Get more sound from Behringer Xenyx 320 USB using higher impedance headphones

The goal

More power on headphones on Behringer XENYX 320 USB mixer

Usability

Fun & Pleasure

Hardware

• Behringer HENYX 320 USB mixer

Description

Some time ago I bought Behringer XENYX 320 USB mixer to listen and record digital piano (Yamaha P35) that I play. This was mostly for shaping my piano skills, is good practice to record and listen your playing, especially when you're in a first stage of learning piano.

Mixer

XENYX 320 has some quite nice features, e.g. when you connect it to PC by usb, it will be recognized as a sound card, and you can use it as a regular sound card, so recording and playing stuff is a not big deal for it.

Behringer Xenyx 320 USB mixer

Phones

When you connect low impedance phones everything is ok, even on Sennheiser's HD202 which are 32 Ω but one with bigger impedance can be slightly quieter.

My AKG K271 MKII which are about 60 Ω I use 90% for piano (they have flat characteristics) and 10% for non classical music, needed something more than a AD8602 amp which is in the mixer that I refer to.

Ok, I've got two paths from this point, first is to replace this amp which is impossible, because I don't have anything similar and it's about 11 pm at Saturday and I want it to work in now ;) The second path is to check the manufactures note about this amp and see that I can boost anything in oryginal Xenyx 320 circuit.

I've downloaded Analog Device's AD8602 datasheet and there is a template circuit for PC100-Compilant Line Output Amplifier which is described like this:

"The 100 μF output coupling capacitors block dc current and the 20 Ω series resistors protect the amplifier from short circuits at the jack."

Hmm, 20 Ω it's a difference when you're using 32 Ω vs 60 Ω headphones, so I've looked into Xenx to find out what impedance output resistors have. The result was 47 Ω, so I've short circuit them and really it makes a difference when you're using AKG's, especially when you love to listen with enhanced bass (Xenyx 320 have simple equalizer).

AD8620 output resistors short circuit

Doing this mod, you lose short circuits protection on phone jack, but when you've got headphones connected all the time, and never connect any unreliable output, in my opinion, it's nothing to worry about.

After mod headphones sound a little bit louder. You could always say, that this does not make any difference, and I could always turn the volume knob to higher position. Volume knob controls the input of AD8602, but when I listen to music from PC/usb using equalizer to boost bass to the max, there is an overdrive but it's on the input of AD8602, so lowering the impedance in output circuit in fact helped me to get better experience of sound form this little one ;)