Doug_
Posts: 52
Joined: Tue Oct 08, 2019 6:40 pm

Re: Please improve the sound quality of the Raspberry Pi product.

Thu Jul 30, 2020 11:37 pm

I'm late to this discussion but I need to say that the primary use I have for my RPI4 is for recording and reproduction of HQ audio. The RPi ticks the box as a completely silent pc and works well with most of the audio interfaces I use.

It works well with the Steinberg UR22Mk2 (2 channel) and Behringer UMC404HD (4 channel) both of which give 24bit 192kHz record and replay with a quality level that is more than adequate for my purposes. Reaper also runs very well and seamlessly interfaces to both. My older and non class compliant UR22 records fine but replay is affected with clicking and popping. This a clocking issue with the USB driver but I fixed it by purchasing the UMC404HD i/f.

Initially these interfaces were not properly recognised by Raspbian / RaspiOS but in later upgrades these faults were rectified.

I almost never use the analogue audio output but when I do it is with headphones the LF roll off is noticeable but that is fine in those situations, otherwise I use the interfaces for monitoring. On some occasions when I need to use this to drive an external amplifier it works impressively well provided it drives a high impedance input. Typically these type of inputs are >20k ohms.

My point is - If you want High Quality use an Audio interface, they are relatively inexpensive. The analogue output works very well but it needs to see a sufficiently high input impedance.

wh7qq
Posts: 1475
Joined: Thu Oct 09, 2014 2:50 am

Re: Please improve the sound quality of the Raspberry Pi product.

Fri Jul 31, 2020 2:28 am

"Relatively inexpensive" becomes dirt cheap if CD level audio is sufficient to your need. AudioInjector and Fe-Pi both have boards that fit onto the RPi GPIO header, have Rpi drivers built in, work with Alsa, Audacity etc., and are laughably cheap while featuring both A-D and D-A conversion...they will play and record audio. The AudioInjector is for sale on Amazon in the low $20 range (US) and the Fe-Pi for less than $15 direct. There may be others out there but I have experience with both of these. I can't hear the difference between either and CDs but I am nearly 76 and my ears aren't what they used to be. The AI boards have RCA jacks while the Fe-Pi has 3.5 mm jacks. I record mixes from vinyl and CDs. Even fairly old (40-50 yrs) vinyl sounds amazing with a good, CLEAN record and a very clean stylus. The recorded sound can be played back from the built-in USB ports.

Gnyueh
Posts: 44
Joined: Sat Jun 27, 2020 8:15 am

Re: Please improve the sound quality of the Raspberry Pi product.

Fri Jul 31, 2020 10:56 am

You cannot expect too much from PWM wave even after passing a low-pass filter.
Kállio ínai mias óras elev́theri zoí, pará saránda khrónous, sklaviá kai filakí.

jdb
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 2439
Joined: Thu Jul 11, 2013 2:37 pm

Re: Please improve the sound quality of the Raspberry Pi product.

Fri Jul 31, 2020 11:52 am

Gnyueh wrote:
Fri Jul 31, 2020 10:56 am
You cannot expect too much from PWM wave even after passing a low-pass filter.
Wrong.

Counterexample here: https://en.wikipedia.org/wiki/Super_Audio_CD

SACD's data format is a 1-bit digital "PWM" bitstream (actually pulse-density modulation, but the same maths applies in terms of noise shaping). The 2.8224MHz bitrate is sufficiently high that the D/A conversion and filtering even with an RC lowpass filter results in quality that exceeds PCM CD audio.

Given an arbitrarily large oversampling ratio, you can have an arbitrarily low digital noise floor in your frequency band of interest.
Rockets are loud.
https://astro-pi.org

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