The Markbass TA503 has a premium tube preamp that gives this bass amp head the advantage of tube warmth and analog clarity simultaneously. The TA503 bass head boasts a flexible EQ with 4-band semi-parametric tone control and Markbass' signature VLE (Vintage Loudspeaker Emulator) and VPF (Variable Pre-shape Filter) filters. Markbass gave the TA503 bass amplifier a Pre EQ/Post EQ switch to determine whether the output signal is affected by the EQ settings or not, as well as Send and Return Effect I/O to insure your main signal continues even if something along your effect chain breaks or runs out of batteries. An optional footswitch provides mute-to-tune and EQ bypass control.
Tube preamp analog bass head
Provides 300W RMS at 8 ohms, 500W RMS at 4 ohms
1/4" input jack works with active or passive basses
Gain and Master volume controls
Clip warning light
Line out volume control knob
EQ includes controls for Low, Mid Frequency Low, High Frequency Low, and High
Mid Frequency High and Low level controls for deciding how much frequency area will be affected
VLE (Vintage Loudspeaker Emulator) and VPF (Variable Pre-shape Filter) filters
Neutrik Speakon Combo out jacks for use with 1/4" or Speakon speaker cables
Balanced XLR out
Pre EQ/Post EQ switch to determine whether the output signal is effected by the EQ settings or not
Ground lift switch to eliminate hum
Tuner out sends unbalanced signal sent to a tuner, amp or recording equipment not needing a balanced signal
Send and Return Effect ensures main signal continues even if something dies in your effects chain
Dual-sided fiberglass PC boards with lined perforations for high-quality solder connections
Surface-mount components are silicon-sealed to isolate vibrations
Computer-grade pre-assembled ribbon connector cable harnesses and ribbons for noise-free operation
Integrated threaded posts for easy assembly/disassembly and added durability
Rigid 2mm thick aluminium chassis for a long-lasting finish
Power
Passive Input impedance: 500Kohm, max. voltage: 4 Vpp
Effect return impedance: 500Kohm, max. voltage: 10 Vpp
Active Input impedance: 500Kohm, max. voltage: 10 Vpp
Output Power: 300W RMS at 8 ohms, 500W RMS at 4 ohms
Power Requirement: 100/120V; 230V; 240V; 50/60Hz
Controls
GAIN: 80dB to +35dB range
LINE OUT: Level control on front panel
PRE/POST EQ (for line out): Switch on rear panel
GROUND LIFT: Switch on rear panel
MASTER VOLUME
FOOTSWITCH: Mute, EQ bypass
Equalization
LOW
Center frequency: 40-300Hz; level ±16dB
LOW-MID
Semi-parametric: frequency 100 800Hz, level ±16dB
HIGH-MID
Semi-parametric: frequency 700Hz 6kHz, level ±16dB
HIGH
Semi-parametric: 1.5-10kHz shelf; level ±16dB
VPF (Variable Pre-shape Filter)
Center frequency: 380Hz (cut)
VLE (Vintage Loudspeaker Emulator)
250Hz 20kHz cut
Outputs
EFFECT SEND
Unbalanced, max. voltage 20 Vpp (pre-EQ)
TUNER OUT
Unbalanced, max. voltage 2 Vpp
LINE OUT
Balanced XLR, max. voltage 15 Vpp
SPEAKER OUT
Speakon, 1/4"
Other
Dimensions: 14.5"(W) x 3.39"(H) x 11.89"(D)
2U tall
19"(W) with rack ears
Weight: 8.6lbs.
Tubes: 1 x EECC81, 1 x ECC83 (JJ Electronic)
Korpa 
