Linear Tube Audio ZOTL40 Reference User manual

USER GUIDE: ZOTL40 Reference
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 ZOTL40 Reference is a Class AB tube amplifier utilizing ZOTL
(Zero-hysteresis Output Transformer-Less) technology. It is a stereo
power amplifier that can also be used in a mono-block
configuration.

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 such 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 AB
Power Output: 51W (4 Ohm), 46W (8 Ohm)
Input Sensitivity: 1.2V RMS for full output
Input Impedance: 50K
Output impedance: 1.6 Ohms
Gain: 23dB
Noise: -94dB
Frequency Response: +0dB, -.5dB, 8Hz-50kHz
Input Voltage: Universal
Tube Complement: (2x) 12AU7, (2x) 12AX7, (4x) EL34
Size: W: 17” (43cm), H: 5” (12.7cm), D: 13.875” (35.2cm)
Weight: 17.5 lbs (7.9kg)

Quick Start
Remove amplifier from the box.
Check that the MONO/STEREO switch on the back is in the correct
position for your setup. (see Operating Modes for more
information)
Attach the power cable to the IEC connector and plug into an
outlet. The ZOTL40 Reference uses a Berning-designed auto-
switching power supply and can be used universally.
Hook up your source and speakers.
Once your system is set up and everything is plugged in, turn your
system on. The Z40 Reference is powered on and off via the toggle
switch in the center of the face plate.
When first powering on, the tubes can take 30-45 to warm up
before music starts playing. Sometimes there is a high-pitched or
distorted sound during this time. This is normal and will go away
once the amp is warmed up.

Operating Modes
MONO/STEREO Switch: Two ZOTL40 Reference 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 MONO/STEREO switch to Mono.
2. Use the left RCA input.
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 bright, white LEDs will
light up on the audio board, which should be visible through the
top of the case on the left side (if you are looking at the front of
the amp). More obviously, if the amplifier goes into protection it will
stop playing when turned on. Be sure to check that it is the
amplifier causing the problem and not another component.
To reset the circuit, simply turn it off, wait a few minutes, and turn
the amplifier back on. If the amplifier does not reset successfully,
or goes into protection again immediately, try waiting an hour
before turning back on. If the amp is still unresponsive, or if the
protection circuit is continuously triggered, contact us.

Tubes
The ZOTL40 Reference is supplied with selected vintage tubes
including old-stock Mullard EL34s. The tubes operate at low
current, which allows them to have an extended life.
Changing tubes:
EL34: The power tubes are self-biasing and do not need to be
matched for gain.
12AX7: The 12AX7s should be a matched pair.
12AU7: The 12AU7s should be a matched pair.
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.
Fuses: The ZOTL40 has two fuses on the power board and a fuse in
the IEC assembly. The fuses on the power board are one 3AG size,
4A, slow-blow fuse and one 5x20mm, 2.5A, slow-blow fuse. In the
IEC assembly, there is a 5x20mm, 4A, slow-blow fuse.
For more information and FAQs, please visit
www.lineartubeaudio.com or contact us at
[email protected].

NOTES