Fender 5E3 Deluxe tone stack
Tone stacks and tone controls from amps and pedals, from their schematics, with the stage that drives each one and what it feeds. Turn the knobs and watch the curve. Pin a setting to compare, change any part, and listen through a speaker. Pickups and guitar knobs are on the Guitars page.
One tone knob and two volumes, all three pots meeting at the second stage’s grid. Each channel’s signal comes in on its volume’s wiper. The tone pot sits between 500 pF from one channel and 5 nF to ground.
Swipe sideways for the whole drawing. Tap a part to change it. The source drives the end marked in, and the load hangs on the end marked out.
At this setting
0 dB is the source’s voltage with nothing hooked to it, so the curve shows what the stack cuts. A tube source changes the curve only through its output resistance, not its gain.
Pin this curve keeps what the graph shows, up to three pins in their own colors. Pins stay when you switch stacks, so you can lay a Marshall treble sweep over a Vox one. In a sweep, the lightest line is the knob at 0 and the darkest is 10.
Listen
You hear a picked string through a guitar on full, with 15 feet of cable. Play without it leaves the stack out.
Source and load
Driven by
Driving
The knobs
- Tone
- A 1 MΩ pot with its wiper on the grid. One end goes to 500 pF from the first channel’s signal, the other to 5 nF to ground. What it does depends on both volumes.
- Volume (instrument)
- The signal comes in on the wiper. Turned up, there’s less track in series with the grid and less shunting to ground.
- Volume (mic)
- Turned up, it hangs the mic channel’s plate on the grid through less track, which loads the instrument channel.
Parts
- 100 nF
- Coupling cap from the instrument channel’s plate to its volume pot’s wiper.
- Vol 1M
- 1 MΩ, Instrument channel volume, 1 MΩ audio. The signal comes in on the wiper. The track above it is in series with the next grid, and the track below shunts signal to ground.
- 500 pF
- Treble cap, 500 pF, from the instrument channel ahead of its volume to the tone pot. It carries treble around the volume, so the channel gets brighter turned down.
- Tone 1M
- 1 MΩ, Tone, 1 MΩ, wiper on the second stage’s grid. Up puts the grid near the 500 pF. Down puts the 5 nF to ground on it, which cuts treble. The drawing doesn’t mark which way is up, so up is assumed to be brighter.
- 5 nF
- Treble cut cap, 5 nF to ground from the other end of the tone pot.
- Vol 1M
- 1 MΩ, Mic channel volume. It matters even with nothing plugged in: turned up, it hangs the mic channel’s plate on the second grid through less track, which loads the instrument channel.
- 100 nF
- The mic channel’s coupling cap.
- 24 kΩ
- The mic channel’s plate as the grid sees it: its 100 kΩ plate resistor in parallel with the 12AY7’s plate resistance, about 32 kΩ at the bias of the bench’s 5E3, about 24 kΩ together. It carries no signal here.
Source and load
Driven by: triode plate, 100 kΩ plate resistor. Driving: next grid, 1000 MΩ. From Fender’s 5E3 schematic. Source: one triode of the 12AY7, with a 100 kΩ plate resistor fed from 218 V, the preamp supply at idle in the bench’s 5E3. The shared 820 Ω cathode resistor carries both triodes’ current, so it’s entered as 1.64 kΩ. Load: the 12AX7 second stage’s grid, about 110 pF with its Miller capacitance. There’s no grid resistor: the pots are the grid’s path to ground, and the 1 GΩ in the load only stands in for grid leakage. Both volumes are part of the network, so they’re knobs here, and with Every tone setting on they stay where they’re set. The schematic doesn’t mark which way the tone pot turns, so up is assumed to be brighter. Pot tapers are assumed to be audio.
Values and wiring are the same as in the push-pull 6v6 amp circuit on the bench, so the two always match.
Warnings. The summary above the graph turns red if the stack can’t be solved as set, usually from a part at zero or a shorted pot track.
How this tool works. We solve each stack with the circuit bench’s engine: the source stage’s operating point first, then every part at 161 frequencies from 20 Hz to 20 kHz. A stack that’s also in a bench circuit is built from that circuit file, so the two always match.
The curves are small-signal. They don’t show clipping or grid current in the next stage. For the stage before or after a stack, try the gain stage tool.
Spot an error, or want a circuit added? Email info@swellamps.com. A schematic or a clear photo of one helps. Anything you send may be used to improve these models and our desktop app.
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