MONOPRICE Monolith 38967 Liquid Gold X Balanced Headphone Amplifier User Manual

: June 6, 2024
: Monoprice

Monolith 38967 Liquid Gold X Balanced Headphone Amplifier

Liquid Gold X Balanced Headphone Amplifier and DAC by Alex Cavalli

P/N 38967 User’s Manual

SAFETY WARNINGS AND GUIDELINES

Please read this entire manual before using this device, paying extra attention to these safety warnings and guidelines. Please keep this manual in a safe place for future reference.

This device is intended for indoor use only.
Do not expose this device to water or moisture of any kind. Do not place drinks or other containers with moisture on or near the device. If moisture does get in or on the device, immediately unplug it from the power outlet and allow it to fully dry before reapplying power.
Do not touch the device, the power cord, or any other connected cables with wet hands.
Do not expose this device to excessive vibration.
Do not subject the product to extreme force, shock, or fluctuations in temperature or humidity.
Do not expose this device to excessively high temperatures. Do not place it in, on, or near a heat source, such as a fireplace, stove, radiator, etc. Do not leave it in direct sunlight.
This device ventilates excessive heat through the slots and mesh openings in the case. Do not block or cover these openings. Ensure that the device is in an open area where it can get sufficient airflow to keep from overheating.
Do not place or install this device in an area where it can be exposed to excessive amounts of dust, humidity, oil, smoke, or combustible vapors.
Use only in a well-ventilated area. Do not use in close, confined spaces.
Prior to operation, check the unit and power cord for physical damage. Do not use if physical damage has occurred.
Before plugging the unit into a power outlet, ensure that the outlet provides the same type and level of power required by the device.
Do not use any AC power adapter other than the one provided with the unit. The adapter is closely matched with the MCU to provide the proper high current influx when power is applied. Use of aftermarket power adapters is likely to damage the amplifier.
Unplug this device from the power source when not in use.
Take care to prevent damage to the power cord. Do not allow it to become crimped, pinched, walked on, or become tangled with other cords. Ensure that the power cord does not present a tripping hazard.
Never unplug the unit by pulling on the power cord. Always grasp the connector head or adapter body.
Ensure that power is turned off and disconnected before making any electrical connections.
Clean using a soft, dry cloth only. Do not use chemical cleaners, solvents, or detergents. For stubborn deposits, moisten the cloth with warm water.
This device has no user serviceable parts. Do not attempt to open, service, or modify this device.

INTRODUCTION

The MonolithTM Liquid Gold X Headphone Amplifier and DAC by Alex Cavalli is a miniaturized version of the original and popular Cavalli Audio® Liquid Gold Amplifier that uses ±18V rails to achieve high power in a small package. The Liquid Gold is a fully differential, balanced, current feedback, solid state amplifier and has a built-in, fully balanced DAC based on the AKM® AK4493EQ DAC chipset. The amplifier is microprocessor controlled using precision A-to-D and D-to-A conversions to manage and monitor the runtime behavior of all critical aspects of the circuitry. It features a balanced 4-pin XLR output and an unbalanced 1/4″ TRS output. The TRS output is provided for compatibility with TRS terminated headphones, but it is recommended to use the amp in fully balanced mode using balanced headphones. The amplifier has 4x and 6x gain settings and an approximate full output power of 3.6 watts per channel into a 50-ohm load. The MonolithTM Liquid Gold X Headphone Amplifier and DAC by Alex Cavalli will take your listening enjoyment to new heights!

CUSTOMER SERVICE

The Monoprice Customer Service department is dedicated to ensuring that your ordering, purchasing, and delivery experience is second to none. If you have any problem with your order, please give us an opportunity to make it right. You can contact a Monoprice Customer Service representative through the Live Chat link on our website www.monoprice.com or via email at support@monoprice.com. Check the website for support times and links.

