The JMR Reverb 12 Special plugin interface

Behind the Model

Reverb 12 Special began with a specific amplifier, not a generic idea of what a vintage guitar amp should sound like. Our reference is an original Marshall Reverb 12 (model 5205), converted into a standalone head in June 2024. The conversion changed the enclosure, not the amplifier circuit.

Our actual reference amplifier — the original electronics in a custom head enclosure.

01 / The hardware reference

The Reverb 12 is a compact vintage solid-state amplifier. For this project, we kept its original circuitry intact and used the physical amplifier as the reference for the digital version. That matters: the goal was to work from the behavior and sound of a real unit, rather than assemble an amp sound from unrelated virtual components.

02 / Original Signal Chain

The reference recordings were made using one real amplifier, one specific cabinet and one microphone. The speaker cabinet and microphone are integral parts of the recorded tone; the plugin is not presented as a collection of interchangeable cabinet simulations.

03 / Measurement & Validation

Measured with precision. Refined by listening. Development used a combination of individual sine-wave test tones, frequency sweeps and real guitar recordings. These different sources helped us investigate the response of the physical amplifier and its complete recording chain.

We made numerous reference recordings across a range of amplifier settings, paying particular attention to the gain structure and the behavior of the Volume control. The model was not developed from a single static setting.

Real guitar performances and direct-input (DI) recordings were used for A/B comparisons between the physical reference and the plugin. This let us assess the result with actual playing material as well as controlled signals. We do not claim a numerical accuracy figure or a particular internal modeling technique that has not been independently documented.

04 / Reverb — an important limitation

05 / What makes this a Special

In the JMR Sound lineup, the One Series takes inspiration from familiar processor designs. The Special Series is different: it starts with physical hardware we can actually access, record and compare against during development. Reverb 12 Special follows that approach, using our own amplifier and a fixed recording chain.

What we are not claiming

Reverb 12 Special is not presented as a universal model of every Reverb 12 ever made. It is based on our own reference unit and one specific cabinet and microphone setup. The specific cabinet and speaker models are documented above. We do not claim that the model reproduces every possible microphone position or every example of the original amplifier.