mavrim wrote:Thank you for clarifying! Still undecided if I build JTM circuit or combine output section with another preamp design. I wondered how the amp would sound with a standard Marshall preamp design as used in those 18 watt builds.
I used google translate to read the original discussion on other forum.
I also listened to sound samples of the Marshall 1 watt amps. The JCM-1 was my first choice. I think I will build this amp. Would you happen to have a schematic drawn without the external tone boards? I plan to use a turret board, and would find it easier looking at a schematic with components shown fully connected instead of routed to other boards. Thank you!
mavrim wrote:On the jcm circuit, that lnd150 fet or transistor is to boost the signal going into the tone stack, right? I may want to omit this or use another tube stage in its place. I have mounts for 4 tubes. Was planning on adding a tube effects loop, but not sure if I really needed that.
mavrim wrote:Since I don't have a lot of realastate on that turret board, I probably should stay with the mahaffay plexi preamp circuit and feed that into the Marshall 1 watt output stage. Online the jcm-1 sounded incredible! I have one 10" celestion mounted into the matching slant cabinet. I found that I preferred the cheaper China celestion ten thirty speaker over the stock celestion.
Nice tidy work, but just wondering why you don't mount the transformers on the other side of the chassis like all other valve amps. Same with the valve bases - use a chassis punch and mount them the normal way. I'd probably avoid punching the chassis for the can caps as holes that big are a pita to do - especially in those old steel chassis that Marshall had (I've done a SS-tube conversion too).
sturgeo wrote:Did you stick with the JCM1 build or do the mahaffay plexi preamp? Any gut shots and did you stick with the transformers pictured?
cassoulet wrote:Hi everyone,
Here is my own redrawn JCM1 schematic, from Matec's original. Details such as heaters and grounding are omitted on purpose to help clarify. Hope this helps.
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