Atma-Sphere M-60 Mk. 3.2 Setup And Operation

Atma-Sphere M-60 Mk. 3.2
amplifier setup and operation
Installation
Place the amps in your system. Allow for adequate cooling- do not set the amp on a carpet, and if in a cabinet you may have to
set up a cooling fan as well. Connect the preamp cable to the appropriate input connector on the rear of the amp. If you use the
RCA input connector, make sure a shorting jumper is installed between pins 1 & 3 on the XLR connector else a buzz may 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 middle four sockets take the 6SN7GT driver tube (if using NOS 6SN7s, the front location
should have either a -GTA or -GTB suffix). All other sockets take the 6AS7G output tube. A total compliment of four driver and
eight output tubes are required per each chassis. Engage the main power switch (left edge of chassis, amber lamp) and verify that
the amber indicator lights. In about 15 seconds, the filaments of all tubes should be visibly glowing orange. Wait at least one
minute, then engage the standby switch (right side of chassis) and verify that the red indicator lights. The amplifier is now fully
powered up.
Meter Range/Meter Switch
The meter operates all the time. The middle toggle switch controls its range. Up is is the high range- full output from the amplifier
will result in full scale deflection. Down is 1 watt for full scale, and is useful on high efficiency speakers and the DC Offset Null
adjustment. The meter is calibrated for 8 ohms.
DC Offset Null adjustment:
Place Meter Switch in the down position. Examine the reading on the VU meter and adjust the DC Offset control to produce a
-20db reading (all the way to the left). Note that if you overshoot the setting the meter will rise again- set for the lowest reading.
Bias is automatic. Note: It may not be possible to null the DC Offset if there are defective tubes in the amplifier.
Operation
The amplifier is now completely operational. It can be set in Standby or fully On at will. Some bluish florescence of the output
tubes is normal.
The M-60 is the most neutral and musical 60-watt amplifiers available. It is quite transparent. Be prepared to hear things you have
not heard before- both good and bad. Many preconceived notions may have to go in order for you to get the most out of the M-
60. We recommend that as you make improvements in your system, make only one change at a time in order to understand its
significance. Feel free to contact Atma-Sphere for advice.
Fuses
The first fuse by the power cord entry is the Output section B+ and is 3 Amp Slow (1.5A slow for 235V). The second fuse is for the
output filaments and is 3 Amp Slow (1.5A for 235). The last fuse controls the driver circuit and is 0.5 Amp slow (0.25A Slow for
235 Volt). WARNING! To avoid fire hazard, always replace fuses with same type and rating.
ROHS
© 2012 Atma-Sphere Music Systems Inc
1742 Selby Ave.
St. Paul, MN 55104
651-690-2246