Specifications

S E T T I N G U P
The Pre 1 comes with seven tubes, as follows:
5AR4 RECTIFIER TUBE
The tube socket for this tube is located in the power supply.
This tube functions as a full wave rectifier, converting the AC
supply to DC. A tube was chosen for this function because
a semiconductor tends to sound harsh in this application.
As well, when switching to high voltage, the tube has a slow
turn-on, providing a gradual “soft” start which is easier on
the circuitry and the other tubes. This tube may be replaced
with the 5Y3 rectifier tube; but note a difference in perfor-
mance may be heard, the 5AR4 performs better than the
5Y3 when the operating voltage is low.
6922 (LV1 & V1) FIRST INPUT STAGE TUBES
These Russian Sovtek tubes were chosen for their reliabili-
ty and extremely low noise performance. When dealing
with the low voltage, sensitive signals of phono cartridges,
this is imperative that a tube is quiet. The 6922 tubes may
be replaced with a matched set of ECC88/6DJ8s or
E188CC/7308s with no circuit modification.
1 2 AT7 (LV2 & V2) SECOND INPUT STAGE TUBES
These tubes provide the drive as the output stage of the
phono section. The signal levels are padded by the
High/Low gain slide switches preceding the linestage
(typically set to “high” for MC-moving coil and “low” for
MM-moving magnet). The 12AT7 tubes may be replaced
with a matched set of ECC81s or 6201s with no circuit
modification.
6922 (LV3 & V3) LINE STAGE TUBES
These tubes were again chosen for their reliability and
extremely low noise. This single tube configuration delivers
good drive and output current to the power amplifier. The
tubes’ quietness heightens dynamics and they are tonally
natural. The 6922 tubes may be replaced with a matched
set of 6DJ8s with no circuit modification.
INSERTION OF THE TUBES
1. Using the screwdriver supplied, remove the cover of
the Pre 1. For your convenience, only two of the screws
are installed at the factory.
2. When handling the tubes, it is recommended that the
cotton gloves provided be worn to prevent skin oils from
depositing on the glass surface and possibly causing the
tube to become prematurely “gassy”, thereby shortening
the tube’s useful operating life.
3. Noting the location of the tube sockets in the top view
photo/or directly on the PC Board, inspect the tubes for
corresponding labels and markings. Once locations are
mapped, take a tube and inspect the pins, noting the
larger space between two of the pins or the key peg on
the 5AR4 (see Figures 1 & 2). This space or key will
match with the socket. Insert each tube into the appro-
priate tube socket, making sure all pins and pin holes are
aligned. Do not force the tubes into the sockets. “Rock”
the tubes gently while pushing slowly until each tube is
firmly seated.
WARNING- DISCONNECT THE AC
DETACHABLE POWER CORD FROM THE
PRE 1 AND WAIT 5 MINUTES BEFORE
REMOVING COVER, TUBES OR FUSE.
Note the larger space
between two of the pins and
holes for proper alignment
of tube and socket.
Note the key on the centre
peg and hole for proper
alignment of tube and socket.
Figure 1
Figure 2