PACKAGE CONTENTS

Please take an inventory of the package contents to ensure you have all the items listed below. If anything is missing or damaged, please contact Monoprice Customer Service for a replacement.
1x MonolithTM Liquid Gold X Amplifier and DAC 1x AC Power Adapter 1x User’s Manual

PRODUCT OVERVIEW

Front Panel

front panel

POWER: Momentarily press the button to signal the MCU to turn the amplifier on or off.
SE: Unbalanced TRS headphone output.
B: Balanced 4-pin XLR headphone output.
STATUS LED: The LED illuminates or blinks red and/or white to indicate a normal operating or fault condition. Refer to the table in the BLINK CODES section for details.
GAIN: This toggle button determines the amount of gain to apply to the signal. When the button is IN, the gain is 6x and when it is OUT the gain is 4x.
VOLUME: Turn the knob clockwise to increase the volume level and counterclockwise to decrease the volume level.
DAC SELECT: Momentarily press the button to cycle through the DAC inputs. When power is first connected, it defaults to the USB input. The cycle order is USB, Coaxial, and Optical, then back to USB.
INPUT SELECT: Momentarily press the button to cycle through the inputs. When power is first connected, the input defaults to the balanced XLR input. The cycle order is Balanced XLR, Unbalanced RCA, and DAC, then back to Balanced XLR.
DAC LEDs: The three LEDs indicate which DAC input is selected. From top to bottom, they indicate USB, Coaxial, and Optical.
INPUT LEDs: The three LEDs indicate which input is selected. From top to bottom, they indicate DAC, Balanced XLR, and Unbalanced RCA.
Rear Panel
BAL: Balanced XLR inputs.
SE: Unbalanced RCA inputs.
USB: USB digital audio DAC input.
COAX: Coaxial digital audio DAC input.
OPTICAL: Optical digital audio DAC input.
AUTO/OFF: This switch enables or disables the auto-off feature.
POWER: DC barrel connector for connecting the included AC power adapter.

BLINK CODES

CONDITION

|

STATUS LED

---|---

Normal Power Off

|

Blinks red (0.5 sec on, 0.5 sec off) 5 times

Ground Failure

|

Blinks white (0.1 sec on, 0.1 sec off) 75 times

DC Offset Failure

|

Blinks red (0.1 sec on, 0.1 sec off) 75 times

EU Shutdown Final Minute

|

Blinks white (1 sec on, 1 sec off) 30 times

DC Module Wrong Voltage

|

Blinks red and white alternately (1 sec on, 1 sec off) 8 times

Firmware Unknown State

|

Blinks red and white alternately (3 sec on, 3 sec off) 5 time

MICROCONTROLLER UNIT (MCU) INTELLIGENCE

The built-in MCU controls all of the amplifier’s operational behaviors. It turns the amplifier on and off, monitors various DC voltages for acceptable values, detects bad ground and output DC offset conditions, performs various timings, manages input and DAC selectors, manages EU auto shutdown, and shows various normal and error/fault conditions. The red/white STATUS LED on the front panel is used to indicate these conditions with various colors and blink rates. Refer to the BLINK CODES section for details. Please review this section before attempting to operate the MonolithTM Liquid Gold X amplifier.

DC Plug-In Delay

The MonolithTM Liquid Gold X amplifier has several built-in delays to ensure that all DC voltages are in their proper ranges before allowing you to power up and connect headphones.
The first important delay is immediately after plugging in DC power. The MCU waits 3 seconds before measuring the DC voltage of the power source. If this source is not within range the MCU will show a blink code using the STATUS LED on the front panel. You will not be able to power on the amp until the MCU determines that the DC source is within acceptable range. Pushing the power button will only cause the LED blink cycle to be repeated. If the DC power is detected out of range, unplug the AC power adapter for 30 seconds, then plug it back in to reset the MCU. If no blink code is shown after 3 seconds, press and release the POWER button. The STATUS LED will illuminate red and the three INPUT LEDs will illuminate, indicating that the amplifier is ready for operation.

Ground Test Delay

The MCU will wait for about 3 seconds and then measure all of the important internal ground relationships. If these are not within acceptable range, the MCU will power down the amp and show a ground failure blink code. If this failure occurs mulitiple times, please contact MonopriceTM Technical Support for assistance.

DC Offset Delay

If the ground connections are acceptable, the MCU will wait about 15 seconds while the amp finishes powering on. After 15 seconds the MCU will measure the DC offsets at the headphone outputs. If these are acceptable, it will connect the headphones (relay click) and the STATUS LED will change from red to white. If the DC offset is not acceptable the MCU will power down the amp and show an offset failure. If the amp consistently shuts down during power up due to offset failure, please contact MonopriceTM Technical Support.

