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Page 10
1.4 Basic Operation of the Amplifier
The Audio Signal enters the amplifier via the RCA sockets in the back of the unit - the right (R)
and left (L) audio go directly to the selector switch along with 2 other pairs of RCAs. The Ground
from the RCAs are all connected together and go all the way to the GND connection on the
Volume Pot PCB via a solid core Black wire. The selected audio signal R & L goes to the input of
the volume pot. The output of the volume pot goes into the 12AU7 Input Buffer PCB – this is just
a low gain tube stage acting as a pre-amplifier. The output of the 12AU7 stage goes to the input
of the large ECF80/EL34 PCB. This PCB connect directly to the Output Transformers Primary
(Red and Black wires) – the Secondary or “output” of the Output Transformer connects to the
speaker posts. The ground and 8 Ohm of the speaker post connect back to the ECF80/EL34 PCB –
this is the feedback. That is the complete audio path of the EL34 Integrated!
The power supply consists of the Mains transformer and Choke, IEC/IEC PCB and rocker switch
– the AC 120V (North America) enters into the amplifier through the IEC and is sent to the
Primary of the Mains transformer where it is converted to various AC voltages that are
required by the amplifier. The first AC voltage is 0-275 AC which is used to create the HT (High
Tension) or maximum DC voltage that is required for the tubes to operate – it also creates a
pair of 6.3V AC 6A pairs which are used as filaments for the EL34 tubes to “light up”. Another
6.3V AC 1A pair is used to supply the filament voltage for the ECF80 driver tubes.
