Cavalli Audio Liquid Glass User manual

Liquid Glass
Headphone Amplifier
®
Cavalli audio
Copyright © 2012-2015 Cavalli Audio, LLC
All Rights Reserved
®

Page 2of 20 Copyright © 2012-2015 Cavalli Audio, LLC

Copyright © 2012-2015 Cavalli Audio, LLC Page 3of 20
Before You Use Your Liquid Glass®Amplifier
For Your Protection
Dangerous High Voltages: This amplifier uses dangerous and possibly lethal high voltages.
NEVER operate with the cover open. When the amplifier is powered on dangerous high
voltages are present on the tube sockets in the tube cage. NEVER insert fingers, hands, or
other objects, particularly conductive objects, into the tube cage area when the amplifier is
powered on or at any other time. See the rest of this manual for procedures to change the
tubes.
Children: Along with the presence of high voltages, the tubes in this amplifier, as in many other
vacuum tube amplifiers, get hot enough to cause severe burns. In addition the amplifier may
contain sharp pieces. Keep the amplifier out of reach of children at all times.
Ventilation: In order to improve sound quality, your Liquid Glass® amplifier runs warm and
thus requires free air circulation of at least 6” around the top and sides of the product. Never
place the amplifier in an enclosed space with restricted air flow. Never place it near another
source of heat. Excessive heat will shorten the life of the product and may cause a fire.
Water and moisture: NEVER use the Liquid Glass® amplifier near water. NEVER handle the
amplifier while in contact with water. NEVER let the amplifier come into contact with water.
NEVER spill water or other liquids into the amplifier or on the amplifier.
Power Sources: Make sure that the voltage/frequency stated on the back label of your
amplifier is compatible with the line/mains voltage in your location.
Grounding: The electrical ground in this amplifier is an important safety feature. Do not defeat
ground with special plugs, power cords, etc. Doing so will void your warranty and may lead to
a dangerous condition.
Power Cords: If you use your own power cord, use one that meets the standards of your
location.
Power and Signal: Cables should never be connected or disconnected with equipment powered
up. Failure to heed this warning may damage or destroy equipment.
Servicing: To reduce the risk of electrical shock or other injuries, the user should not attempt to
service the device beyond replacing tubes. All other servicing must be referred to authorized
service personnel.

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Copyright © 2012-2015 Cavalli Audio, LLC Page 5of 20
Congratulations! You’re now the owner of the Cavalli Audio
Liquid Glass®Headphone Amplifier!
Amplifier Break-In
Most amplifiers, especially amps with tubes, need at least 150 hours of continuous use, playing
music, to reach their full sound signatures.
Your Cavalli Audio Amplifier has been playing music for at least ____________ hours at near full
volume. Confirmed by _______________________________.
Because the Liquid Glass® can operate with many different tube types, the amp can only be
broken in using the stock tubes. This break in period will settle the solid state components of
the amplifier and the power supplies, but you will have to take care of breaking in each set of
tubes that you want to use.
This means that the non-tube sections of the amp should reach their optimum sound quality
after about 150-200 hours and then the sound quality will be determined by the condition of
the tubes.
Before you judge the sound quality of the amp please be sure that you have let the tubes as
well as the solid components fully break in!
Return Policy
If, after delivery, you decide you don’t like your Liquid Glass amplifier, returning the amplifier
will incur a 30% of the retail price restocking fee and must occur within 30 days of delivery.

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Important points to remember about the Cavalli Audio Liquid
Glass®headphone amplifier
The Liquid Glass® is a unique hybrid headphone amplifier. The Liquid Glass® can support many
different tube types, both octal and noval, so long as they conform to 6SN7 or 12AU7 pinouts
and fall with reasonable operating conditions.
The LG is a conventional capacitor coupled hybrid with a tube front end and a solid state buffer.
The solid state buffer is designed to be as transparent as possible to the sound of the tubes in
use. It has a very high input impedance which means that the tube is barely loaded and this
means that the sound of the amplifier is almost exactly the sound of whatever tube is being
used. There is no global feedback mechanism so the sound features of the tube are transmitted
to the headphones with as little change as possible.
The tube front end of the LG is a classic totem pole of two stacked triodes. This arrangement
allows the front end to self-adjust to the triodes in use, placing ½ of the plate voltage on each
triode. The resistor values have been chosen to handle a wide range of tubes without requiring
complicated user adjustments.
Power is controlled by a standby power circuit activated by a custom made Piezo power switch.
The LG has the standard Cavalli Audio heater delay circuit to protect the tubes and offset
detector to protect your headphones.
Operation
Your Liquid Glass® amplifier has been operated for at least 50 hours for quality control and to
give the stock tubes (Electro Harmonix 6SN7) and other parts an opportunity to break in.
However, most amplifiers don’t fully settle, open up, and “relax” until they are played for at
least 100 to 150 hours of operation. The Liquid Glass® also follows this timeline (see page 5).
Your new amp will continue to improve with regard to bass impact, more open sound, warmth,
and “sweetness,”depending on tube type, so we strongly recommend that you accumulate
these important hours on your Liquid Glass® headphone amplifier by playing it as much as
possible so that you may fully enjoy its performance as soon as possible.

