Hello. Raspberry Pi noob here.

I see quite a number of discussions here about which sound card is better but is Raspberry Pi's internal DAC so bad it can't be used for decent sound generation? Let's say I need one stereo output and no inputs for now.

I installed PurrData/pd-l2ork on my Pi Zero W and tried generating a sine tone as a test (sound was sent to my TV via HDMI). It was quite weird and uneven and occasionally would drop completely to silence. Does that mean that Pi Zero is not powerful enough? I feel like even on Arduino the sound was better.

@lzr If you send audio to the TV via HDMI you are not using the sound card of the RPI. The audio is being sent as a digital signal and you are using the dac in the TV.

If you sent a single sine signal to both of the TV speakers (mono sine to stereo speakers) then you could have been experiencing phase cancellation, depending on the position of your head relative to the two speakers of the TV.
Try sending (in PD) just to [dac~ 1] or [dac~ 2]........ but not both [dac~]...
You might still experience some variations in level due to reflections from the walls and ceiling, but they should be much reduced.

The real test will be with music...... can you tell the difference between a wav and an mp3 of the same track? If you can spot the very subtle loss of information in the mp3 then the sound reproduction of the PI (or the TV in this case) is good enough!
David.

@whale-av Good point! I guess I need to solder some header rows and connect an audio jack first. But do you think the performance of Raspberry Pi Zero is generally enough to generate sound in PureData without artifacts?

By the way, I tried switching to just [dac~ 1] while being connected using HDMI but I heard the same weird glitching sound. I recorded it (warning: loud sound; and sorry for my 3D printer in the background):

@lzr I don't have a PI Zero, and Google gives up little information.
I suppose that there is no reason to expect "great" quality, but it could be sufficient. External cards are pretty cheap though. The main reason to use external cards is to reduce latency. There might be other benefits..... impedance matching..... reduced noise..... better dithering.... immunity to ground loops......etc.
If you are only going to send to devices with digital audio inputs then it will be pointless buying a card, and digital is no longer "the future"..... it is "now". Dac to Adc can only be a bad idea.

Ignore what is to follow if I should be listening to the high pitch very low background sound. I cannot hear anything at 440Hz so I assume it is the loudest sound on the recording that is coming from PD.

If it is the loud sound that is your "sine" then it is no longer a sine..... it has either been "squared off" by overloading the dac in the TV (unlikely as your patch has reduced the volume to 0.05) or you have a sample-rate mismatch.
Video devices (like your TV) almost always clock audio at 48000Hz (as it is the standard for professional film and video cameras) and as your RPI is sending digital audio directly to that DAC you should set Pd to run (PD......"audio settings") at 48000.
David.

@whale-av Thank you, David! I played around with audio settings (don't know why I didn't think of that before). Changing sample rate and block size didn't help (just produced more types of glitch sounds) but changing "delay (ms)" helped. At sample rate of 48K I heard clear sine at 22 ms of delay but glitches at 21 ms.

Awesome! Now I can have some fun with a Raspberry Pi!