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Need advice: apply EQ filter to multiple sources with Raspberry Pi 4

Springfeel

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Hi all,

I am currently running a setup such that I have a PC and TV, which use USB and TOSLINK respectively to connect to a DO 100 DAC -> Buckeye Amp. I made a REW profile to apply an EQ filter to my PC audio and would like to be able to apply it to all sources. I have read that you can load an EQ profile on the Raspberry Pi 4 and process the signal before passing it to the DAC. Unfortunately I am new to RPI and have some questions and concerns. One being that adding a RPI4 to the flow could negatively impact sound quality. I have also read that the RPI4 is unable to handle accepting signal from multiple sources with different sample rates and I don't know if there is a practical solution that won't affect sound quality. I know there are some members that have worked on similar solutions and would be grateful for recommendations on what hardware/accessories I will need? Thanks.
 

IAtaman

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Hello. If you haven't already, check out these threads:


 

somebodyelse

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Springfeel

Springfeel

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If it is possible to do a display switch on the RPI4 then I would like to pursue that, but a network control would work aswell
 

somebodyelse

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Many things are possible - the internet is full of examples of people connecting Pis to all sorts of things, often with great detail about what they did and why. How easy they are will depend on your existing skills and experience, what you're willing and able to learn, and what help you can get others to put in. Have a look through the threads linked earlier to see how comfortable you are with them. The first one includes a monochrome OLED display and IR remote so should give you a good idea of what is involved. Let us know where it is on a scale of "I could do that in my sleep" to "RUN AWAY!!!" and whether that applies to all of it or just some bits. You might be fine with programming but not want to touch electronics.

A good starting question might be whether you already have a Pi4 as they have been hard/expensive to obtain. They claim that should get easier through the rest of the year.
 
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Springfeel

Springfeel

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Update: Got a RPi4 and installed camillaDSP on it. RN working on creating config files for my DO 100 DAC.
 

mdsimon2

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I know you posted in my RPi4 + CamillaDSP thread, but just some thoughts on your proposed setup.

Like you mentioned it is difficult to have sample rate switching AND multiple sources. @phofman's gaudio_ctl as described in @DeLub's thread linked earlier by @IAtaman will do sample rate switching while using the RPi4 as a USB gadget. The only issue is that gaudio_ctl controls how configurations are applied so it doesn't work well if you want to change to a different capture device (like the UR23 for TOSLINK) via configuration change.

IMO the easiest solution is to switch between a configuration which uses the UR23 as a capture device for your TV and one that uses the RPi as a USB gadget. I assume your TV outputs at a constant sample rate (likely 48 kHz). For simplicity you could restrict the USB gadget to a single sample rate and then use something else to resample. I am not very familiar with PC audio so can only offer limited help, do you have a specific audio source program or are you looking for system wide output? On Mac CoreAudio resampling is quite good for system wide resampling and I would have no issue using it, I understand that historically the Windows resample may not have been so good but I really do not know much about it.

Michael
 
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Springfeel

Springfeel

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I know you posted in my RPi4 + CamillaDSP thread, but just some thoughts on your proposed setup.

Like you mentioned it is difficult to have sample rate switching AND multiple sources. @phofman's gaudio_ctl as described in @DeLub's thread linked earlier by @IAtaman will do sample rate switching while using the RPi4 as a USB gadget. The only issue is that gaudio_ctl controls how configurations are applied so it doesn't work well if you want to change to a different capture device (like the UR23 for TOSLINK) via configuration change.

IMO the easiest solution is to switch between a configuration which uses the UR23 as a capture device for your TV and one that uses the RPi as a USB gadget. I assume your TV outputs at a constant sample rate (likely 48 kHz). For simplicity you could restrict the USB gadget to a single sample rate and then use something else to resample. I am not very familiar with PC audio so can only offer limited help, do you have a specific audio source program or are you looking for system wide output? On Mac CoreAudio resampling is quite good for system wide resampling and I would have no issue using it, I understand that historically the Windows resample may not have been so good but I really do not know much about it.

Michael
Hi Michael, thanks for your response. I am actually open to whatever configuration you recommend, yes I have a windows pc but can just connect that directly to my DAC as I already have Equalizer APO on it, so perhaps I can just skip the USB gadget configuration. The TV output is 48 kHz, but as long as I can get an optical connection to the RPi4 and then have it apply an EQ filter, then that would make me happy.
 

mdsimon2

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Hi Michael, thanks for your response. I am actually open to whatever configuration you recommend, yes I have a windows pc but can just connect that directly to my DAC as I already have Equalizer APO on it, so perhaps I can just skip the USB gadget configuration. The TV output is 48 kHz, but as long as I can get an optical connection to the RPi4 and then have it apply an EQ filter, then that would make me happy.

Skipping the USB gadget would simplify things but you would need to physically change the USB cable to the DAC between the RPi4 (optical / CamillaDSP) and the PC (USB / PC). Maybe you could get a USB switch of some kind?

There are lots of different ways to get the functionality you want. The USB gadget would allow you to switch sources in CamillaDSP which would be nice if you were using a CamillaDSP based display that showed sources, volume, etc. But to be honest for a two channel setup this probably isn't worth the effort.

Michael
 
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