Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Backwoods Joe on December 12, 2019, 05:45:33 pm
-
Sorry I can't remember the name of the schematic, but someone on this board has a schem for a 2 channel JCM800 type with channel switching that is tried & true. THX, joe
-
Are you maybe referring to my Marshall Dual 50? Look in Hoffman's schematic library.
-
Sluckey the schematic i'm thinking about has a master vol for each channel
-
I seem to remember that. I think each channel also had it's own tone stack? I don't recall the particular thread though. But if it was on this forum you should be able to find it using the search button.
-
Yea it was two complete separate channels & it used relays (for & aft) for switching.
-
I found this thread but this one has shared tone stack so not sure if its the one you were looking:
http://el34world.com/Forum/index.php?topic=24600.0 (http://el34world.com/Forum/index.php?topic=24600.0)
-
I simply modified Sluckey's Dual Marshall so each side has it's own tone stack. On the attached SCH file there is a second page with the B+ rail, bias and PT. I haven't built it but see no reason why it shouldn't work well.
With respect, Tubenit
-
Hi All,
Looking at the schematic Tubenit shared with us, I wonder if it would be possible to switch between the 2 preamps right after the CF and eliminate V4?
-
Sluckey's dual plexi does that very thing. However, the original poster was wanting two channels with each having a tone stack.
With respect, Tubenit
-
Hi Tubenit,
I think I messed up with what I wanted to ask. Therefore here's a schematic (quick and dirty) with my idea.
-
The switch connected to the cathode will have big DC voltage on it.
-
Thanks Sluckey, now it makes sense to not do it that way!
-
Hi All,
Looking at the schematic Tubenit shared with us, I wonder if it would be possible to switch between the 2 preamps right after the CF and eliminate V4?
That cf can drive multiple tone stacks, you can do it like this. Similar to JVM models.
https://el34world.com/charts/Schematics/files/Marshall/Marshall_jvm410_sch.pdf (https://el34world.com/charts/Schematics/files/Marshall/Marshall_jvm410_sch.pdf)
-
concept - dual 2004/1987 circuits with separate preamps all the way to the LTPI.
from the LTPI to output stage it is essentially the same circuits for both models. UL output depicted.
a complex build for sure and not one for a novice builder. no layout provided - meld from the many existing layouts. respectfully, if you can't create your own layout, then probably something you shouldn't tackle.
--pete