PI2Media 502HTA
Hardware Reference Manual – P3 - 8/31/2017
PAGE 9
noise and overall power consumption. For the best experience, the user
should start at the highest resistance and reduce only if the output levels
are not satisfactory.
2. There is a 25 second delay from power up before the headphone output is
enabled. This allows the tube to warm up and reduces power on thumps.
The output is disabled immediately when power is removed.
4.5
6.3V HEATER SUPPLY
A low noise, high performance switching supply provides the 6.3V for the Tube Heaters.
This supply also feeds the 5V LDO used to power the RPi (up to 3A).
4.5.1
6.3V HEATER SUPPLY NOTES
1. A 3-Pin Jumper is used to select how the power to the Tube Heater is fed.
In 6V mode a jumper is placed on pins 2-3, while in 12V mode a jumper Is
placed on pins 1-2. Note that 12V mode only works with tubes that allow
6.3V parallel operation, such as the 12AU7, not true 12V heaters. The
following circuit illustrates this:
