Revision 1.5 - August 24, 2015

Safety Instructions



To reduce the risk of electric shock (and to keep from voiding the warranty), never open the device.


When connecting the device to AC power, be sure to use the included AC power cord, or one with identical connectors. Never remove the ground pin from the AC power cord.


Plug the device into a surge protection device whenever possible.


When connecting the device to any other components, make sure all components are powered off, and volumes are turned completely down (whenever possible).


Be sure to only clean the device with a dry cloth.


Be sure to place the device in a location with plenty of ventilation to avoid potential issues with overheating.


Geek Pulse is a high performance desktop USB digital-to-analog converter (DAC) and headphone amplifier that draws upon the proven design of the Geek Out. It has been designed to decode almost any music file format and resolution available, up to and including Direct-Stream Digital (DSD).

The Geek Pulse accepts digital audio signals through the following inputs:

  • USB
  • S/PDIF

The Geek Pulse delivers audio signals from the following outputs:

  • ¼” single-ended TRS headphone jack
  • Balanced XLR 4-pin headphone jack
  • RCA Line Out
  • Dual balanced XLR 3-pin connectors

* X versions required for balanced input/output connectors

When used in conjunction with the appropriate playback software, the Geek Pulse supports the following PCM sample rates in 16, 24, and 32-bit depths:

  • 44.1 kHz
  • 48 kHz
  • 88.2 kHz
  • 96 kHz
  • 176.4 kHz
  • 192 kHz
  • 352.8 kHz
  • 384 kHz

Geek Pulse also supports the following DSD formats:

  • Native 1-bit DSD64 and DSD128 (for Infinity Models)
  • DSD-over-PCM (DoP) support.

This document provides the steps necessary to setup the Geek Pulse, connect it to a computer, and configure it as the default audio output device.

Getting Started

Front Panel

  1. 1/4” Headphone Jack
  2. Balanced XLR 4-pin Headphone Jack *
  3. Sample Rate/Input Source Display
  4. Volume Level Display
  5. IR Remote Control Sensor
  6. Volume/Menu Selector Knob

Rear Panel

  1. RCA Line Out
  2. Balanced XLR 3-pin Outputs * 
  3. USB (Type B) Input
  4. AES/EBU Digital Input
  5. SPDIF RCA Digital Inputs
  6. TOSLINK Digital Input
  7. Power Switch
  8. 12V DC Input

* Available on Geek Pulse X versions only


  1. Unbox the Geek Pulse and remove it from the plastic wrap.
  2. Remove the power supply and plastic feet from the box. If included, remove the LightSpeed 1G USB cable (not included with all units).
  3. Peel the rubber feet from the strip and attach them to the bottom corners.
  4. Connect the power supply to the Geek Pulse, and plug into wall outlet.
  • If using a Geek LPS/LPS4 to power the Geek Pulse, use a 1.2A power connection instead of the included Geek Pulse power supply.
      5.  Connect the USB cable (preferably LightSpeed 1G/2G/10G) to the source and USB input on the back of the Pulse.

  • If using a Geek LPS/LPS4 with the Geek Pulse, connect the USB cable to the source and USB Source input on the back of the Geek LPS/LPS4, then connect a second USB cable to the USB DAC output of the Geek LPS/LPS4 and the Geek Pulse USB input.

  • If using a Geek LPS/LPS4 with the Geek Pulse, along with a split USB cable, connect the signal/data leg of the cable to the source, the power leg to the USB DAC output of the Geek LPS/LPS4, and the other end to the Geek Pulse USB input.
      6.  Power on Geek Pulse (without headphones or any other external components connected/powered on).
      7.  If using with a Mac OS X or Linux computer, no drivers are required.
      8.  If a Windows PC is being used, download the Windows driver and Light Harmonic Audio Driver Setup Guide from the LH Labs support site, and then install the driver:


In order for the computer to play sound through the Geek Pulse, the Geek Pulse must be set as the default audio output device.


After installing the Windows driver and Light Harmonic Control Panel, continue to follow the steps in the Light Harmonic Audio Driver Setup Guide to set the Windows Default Sound Output to the Geek Pulse.

Mac OS X

In OS X, go to the Apple menu at the top left of the screen, and open System Preferences...

Click on Sound and select Geek Pulse 1V1 Output (or newer version if applicable) as the audio output device.

Using The Geek Pulse


When the Geek Pulse is turned on and off there will be a popping noise sent through the headphone output, as well as all line outputs. These are the power caps in the signal chain charging and discharging. This is a conscious design decision to not add a buffer as it would affect the sound quality.

It is recommended that the Geek Pulse be left on at all times as it will keep the components warm, providing the optimal sound quality. However, if a power off/cycle is required, be sure to unplug headphones and/or power down the preamp/amp/active speakers to avoid any potential damage.

LH Labs will not be held responsible for any damage to equipment due to this design implementation.


Power On

When powering on the Geek Pulse, it will run through a startup routine (“Geek Pulse” is shown on the display), then show the last sample rate processed, as well as the last volume level.

However, for safety reasons, the actual volume upon startup is -80dB, regardless of what is displayed. To return to the displayed volume, turn the volume knob 2 clicks in either direction.

Volume Adjustment

Volume adjustments are registered as 0.5dB steps up or down. Each step is a turn of 2 clicks either way on the volume knob.

Swift turns of the volume knob allow for the volume to be increased/decreased in much larger steps (i.e. +/- 20-25dB) at one time. Be very careful when swiftly increasing the volume as it could cause equipment damage, or personal injury to hearing.

Volume adjustments affect the signals for the headphone output and line outs. When using an external preamp or active speakers, the volume may seem incorrect. A volume of -0.0dB is recommended in this instance.

Menu Navigation/Selection

To access the menu options of the Geek Pulse, press the volume knob once. Turn the knob left or right to view the options. Press the volume knob again to select the option displayed.

After 10 seconds of no movement on the volume knob, the menu will close back to the playback display screen.

The menu options with their corresponding submenu options are:

  • USB
  • AES
  • SPDIF 1
  • SPDIF 2

  • LOW
  • HIGH

  • TCM
  • FRM
  • SSM
  • FTM



Input Select

The Geek Pulse primary input is USB, however it will accept digital input from external sources via AES, SPDIF, and TOSLINK.

Gain Select

Using an internal silver relay, the gain stage is selectable to better match the sensitivity and impedance of the headphones being used with the Geek Pulse.

Low is best suited for high sensitivity/low impedance headphones, such as IEMs.

Mid is best suited for mid sensitivity/mid impedance headphones.

High is best suited for low sensitivity/high impedance headphones, such as large on/over ear models.

Be sure to test all modes to see which works the best for the given situation.

Digital Filter

Digital filters are used to remove artifacts in the digital signal caused by audio sampling. The Geek Pulse offers the following filters:

TCM (Time Coherence Mode) – Uses LH Labs minimum phase digital filter and time optimization algorithm which removes all post ring from the original signal, and realigns the impulse response. This presents the listener with a more well- defined and natural soundstage.

FRM (Frequency Response Mode) – Uses LH Labs slow roll-off linear digital filter and frequency domain optimization algorithm to provide a smoother and clearer sound with even lower THD+N.

SSM (Stable Streaming Mode) – A digital filter to optimize audio from streaming sites such as Spotify and Tidal.

* This filter is still in development, and will be added via future firmware update.

FTM (Femto Time Mode) – Uses an optimization algorithm that reduces time related distortion from the Femto Clock source, while providing better jitter performance. It also brings out the best of both TCM and FRM filter modes.

* FTM can be selected on Geek Pulse units but will not enable if the Pulse is not equipped with Femto Clocks.

Volume Setting

The Geek Pulse allows for 2 ways of controlling the volume:

Knob Control – Uses the physical volume knob to increase/decrease volume.

USB Control – Uses the computer system/application software volume controls to increase/decrease the volume.

Firmware Version

The firmware versions for the following are displayed:

Main – Displays the version of the DAC board firmware.

MCU – Displays the firmware version of the matrix control board (display and volume).

Remote Control

The Geek Pulse allows remote access to volume functions (increase/decrease/mute), as well as menu navigation and selection. At this time the Apple Remote is the only supported device.

To pair the remote to the Geek Pulse, press the Menu and right directional button at the same time while pointing the remote at the Geek Pulse. After 5 seconds a Pairing Code will appear on the display.

A video demonstrating how to use the Apple Remote with the Geek Pulse can be found here:

Geek Pulse - Apple Remote Pairing Demonstration Video

* Once an Apple Remote has been paired with a Geek Pulse it cannot be unpaired.

Geek Pulse Firmware Upgrade

From time to time newer versions of the Geek Pulse firmware will be released to fix bugs, and/or add functionality. The Device Firmware Upgrade (DFU) utility will need to be used to complete the upgrade.

