WM8904 headphones jack voltage range

Delta Prime

Joined Nov 15, 2019
1,149
Hello there! :) You are going to have to be more specific, this is an assumption but it is a beginning.
Maybe you are referring too.Table 45 Volume Control for HPOUTL and HPOUTR . Register Address, bit7, Default bit0."Headphone Output Volume Update Writing a 1 to this bit will update HPOUTL and HPOUTR volumes simultaneously."
Or!
2278 lines (1883 sloc) 61.9 KB
Linux-3.8.13 CODECS
wm8904.c -- WM8904 ALSA SoC Audio driver
*
* Copyright 2009-12 Wolfson Microelectronics plc
*
* Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
I hope this helps.If not please do not hesitate to ask!
 

Delta Prime

Joined Nov 15, 2019
1,149
Hello there! :) You are going to have to be more specific, this is an assumption but it is a beginning.
Maybe you are referring too.Table 45 Volume Control for HPOUTL and HPOUTR . Register Address, bit7, Default bit0."Headphone Output Volume Update Writing a 1 to this bit will update HPOUTL and HPOUTR volumes simultaneously."
Or!
2278 lines (1883 sloc) 61.9 KB
Linux-3.8.13 CODECS
wm8904.c -- WM8904 ALSA SoC Audio driver
*
* Copyright 2009-12 Wolfson Microelectronics plc
*
* Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
I hope this helps.If not please do not hesitate to ask!
Perhaps?
From the data sheet page 79
The headphone outputs are designed to drive 16Ω or 32Ω headphones. These outputs are ground-
referenced, i.e. no series capacitor is required between the pins and the headphone load. They are
powered by an on-chip charge pump (see “Charge Pump” section). Signal volume at the headphone
outputs is controlled as shown in Table 45.
The ground-referenced outputs incorporates a common mode, or ground loop, feedback path which
provides rejection of system-related ground noise. The return path for the HPOUTL and HPOUTR
outputs is via HPOUTFB. This pin must be connected to ground for normal operation of the
headphone output. No register configuration is required.
Or Figure 38 Zobel Network Components for HPOUTL, HPOUTR, LINEOUTL and LINEOUTR
Or once again. Page 80 from the datasheet
EXTERNAL COMPONENTS FOR GROUND REFERENCED OUTPUTS
It is recommended to connect a zobel network to the ground-referenced outputs HPOUTL, HPOUTR,
LINEOUTL and LINEOUTR in order to ensure best audio performance in all applications. The
components of the zobel network have the effect of dampening high frequency oscillations or
instabilities that can arise outside the audio band under certain conditions. Possible sources of these
instabilities include the inductive load of a headphone coil or an active load in the form of an external
line amplifier. The capacitance of lengthy cables or PCB tracks can also lead to amplifier instability.
The zobel network should comprise a 20 resistor and 100nF capacitor in series with each other, as
illustrated in Figure 38.
Note that the zobel network is recommended for best audio quality and amplifier stability in all cases.
Now you see my dilemma. :)
 

Audioguru again

Joined Oct 21, 2019
3,540
Page 15 shows a fairly low output voltage of 0.92V RMS into 30 ohms when the distortion is fairly high at 1%.
It shows the power output is only 28mW (for low level background music). 100mW is a normal loud level peak sound on headphones.
 
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