BT355 HD Radio Line Leveler And Pre-Amp Adapter for 2014 and Up

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1.00 LBS
BT355 HD Radio Line Leveler And Pre-Amp Adapter for 2014 and Up

New information about flash - call 800-735-2419 for details

Our new BT355 Line Leveler allows you to install an aftermarket amp and speaker system on your 2014 and up HD.

Included in our 2014+ amp packages.


  • Removes bass distortion when connecting an amp to the factory 2014+ radio
  • High quality three stage circuit for optimal sound quality and precise filtering
  • Adjustable level and frequency
  • Adapts high (speaker) level inputs to pre-amp outputs


  • For 2014 and up stock HD radio*

*NOTE - Ultra models do not have a rear speaker connector in the fairing. For plugging in rear speakers, please see the Breakout Connector for Ultras.



  • 5
    Worked for 18 Road Glide Special

    Posted by Ryan S on 31st May 2020

    Product is as described. Worked without having to reprogram at the dealer. Quick shipping. Plug and play.

  • 5

    Posted by Unknown on 20th May 2020

    Exactly what I needed! Nice and clean sound now.

  • 5
    Worth every penny

    Posted by Shorty on 25th Jun 2018

    Totally fixes stock HU eq curve without having to get the bike flashed and makes good clean audio.

  • 5
    Works like a charm

    Posted by on 7th May 2018

    Installed an amp and it didn’t sound right. Put the Bt355 in and adjusted the amp and now it’s clear and loud. Worth every penny since I put in a common amp. Stage 1 Boom speakers.

  • 5
    Overcoming Harley

    Posted by David Boullion on 4th Mar 2018

    I did not want to be stuck with Harley’s stage 2 stuff but was going to. Then I found out Biketronics has developed these line levelers. I installed a different audio system for reasons untold. These units installed as per their instructions results in trouble free audio. I did not have to go to Harley for anything. On a side note. The people & products at Biketronics are extremely awesome. Call them up if you’re looking at upgrading. I promise you they will do their absolute best to fix you up.

  • 5
    Just what the sound doctor needed

    Posted by Lawrence Bush on 27th Feb 2018

    Customer service is A1. Product shipped fast and arrived as described with great instructions. Will definitely recommend to anyone wanting great sound with the factory boom audio unit

  • 5
    Clean/easy to adjust

    Posted by Dan Miller on 12th Jan 2018

    Worked as advertised. Very clean sound by eliminating unwanted frequencies. Had to tweak HPF just slightly to achieve ultimate settings with Fosgate AMP. Then you can boost gains on AMP to get ultimate volume. Must have for Fosgate system to crank to FULL volume. Very impressive after that.

  • 5
    Forget The Flash!

    Posted by Jason on 5th Jan 2018

    Taking my bike to Harley to get them to flash the the stock head unit to flatten out the audio proved to be a pain. I was literally paying them to do something they could not figure out how to do. Save yourself time and headaches by doing this yourself with these line levelers. After installing a complete Rockford Fosgate kit in my 2018 SGS, I added these line levelers and now my audio is loud, bright and clear with zero distortion; it actually hurts my ears if I crank it all the way up and I have a stage 1 done with a Python exhaust. If that's not loud enough for you - get your hearing checked. I did have to make some adjustments a few times to get the gain set perfectly as I am sure you will need to as well, but this is something that is done easily, by yourself and without having to pay a shop to do it. The only thing you need to do at Harley after completing this is to tell them to turn on all four speakers so you can have true fade functions. Technically you don't NEED to do this, but if you have OCD like me, then you want everything done right. Bottom line is this; if you are adding after market amps and speakers - through these line levelers on and your upgrade is compete!

  • 5

    Posted by Unknown on 27th Oct 2017

    I bought the BT355 line leveler & works great. Nothing else had to be done. 2017 street glide special.