Adding a High Quality Headphone Output

#1

I wanted to add a headphone output to my fantastic Zynthian box without drilling the lovely new metal case. This is how I did it:-

PARTS NEEDED:-

ASSEMBLY INSTRUCTIONS:-
If not already fitted, carefully solder the 2 pin and 3 pin headers to the HiFiBerry DAC here:-

Next solder header pins on to the amp board in the (9) locations shown:-

Now turn the amp board over and solder a small length of wire between the 2 points below (this is because the amp board is designed for balanced input, but the HiFiBerry outputs unbalanced only):-

Now make the following connections:-

From/Pin…To/Pin…(Description)
FROM…HiFiBerry DAC /5V+…TO…Amp Board /VCC …(5 volt supply)
FROM…HiFiBerry DAC /5V -… TO…Amp Board /GND …(Power supply ground)
FROM…HiFiBerry DAC /L …TO…Amp Board /L- …(Left signal in)
FROM…HiFiBerry DAC /Gnd…TO…Amp Board /R+ …(Signal ground)
FROM…HiFiBerry DAC /R …TO…Amp Board /R- …(Right signal in)
FROM…Amp Board /R …TO…Headphone sckt /Sleeve…(Right headphone out)
FROM…Amp Board /G …TO…Headphone sckt /Ring…(Ground headphone out)
FROM…Amp Board /L …TO…Headphone sckt /Tip …(Left Headphone out)

Finally, wrap the amp board in insulation tape to secure the connections and insulate it from the metal case. Then mount the stereo headphone socket into the case. Reassemble the case and all is finished.

NOTE
These instructions will mean that you lose the ¼ inch signal outputs. Also. because I have not incorporated a potentiometer for volume control, be very careful when changing synth engines or patches as the volume level may be too high (this can be adjusted on most patches with the CH encoder).

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New Aluminum Case 2.1: MIDI IN/THRU/OUT + MIDI activity LEDS
#2

Great Chris!

This tutorial will be very helpful for other people.

Thanks!

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#3

Hi @cdswift,

many thanks for your description!

I have bought two headphone amps and tried to install one. But If it is connected, no sound is produced on any output. I have seen that there is a pin labled CTRL. But on the circuit description this one seems not to be used.

Any idea what I am doing wrong?

Regards, Holger

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#4

Hi holger,
Have you tried connecting a different audio source to the headphone amp? Also, have you tested audio output from the dac card L and R. Mame sure L+ and R+ are connected together. Make sure signal from dac L and R and gnd are connected to amp L- and R- and gnd goes to either L+ or R+. Finally, check 5v and 0v to amp. Ive used 2 of these amps connected as described and they work ok.
Good luck
Chris

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#5

Hi Chris,

thanks for your fast answer. Most of the tests I had done yesterday. I will try to use another audio source to check if the amp works.

Regards, Holger

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#6

Hi @all!

I’ve succesfully added a headphones output to one of my zynthians.
@cdswift, I’have followed your instructions, but i’ve added an extra mini-jack to the case:

The sound is quite good!! Really! Thanks for sharing, @cdswift!

Regards!

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#7

@C0d3man
Have you solved your problem?
I would like an amplifier in the hope to get rid of the noise when rotating the encoders.
But I don’t want to lose the cinch out.

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#8

No - I havn’t tried anymore. Just found the mini-headphone-PCBs while cleaning my lab… I hope I can try again the next weeks.

Regards, Holger

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#9

Just adding another option for Headphones. Some lower cost boards like the Audio Injector use a chip for portable consumer products that includes a headphone driver. Headphone specs from the WM8731 data sheet include.

50mw for 16 ohm, 30mw for 32 ohm.
THD -65 db @ 10mw, -45 db @ 20mw (32 ohm)
Programmable +6dB to –73dB gain and mute, 0 db = 1 volt.

Looks like ear bud fidelity numbers.

I see zynthian block diagrams showing the Hifiberry card provides 3W headphone outputs.

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#10

This diagram includes an amplifier for headphones output. Hifiberry doesn’t have amplified outputs.

Regards,

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