The RA53b is a high powered headphone amplifier with five 1/4" and 1/8" (3.5mm) headphone outputs. Two RA53b units may be linked together and mounted side-by-side in a universal rack tray for a total of 10 outputs.
 
Specifications
Input Impedance: 10 K Ohms
Maximum Input Level: +18 dBV
Max Gain: 26 dB per channel
Output Power: 221 mW per side, 442 mW per channel (@ 32 Ohms)
Output Impedance: 10 Ohms
S/N Ratio: >90 dB
THD: <.08%
IMD (SMPTE): <.08%
Power: 12 VAC (Adapter provided)
Size: 8.4 x 1.7 x 5" (21.3 x 4.3 x 13 cm)
Weight: 2.5 LBS (1.14 kg)
# 5: 1/4" TRS Headphone Outputs with Level Control.
Lots of Gain.
1/4" and RCA Right and Left Inputs.
Inserts on Two Channels.
1/4" TRS Stereo Input, 1/4" Mono Input.
Link Input/Output for Connecting Two Units Together.