Mike Fox
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Marigold Power Amp

buildsamplifierstube

Custom power amp and cabinet! Salvaged from trash and bits around the house.

A few years back I decided I wasn’t going to buy gear if I could build it instead. Buying parts though has been a kind of sneaky workaround for that rule, so with this one I made it a point to build the thing mostly out of stuff I already owned, and to make it as nice as I could.

The cabinet was the one big exception. A lot of used gear shops keep a scrap bin of real cheap parts and materials, and Rock and Roll Vintage up in Ravenswood has the best scrap in Chicago imo. They sold me this old cab for $35 (the Jensen speakers inside could probably be sold for more than that). The metal enclosure, the knobs and the pots I already had. The power supply materials, the plugs and the switches were all scavenged! (I used an old laptop supply)

The amp itself is a cheapo class D board, with an added mute circuit and speaker output added.

Why a power amp with no preamp

I wanted a REAL FLAT amplifier that was still fundamentally a guitar amp. Building preamps has become relatively trivial these days. It’s easy enough to make accurate transistorized versions of a given gain structure and break-up using RunOffGroove’s Fetzer Valve as a template. So this amp and cab are a baseline for playing those clones live in a room without piling on a bunch of additional color.

Marigold because I like them, and my Mom likes them. (Hi ma!)

  • The donor cabinet before any work started, grille cloth intact
  • A corner of the new cabinet, plywood glued and pinned
  • A cabinet joint from inside, splines set into the corner
  • The cabinet carcass standing open in the workshop
  • The cabinet with its grille cloth fitted and the wood finished
  • The same cabinet with its carry handle mounted
  • A small metal part soaking in solvent, being cleaned up
  • The finished cabinet up on the workbench
  • The cabinet standing in the workshop doorway
  • The cabinet face on, grille cloth stretched and even
  • The amp chassis on the bench beside the soldering station
  • The cabinet from above, showing the depth of the box
  • The cabinet standing on a rug at home, a double bass behind it
  • The control panel, knobs mounted and the marigold nameplate printed on
  • The chassis end on, control panel facing out
  • The amp assembled — chassis sitting on top of the cabinet
  • The bare chassis on the bench, its power inlet fitted
  • The chassis clamped down for drilling
  • A small circuit board held in hand
  • The finished amp in the room, a pedal on the floor in front of it
  • The top corner of the cabinet, showing the mitred wood frame
  • The chassis with the marigold wordmark across its face
  • Close on the controls — input jack, toggle switch and volume knob