Ground Switch - YORKVILLE AP4020 - V2 Manual

Introduction
Your new Yorkville AP4020/4040 power amplifier is designed and built to provide years of trouble free performance. The
AP4020/4040 combines the field proven reliability of our Audiopro amplifiers with customer requested features such as switch-
able limiters, a Mono/Stereo/Bridge switch, and SPEAKON™ output connectors as well as binding posts.
The AP4020/4040 weighs a comfortable but solid 42 pounds, fits into two rack spaces, and reproduces music with over 4000 Watts of
headroom. It will drive reactive phase shifted loads with no difficulty - even though it is fully protected from accidental short circuits. Our
design goal was to create an amplifier which would do exactly what an amplifier should do: reproduce music with great power, com-
plete reliability, and uncompromising signal fidelity. We think you will agree that the Yorkville AP4020/4040 does exactly that.
Inputs
Balanced Inputs
Either XLR or two–circuit 'Ring, Tip, Sleeve' Stereo 1/4-inch
PHONE cords may be used. Each channel's XLR input is inter-
nally paralleled with its phone input (The TIP of the channel 'A'
PHONE input is connected to pin 2 of its XLR input, the RING is
connected to pin 3, and the Sleeve is connected to PIN 1). PIN
2 is in phase, PIN 3 is 180 degrees out of phase, and PIN 1 is
ground. We recommend using balanced lines for the best hum-
free performance, particularly when chaining multiple amplifiers.
Unbalanced Inputs
Ordinary single circuit Standard 1/4-
inch PHONE plugs may be used to con-
nect unbalanced signals. IMPORTANT
NOTE: Such plugs effectively connect
the ring terminal to sleeve ground, so
they work correctly. However, if you use
a Stereo 1/4-inch PHONE plug on an
unbalanced line, you MUST short the
Ring terminal to the sleeve terminal, oth-
erwise the sensitivity will be 6dB lower
than is specified! (The same applies to
the XLR input: To connect an unbal-
anced source via the XLR input, you must
connect the signal to Pin 2 and ground
BOTH Pin 1 and Pin 3).
Remote Referencing
You can approach balanced perfor-
mance with unbalanced sources by utiliz-
ing the remote reference feature of the AP4020/4040 . Connect
a balanced cable to the AP4020/4040 just as you would if you
were running a balanced line. At the other end, connect Pin 3
and Pin 1 together, (or connect ring to sleeve if you are using
a PHONE plug cable), and plug this modified end into your
unbalanced piece of equipment. This connection enables the
AP4020/4040 's input to look down the cable directly at the
output jack of the unbalanced equipment. Any hum voltage
generated across the cable's impedance will be attenuated by
the common mode rejection of the AP4020/4040.
Driving Multiple AP4020/4040's
In large installations it is often desirable to operate many
amplifiers in tandem. Since each channel's XLR input is inter-
nally paralleled with its phone input, you may use the remain-
ing input jack as an output to the next amplifier. Obviously
you will need both XLR to XLR and PHONE to PHONE patch
cords if you are going to tandem more than two amplifiers.
NOTE: These patch cords MUST be balanced whether the
input signal is balanced or unbalanced!

Ground Switch

Switching the ground switch on
the rear panel will disconnect chas-
sis ground from circuit ground. Safety
(earth) ground is still connected to the
chassis. We do not recommend lifting
the ground strap unless you are experi-
encing problems with ground loop hum
in multiple amplifier setups where lifting
the ground straps of all but one ampli-
fier cures the hum problem.
CAUTION: Sometimes hum problems
are an indication of improper AC wir-
ing somewhere else in your system.
Don't just doctor the symptom by lifting
grounds. Fix the cause by making sure
that the proper electrical wiring safety
regulations have been adhered to.
Modes
Mono Mode
• Channel A & B inputs are paralleled
• Each gain control adjusts the signal level for its respec-
tive channel
• Output signals are of equal phase.
• Two loads are driven.
• Loads are connected between the BLACK and RED post
on each channel.
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