Instruction manual

DAC2 DX Instruction Manual Rev A Page 28
Headphone Attenuation Jumpers (JP3 and JP4):
The gain range of the HPA2™ can be set using jumpers JP3 and JP4:
 0 dB attenuation - see Figure 3
 10 dB attenuation - see Figure 4 (Factory Default)
 20 dB attenuation - see Figure 5
The attenuation is inserted before the HPA2™ headphone amplifier. This attenuator location keeps
the output impedance of the HPA2™ constant and very near 0 Ohms. External attenuators should
never be inserted after a headphone amplifier as this would change the output impedance.
Proper attenuator settings are important for maximizing the SNR of the headphone monitoring
system. With proper settings, the full performance of the DAC2 can be delivered to the
headphones for critical monitoring tasks, or maximum musical enjoyment.
When the headphone attenuation jumpers are set properly, a normal listening level will
be achieved between the 10 o'clock and 2 o'clock volume-control positions.
If a normal listening level is achieved below a 10 o’clock volume-control position, the headphone
gain is too high, and the attenuation should be increased.
If the level is too low at a 2 o-clock volume-control position, the headphone gain is too low, and
the attenuation should be decreased.
Figure 3 - 0 dB Headphone Attenuation