The start of my build project and it is going quite well but due to my workload of repairs, taking a bit longer than anticipated.
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Getting there.

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Heater and HT wiring, wired and tested. Output stage, phase splitter and controls in progress.

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15th April 2019. The finished items, tested and ready for the case to be built.

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Below, the finished matched pair of type 66 all valve amplifiers.

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It has been two years since the conception, to design and build. Very satisfying to build from scratch a finished product. The output valves are Russian made matched quads of 6L6GC from the 60s, the preamp, phase splitter and drivers are 6AX7, (a Russian built ECC83 with twin 3.15 volt heaters instead of twin 6.3 volt). Nice smooth sound in both Ultra Linear and Pentode mode, which is switchable on the rear of the amplifier and has now a -3dB power drop switch alongside the Speakon output socket. The line up is Volume for Bright, Volume for Bass, Treble, Middle and Bass with Switchable Treble Boost for both inputs, Master Volume control and a Slope control for that extra little bit. The power meter gives a relative reading of the power leaving the amplifier. The amplifier draws 45 Watts in standby and 92 Watts in power on mode up to around 190 Watts depending on the power demanded from the musician. It boasts a Neutrik three pole 20Amp power connector and a Neutrik Speakon 4 pole socket for 3.75 - 7.5 Ohm (4 - 8 Ohm) speaker connector, (1+ and 1- are the poles used, as in standard 4 pole connectors) and a standard 1/4" jack socket for 7.5 - 15 Ohm (8 - 16 Ohm) speakers. This amplifier can use either four 6L6GC (5881) or two KT88 (6550) valves.

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Cabinet making now. Covering and strengthening batons, for the case, ordered along with corners, feet and leather handles.

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It gives me pleasure to pass on the feedback from professional guitarists, which are are extremely positive. Superb bass and clean treble is achieved, and enjoyable to play through. The opinion on the whole was it has a bit too much power in small venues, so I have fitted a -3dB switch to overcome that slight issue.

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Here it is on the test bench putting the 66 through its paces.

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The technical bit

Power Factor 0.86. Standby power 44Watts. Half Power mode 72Watts U/L mode 74Watts in P mode. Full power mode 90Watts in U/L mode and 95Watts in P mode. All measured with 245Volts 49.91HZ mains power and no signal.

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U/L mode is Ultra Linear Mode with 43% screen tapping. P mode is Pentode mode. No Signal is volume at zero with loudspeaker connected to SpeakOn output; 8R loading.
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