
41
PHONO INPUT MODULE JUMPER LOCATIONS
GAIN
J3, J4
HIGH GAIN
60dB
J3, J4
LOW GAIN
40dB
12Hz SUBSONIC FILTER (HPF)
J5, J6
HPF ON
HPF OFF
J5, J6
R14
C6
J3, J4: Closed: Hi Gain
-18
V
+18
V
R9
R23
C22
U4
J5
C21
L G R
U2
R16
R13C10
C13
R18
U3
R20
C12 C15
C7
U1
R11
R10
C8
C9
C11
C16
nE
N
R22
C18
G
N
D
R27
R26
R25
C1
9
C14
C17
R24
R28
R3
0
J6
R32
R31
C2
0
R2
9
D2
C23
MH2
Q4
C24
R3
3
R3
4
Q3
K2
Output
R15
R17
R19 R21
AT171
R G
Input
L
J3
J1, J2: Input Z
VR1
D
1
K1
MH1
R2
R1
Q2
R3
REV
GN
D
R4
R
6
C
2
J2
Q1
R5
R8
C1
R7
J1
-15
V
VR2
J4
+15
V
C4
C5
R12
C3
P1
71
Re
vA
J5, J6:
Closed:
Subsonic
Filter
CARTRIDGE LOADING
J2
J1
VARIABLE
0-500
Ω
FIXED
100
Ω
J2
J1
FIXED
47K
Ω
J2
J1
500
Ω
0
Ω
VR1, VR2
PHONO INPUT MODULE PCB
CARTRIDGE LOADING -
J1 and J2 and VR1-VR2 set the cartridge loading. Moving magnet cartridges will
typically be best matched by the 47k Ohm setting. The ideal load for a moving coil cartridge is typically
indicated in the product specifications. There are two options for loading moving coil cartridges: 100
Ohms and 0-500 Ohm variable. If you do not know the recommended load for your cartridge, 100 Ohms is
a good place to start. If you know the recommended load then you can use the adjustable setting.
To adjust the cartridge loading to your specified value, connect an Ohm meter to the Left channel RCA
input jack on the rear panel of the m905. Then, using a small screwdriver, turn VR1 until the desired resis-
tance is reached. Repeat for the Right channel by turning VR2.
GAIN -
J3 and J4 set the preamplifier gain. Use the low gain setting for most moving magnet (MM) car-
tridges. These cartridges will typically have an output voltage of 3-10mV RMS. For low output moving coil
(MC) cartridges use the high gain setting.
SUBSONIC FILTER -
J5 and J6 enable the 12Hz subsonic filter. This is a first order (6dB/octave) high pass filter
for reducing very low frequency information. This is typically turntable rumble and low frequency excur-
sion caused by warped records. Use this to protect the woofers in your speaker system from unnecessary
excursion.