Tuesday, 2 October 2018

Marshall JCM800 Super Lead

Next up we have the Marshall JCM800 Super Lead.



With a switch to go between channels


With 2 separate inputs like the amp


With both channels jumpered



Note: I'm certain it will work, it's the same as the Sunn Model T preamp with modified component values, but will not mark it verified until someone builds it and verified the tone.

6 comments:

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  2. If I build the version with the switch to go between the channels, is the center position jumpered with an on/on/on?

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    1. Well it shouldn't be because in a real 2204 the low input skips the first triode while the high input goes into the first triode which then goes to the second triode. So the first two tube stages are used in series rather than the typical parallel of the Bassman and Plexi. The switch should really be only two positions. And I don't know of anybody who uses the Low input because it is a LOT lower than the high input. The first triode is used pretty much as a clipping stage - it's not a normal gain stage.

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  3. Comparing with the Laney Supergroup 100 MKI Preamp layout, it's very similar. With all of these preamp circuits being virtually the same, one could probably build the vero with sockets where the modifications happen. I built the Laney with the middle, polarized caps socketed. If I toss in the JCM800 values, should I expect more low-end?

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    1. You’re dead on. As I mentioned in the Fender Bassman preamp all these amps are basically the Fender Bassman with value changes giving them their distinctive characteristic. The Laney is much thicker sounding compared to the Marshall, which is one of the reasons Tony Iomi used a treble booster in front of his Laney Supergroup.

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