Fender 5D8 Twin 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 Treble and Bass controls of the Fender 5D8 Twin, with every part as on the bench.
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
- Treble
- Treble, 1 MΩ. Its wiper is the driver’s grid. One end has the 220 pF from the follower, the other goes to ground through .003 µF. Clockwise moves the wiper toward the 220 pF, so more treble.
- Bass
- Bass, 2 MΩ, with a cap across each half of its track and its wiper on the way to the driver. Clockwise the wiper moves to the top and the lows come straight through, with the .0047 µF and 56 kΩ under them. Counterclockwise the wiper shorts the .0047 µF to the 56 kΩ, and only the highs get through the 100 pF.
Parts
- 220 pF
- Treble cap, 220 pF (.00022 µF on the drawing), into the bright end of the treble pot.
- Treble 1M
- 1 MΩ, Treble, 1 MΩ. Its wiper is the driver’s grid. One end has the 220 pF from the follower, the other goes to ground through .003 µF. Clockwise moves the wiper toward the 220 pF, so more treble.
- 3 nF
- From the far end of the treble pot to ground, .003 µF 600 V. Turned down, the wiper sits near it and the highs bleed off.
- 100 nF
- Coupling cap from the follower into the bass path, .1 µF 200 V.
- 270 kΩ
- From the bass path to ground, 270 kΩ. It holds the node at 0 V and loads the follower lightly.
- 270 kΩ
- From the bass path to the top of the bass pot, 270 kΩ.
- Bass 2M
- 2 MΩ, Bass, 2 MΩ, with a cap across each half of its track and its wiper on the way to the driver. Clockwise the wiper moves to the top and the lows come straight through, with the .0047 µF and 56 kΩ under them. Counterclockwise the wiper shorts the .0047 µF to the 56 kΩ, and only the highs get through the 100 pF.
- 100 pF
- From the bass pot’s top to its wiper, 100 pF (.0001 µF). It carries the highs around the upper track.
- 4.7 nF
- From the bass pot’s bottom to its wiper, .0047 µF. With the 56 kΩ it sets how much of the lows drain to ground.
- 56 kΩ
- From the bass pot’s bottom to ground, 56 kΩ.
- 270 kΩ
- From the bass pot’s wiper to the driver’s grid, 270 kΩ. The bass path and the treble wiper mix here.
Source and load
Source: 820 Ω, the output resistance of the stage before it on the bench at 1 kHz. Load: 2 MΩ with 60 pF across it, the input of what follows it on the bench, from its impedance at 1 and 10 kHz.
Values, wiring and drawing are taken from the Fender 5D8 Twin 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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