Tramp

15 January 2011

This is a little single ended Class A amp design from Trinity Amps called the Tramp (a play on the Fender Champ, get it?). The amp is single channel with one 12AX7 and one output tube. The amp can run 6V6, 6L6, EL34, 5881, KT66, KT66, etc for the output tube. With the variety of output tube capabilities the amp can run from 5W-12W.

With only two tubes and one channel you’d think the amp would not be very versatile but that is not the case. The Tramp has two modes Tweed and Tude. Tweed mode is a nice full clean sound. Pull the push-pull volume pot for Tude mode which produces a grittier dirtier tone, great for overdrive. Tude mod is very large sounding with a sweet singing tone. A huge range of tones are covered with just two tubes. Many great sounds to be had!

The Tramp also includes Treble, Bass, Master Volume and a VRM (Voltage Regulation Module) power scaling controls. The Bass control is a push-pull pot enable a fat boost/mode. With Volume and Master Volume controls you can dial in even more tones at various volume levels. The VRM control scales the high voltage inside the amplifier and acts as another master volume/attenuator.

The Tramp uses Heyboer made transformers. Both the power transformer and “fat stack” output transformer are very robust and over spec. The well designed output transformer allows the amp to run the various output tubes at their optimal specifications.

The back panel of the amp has two speaker outputs, a bias switch for different tube types, a rotary switch for 4Ω, 8Ω and 16Ω speaker output with either 2.5KΩ or 5KΩ on the primary side of the output transformer. I also added a modification for footswitch to connect on the back panel. This footswitch allows for the tonestack (tone controls) to be partially lifted from the circuit. This adds volume/gain and mids so the footswitch is affectively a unique boost switch.

The cabinet is solid pine and uses box joints. I decided to not tolex the cab but rather stain it and then add varnish. To top everything off I used “wheat” grill cloth to finalize the rustic simple look of the amp.

The speaker is a 10″ Jensen Blackbird which is a very nice balanced AlNiCo speaker. The speaker has very tight bass response which is important because I find Class A amps can often have loose/flubby low end. The highs are clear and balanced while not being too shrill or sharp. Overall the speaker is very balanced and I would not hesitate to recommend it.

Overall the Tramp is a fun little amp with a huge sound. I use this amp a lot when I need a quick setup to grab and go. With its wide range of tones and various output level it makes it a great practice amp as well as recording amp.

Schematic:

tramp-schematic

 

Modifications:

tramp-raw-mod_0

Boost footswitch implementation.

tramp-z3-labelled

Wiring the 2 pole 6 throw impedance switch.

tramp-z4

Wiring of the impedance switch (secondary connections).

tramp-z5

Wiring of the impedance switch (primary side).

 

 

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