Notes:

You can change the selected input and selected DAC source while the amp is powering on.
We recommend setting the volume level to minimum during power on.
After the STATUS LED changes from red to white and the headphones are connected, all normal amp features should be operational.

EU Compliant Auto Shutdown

To comply with EU Regulation (EC) No. 1275/2008, this amplifier features an auto-off function, which is enabled or disabled using the AUTO/OFF switch on the rear panel. When the switch is placed in the OFF position, there is no effect on the amplifier’s operation. When the AUTO/OFF switch is placed in the AUTO position, the MCU monitors the selected input for a valid audio signal.

If the input signal falls below a very low threshold continuously for 4 hours, the MCU will power down the amp to save electricity. If an audio signal is detected at any time, the timer will reset. If the AUTO/OFF switch is set to the OFF position during the countdown, the timer will reset. During the last minute before automatic shutdown, the STATUS LED will show a blink code. If the power button is pressed while this blink code is displayed, the timer will reset.

DC Offset or Ground Fault

if the MCU detects either of these two conditions during operation, it will disconnect the headphones and the STATUS LED will change from white to red. If either condition is an extreme failure, the MCU will also shut down the amplifier with the associated blink code. If the either condition is deemed abnormal, but not extreme, the MCU will attempt to recover normal operation. If the MCU recovers, it will reconnect headphones and change the STATUS LED red to white. If it cannot recover after a determined period of time, it will shut down the amplifier with the associated blink code.

Firmware Enters Unknown State

In the event a critical failure occurs and the firmware enters an unknown condition, it will power down the amp and indicate this condition with a specific blink code. Unplug the AC power adapter for 30 seconds, then plug it back in to reset the MCU. If this condition persists, please contact MonopriceTM Technical Support for assistance.

OPERATING GUIDELINES

To get the most out of your amplifier and to protect it from possible damage, follow the guidelines listed below.

Gain Setting

While the amplifier supports hot switching the gain setting, changing gain introduces a small DC transient at the output. Depending on the sensitivity of your headphones, this transient might be quite loud or damaging. We highly recommended that you turn off the amplifier before changing the gain setting.

Connecting Headphones While Audio is Playing

Under many conditions, if you plug or unplug your headphones while the amp is delivering power, you will trip the output offset detector. This is the MCU protecting the amp from damage. This condition is likely to occur more frequently when using the TRS output because of the output shorting that occurs when the TRS plug is inserted into the jack. For best results and the safest operation, turn the amplifier off before plugging or unplugging your headphones.

Electrical Connections

You should power down the amplifier and unplug it from the power source before making any electrical connections, including the inputs and the headphone outputs. This ensures that no transient voltage spike can occur, which can cause damage to the amplifier and/or other equipment.
Volume
For best results, set the volume control to the minimum level before starting audio playback, then increase volume to a comfortable listening level.

Amplifier Break-In

Most amplifiers need at least 100 hours of continuous music playback to reach their full sound signature. It is not necessary to set up a break-in period. The amp will change character as you listen normally and you will hear it evolve into its natural sound signature. If you do employ a break-in period, we recommend about 100 hours of continuous music playing with no headphones connected and the volume set to about 10 o’clock.
Constant On
Other than the aforementioned break-in period, the amplifier should be powered down when not in use to ensure the longest possible life for the components.
Balanced vs. Unbalanced
To get the best performance from your amplifier, use the balanced headphone output, as well as the balanced XLR inputs. The amp is designed to run with a balanced input and output. If you only have TRS terminated headphones, we recommend that you find a way to listen with balanced headphones before making any judgement on the performance of the amp. Remember that the unbalanced output is provided for convenience only.

Power Source

This amplifier is supplied with a universal AC power adapter, which can operate with voltages from 100 ~ 240 VAC, 50/60 Hz. It has a NEMA® 1-15 plug for use with standard US AC outlets, but will work with a physical adapter suitable for your location.
Aftermarket AC Power Adapters
The AC power adapter is matched to the onboard power control circuit. A particular feature of this matching is to control the high current influx when DC power is plugged in and when the amp is turned on. Therefore, DO NOT USE AFTERMARKET LINEAR SUPPLIES AS THEY ARE VERY LIKELY TO DAMAGE YOUR AMPLIFIER.

Grounding

This amplifier shares the ground of the source it is plugged into. In unusual circumstances, ground noise may occur, depending on the exact grounding of the source equipment.