Copyright © 2012-2015 Cavalli Audio, LLC Page 7of 20
DO NOT
ABSOLUTELY DO NOT:
1. CHANGE THE HEATER VOLTAGE
WHEN THE AMP IS ON
2. CHANGE THE PLATE VOLTAGE
WHEN THE AMP IS ON.
3. CHANGE TUBES WHEN THE
AMPLIFIER IS ON.
ANY OF THESE ACTIONS MIGHT
DAMAGE THE AMP OR THE TUBES.

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Amplifier Gain
Most amplifiers and preamplifiers have a fixed gain. Some have a small number of fixed gain
selections. The Liquid Glass®, however, because of its design, which highlights the tubes in use,
has a gain which is entirely dependent on the tube choice. The gain of a triode is called its mu
and is theoretically the maximum voltage gain that a triode can provide. The LG’s gain is always
half of the mu of the triodes in use. For example, 6SN7s have a mu of 20 so the LG gain with
6SN7s is 10. 12AU7s have a mu of 17-20 so the LG gain is 8.5-10. Etc. Please pay attention to
the mu of the triodes so that you know why the amp has the gain it does.
Changing Tubes
The octal and noval tube sockets are arranged to create interference between the two tube
types in each channel. This interference makes it impossible to insert both an octal and noval
tube into a single channel. This exclusive insertion protects the front end components and the
power supply.
You can, obviously, insert one type of tube into one channel and another into the other
channel. Do no put different tube types in separate channels.
Before changing tubes, be sure that the amp has been powered off for at least 10 minutes.
Remove the tubes that are in the amp, if there are any, and insert the new tubes.
Before powering the amp on again, make the necessary heater and plate voltage settings.
Failure to set these values correctly may damage the tubes, the amplifier, or both.
Selecting Heater and Plate Voltage
Setting heater and plate voltages requires some knowledge of tubes, particularly their heater
voltages, heater currents, and maximum plate voltages. If you don’t know how to determine
these please get help from someone who does.
Before doing anything, check carefully that the amp is off. Both front panel recessed indicator
lights should be dark along with the tube heaters, but the power switch light can be on
indicating that the amp is in standby mode.
Familiarize yourself with the switches and their labeling so you don’t make a mistake.

Copyright © 2012-2015 Cavalli Audio, LLC Page 9of 20
Heater Setting
There are two small recessed toggle switches on the left side of the amp. The leftmost switch
selects the heater voltage, either 6.3V or 12.6V. Set this switch to the heater voltage required
by the tubes in use. See the tube datasheet to determine this value. It is not possible to damage
12.6V tubes if you accidentally use the 6.3V setting, but it is possible to damage 6.3V tubes if
you use the 12.6V setting. The heater current is limited, but this limiting cannot protect for all
possible 6.3V tubes. PLEASE CHECK YOUR HEATER SETTING CAREFULLY BEFORE YOU TURN ON
THE AMP.
Plate Voltage Setting
The rightmost switch on the left side of the amp selects the plate voltage. Most of the tubes
that will work in the Liquid Glass® can operate at the 300V setting. This includes 6SN7s and
12AU7s and their equivalents.
However, some tubes like 6922s cannot handle the higher plate voltage. For these tubes select
the 200V setting.
Remember that in a totem pole arrangement each triode sees only half the applied plate
voltage. This means that at 300V each triode sees 150V and at 200V each triode sees 100V.
To determine which settings to use find the data sheet on the tube type you want to use.
Locate the maximum plate voltage in the data sheet. If this voltage is 150V or higher use the
300V setting. If this voltage is less than 150V, use the 200V setting.
Setting the plate voltage to 200V for tubes capable of 300V will not harm them, but setting
plate voltage to 300V for 200V tubes can cause internal arcing in the triodes and damage both
the tubes and the amp. Please be careful with this setting
Heater and plate voltage are the only two settings you need to make in the Liquid Glass. The
amp handles the rest. 
Maximum Values
Please pay attention to these maximum values when selecting tubes:
Heater Current –the heater circuit can handle about 1.2A of heater current. This means that
6.3V tubes can have a maximum of 1.2A heater draw, but 12.6V tubes can only have a
maximum of 600mA.
Plate Current –the Liquid Glass HV supply can deliver a maximum of about 40mA. The HV
supply has an automatic shutdown feature that will turn off the amplifier if this maximum value
is exceeded.

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Front Panel Controls
This diagram shows the Liquid Glass front panel controls. The heater switch and B+ switch are on the
lower left. The input switch and output switch are on the lower right.