Fender 6G3 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.
The bright channel of the 6G3. Same tone network, with 20 nF for the treble cut and no cap at the plate.
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 the signal on its wiper. One end goes through 500 pF to the volume’s wiper, the other through a cap to ground. Up is the bright path. Down is the treble cut.
- Volume
- Part of the network. The 500 pF connects to its wiper, so the tone control changes with it. With Every tone setting on, it stays where it’s set.
Parts
- 20 nF
- Coupling cap from V1’s plate to the top of the volume pot and the tone pot’s wiper.
- Vol 1M
- 1 MΩ, Volume, 1 MΩ audio. The signal comes in at its top, and its wiper feeds the 220 kΩ mixing resistor. The tone control’s 500 pF connects to the wiper, so the volume setting changes what the tone control does.
- Tone 1M
- 1 MΩ, Tone, 1 MΩ audio, with the signal on its wiper. Toward one end, 500 pF passes treble around the volume pot to its wiper. Toward the other, 20 nF shunts treble to ground.
- 500 pF
- Treble cap, 500 pF, from the tone pot to the volume’s wiper, a bright path around the upper part of the track. Turning the volume down leaves more treble than bass.
- 20 nF
- Treble cut cap, 20 nF, from the other end of the tone pot to ground.
Source and load
Driven by: triode plate, 220 kΩ plate resistor. Driving: mixing resistor, 220 kΩ. From Fender’s 6G3 schematic, the bright channel. Source: one triode of the 7025 (a low-noise 12AX7), with a 220 kΩ plate resistor from about 270 V. The shared 1500 Ω cathode resistor carries both triodes’ current, so it’s entered as 3 kΩ. That matches the drawing, which shows +1.5 V on the cathodes and +165 V on the plates. Load: the 220 kΩ mixing resistor into V2’s grid. The other channel’s 220 kΩ goes to ground, as if its volume were at zero, and there’s no other grid resistor. The schematic doesn’t mark which way the pots turn, so up is assumed to be brighter and louder.
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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