pHAT DAC Speaker to Headphone switching


#1

Hi all, I have my pHAT DAC working on my PiZero, sounds great.

I am currently using the headphone jack. I’m wondering if I wire up speakers to the L&R output of the DAC so I can hear the sound, will it automatically mute the speakers when I plug in headphones to the jack? Just like mobile phones do. Or is this not supported on the pHAT DAC?


#2

no, but you are not supposed to plug-in headphones into the pHAT DAC either… it might work with some but that is not recommended.


#3

Oh really? how come it is not recommended to plug headphones in? There isn’t anything on the product page which says that.


#4

It is a line out level… I just checked the product page and it’s part of the facts list. But I can imagine it’s not necessarily clear enough depending on your experience plugging in headphones and seeing that they do work.


#5

ok thanks for clearing that up. Does that mean it could possibly damage headphones then, is that why it isnt recommended?
So how should a line out level be used correctly?
Thanks.


#6

No, I don’t think you can damage headphones, but you may find that even with maximum volume on the Pi side, you hardly get enough volume to hear your music comfortably (numb!).

… in other words, the line out jack is meant to be fed into an amplifier, by design. That is partly why there is no circuitry to mute the output even when the RCA are connected (or vice versa, typically), since you would normally use one or the other.

That said, you can use headphones if you want but you might find the audio unacceptably low.

… well, at least that is my take on all of this, with my usual degree of understanding just above sea level. I’ll ask a captain to show up and confirm!


#7

Thanks again, very useful.

However it now makes this card a little less useful as I, and many others from posts i follow, use this to create a handheld gaming unit with a ‘headphone’ jack direct from the pHAT.
Is there a way (maybe a simple circuit) to modify this to allow headphones? and ideally speakers at the same time as my OP was asking? Maybe a revision 2 of the pHAT DAC is in order :)

Any help would be appricated as I dont really want to have to plug this output into an amp just to get headphones.


#8

Again, it depends on your headphones. The impedance of the output is such that this may be a problem with some. Less so with others.


#9

This might be useful to others. It turns out that this pHAT DAC does already supports speaker/headphone switching. This means that while nothing is plugged into the line out jack the R&L circuit is active, meaning if you wire speakers to it you will hear your sound. However when you plug something into the line out jack, it has a tiny switch internally which disconnects the R&L circuit so that all the sound goes via the headphone, or whatever you have plugged in and the speakers will go silent. Just like a mobile phones etc… and just what I was after :)

Hope this helps.