Virtual Oscilloscope - DiMastro GTA

Simulates the scope trace of a preamp → tone stack → phase inverter → power stage chain. Same tone-stack solver and clean-headroom math as the live site tools, plus a three-stage asymmetric clipper with voicing-dependent gain staging, global NFB, B+ sag, and OT compression. Choosing an amp profile loads the matching tone stack profile and stock tubes (e.g. Deluxe → 6V6GT, Super → 6L6GC, Marshall → EL34, Vox → EL84). Stylized model — not full SPICE of each amp.

Install on your phone This tool is also available as a mobile app — full offline access, right from your home screen, no browser tab required. Get the Virtual Oscilloscope app

Amp profile

Brand Model

Deluxe Reverb ~22 W: 6V6GT PP, 12AX7 + 12AT7, Blackface AB763 light NFB (820 Ω + 47 Ω). Volume uses Fender’s J-taper (~30% at noon).

Preamp Stage

V1 (gain stage) Phase inverter

Lower-μ tubes need more Volume to clip. A hotter PI breaks up earlier on push-pull profiles; single-ended amps have no PI.

Deluxe Reverb stock pairing: 12AX7 (V1) + 12AT7 (PI).

Power stage

Power tube

Topology

Push-pull

B+ V Plate-to-plate Z Ω

Power tube follows the amp profile (6V6GT, 6L6GC, EL34, or EL84). B+ and plate Z load from that amp’s operating point so full-blast power sits near the real rating — edit for your amp’s measured numbers.

Bias dissipation %

Idle plate dissipation

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Negative feedback (AB763)

NFB resistor Ω NFB tail Ω

Blackface AB763 light NFB: 820 Ω + 47 Ω tail. Set the resistor to 0 any time to open the loop.

Tone stack

Amp designation

Fender Deluxe Reverb (Blackface AB763)

Signal generator

Frequency Presets

Plays the current frequency out of your device speaker — matches the knob and Scope trace live.

BUILD: draft9

Scope

Frequency 1000 Hz

Time/Div 1.0 ms

Volts/Div 100 V

Output power

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Total harmonic distortion

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Clean headroom

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Per-stage contribution

Preamp (V1b) distortion

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Phase inverter distortion

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Power section distortion

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These read the actual audible compression at each stage, not how close it is to its own ceiling. Swap in a hotter PI tube, or push the power stage into its own clipping (lower B+, lower Z, hotter bias), to see PI/Power engage.

Shared signal path: V1a (clean half) → Volume → V1b (preamp clip) → tone stack → phase inverter → power stage. Single-ended profiles (Champ, AC4) skip the phase inverter. Volume sits where it does on a Normal channel. Preamp/PI tube choice scales gain by published μ only (not a full triode model).

Amp profile (top of page) sets cascade character and stock tubes / NFB / operating point:

Fender Blackface Deluxe Reverb — 6V6GT PP ~22 W, 12AX7 + 12AT7, NFB 820 Ω + 47 Ω. TB stack (no Mid). Cleaner preamp.
Fender Silverface Deluxe Reverb — 6V6GT PP ~22 W, 12AX7 + 12AT7, same NFB as blackface (820 Ω + 47 Ω), slightly cooler bias. TB stack.
Fender Tweed Deluxe (5E3) — 6V6GT PP ~15 W, 12AY7 + 12AX7, NFB off. Single-tone control.
Fender Vibrolux Reverb — 6L6GC PP ~35 W, 12AX7 + 12AT7, NFB 820 Ω + 100 Ω. TB stack (no Mid), sized between Deluxe and Pro.
Fender Super Reverb — 6L6GC PP ~40 W, 12AX7 + 12AT7, NFB 820 Ω + 100 Ω. TMB stack.
Fender Pro Reverb — 6L6GC PP ~40 W, 12AX7 + 12AT7, NFB 820 Ω + 100 Ω. TMB stack, same cascade as Super.
Fender Twin Reverb — 6L6GC PP ~85 W, 12AX7 + 12AT7, NFB 820 Ω + 100 Ω. TMB stack, highest B+ in the line.
Fender Princeton Reverb — 6V6GT PP ~12 W, 12AX7 + 12AT7, NFB 2700 Ω + 47 Ω (much lighter than Deluxe — split-load PI). TB stack, smaller output transformer.
Fender Princeton Amp — 6V6GT SE ~9 W, NFB off. Single-tone control, same network as Champ.
Fender Tweed Bassman — 6L6GC PP ~45 W, 12AY7 + 12AT7, NFB ~47 kΩ (documented 27–56 kΩ range, single-resistor topology). Genuine tweed tone stack, not blackface.
Fender Tweed Champ 5F1/5F2A — 6V6GT SE ~5 W, NFB off, hot bias.
Fender Vibro Champ — 6V6GT SE ~5 W, NFB off, hot bias. Same power section as Champ, plus tremolo.
Marshall JCM style — EL34 PP ~50 W, 12AX7 + 12AX7, lighter NFB. Hotter preamp.
Marshall Plexi style — EL34 PP ~50 W, 12AX7 + 12AX7, lighter NFB than JCM800 (47 kΩ vs 100 kΩ). More dynamic response.
Vox AC-30 style — EL84 PP ~30 W, 12AX7 + 12AX7, NFB lifted. Top Boost TMB.
Vox AC15 style — EL84 PP ~15 W, 12AX7 + 12AX7, NFB lifted. Same Top Boost TMB as AC30, lower power.
Vox AC4 — EL84 SE ~4 W, NFB off, hot bias.

B+ and plate Z load from each amp profile’s operating point (aimed at real rated power) and stay editable. TMB stacks use the same nodal solver as the Tone Stack Calculator; Champ/AC4 use a classic single-knob treble-cut network. Power stage: swing/clean-fraction math with B+ sag and mild OT compression. Clip stages use asymmetric soft-clip knees — not SPICE. The PI is a stylized curve (no full LTP cross-coupling); SE amps have no PI stage. No full transformer saturation model, and no tube-to-tube variance.