"Thinking" noise in the audio outout

[Rawit-git]

I've bought one of the units available on Ebay and I've noticed that there is noise in the output. LED and MIDI activity are audable along with a constant ticking sound. With normal listening levels it's not noticeable. It can be heard on the more quite pieces when the listening/recording levels are higher.

Noise almost disappears when the Pi enters power saving mode. The corner where the DAC resides is sensitive to interference as well. Can I fix this? Sorry if this is the wrong place to ask.

[scrapcomputing]

Hmm I haven't noticed any noise on mine, and this is the first time that someone has raised this issue. Let me check again with some external amplification and I will get back to you.

In the meantime, could it be that it is your sound card that it is somehow picking up this noise ? Have you tried it on a different one?

By the way I was not aware that this is sold on ebay. Getting the boards made by a PCB manufacturer is straightforward, you just upload the gerber zip file and you are done.

[Rawit-git]

I'm using it in a Terrasoniq Phase X64 external sound card which has a Waveblasterheader. I will try it on my CHiLL III Waveblaster board to see if it makes a difference. I don't hear any noise with a X2GS installed in the Terrasoniq.

I was guessing that you were the seller on Ebay selling extra's but I guessed wrong :/ .

[Rawit-git]

Same ticking noise on the CHiLL III Waveblaster board. Both the CHiLL III Waveblaster board and the Terrasoniq rely on a 9v power supply. I'm going to test with another power supply later. Both an X2GS and a Yamaha DB51XG don't suffer from noise with this setup.

[Rawit-git]

The ticking noise only happens in MT-32 mode. In soundfont mode it's more of a whine.

[scrapcomputing]

Could you try connecting a capacitor on the pins shown in the picture ?
I would try a ceramic 10uF ceramic capacitor, and perhaps a 220uF electrolytic (ground is at the top as shown).

[Rawit-git]

Ok, I will try that when I have time.

[Rawit-git]

I've installed both a 10uF ceramic capacitor and a 220uF electrolytic capacitor. The ticking noise is gone but it changed to a faint high pitched constant hum.

[Rawit-git]

In MT32 mode the ticking noise is still present but more faint then before

[scrapcomputing]

Another thing to try is to feed 5V using a separate wire: Find where 5V is generated on your card and solder a wire between that point and the + of the capacitor you just added. This may get rid of some of the noise.

[troydm]

Just soldered a unit and have same low pitch whining noise when using with Picogus v2, you can clearly hear it when using headphones and nothing is playing, during usual music playback it's barely noticeable, tried soldering capacitors as suggested but it didn't helped much, it seems like it it's either an output of a dac that gives such noise or atx power supply, will investigate later with oscilloscope

[Hendrix900]

Hi
I'm having the same problem when connecting the wavetable to a Picogus 2.0. I hear a ticking sound in MT32 mode. In Soundfont mode, it's more of a constan noise sound. With the picogus without the wavetable no noise is appreciated.

When changing the audio selector jumpers and configuring mt32-pi.cfg to use PWM or I2S, I don't notice any differences.
If I connect it to an external power supply, even when the PC is off, it still generates the same noise.
If the wavetable is connected but has no jumpers set, no noise is heard.

I bought the wavetable board. And the board shows rev 0.3.

[troydm]

There seems to be gnd voltage difference (about 0.5v) between the picogus gnd and dac amplifier gnd output for L and R channels that are fed back to picogus wavetable header, I think this contributes to the noise creating an hearable differnce, probable fix would be to level those to same voltage, but I'm not quite sure how to do it yet