Linear Tube Audio ZOTL10 Mk.II User manual

USER GUIDE: ZOTL10 Mk.II
Linear Tube Audio Takoma Park, MD, USA
301-448-1534 [email protected]
WARNING: For safety, the cover of this amplifier should be secured
at all times.
This amplifier contains extremely high voltages and the user should
not attempt to service the amplifier. Furthermore, this amplifier
generates radio-frequency energy that can interfere with
communications equipment.
Introduction
The ZOTL10 is a Class AB tube amplifier utilizing ZOTL (Zero-hysteresis
Output Transformer-Less) technology. It is designed as a power
amplifier, but has a volume control in order to be used directly
from high-output sources.

Limited Two-Year Warranty*
1. Your new product is covered by a limited two-year warranty
against defects in material and workmanship. Any repairs
required will be made at no charge within the first two years after
purchase as a new unit.
2. Any units returned for warranty repair must be shipped prepaid
after receiving return authorization. If possible, the unit should be
shipped in its original packaging. If this is not possible, the unit
should be well packed with particular attention paid to protection
of all corners and avoidance of any looseness in the carton.
3. This warranty does not apply to damage resulting from physical
abuse or unauthorized alterations or repairs, or from tube rolling or
adapter use, or from the use of third-party components, or
damage to exterior finish resulting from careless use.
4. The warranty is void if the serial number has been removed,
altered, or defaced.
5. This warranty is void if improper voltage is applied to any input or
output.
6. If Linear Tube Audio determines after receiving the unit that
damage was misrepresented and has been caused by something
not covered by the warranty, the customer must pay for any
necessary repairs before the unit is returned to the customer.
7. Linear Tube Audio reserves the right to improve or change its
products without obligation to modify previously manufactured
units.
* Applicable for domestic sales only. There is a one year warranty
for overseas customers. Handling and shipping costs are the
responsibility of the overseas customer.
Service Note
ZOTL amplifiers use a unique circuit and even trained technicians
familiar with tube amplifiers may not know how to correctly work
on LTA products. Please contact us before attempting any
alteration or repair, whether you are concerned about the
warranty or not.!

Specifications
Circuit Type: Push-Pull Class A
Power Output: 12W (4 Ohm), 10W (8 Ohm)
Input Sensitivity: 1.2V RMS for full output
Input Impedance: 50K
Output impedance: 1.2 Ohms
Preamp Output Impedance: 50 Ohms
Gain: 18dB (8 Ohm load)"
Noise: -94dB
Frequency Response: +0, -0.5dB, 6Hz-60kHz (8 Ohm Load)
THD: 0.5%
Input Voltage 110/220 Selectable
Tube Complement: (2x) 12AU7, (2x) 12AT7, (4x) EL84
Size: Amplifier: W: 9” (23cm), H: 8.5: (22cm), D: 18” (46cm)
Shipping Weight: 14 lbs (6.4kg)

Quick Start
Remove amplifier, power supply, and included cables from the
box.
Attach the AC umbilical cable to the power supply and amplifier.
Be sure to tighten the cable’s locking connectors.
Check that the Stereo-Mono and Direct-W/Vol switches (see
Operating Modes for more information) on the back are in the
correct position for your setup, and that your interconnects and
speaker cables are hooked up to the appropriate connectors.
Only one source should be connected at a time.
Attach the power cable to the IEC connector on the power
supply, and plug into an outlet. Above the IEC outlet on the power
supply there is a window showing the selected AC input voltage.
Be sure that it is set correctly for your country’s voltage. If it does
not match, or if you would like to change it, contact us for
instruction.
Hook up your preamp (or other source) and speakers.
Once your system is set up and everything is plugged in, turn your
system on.

Operating Modes
DIRECT: RCA inputs go directly to the amplifier, bypassing the
volume control.
W/VOL: RCA inputs go through a volume control, adjustable via
the front panel knob.
Stereo/Mono Switch: Two ZOTL10 amplifiers can be operated as
mono-blocks, which deliver approximately 1.7x the power into 8
Ohms. To operate in the mono mode:
1. Set the Stereo/Mono switch to Mono.
2. Use the left input of either the DIRECT or W/VOL pairs of
RCAs, depending on which you plan to use.
3. Using jumpers cables, bridge the two positive (red)
speaker terminals together and bridge the two
negative (black) speaker terminals together. DO NOT
CONNECT the red and black speaker output terminals
together, as this shorts the amplifier. Once bridged,
either positive terminal and either negative terminal
can be used to connect your speaker.
Protection Circuit
The amplifier is DC-coupled and has a protection circuit that will
shut down the amplifier internally if certain parameters are sensed.
The protection circuit can also be triggered by over-driving the
amplifier. If the amplifier goes into protection, which is signaled by
the amplifier being turned on but not playing music (be sure to
check that it is the amplifier causing the problem and not another
component), simply turn it off, wait a few minutes, and turn the
amplifier back on. If the amplifier does not reset successfully, try
waiting an hour before turning back on. If the amp is still
unresponsive, or if the protection circuit is continuously triggered,
contact us.
Fuses
There are two 5x20mm 4A Slow Blow fuses in the IEC inlet of the
Power Supply.

Tubes
The ZOTL10 Mk.II is supplied with selected vintage tubes. The tubes
operate at low current, which allows them to have an extended
life.
Changing tubes:
EL84: The power tubes are self-biasing and do not need to be
matched for gain.
12AT7: The 12AT7s should be a matched pair.
12AU7: The 12AU7s should be a matched pair and each individual
tube should have both of its triode sections matched as well.
The sockets are tight, so gently rock the tube pins until you are
able to remove the tubes. We use high-quality ceramic tube
sockets with gold pins which are designed in such a way that the
white ceramic part may shift slightly. This is an intentional design;
the tube socket is very secure.
Before changing tubes, turn off the amplifier and wait at least 10
minutes to allow the stored power to discharge. Avoid touching
any of the components on the circuit board, especially the
vertical circuit boards.
Note on using 7062 tubes:
The 7062 is often used as a replacement for the 12AT7. This is
usually not a problem, but they do require slightly more heater
current than a standard 12AT7, which in turn requires slightly less
current than a standard 12AU7. If you want to use 7062 tubes,
you’ll need to replace both the 12AT7s and the 12AU7s with 7062s
in order to ensure that all tubes receive adequate heater current.
For more information and FAQs, please visit
www.lineartubeaudio.com or contact us at
[email protected].

NOTES