Atma-Sphere MA-1 Mk.II Owner's Manual

ATMA-SPHERE MUSIC SYSTEMS, Inc.

160 So. Wheeler
St. Paul, MN 55105
Phone: [phone]
FAX: [phone]
http://www.atma-sphere.com

MA-1 Mk.II.2 amplifier quick setup and operation instructions

Installation:

Emplace the amps in your system. Connect the preamp cable to the appropriate input
connector on the front of the amp. If you must use the RCA input connector, make sure the shorting plug is
installed between pins 1 & 3 on the XLR connector else a buzz will result. Verify that both power switches
are OFF and connect AC power to the AC input connector on the rear of the amp. Connect the negative
speaker cable to the negative output terminal and the positive speaker cable to the positive output terminal.

Setup:

Install the tubes in their sockets. The front group of four sockets (no cooling holes) take the
6SN7GT driver tube. All other sockets take the 6AS7G output tube. A total compliment of four driver and
fourteen output tubes are required per each chassis. Engage the main power switch (edge of chassis) and
verify that the amber indicator lights. In about 15 seconds, the filaments of all tubes should be visibly
glowing orange. Rotate the BIAS control (beside the input connectors) fully counterclockwise. Wait at least
one minute, then engage the standby switch (other big toggle switch) and verify that the red indicator lights.
The amplifier is now fully powered up.

Bias adjustment:

Initially, rotate the Bias control (next to the input connector) fully
counterclockwise. Depress both the Test/Operate switch (edge of chassis opposite the power switches)
and the Bias Test switch (next to the Test/Operate switch) and the meter will rise to indicate the bias
reading. Use the Bias control (next to the input connectors) to set the meter as follows: Cold amp = .650A /
Hot amp (final setting) = .750A. Release the Bias Test switch as soon as you have made your adjustment.
If the amp is biased when cold, you can expect the bias to increase notably as it warms up, thus the
difference in settings between cold and hot. Check bias on a new amp daily until it has stabilized, typically
after 10-20 hours of use. When bias has stabilized it can be expected to stay in adjustment for extended
periods.

DC Offset adjustment:

Depress the Test/Operate switch (at the edge of the chassis, opposite the
status indicators). Examine the reading on the bias meter. If it is NOT zero (above OR below) adjust the DC
offset control (closest to the bias test switch) to bring the meter to a zero reading. The bias and DC offset
controls interact somewhat, so the bias and DC Offset procedures must be repeated.

Operation:

The amplifier is now completely operational. The amplifier can be left in either standby
or operational mode indefinitely. We recommend using the Standby feature if you are not listening to the
amp.

Fuses:

The first fuse by the power cord entry is the Output section B+ and is 5 Amp Slow (2.5A
slow for 235V). The middle fuse is the filament fuse and is 5 Amp Slow (2.5A for 235). The last fuse
controls the driver circuit and is 1 Amp slow (.5A Slow for 235 Volt). WARNING! To avoid fire hazard,
always replace fuses with same type and rating.

©1999 Atma-Sphere Music Systems Inc. 160 So. Wheeler St.Paul, MN. 55105 651.690.2246 / fax [phone]

ATMA-SPHERE MUSIC SYSTEMS, Inc.

160 So. Wheeler
St. Paul, MN 55105
Phone: [phone]
FAX: [phone]
http://www.atma-sphere.com

LIMITED WARRANTY ON ATMA-SPHERE® MUSIC SYSTEMS PRODUCTS

This warranty on your ATMA-SPHERE® MUSIC SYSTEMS product, which is distributed and warranted by
ATMA-SPHERE® MUSIC SYSTEMS, shall remain in effect for two (2) years from the date of consumer
purchase, provided the enclosed registration form is completed and returned to ATMA-SPHERE® MUSIC
SYSTEMS within ten days of purchase.

WHAT IS COVERED:

Except as specified below, this warranty covers all defects in materials and workmanship. The following are
NOT covered by the three year limited warranty:

• Vacuum tubes are covered for one (1) year, with the following exclusions, as per the rest of the warranty:

• Damage occurring during shipment (present claims to carrier).

• Damage resulting from failure or inability to follow proper instructions.

• Damage resulting from the performance of repairs or modifications by other than ATMA-SPHERE® MUSIC
SYSTEMS.

WHAT WE WILL PAY FOR:

ATMA-SPHERE® MUSIC SYSTEMS will pay for all labor and material expenses for repairs covered by this
warranty.

HOW TO OBTAIN WARRANTY SERVICE:

If your unit requires repairs covered by this warranty, you MUST obtain a return authorization number from
ATMA-SPHERE® MUSIC SYSTEMS. You are responsible for transporting the unit to ATMA-SPHERE® MUSIC
SYSTEMS, 160 So. Wheeler St., St. Paul, Minn. 55105. You must pay the initial shipping charges, but ATMA­SPHERE® MUSIC SYSTEMS will pay the return charges, if the repairs are covered by the warranty. All
products MUST be shipped in the original carton(s) or in replacement cartons supplied by ATMA-SPHERE®
MUSIC SYSTEMS. Contact ATMA-SPHERE® MUSIC SYSTEMS for replacement cartons and cost.

LIABILITY IS LIMITED TO THE REPAIR OR REPLACEMENT, AT OUR OPTION, OF ANY DEFECTIVE

PRODUCT AND SHALL IN NO EVENT INCLUDE INCIDENTAL OR CONSEQUENTIAL DAMAGE OF ANY

KIND.

This warranty is not transferable. Implied warranties of merchantability and fitness for a particular purpose are limited in duration
to the length of this warranty. This warranty sets forth all expressed warranties made with regard to the above-referenced
product. We neither assume nor authorize any other liability in connection with the sale or any shipment of products. This
warranty gives you specific legal rights and you may also have other rights which vary from state to state. We reserve the right to
make changes and improvements in our products without incurring any obligation to similarly alter products previously
purchased.