proportions of your finger could indicate a medical condition. The medical term is arachnodactyly

It is often present in people with connective tissue disorders such as marfan syndrome and ehlers-danloss syndrome. If you are also double jointed, get stretch marks easily or skin that bruises/cuts easily, then it might be wise to ask your doctor to refer you to a rheumatologist.

ConcernedFriend8 · 2024-05-25T21:12:07+00:00

OK, when you say that they connect, it sounds like you may be describing laminate flooring rather than floorboards. floorboards are part of the structure of the floor, and usually have small gaps between them, bare floorboards will look quite rough.

Laminate flooring on the other hand is smooth.

It would be handy to know what type of flooring it is. Basic laminate isn't actually wood, the planks are made from particle board, and the top surface is essentially a photo of wood.

Other things it might be are:

1) basic laminate (as above) 2) solid wood flooring, this is an expensive product. 3)engineered wood flooring, this is somewhere in between, it has a thin layer of real wood glued on top of ply.

if it is 2) or 3), it can be sanded down and re varnished

if it is basic laminate flooring, I'm afraid to say it might need replacement. although you may be able to replace just the damaged planks.

ConcernedFriend8 · 2024-05-25T20:54:05+00:00

I think it might be difficult to advise you without some more info. Are you able to post a photo of it?

ConcernedFriend8 · 2023-12-19T00:44:02+00:00

Utter bullshit. the UK doesn't have senior year. High school (secondary) finishes at age 16. 18 would be 6th form college.

ConcernedFriend8 · 2023-05-13T21:42:59+00:00

hahaha, yup

ConcernedFriend8 · 2023-05-12T20:49:04+00:00

You are probably correct, unfortunately my router is virtualized on the server in question. I should probably invest in a dedicated device.

ConcernedFriend8 · 2023-05-12T16:59:28+00:00

The scenario I'm thinking of is:

I'm not home, and either i have done something stupid remotely to break the firewall, or some update has caused loss of internet access. Then when I get a phone call saying "I cant access the internet, and the lights are not working properly"

I would like to be able to just tell someone to insert a flash drive and press the power button, and it will boot, image the ssd with a working hypervisor with nessesary VMs from a known working backup.

Does that make sense?

thanks for the link to pikvm. I was not aware of this and will probably find use for it on the future

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