TECHNICAL SUPPORT

Monoprice is pleased to provide free, live, online technical support to assist you with any questions you may have about installation, setup, troubleshooting, or product recommendations. If you ever need assistance with your new product, please come online to talk to one of our friendly and knowledgeable Tech Support Associates. Technical support is available through the online chat button on our website www.monoprice.com or through email by sending a message to tech@monoprice.com. Check the website for support times and links.

SPECIFICATIONS

Model

|

38967

---|---

Frequency Response

|

5 Hz ~ 60 kHz ±0.05dB

Maximum Output Balanced

|

Watts

|

Vrms @1%

33 Ohms

|

6.22

|

14.33

56 Ohms

|

3.93

|

14.83

150 Ohms

|

1.59

|

15.44

300 Ohms

|

0.82

|

15.68

Maximum Output Unbalanced

|

Watts

|

Vrms @1%

---|---|---

33 Ohms

|

1.77

|

7.64

56 Ohms

|

1.11

|

7.88

150 Ohms

|

0.45

|

8.20

300 Ohms

|

0.23

|

8.32

THD+N

|

0.0012% @1Vrms, 0.0023% @5Vrms

IMD CCIF

|

0.00019% @1Vrms, 0.00019% @5Vrms

IMD SMPTE

|

< 0.00025%

Crosstalk

|

-88dB

Output Impedance

|

0.13 ohms (Balanced),
0.17 ohms (Single-Ended)

Analog Inputs

|

XLR (Balanced), RCA (Single-Ended)

Digital Inputs

|

USB, Coaxial, Optical

Dimensions

|

8.7″ x 8.5″ x 2.0″ (222 x 216 x 51 mm)

Product Weight

|

4.3 lbs. (1.96kg)

Package Weight

|

5.9 lbs. (2.68 kg)

REGULATORY COMPLIANCE

Notice for FCC

This device complies with Part 15 of the FCC rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation. Modifying the equipment without Monoprice’s authorization may result in the equipment no longer complying with FCC requirements for Class B digital devices. In that event, your right to use the equipment may be limited by FCC regulations, and you may be required to correct any interference to radio or television communications at your own expense. This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures:

Reorient or relocate the receiving antenna.
Increase the separation between the equipment and receiver.
Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
Consult the dealer or an experienced radio/TV technician for help.

Notice for Industry Canada
This Class B digital apparatus complies with Canadian ICES-003.

EU Declaration of Conformity
Monoprice, Inc. declares the product described within this user guide or manual is in compliance with below applicable directives. The full text of the EU Declaration of Conformity is available at the following internet address:
https://www.monoprice.com/product?p_id=38967 or the CE DoC can be found within this user manual.

EMC Directive 2004/108/EC
Low Voltage Directive 2014/35/EU
RoHS2 Directive 2011/65/EU
WEEE Directive 2012/19/EC
Packaging & Packaging Waste Directive 94/62/EC
REACH Directive 1907/2006/EC

WEEE Information

User information for consumer products covered by EU Directive 2012/19/EU on Waste Electric and Electronic Equipment (WEEE). This document contains important information for users with regards to the proper disposal and recycling of Monoprice products. Consumers are required to comply with this notice for all electronic products bearing the following symbol:
For Consumers in the European Union: This EU Directive requires that the product bearing this symbol and or its packaging must not be disposed of with unsorted municipal waste. The symbol indicates that this product should be disposed of separately from regular household waste streams. It is your responsibility to dispose of this and other electrical and electronics products via designated collection facilities appointed by the government or local authorities. Correct disposal and recycling will help prevent potential negative consequences to the environment and human health. For more detailed information about the disposal of your unwanted product, please contacts your local authorities, waste disposal service, or the shop where you purchased the product.

Safety Notice

WARNING: Do not use this product near water, for example, in a wet basement or near swimming pool or in an area where accidental contact with water or liquid might occurs. WARNING: Avoid using this product during an electrical storm. There may be a remote risk of electric shock from the surge caused by lightning. WARNING: The external power adapter or AC power cord is the equipment’s disconnection device. The power outlet must be located nearby the equipment and its access must be easy.
MonopriceTM, MonolithTM, all Monoprice logos, and the Monolith logo are trademarks of Monoprice Inc. NEMA® is a registered trademark of National Electrical Manufacturers Association.