Why Riders Reach for a LOC — and Where It Breaks Down
Line output converters work well on older Harley-Davidson Touring models. Tap into the factory speaker wires, step the signal down, feed an aftermarket amplifier — it's a known approach that has been used for years on 2014–early 2023 bikes.
On 2023.5+ models with Skyline OS, it doesn't work. Not because LOCs are poor quality products, but because the signal they're tapping into is fundamentally different on these bikes — and using one creates problems that can't be tuned out.
What a Line Output Converter Actually Does
A line output converter (LOC) takes a speaker-level signal — the amplified output that normally goes directly to the speakers — and steps it down to a line-level RCA signal suitable for an aftermarket amplifier.
On a conventional audio system, this makes sense. The head unit outputs a speaker-level signal, the LOC converts it, and the aftermarket amp takes it from there.
The limitation is that by the time you're tapping into a speaker-level signal, the audio has already been amplified once. Any processing, EQ or limiting that occurred upstream is baked into the signal permanently. The aftermarket amp receives it and amplifies it again — including whatever distortion or tonal shaping was in the original.
On older Harley platforms, this was manageable. The factory processing wasn't extreme, and a skilled installer could partially compensate with DSP downstream. It was a compromise, but it worked.
Why It Fails on 2023.5+ Harley Touring Models
On 2023.5+ Harley-Davidson Touring models, audio doesn't travel through conventional speaker wires between the head unit and amplifier. It travels over an A2B (Automotive Audio Bus) — a digital network that transmits audio data between the head unit, the factory DSP, and the factory amplifier.
By the time any analogue signal exists in this system, it has already passed through the factory DSP and been shaped specifically for the OEM speakers:
- EQ applied for factory speaker response curves
- Dynamic limiting applied to protect OEM components
- Volume-dependent processing applied by Skyline OS
A LOC connected to the factory speaker outputs on these bikes receives that processed signal — not a clean source. You're not tapping into audio that can be worked with. You're tapping into audio that has already been finished for a specific purpose, and trying to use it as a starting point for something else.
The result is a system that can be made loud, but cannot be made accurate. Tonal balance is unstable at different volumes, headroom is reduced, and no amount of downstream DSP tuning can fix a compromised source signal.
The Correct Approach: Replace the Factory Amplifier
The right solution on 2023.5+ bikes isn't to tap into the signal after it's been processed — it's to intercept it before that processing occurs.
That's what the NAV-TV ZEN-H does. It installs in the factory amplifier location — physically replacing the OEM amp — and connects directly to the A2B digital bus. Instead of extracting an already-processed analogue signal, it reads the digital audio stream before factory EQ is applied, then converts it to eight channels of clean 5V RCA output.
What this gives you:
- A flat, unprocessed signal — the audio as the head unit intended it, before the factory DSP touched it
- 8-channel RCA output at 5V — configurable across front, rear and any additional positions
- Remote turn-on output — built into the unit at the factory amp location, eliminating the need to route a trigger wire back under the seat
- Plug-and-play installation — compatible with both the standard factory amplifier and the larger Rockford Fosgate Black amplifier fitted to some models
The factory head unit, handlebar controls and Skyline OS functions all remain fully operational after installation.
ZEN-H vs ZEN-H PRO: Which One
Two versions are available depending on your system architecture:
The ZEN-H is the A2B interface only — 8 channels of clean RCA output, ready to feed an external amplifier or DSP. This is the right choice if you're running a DSP-equipped amplifier (like the Cicada FLX PRO series) or a standalone DSP processor in the signal chain.
The ZEN-H PRO adds a built-in 8-channel DSP to the interface — time alignment, crossover configuration, parametric EQ and phase control, all inside the one module. For builds where space is limited or where you want the DSP work handled at the interface stage rather than at the amplifier, the PRO removes the need for a separate processor unit.
Both replace the factory amplifier in the same location, with the same plug-and-play harness connection. The choice comes down to where you want DSP to sit in your signal chain.
Why This Matters for the Rest of the System
Signal integrity at the source determines everything that follows. An aftermarket amplifier connected to a clean, flat ZEN-H output can be gain-staged correctly, crossed over properly and tuned with confidence. The same amplifier connected to a LOC'd factory output is working from a compromised foundation — and the compromise doesn't disappear with better downstream components.
For the full technical explanation of how the A2B system works and why conventional integration methods fail on these platforms, see: Why 2023.5+ Harley Audio Upgrades Need an A2B Interface