ProtoDAC TDA1387 X8 project

[varunach]

Thats just a default value. When CamillaDSP is running it's being fed by a custom ALSA I-O plugin named alsa_cdsp.
https://github.com/scripple/alsa_cdsp

This plugin specifies the source audio format on the command line when it starts/restarts CamillaDSP.

Like below.

MPD -> alsa_cdsp -> CamillaDSP -> ALSA -> device

@Tim Curtis does that mean it’ll switch between S16LE and S24LE based on the source? If I want to keep both capture and playback device setting at S16LE regardless of the source format what do I do?

[Tim Curtis]

The alsa_cdsp plugin documentation recommends
"It's also suggested you set the playback format to the largest bit depth your hardware can handle"

But if you want to set a specific bit depth or other parameter for the  playback format then:

Open CamillaDSP Config
Turn "Default device" OFF
Click SAVE

Open the Pipeline Editor
Enter changes to Playback device
Click "Apply and save"

ETA: I'll need to look at our ProtoDAC Builder Guide. I may need to make some corrections to section 5.3 CamillaDSP Pipeline Settings.

[varunach]

The alsa_cdsp plugin documentation recommends
"It's also suggested you set the playback format to the largest bit depth your hardware can handle"

But if you want to set a specific bit depth or other parameter for the  playback format then:

Open CamillaDSP Config
Turn "Default device" OFF
Click SAVE

Open the Pipeline Editor
Enter changes to Playback device
Click "Apply and save"

ETA: I'll need to look at our ProtoDAC Builder Guide. I may need to make some corrections to section 5.3 CamillaDSP Pipeline Settings.

Thanks @Tim Curtis yeah given ProtoDAC is a 16 bit device it looks like fixing the bit depth and all processing in Moode to 16 bit (but let the freq KHz to vary based on source) might be the best outcome? Not an expert in these just a thought.

[Tim Curtis]

The alsa_cdsp plugin documentation recommends
"It's also suggested you set the playback format to the largest bit depth your hardware can handle"

But if you want to set a specific bit depth or other parameter for the  playback format then:

Open CamillaDSP Config
Turn "Default device" OFF
Click SAVE

Open the Pipeline Editor
Enter changes to Playback device
Click "Apply and save"

ETA: I'll need to look at our ProtoDAC Builder Guide. I may need to make some corrections to section 5.3 CamillaDSP Pipeline Settings.

Thanks @Tim Curtis yeah given ProtoDAC is a 16 bit device it looks like fixing the bit depth and all processing in Moode to 16 bit (but let the freq KHz to vary based on source) might be the best outcome? Not an expert in these just a thought.

I've updated the Audio Configuration section of the ProtoDAC builder guide. Let me know what you think.

Regarding bit depth I suppose from a purist perspective converting > 16 bit to 16 bit should involve some dither. This would suggest letting CamillaDSP do it. That means turning Default device OFF in CamillaDSP Config and then setting the Playback sampleformat to S16LE in the Pipeline editor and "Apply and save"

The V2-ProtoDAC configuration includes dither for 16 bit samples

Code:

ProtoDAC TDA1387 X8 Non-oversampling DAC. Invert +/- signal polarity on both channels and apply Flat dither to 16 bit samples.

Someone would need to verify my understanding of this chain is correct.

[v12nut]

Hi,
I am building my first protodac and in the process of collecting parts, found these and wondered if they would be ok for this project.
https://www.aliexpress.com/item/10050065...1802Km2V4A

thanks

[hifinet]

Hi,
I am building my first protodac and in the process of collecting parts, found these and wondered if they would be ok for this project.
https://www.aliexpress.com/item/10050065...1802Km2V4A

thanks

I would say no. I would recommend the Audiophiler MKP 6.8uF . There are other sellers. You should look for film caps that are either polypropylene (MKP) or polycarbonate (MKC). Also, you need to know the size of the cap, and with radial caps the lead spacing. Lead spacing should be 27.5mm or 37.5mm. You will have more flexibility with axial caps. Keep the voltage rating lower for a smaller size.

[v12nut]

Hi,
I am building my first protodac and in the process of collecting parts, found these and wondered if they would be ok for this project.
https://www.aliexpress.com/item/10050065...1802Km2V4A

thanks

I would say no. I would recommend the Audiophiler MKP 6.8uF . There are other sellers. You should look for film caps that are either polypropylene (MKP) or polycarbonate (MKC). Also, you need to know the size of the cap, and with radial caps the lead spacing. Lead spacing should be 27.5mm or 37.5mm. You will have more flexibility with axial caps. Keep the voltage rating lower for a smaller size.

Thanks for the reply, but these are in fact MKP.

[hifinet]

How do you really know they are MKP? It says it in the listing line, but not the part label. I wouldn't trust the Ali store. If you can find the spec sheet from the manufacturer. Also, the part will be pretty big in polypropylene at a 600V rating. If the lead spacing is not 27.5mm or 37.5mm, it will be hard to work with on the PCB.

If you can get the cap dimensions, you can tell if it is MKP or polyester (MKS). MKS are substantially smaller, about the size of MKC. Compare it to the size of a similarly rated WIMA MKP.

[hifinet]

Well, I do think they are MKP based on this spec sheet for C3D series from Xiamen Faratronic. LS is 27.5mm. Why did you pick these caps? Do you know how they sound?

[v12nut]

How do you really know they are MKP? It says it in the listing line, but not the part label. I wouldn't trust the Ali store. If you can find the spec sheet from the manufacturer. Also, the part will be pretty big in polypropylene at a 600V rating. If the lead spacing is not 27.5mm or 37.5mm, it will be hard to work with on the PCB.

If you can get the cap dimensions, you can tell if it is MKP or polyester (MKS). MKS are substantially smaller, about the size of MKC. Compare it to the size of a similarly rated WIMA MKP.

The cap dimensions are shown in the picture of the item and here is a link to the Manufacturer spec sheet
http://www.faratronic.com/en/searchall.asp 
The item is C3D

I do appreciate that some sellers on Ali are less than truthful when it comes to descriptions.

thanks