my head unit has one RCA sub output. the amp is two-channel, and so it has a left and right input.

what is the best way to connect them?

is a Y-adapter a good option? or would that result in halving the voltage sent to the amp?

are there other options?

the amp is running two subs, one on each channel (2 ohm stable amp, with 2 4ohm DVC subs)

 

it's some generic non-namebrand thing.

Performance Teknique ICBM-779 2-cHANNEL Car Audio Amplifier

# Maximum Output Power @ 2 Ohms: 600W x 2CH
# Power Output @ 2 Ohms: 240W x 2CH
# Power Output @ 4 Ohms: 170W x 2CH
# Power Output Bridged: 480W x 1CH
# THD: 0.02% @ 2 Ohms, 0.1% @ 4 Ohms
# Signal to Noise Ratio: >95dB
# Frequency Response: 15Hz to 40kHz
# Crossover: Separates
# High-pass: 50Hz to 1kHz Variable
# Low-pass: 30Hz to 500Hz Variable
# Slope: 24dB Octave
# Subsonic Filter: 10Hz to 100Hz Variable
# Bass Boost: 0 dB to 18dB Variable
# Input Sensitivity: 200mV to 6V Variable
# Low level Input Impedance: 47K Ohm
# Damping Factor: 180 into 4 Ohm
# Channel Separation: >80dB
# High & Low Level Input through RCA
# Double Sided PCB
# Dual Protection (Thermal & Short Circuit)
# RCA Line Out
# Power & Diagnostic LED Indicator
# 2 Ohm Stable
# Soft Delayed Power On
# Tri-Mode Capability
# Power Supply Consumption (Bridged RMS): 57A
# Fuse Rating: maxi 60A
# Dimension (WxHxL): 9.96" x 2.12" x 17.71"

 

A "Y" adapter is fine and is all you need.

 

Don't waste your time buying a y adapter. Simply plug in into the white rca input(left). One input is all you need.

And FYI, spliting RCA's maintains the same voltage.

 

AAAAAAAA: i have everything installed, and tried what you suggested (no y-adapter, just plugged into the amp's left), and it works great. thanks.