Fet version of the JCM800

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Frequency response in comparison with the original tube version

The first stage

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The second stage with different gain settings

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The third stage

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Schematics (pdf)

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Ready to transfer PCB (pdf)

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Upper side assembly (pdf)

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Bottom side assembly (pdf)

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Assembled board.

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With proper assembly, tuning is reduced to the adjustment of the drain voltage of transistors in accordance with the schematic by trimmer resistors.

Controls and input jacks (pdf)

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The process of assembling with micro PA.

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Samples kindly recorded Denis Soloviev (Denn).

Line recording, checking boost by Marshall Guv'nor Plus

Settings: Bass=7, Mid=6, Treble=6, Gain=7, Presence=6, Vol=8

Normal Output (external speaker simulator Behringer Ultra-G)

1st fragment - Guitar directly

2nd fragment - Guitar trough Marshall Guv'nor Plus (Gain=1, Vol=9)

3rd fragment - Guitar trough Marshall Guv'nor Plus (Gain=7, Vol=9)

Fragments in consecutive order

Trough Marshall Guv'nor Plus (Gain=1, Vol=9)

Settings: Bass=7, Mid=6, Treble=6, Gain=7, Saturation=1, Presence=6, Vol=8

Normal Output (external speaker simulator Behringer Ultra-G)

1st fragment - bypass on (bypass micro PA)

2nd fragment - bypass off (trough micro PA)

3rd fragment - bypass on (bypass micro PA)

4th fragment - bypass off (trough micro PA)

5th fragment - bypass on (bypass micro PA)

Fragments in consecutive order

Trough Marshall Guv'nor Plus (Gain=1, Vol=9)

Settings: Bass=7, Mid=6, Treble=6, Gain=7, Saturation=sweep, Presence=6, Vol=8

EQ Output (internal speaker simulator V30)

1st fragment - bypass on (bypass micro PA)

2nd fragment - bypass off (trough micro PA)

Fragments in consecutive order