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Green God: Manifesto SE Breadboard Amp
Manifesto SE Top View
Manifesto SE Front View
Manifesto SE Front View
DT667's new SE amplifier project.
The Green God "Manifesto" is a SE breadboard style amplifier for experimenting with 6V6 tube types and octal twin triode driver stages.
Manifesto SE Front View
Manifesto SE Front View
Manifesto SE Front View
The Green God Manifesto SE breadboard amplifier: power supply and signal circuit modules resting inside their enclosure.
Ready for subjective review with Altec 414-8B/811B/808-8A two-way horn system.
Green God: Manifesto SE Power supply
Power Supply Top View
Power Supply Bottom View
Power Supply Bottom View
The power supply features: Hammond ICT 460VCT, 5U4G rectifier tube bypassed with UF4007 diodes, Triad and Edcor chokes configured in a LOW DCR choke input flywheel filter - LCLCRC with 200K ohm bleeder resistor.
Power Supply Bottom View
Power Supply Bottom View
Power Supply Bottom View
All amplifier grounds connect to a single point on the power supply module. The IEC socket is a filtered type. Wima DC Link and Nichicon filter caps with GE Genteq bypass. Daven wirewound dropping resistor for driver stage B+. The power supply connects to the signal circuit via umbilical that uses 400VAC rated aviation connectors.
Green God: Manifesto SE signal circuit
Signal Circuit
The signal circuit features an octal twin triode with active plate load driving single ended triode-connected beam tetrode finals which are cathode biased.
The driver tube is an octal 6SL7 and output tube is a loktal 7C5.
Parts used: Vishay 400K ohm 1% grid resistors, 290 ohm cathode bias resistors with Sanyo OsCon 56uF 25V bypass capacitors, and green DuPont Mylar .1uF coupling capacitors - these might get upgraded eventually but sound absolutely fine.
Heyboer SE 5K/8 14W output transformers - secondary common leads are floating.
B+ for driver and output stages is about 300VDC.
AC ripple measured at speaker posts = 0 - 1 mV, the amplifier is silent at idle.
DT667 5/14/2023
Measurement DATA
Operating Points
7C5 left channel: 286V plate, 285V G2, 14.86V cathode.
7C5 right channel: 287V plate, 286V G2, 14.40V cathode.
Rk = 290 ohms with 56uF bypass.
7C5 finals biased to 13.5 - 14 watts on plate.
855mW before clipping in triode mode.
6SL7 left channel: 182.50V plate, 1.67V cathode.
6SL7 right channel: 182.50V plate, 1.75V cathode.
C4S set to 1.35mA, Rk adjusted to set plate voltage.
DT667 5/29/2023
Square Waves at output with 8 ohm loading
100Hz
100Hz
100Hz
100Hz square wave just before clipping.
NOTE: significant tilt to the waveform.
1KHz
100Hz
100Hz
1KHz square wave just before clipping.
NOTE: there is a slight tilt but no significant overshoot or ringing.
10KHz
100Hz
10KHz
10KHz square wave just before clipping.
NOTE: the output of the C4S loaded 6SL7 driver stage was producing this triangle waveform and it was amplified by the final stage.
Subjective review with determine if the active loaded driver stage will remain or be replaced by a plate load resistor.
DT667 5/29/2023
Coupling Capacitors
Gudeman Oil Capacitors
The green DuPont Mylar .1uF 600V capacitors were removed in favor of Gudeman .056uF 600V oil capacitors.
Prior to installing the Gudeman capacitors: the outer foil side was identified with an o-scope, outer plastic covers were removed and Kimber TCSS 19AWG copper wire installed as lead out wires.
Like other Vitamin Q oil capacitors, the Gudeman capacitors seem to require some breaking in to sound good. These caps were veiled and harsh sounding at first, but seem to be slowly smoothing out with additional service hours.
DT667 has also acquired Sprague Vitamin Q .15uF 400V oil capacitors to try at some point in the future.
DT667 6/4/2023
