13
Agency.
The MC901 will function optimally with any correct
tube type that is functioning within the design
specifications of the MC901. Only when a Tube falls
outside of the acceptable range will any diminishing
of performance be heard. Because McIntosh Tube
Amplifiers are engineered to use Tubes in a way that
does not rely on the Tube’s individual character and
can perform perfectly provided the specifications are
met, there is no advantage to seeking out expensive
esoteric tubes.
Over time, a Tube may fall out of the proper
specification range. New Tubes that meet the
MC901’s specifications can be ordered using the Part
Numbers on page 12. For the positions of the tubes,
see Figure 15. This pattern is found on each side of
the MC901.
The Front of the MC901
The Dual Meter
The MC901 has a custom Dual Meter which
displays the power output for both the Vacuum Tube
and Solid State Amplifiers. The Vacuum Tube scale
is displayed on the top and the longer needle will
point to the current output. The Solid State scale is
on the bottom and indicated by the shorter needle.
The Dual Meter provides an accurate measurement
of power to safely know what wattages are sent to
the attached speaker.
The Dual Meter uses a logarithmic scale represented
as decades on the meter scales. This means that the
scale is increasing 10-fold at each marker. In this
way, small changes can be visible when listening at
lower volumes. Output peaks are held momentarily
and then decay so that the values are easier to track.
Without this feature the pointer might appear like an
endlessly moving blur.
KT88
KT88
KT88
KT88
12AX7A
12AT7
12AT7
Figure 15– Vacuum Tube Positions
60
600
6.0
.60
- 50
- 30
- 40
-20
-10
0
1.
2K
60
6.0
m
m
30
300
3.0
.30
- 50
- 30
- 40
-20
-10
0
60
0
30
3.0
m
m
WAT T S
D E C I B E L S
P O W E R O U T P U T
Figure 16– Dual Meter
