Coda Effects Black Hole

The Coda Effects Black Hole is a preamp pedal that puts the Sunn Model T preamp in a stompbox. Coda Effects describes it as "my version of the almighty Sunn Model T preamp," a JFET reproduction of the circuit that made the Model T amp a favorite of heavy players¹. It is built for players who want that thick, amp-like front end on a pedalboard, and Coda Effects says it is optimized for guitar and bass¹.

The pedal was first presented in December 2017, when the builder announced it with a waiting list and a PCB for self-building². It is made by hand in Paris, France, with Wima and Panasonic capacitors, Fairchild semiconductors and Amphenol jacks¹. The maker's page lists it at a price of 207 €¹.

A Sunn Model T preamp in a pedal

The Sunn Model T is an amp with a following among doom and heavy players, and the Black Hole exists to put its preamp section on a board. Coda Effects' own technical write-up explains the goal: "The preamp is wired with both channels added for more gain"². The result sits somewhere between a preamp, an overdrive and a distortion pedal, depending on how the channels are set.

The maker's description of what it can do is direct:

With the built-in boost engaged, the builder describes the sound as "super heavy, almost fuzzy drive that sounds actually quite like the Sleep Dopesmoker album"². That puts it in the territory where fuzz and doom tones overlap, driven by the pedal's own gain staging rather than a fuzz circuit.

The controls

The Black Hole has seven controls on the PCB version³, centered on two channels and a shared EQ.

The two channels are the heart of the pedal. Each has a different voicing and gain, and they can be used one at a time or both at the same time³. Mixing them in parallel gives a heavier sound¹. Turning a dial up makes that channel louder, and putting a pot at zero cuts the channel entirely².

The boost switch is worth a note for players chasing heavy tones: it "activates a LPB1 boost to have more gain and go to doom territory"³. The LPB1 is a classic simple boost circuit, and here it pushes the preamp harder rather than acting as a standalone boost.

Inside the circuit: JFETs and a passive tonestack

The Black Hole is an all-JFET design, and Coda Effects has documented how it works in detail².

The signal path runs through the two channel stages and into a gain stage:

• The Normal channel has a low pass filter (R7 and C4) that removes some treble for a bassier sound, and its biasing resistor was removed for more gain².
• The Bright channel input has a 1M resistor that raises input impedance and avoids pop noises when the effect is switched on².
• A 470pF capacitor in the bright channel removes a bit of treble; increasing its value gives more treble in that channel².
• A trimpot biases the first JFET of the bright channel correctly, with a 220uF capacitor adding a bit of gain².

After the channels, the two signals meet: "The JFET Q3 is smashed with the amplified signals of both channels, and start to saturate. It is this transistor which creates the gain of the pedal," followed by another transistor that re-amplifies the signal before the tonestack². This is where the drive character comes from, and it is why running both channels together gives a heavier result.

The EQ is a classic passive tonestack: "basically three low pass RC filters that will cut bass, mids and trebles respectively," the same style made popular by Marshall amps². Passive tonestacks cut rather than boost, so the EQ section shapes the sound by trimming frequencies.

On components, the builder notes that genuine through-hole JFETs are difficult to find and most sold online are fakes, so the design uses Fairchild SMD J201 JFETs, though through-hole transistors are also possible². The PCB version can be ordered presoldered with genuine Fairchild Semiconductors J201 SMD JFETs, which Coda Effects describes as best in class³.

The DIY PCB version

Alongside the finished pedal, Coda Effects sells the Black Hole as a PCB for self-building³. The board is described as "the infamous Sunn Model T preamp in a box, with a boost to make it even louder and heavier"³.

What the PCB version offers:

• Seven controls, the same channel and EQ layout as the finished pedal³
• Spaced pads for easier soldering³
• A presoldered board option with genuine Fairchild J201 SMD JFETs³
• A detailed build document³
• Layout compatible with SMD JFETs or through-hole transistors²

The PCB product page carries a notice that the product has moved to a new store³, so builders looking for it should expect a redirect.

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