так отвечаю сам на свой вопрос, думаю инфа может кому-нибудь пригодиться
Revision A
Date: 6/20/67
Serial Numbers: 101-125
•Original 1176 designed by Bill Putnam.
•Used FET as voltage variable resistor to control the gain.
•Input Stage: 600 ohm input transformer.
•Used ‘T-pad’ resistive attenuator to drop the input voltage.
•Signal Preamp: Used FET in a voltage divider configuration for GR.
•Used FET followed by bipolar as preamp.
•Output amp: Used essentially the same circuit as in the preamp, but followed it with a 2N3053 operating in class A.
•Output transformer: Used a UA-5002. This transformer has split secondary, tertiary winding for negative feedback, emitter winding. The design was basically that of the 1108 preamp.
•Faceplate is brushed aluminum with blue paint and red power light.
Revision AB
Date: 11/20/67
Serial Numbers: 125-216
•Changed several resistor values in signal pre-amp stages. # This improved stability as well as noise.
•Added bypass cap around the resistor feeding the GR FET. # This improved stability.
Revision B
Date: Not indicated
Serial Numbers: 217-1078
•Replaced FETs in the signal pre-amp with bipolar transistor (2N3391A).
•Tapped off of the emitter of the first transistor in the input stage.
•This provides a replica of the input voltage to the voltage variable resistor.
Revision C (1176 LN)
Date: 1/9/70
Serial Numbers: 1079-1238
•Low noise ‘LN’ circuitry was added in the signal preamp.
•Reduces DS voltage on the GR FET. Keeps the FET within its linear range.
•Q-bias pot added which is used to adjust for minimum distortion.
•The LN Circuitry was built in a module that was encased in epoxy to protect the circuit.
•This module was mounted on the Rev B circuit board
•Faceplate is black
Revision D
Date: Not indicated Serial Numbers: 1239-2331
•No circuit changes.
•The LN module was no longer used and the circuit board was redesigned to accommodate the LN circuitry on the main board.
Revision E
Date: Not indicated
Serial Numbers: 2332-2611
•The power transformer was changed to accommodate 220V operation.
•A switch was added to change between voltages.
Revision F
Date: 3/15/73
Serial Numbers: 2611-7052
•Output amplifier changed to a push-pull configuration from the original class-A design. This provided more output drive, and was based on the 1109 preamp.
•Changed the metering circuit to use an op-amp.
Revision G
Date: Not indicated
Serial Numbers: 7053-7651
•Removed the input transformer, and replaced it with a differential amplifier.
Revision H
Date: Not indicated
Serial Numbers: 7652- 8000+
•Faceplate is silver with red “Off’ button.
•This is the only revision with a blue UREI logo.
