The Marshall DSL40C is a 40 Amp “combo” tube guitar amp; integrating the amp and a single 12” speaker into 1 cabinet.


I swapped out the OEM Seventy/80 speaker and put in a Celestion G12 H-75 Creamback to try and tame the harshness of the OEM speaker.

The result was a fuller-sounding combo amp that now weighed in at 60 pounds. The issue of tube life from speaker vibration remained a concern (as it is for any combo tube amp). My solution was to separate out the amp from the speaker and create a “mini-stack”.

I sourced the bare cabinets from a guy on eBay who does excellent work with tight, dovetail joints, solid wood, and baby-butt smooth finish sanding.


I then sourced the heavy duty “Elephant Hide” Tolex and various hardware odds and ends to finish it out.

I put both the OEM Seventy/80 and the G12 H-75 into the new 2x12” cabinet. Converting it from the OEM open backed cabinet to a closed back design gives it a punchier (tighter) bass sound IMO. The 2 speakers compliment each other. The Seventy/80 was a little harsh on the highs which the warmth of the G12 H-75 moderates.


I’ve been playing it for a few months now and am glad I did the work. The sound is improved but it’s also less cumbersome to lug around. Only the head needs to be moved to do tube swaps.

Modifying A Marshall DSL40C Amp