WIRING THE INPUT TRANSFORMER
The input transformer for the kit uses
a 4:1 ratio — a loss of about 12dB — to tame levels before they hit the
gain reduction FET. The FET can’t handle high input levels so the transformer
is used to step the input signal down.
The Cinemag transformer offered with the
kit is a 4:1 ratio transformer. The leads attached are different colors
Red, Black and Green. Twist these 3 wires together before soldering. Connect
the Input XLR's pin-2 (hot) to the Cinemag's red wire. Connect Input XLR's
pin-3 (low) to the Cinemag's black wire. Connect the Input XLR's pin-1
to the Cinemag's green wire.
Position the input buffer amp PCB and the
transformer in close proximity to the Input XLR. Trim the transformer leads
if necessary to keep the runs as short a possible.
The secondary of the transformer consists
of blue and white wires. Twist these two wires together, measuring out
a length that will reach the FET input PCB at header J1. Trim the wires
if needed. Punch the white wire to pin-1 of J1’s receptacle. Punch the
blue wire to pin-2 of J1’s receptacle. The input transformer is now connected.
If you use a St. Ives 31267 multi-tap transformer,
you will need to wire the primary in series and the secondary in parallel
in order to use it as a step-down 4:1. Tie pins-3 and -4 together. Pin-2
of the XLR Input connector goes to pin-2 of the transformer. Pin-3 of the
XLR input connector goes to pin-5 of the transformer.
Tie the St Ives secondary — pins-7 and
-8 — together. Run a wire from pin 7-8 to the FET input PCB’s header receptacle
J-1 at pin-2. Pins 9 and 10 will also be tied together. Run a wire from
that junction to header receptacle pin-1. Pin-6 — the screen of the St.
Ives transformer — should be connected to chassis ground.