Sunn Sorado 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 Sunn Sorado (and 200S), 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, 250 kΩ. Its wiper drives the pentode’s grid. The taper isn’t marked, so linear is assumed. Clockwise moves the wiper toward the 470 pF, brighter.
- Bass
- Bass, 1 MΩ, the bass cap on its wiper. Clockwise moves the wiper toward the Treble pot’s bottom, so the lows reach the Treble pot through less resistance and come up. The taper isn’t marked, so audio is assumed.
Parts
- CT
- 470 pF, Treble cap, 470 pF, to the Treble pot’s top.
- RSL
- 56 kΩ, Slope resistor, 56 kΩ.
- CB
- 22 nF, Bass cap, .022 µF, from the slope node into the Bass pot’s wiper.
- Treble
- 250 kΩ, Treble, 250 kΩ. Its wiper drives the pentode’s grid. The taper isn’t marked, so linear is assumed. Clockwise moves the wiper toward the 470 pF, brighter.
- Bass
- 1 MΩ, Bass, 1 MΩ, the bass cap on its wiper. Clockwise moves the wiper toward the Treble pot’s bottom, so the lows reach the Treble pot through less resistance and come up. The taper isn’t marked, so audio is assumed.
- RBB
- 22 kΩ, 22 kΩ from the Bass pot’s bottom to ground.
- R47
- 47 kΩ, 47 kΩ from the Treble pot’s bottom, with the .0075 µF below it to ground. It shunts some of the treble at the Treble pot’s bottom.
- C75
- 7.5 nF, .0075 µF under the 47 kΩ to ground.
- CM
- 22 nF, Mid cap, .022 µF, from the slope node to the 22 kΩ. It sets how deep the mid scoop goes.
- RHB
- 22 kΩ, 22 kΩ under the mid cap. The Hi Boost switch shorts it.
Source and load
Source: 67 kΩ, the output resistance of the stage before it on the bench at 1 kHz. Load: 680 kΩ with 6.5 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 Sunn Sorado (and 200S) 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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