MONOLITH 38967 Liquid Gold X Balanced Headphone Amplifier and DAC User Manual
- June 6, 2024
- MONOLITH
Table of Contents
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 Balanced Headphone Amplifier and DAC by Alex Cavalli is a fully differential, balanced, solid-state amplifier. It is a miniaturized version of Cavalli Audio’s high-end Liquid Gold amplifier. The Monolith Liquid Gold X amplifier circuit topology and component values are identical to the original Cavalli Liquid Gold. 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 amp has both balanced XLR and unbalanced (RCA) inputs. The unbalanced input has an internal, solid-state buffered phase splitter to create a balanced signal and drive the amp fully balanced. The Monolith Liquid Gold X amplifier includes its own built-in, fully balanced DAC with USB, Coaxial, and Optical inputs. The amplifier has 4x and 6x gain settings and approximate full output power of 3.6 watts per channel with a 50-ohm load.
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
-
POWER: Momentarily press the button to signal the MCU to turn the amplifier on or off.
-
SE: Unbalanced TRS headphone output.
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B: Balanced 4-pin XLR headphone output.
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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.
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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.
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VOLUME: Turn the knob clockwise to increase the volume level and counterclockwise to decrease the volume level.
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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.
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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.
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DAC LEDs: The three LEDs indicate which DAC input is selected. From top to bottom, they indicate USB, Coaxial, and Optical.
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INPUT LEDs: The three LEDs indicate which input is selected. From top to bottom, they indicate DAC, Balanced XLR, and Unbalanced RCA.
Rear Panel
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BAL: Balanced XLR inputs.
-
SE: Unbalanced RCA inputs.
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USB: USB digital audio DAC input.
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COAX : Coaxial digital audio DAC input.
-
OPTICAL: Optical digital audio DAC input.
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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, 01 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 an 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 the acceptable range,
the MCU will power down the amp and show a ground failure blink code. If this
failure occurs multiple 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 a 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 the 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 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
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 judgment 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
(voltage for ≈ 1% THD)
| Watts| V rms
33 Ohms| 6.223| 14.33
56 Ohms| 3.927| 14.83
150 Ohms| 1.589| 15.44
300 Ohms| 0.820| 15.68
Maximum Output Single-Ended (voltage for ≈ 1% THD)| Watts| Vrms
33 Ohms| 1.769| 7.64
56 Ohms| 1.109| 7.88
150 Ohms| 0.448| 8.20
300 Ohms| 0.231| 8.32
Crosstalk (@1kHz 1 Vrms input unit gain balanced in/out)| **** -88dB
Channel Balance (with pot at unit gain balanced out)| 0.1dB
Input Power| 36 VDC, 1.4A
AC Adapter Input Power| 100 ~ 240 VAC, 50/60 Hz
Dimensions| 8.7″ x 8.5″ x 2.0″
(222 x 216 x 51 mm)
Weight| 3.3 lbs. (1.5 kg)
Analog Inputs
THD+N | 0.0012% |
---|---|
THD+N @ 1kHz | 0.0023% |
IMD CCIF (1 Vrms output) | 0.00019% |
IMD CCIF (5 Vrms output) | 0.00019% |
IMD SMPTE (1 Vrms output) | 0.00025% |
Noise (unweighted 20Hz~22kHz, balanced 47-ohm load, high gain) | **** -101dB |
Noise (unweighted 20Hz~22kHz, balanced 47-ohm load, low gain) | **** -103dB |
Noise (relative to 1 Vrms, single-ended, low gain) | -102dB |
Noise (relative to 1 Vrms, single-ended, high gain) | -99dB |
Output Impedance (balanced) | 0.133567 ohms |
Output Impedance (unbalanced) | 0.173573 ohms |
DAC Inputs
THD+N | 0.0028% |
---|---|
THD+N @ 1kHz | 0.0025% |
IMD CCIF (1 Vrms output) | 0.00115% |
IMD CCIF (5 Vrms output) | 0.00223% |
IMD SMPTE (1 Vrms output) | 0.00025% |
Noise (unweighted 20Hz~22kHz, balanced 47-ohm load, high gain) | **** -91.7dB |
Noise (unweighted 20Hz~22kHz, balanced 47-ohm load, low gain) | **** -96.1dB |
REGULATORY COMPLIANCE
Notice for FCC
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 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.
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 the 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: Avoid using this product during an electrical storm. There may be a remote risk of electric shock from the surge caused by lightning. WARNING: Do not use this product near water, for example, in a wet basement or near a swimming pool, or in an area where accidental contact with water or liquid might occur.
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
Monoprice™, Monolith™, all Monoprice logos, and the Monolith logo are
trademarks of Monoprice Inc.
NEMA® is a registered trademark of the National Electrical Manufacturers
Association.
References
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