M15Mk1: cascading channels

Luigi

Hello,
I would like to get the J5Mk1 sound in the 15watt format, because of rehearsal and live playing usage.

I think that a possible way to go is to start from M15Mk1 deluxe kit and try some mods. Obviously the easier mod that jumps in mind is cascading the two channels; probably also a tone stack re-shaping and an attenuation after the first gain stage (that was channel 1) are needed.

Do you have some guidelines or experience to share?

Thank you,
Luigi

gazza285

I rewired the remote footswitch relay on my m15 to cascade the channels, although I can't remember the details. The feed into channel two is post tone but before the volume pot, so the tone does affect the front end of channel two. I seem to recall starting with no attenuation, but I'm sure that I have a simple resistor/cap filter in there now, although with channel two gain above half way it does get a little over the top. The other big modification I have is a triode switch on the output valves, which cuts the output and also cuts some of the top end, preventing the amp from getting too fizzy at low levels.

A modification that I have considered but not tried yet is a post phase inverter master volume mod, this would affect both channels. I might try this at a later date, but I'm happy for now.

If you want any specific detail I'll have to pull the amp apart as I can not remember exactly how I have wired any of this as it has been a long time.

Gaz.

Luigi

Hi Gaz,
thank you so much for sharing your experiments, I will take them in count. For now, I want just to collect some ideas.

I think that another possible mod to get more gain is to convert the cathode follower stage of ch2 into a gain stage, feeding directly the tone stack. In this case I would probably lose some volume before the PI, but, speaking of a relatively high gain channel, maybe this is not a real issue.

Luigi

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