What is the AmpliPro Streamer 4 output voltage? I need 1.29Vrms into my amp to get max volume.
Currently the output voltage maxes out at 0.78 Vrms, or around -4.4 dB from what you want.
That said, it should be higher. The DACs actually output 1.1 Vrms (-1.4 dB from what you want), but we had to limit it for a limitation of the old amplified units. That limitation has since been removed in hardware, but for backwards compatibility we never updated the software config. We really are past due on a split in the config so that we can take advantage of the full voltage range on newer amplified units and streamers. I’ve added an issue here:
If you wanted to get your hands dirty, you could manually edit /etc/asound.conf so that pcm.ch0_softvol.max_dB is -4.1 and pcm.ch[1-3].ttable.X.Y are all 1.0 instead of 0.64. I haven’t tested it here but that should get you equalized volume across the DACs and maxed out at 1.1 Vrms. Note that I’m referring to the lastest asound.conf that was just updated in 0.4.3, and this config file will be overwritten the next time you update.
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Cool, this is useful, thanks! I don’t mind editing a file. Can I configure it for 1.29 Vrms rather than 1.1?
The difference is significant. Here’s my 200W amp with various input voltages:
0.78 Vrms: (sqrt(200*8)/1.29*0.78)^2/8 = 73W
1.1 Vrms: (sqrt(200*8)/1.29*1.1)^2/8 = 145W
1.29 Vrms: (sqrt(200*8)/1.29*1.29)^2/8 = 200W
The short answer is you can, but only for Output 1. Setting pcm.ch0_softvol.max_dB to 0.0 in the /etc/asound.conf config file will give you 2.1 Vrms on Output 1.
In the config file the outputs are named as ch0 through ch3, corresponding to RCA outputs 1 through 4 respectively. Outputs 2-4 are driven by a CM6206 USB DAC which is limited to the 1.1 Vrms output. Output 1 however is driven by a PCM5102A I2S DAC and can output up to 2.1 Vrms. Unfortunately the Pi 3 only supports a single stereo I2S which is why we had to use USB for the rest of the channels.
I suggested setting max_dB to -4.1 on ch0 so that all 4 outputs will be matched in output levels (if my math is right, haven’t tried this in reality). But if you don’t care about that, you can increase ch0/output 1 past where you need.
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Gotcha, thank you for the info!