Beginning with version 1.4, separate Geek Pulse firmware files will be made available specific to the individual models of the Pulse:

  • Standard
  • Fi
  • Sfi
  • X
  • Xfi
  • X Infinity

The following article provides links to the various firmware files, or links to additional articles explaining how to receive the correct firmware files:

Light Harmonic Audio Drivers/Firmware Download Page



As of this writing/revision (April 2015), the Geek Pulse firmware can only be upgraded from a Windows computer that has the Light Harmonic Audio Driver installed. The Light Harmonic DFU utility is installed on the computer as part of that process.


The Light Harmonic DFU utility for Mac is currently in development, but because of operational issues beyond our control, it is currently not available for distribution.

The Geek Pulse firmware 1.4 files are not interchangeable between models in any way. Flashing the incorrect file may cause the unit to become inoperable.

Incorrect firmware file upgrades are not covered by warranty, and the Geek Pulse will need to be sent back to LH Labs for repair at the cost of the owner.





Getting Started

In order to download the correct Firmware, the model of the Geek Pulse will need to be verified. This can be done in the Light Harmonic Control Panel utility which is accessible from the Start Menu (All Programs may need to be expanded to find it).

In the Light Harmonic Control Panel, select the Info tab.

In the above screenshot, the Product identifier lists the model as Geek Pulse with the 1V4 firmware already installed. This indicates the model is Standard. The other models will be listed as:

  • Geek Pulse Xfi
  • Geek Pulse X

The version 1.4 (1V4) firmware upgrade files can be downloaded from links at the bottom of this document. Be sure to save the file to a familiar location, such as the computer Desktop.

File Extraction (Applicable To Versions Prior To 1V4 Only)

The zip file should now be visible at the saved location. The file will need to be extracted (unzipped) prior to use.

Right-click the file and the context menu will appear. Select Extract All… from the list of options.

A dialog box asking where to save the extracted files will appear. Click Extract to select the default location. Keep “Show extracted files when complete” checked.


When complete, the FM-GPU-1Vx-UPGRADE bin file will be present in the extraction folder.


Light Harmonic Device Firmware Upgrade (DFU) Utility


To upgrade the Geek Pulse firmware, the Light Harmonic DFU utility will need to be on the computer (it is installed along with the Light Harmonic Audio Driver).


The Light Harmonic DFU utility is installed to the following location by default:


Local Disk (C:) – Program Files – Light Harmonic – USB_Audio_Driver


Double-click the LightHarmonic Dfu file to open the utility (the Geek Pulse must be connected and powered on). The utility interface is shown below:

Click the Browse… button to locate the correct bin file for your Pulse unit. Select the bin file and click Open.



The bin file location will be displayed in the Firmware box, and messages that the device is opened and ready for firmware update will be displayed in the Upgrade box.


Click the Start button to begin the upgrade process. A progress bar will be displayed.


Once the firmware upgrade is complete a message will be displayed that the firmware is being started, and that the firmware upgrade finished successfully.


After the upgrade is complete, close the utility, and power off the Geek Pulse.


After 10 seconds, power the Geek Pulse back on. Be sure to test that the Geek Pulse plays back audio and is free of any bugs that may have been present previously.


If there are any issues completing any of the steps in this document, understanding any of the concepts, with audio playback, or with the device itself, please open a support ticket through the LH Labs support page at:


A knowledgebase with frequently asked questions, and online repository of setup and user guides is available at:












LH Labs Corporation


Manufacturer’s Address:




LH Labs Corporation

920 Reserve Drive Suite 160






Roseville, CA 95678












Phone: 888-­‐842-­‐5988







Declares under our responsibility that the electrical products:


Product Name: Pulse


Model Number: Infinity, X, SE,FI,I,SFI, S,XFI, Standard. 


To which this declaration relates is in conformity with the following standards

and EMC:


EN 60065: 2002 + A1:2006

EN 55013: 2001 + A1:2003 + A2:2006

EN 55013: 2013

EN 55020: 2007 + A11:2011

EN 61000-­‐3-­‐2:2006+A12008+A2:2009

EN 61000-­‐3-­‐3:2013

EN 60065:2002+A1:2006+A11:2008+A2:2010+A12:2011


Supplementary Information:


This declaration attests that the manufacturing process quality control and product documentation accord with the need to assure continued compliance. The attention of the user is drawn to any special measures regarding the use of this equipment that may be detailed in the owner’s manual.


Authorized Signature:

Name: Yuan He

Title: CEO & President

Place, Roseville, California, United States of America

Date: November 8, 2015