Swissonic quadphone - headphone amplifier - schematic

[michielper]

I have been busy creating a personal monitor with more-me function. Fo inspiration, I reverse engineered my Swissonic headphone amplifier. The result of this investigation I post here for others to learn from.
Some highlights:
It uses the NE5532 dual opamp, one for each (stereo) output.
For extra power stability it uses an L7812 (but..... the input voltage is 12V and the output of the 12V regulator is 10V....)
The four headphones use a common ground which is created with a 1000 uF elco connected to the power ground.
The attachment is a KiCad schematic that shows the essentials. Strange that I cannot upload as a real KiCad schematic, so it has to be a PNG.

 

[bertus]

Hello,

It is strange to feed an 7812 with 12 volts.
I would expect an input voltage of 15 volts.
The 10 volts on the 5532 is the lower supply limit.
The NE5532 needs a single supply minimum of 10V (below):


Bertus

 

[michielper]

Yes, indeed, that was my reaction too. I suspect that they switched the power supply at some point from 15 to 12 V without an update of the circuit. But it does work, no doubt largely due to the 1000 uF elco which is quite an effective stabilizer....