Teensy volume in Eurorack

Status
Not open for further replies.

Mowgli

Member
I'm making a Teensy 3.5 based drum module using the audio shield. After I connected the first prototype to my modular, I realised that the volume of the Teensy is way to low for a Eurorack environment. How are people resolving this?
 
I found this setting for sgtl5000_1:

lineOutLevel(both);

Adjust the line level output voltage range. The following settings are possible:

13: 3.16 Volts p-p
14: 2.98 Volts p-p
15: 2.83 Volts p-p
16: 2.67 Volts p-p
17: 2.53 Volts p-p
18: 2.39 Volts p-p
19: 2.26 Volts p-p
20: 2.14 Volts p-p
21: 2.02 Volts p-p
22: 1.91 Volts p-p
23: 1.80 Volts p-p
24: 1.71 Volts p-p
25: 1.62 Volts p-p
26: 1.53 Volts p-p
27: 1.44 Volts p-p
28: 1.37 Volts p-p
29: 1.29 Volts p-p (default)
30: 1.22 Volts p-p
31: 1.16 Volts p-p


I'm not sure if it will fix my issue. Using it in any way, makes my teensy produce a high pitch continuous tone.
I'm confused!
 
You can use a PCM5102 DAC on the Teensy 4.x. It has twice the volume and makes about 3.0Vpp.

// AudioStream connection ----------------

AudioOutputI2S PCM5102A;





PCM5102-Ali.jpg

DAC.png
 
Last edited:
I'm making a Teensy 3.5 based drum module using the audio shield. After I connected the first prototype to my modular, I realised that the volume of the Teensy is way to low for a Eurorack environment. How are people resolving this?

What amplitude are we talking? Perhaps an opamp is needed.
 
Hi friend..
I measured a maximum of 5.3Vpp on the PCM5102A output. The DAC output can be switched directly to line out (see circuit diagram).



PCM5102-A-Lineout.png
 
Hallo Rolf, are you sure you measured 5.3Vpp? That seems strange given a powersupply voltage of 3V3.
Also the datasheet states 2.1Vrms (typ) for output voltage.

Paul

edited: I stand corrected, it's 2.1Vrms ground-centered. I just measured 6.0Vpp, 1kHz.
 
Last edited:
Some audio I2S DACs cleverly do an internal switch-mode power rail of -3.3V using the LRCLK (or a multiple) for the switching, pushing all
the switching noise above the audio band.
 
Hallo Rolf, are you sure you measured 5.3Vpp? That seems strange given a powersupply voltage of 3V3.
Also the datasheet states 2.1Vrms (typ) for output voltage.

Paul

edited: I stand corrected, it's 2.1Vrms ground-centered. I just measured 6.0Vpp, 1kHz.

6.0Vpp can be. I used a sine wave signal with all 8 voices in my Teensy synthesizer for the measurement. Maybe the mixer a little less and thus the output amplitude a little less.
 
Status
Not open for further replies.
Back
Top