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Penncrest 50C5 Tube Console Amplifier
Model # 7703A-46
DT667 found a Penncrest AM/FM Phono console at a local thrift store several years ago.
The radio circuits were removed and chassis repurposed as SE stereo tube amplifier.
Single-ended 50C5 output stage driven by a cap couple 5751 twin triode.
10K ohm gird stoppers were added to 5751 driver stage and FBK network adjusted.
The power supply is a solid state diode rectified voltage doubler type with filter choke.
Schematic with operation points will be published soon.
DT667 2/26/2022
Penncrest SE 50C5 schematicS Pt.1
Signal Circuit
Penncrest Model # 7703A-46 signal circuit redesigned by DT667.
Operating points included on schematic.
DT667 2/27/2022
Penncrest Se 50C5 schematics PT.2
Power Supply Filter
Penncrest Model # 7703A-46 power supply filter redesigned by DT667.
Filter choke and extra filter capacitance added for quiet operation when using high efficiency Altec transducers or similar horn-type speaker systems.
Note: power transformer not shown on schematic.
DT667 2/27/2022
Penncrest 50C5 square waves
1KHz square wave NO FBK bypass capacitor
1KHz square wave with FBK bypass capacitor
1KHz square wave with FBK bypass capacitor
Overshoot and ringing clearly seen without FBK bypass capacitor.
1KHz square wave with FBK bypass capacitor
1KHz square wave with FBK bypass capacitor
1KHz square wave with FBK bypass capacitor
1nF FBK bypass capacitor added.
Overshoot and ringing are diminished.
Transient response of amplifier improved.
10KHz square wave with no FBK bypass capacitor
10KHz square wave with no FBK bypass capacitor
10KHz square wave with no FBK bypass capacitor
Overshoot and ringing clearly seen without FBK bypass capacitor.
10KHz square wave with FBK bypass capacitor
10KHz square wave with no FBK bypass capacitor
10KHz square wave with no FBK bypass capacitor
1nF FBK bypass capacitor added.
Overshoot and ringing are diminished.
Transient response of amplifier improved.