The Broughton Audio State Variable Filter is a tone shaping pedal for guitar and bass that Broughton describes as capable of creating powerful EQ curves that would otherwise be impossible. It is inspired by the Alembic SF-2 Super Filter, and it works by running your signal through a state variable filter topology where you choose a low pass, band pass or high pass filter, then mix that filtered signal back with your direct signal.1
The controls: Frequency and Resonance
The pedal keeps its face simple, with two knobs that shape the filter and how hard it acts1.
| Control | What it does |
|---|---|
| Frequency | Selects the center frequency of effect for the filters1 |
| Resonance | Boosts the knee of the low and high pass filters, and makes the band pass either a cut or boost effect1 |
The three filter modes
Because the filtered signal is mixed with your direct signal, each mode behaves differently depending on how much of it you blend in. Broughton describes the three paths like this1:
- Low pass mode: mixing the LPF signal with your direct signal can be like a boost to your low end, with a specific bump at the cutoff resonant frequency. Broughton says it works as a cab sim or to add heft.1
- Band pass mode: mixing the band pass filter signal is comparable to a variable semi parametric EQ, but more powerful. With resonance past noon it is a boost at the center frequency; below noon it is a cut.1
- High pass mode: mixing the HPF signal with your direct signal can add brightness and clarity, useful for clearing up a muddy sound or a more cutting, aggressive tone.1
If you mainly want one of those jobs done on its own, Broughton makes narrower pedals in the same family, including the Broughton Audio Low Pass Filter, the Broughton Audio High Pass Filter and the Broughton Audio Low + High Pass Filter. For more of this kind of tone shaping, see the filter pedals page1.
Power and practical details
The pedal requires a DC supply, which is not included. The supply must be at least 9V, but no greater than 24V, and the connector must be a boss style, 2.1mm barrel, center negative polarity. A 24 volt power supply may be purchased separately from Broughton Audio. The current draw is 15mA.1
The State Variable Filter carries a list price of US$185.00 and measures 4.77" long by 2.6" wide.1
Questions
Is the Broughton Audio State Variable Filter true bypass?
Yes. Broughton Audio states that the State Variable Filter has a true bypass switch, so when the pedal is off your signal passes through without the filter circuit in the path.
What pedal is the Broughton State Variable Filter based on?
Broughton Audio says the State Variable Filter is inspired by the Alembic SF-2 Super Filter. Like that unit, it uses a state variable filter topology offering low pass, band pass and high pass filters that you mix with your direct signal.
How much current does the Broughton State Variable Filter draw?
The current draw is 15mA, according to Broughton Audio's product page. The pedal takes a DC supply of at least 9V but no greater than 24V with a boss style, 2.1mm barrel, center negative connector.
Does the Broughton State Variable Filter come with a power supply?
No. The pedal requires a DC supply that is not included. A 24 volt power supply may be purchased separately from Broughton Audio.
Sources (1)
- State Variable Filter, Broughton Audio
