ULTIMATE CHORUS
SPECIFICATIONS
Product Release No.: PR 204 (This is not a model number)
Input Impedance: Greater than 1M Ohm
Nominal Level: 100mV
Power output: 65 Watts RMS @ 5% T.H.D. per channel =
130 Watts RMS
Rated Load Impedance: 8 ohms per channel
Mono Effects Loop: Output impedance: 1kΩ
Input impedance: 25kΩ
Nominal level: -10dBV
Stereo Effects Loop: Nominal Level: -10dBV
Output Impedance: 1k Ohms
Input Impedance: 94k Ohms
Specifications for each channel –
Left on Tip, Right on Ring
Dimensions: Height:18 1/2" (47.0 cm)
Width: 26 1/8” (66.0 cm)
Depth: 10 1/4" (26.0 cm)
Weight: 47 lbs. (21.3 kg)
Product specifications are subject to change without notice
THEORY OF OPERATION
NORMAL CHANNEL
The first stage (U1A) sets up the initial response of the amplifier. It provides a second order high-pass filter
with a 3dB down point of 60 Hz, and a gain of about 4. The output of U1A splits to feed the NORMAL and
DRIVE channels. For the NORMAL channel, the signal feeds through the NORMAL VOLUME control
(R11) to U1B. The output of U1B drives through the tone controls and feeds summing amplifier U4A.
DRIVE CHANNEL
The signal from U1A feeds a special tone-shaping circuit which optimizes the frequency response for the
distortion circuit that follows. U2A provides the variable gain adjustment that drives the distrotion circuit. It
also acts as a bandpass filter with 3db down points at 90Hz and 4kHz. JFET Q2 mutes the input to the
distortion circuit when in the NORMAL channel mode. Diodes CR4 and CR5 are used as a voltage clamp
to prevent excessive voltage from damaging the JFET. U2b is the distortion circuit. The signal couples to
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