Building a DIY Eurorack TR-808 Snare
The Roland TR-808 isn’t just a drum machine—it’s a legend. Since its release in 1980, the sound of the 808 snare has shaped countless musical genres, from early hip-hop and electro to house, techno, and trap. Its crisp, snappy character has been featured in thousands of records. After over four decades, producers, musicians, and sound designers still reach for the 808 snare because of its instantly recognizable, punchy sound that cuts through any mix. This simple circuit has transcended its humble origins to become an iconic sound and Eurorack essential.
In this guide, we’ll use the N8 Synth’s 8HP Eurorack Prototype kit to build a DIY Eurorack 808 Snare that captures the original’s magic, adapted for Eurorack modular synthesis and modern performance needs.
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808 Snare Schematic & Module Layout
808 Snare Circuit Overview
Our take on the 808 snare follows the overall topology of the original circuit, but we’ve added a Eurorack compatible trigger section. We’ve tweaked the values of components, both to adapt the circuit for Eurorack, and dial in a sound that we find pleasing. We’ll note these changes below and suggest where you could swap out components to tailor the sound to your liking. Helpfully the original Roland TR-808 service manual explains the 808’s architecture in some detail and is worth checking out.
Trigger & Accent Input
Our Eurorack 808 snare has Trigger and Accent inputs, and both expect a 5V trigger of > 2mS duration or a 5V gate. Except for the Accent Level, both input circuits have identical topologies and are ultimately summed by U1B and inverted by U1A to provide a single trigger pulse to the module’s oscillators and noise generator. As the inputs could be a gate CV ( or longer than the required trigger pulse ), R21, C10, R23, R8, C5, and R12 shape the inputs to generate the required 2mS trigger pulse. The diodes, D1 & D2, protect transistors Q2 & Q4 from any negative voltage that may appear across the inputs.
At rest, Q1 and Q3 are in a cutoff state. The incoming trigger or gate causes Q4 or Q2 to saturate, grounding the base of Q3 or Q1 and causing them to saturate. When fully open, the voltage present at the emitters of Q3 and Q1 is dropped across R14 and R16, respectively. In the case of Q3, this voltage is fixed, but for Q1, it is adjustable and gives us our accent. Also, note that J1 is normalised to J2, so if there isn’t a jack inserted into J1, the trigger signal from J2 will also trigger the accent circuit.
In operation, we can either:
- Provide a trigger to Trigger Input (J2), in which case the Accent Level is used to boost or trim the trigger and change the overall output level of our kick.
- Provide a trigger to the Trigger Input (J2) and a second trigger to the Accent Input (J1). In this case, the output level is louder ( accented ) when the triggers coincide and quieter when they don’t. The Accent Level pot adjusts the difference.
You could reduce the value of R14 to increase the dynamic range, which will increase the effect of the accent; note that this also increases the overall output level.
We picked this approach for the accent circuit because it matches that of the TR-808 and works well with trigger sequencers; however, an alternative approach is to have a single trigger with its level set by CV. This would allow continuous adjustment of the snare’s level with each hit. The velocity output of a keyboard, drum pad, or sequencer could potentially drive the accent CV.
Bridged -T Oscillator
Two Bridged-T oscillators tuned approximately an octave apart form the core of the TR-808 snare’s sound. The Tone potentiometer RV2 adjusts the mix of the two oscillators arriving at the output. Bridged-T oscillators are great for drum voices as they are self-damping and do not require an envelope generator and VCA to shape the sound. The Bridged-T oscillator is a twin-T oscillator modified to be self-oscillating when excited by an external trigger. Both oscillators are the same in operation, so we’ll look at the lower-frequency one as an example.
A trigger pulse arriving at the non-inverting input of U2B momentarily disrupts the balance of the oscillator, “kicking” it into motion. C7, C8, R17 & R19 in U2B’s feedback loop form a resonant filter, setting the oscillation to a specific frequency, around 200Hz, with the specified components. The amplitude of the oscillation starts strong and naturally decays over time, similar to a real drum skin vibrating after being struck.
We’ve tuned both oscillators a little lower than the original TR-808. If you’d prefer the original tunings of 250Hz and 500Hz, replace C7 and C8 with 27nF devices, R1 with a 1M ohm resistor, and R2 with a 2K2 resistor.
The Bridged-T oscillator's frequency is given by:
Where R1 is the total resistance to ground from the junction of the two capacitors and R2 is the feedback resistance.
Inserting our component values:
and
Trigger Shaping
In addition to kicking the oscillator into motion, the trigger pulse is part of the sound of the snare. This sharp pulse replicates the high-frequency noise component of a physical drum, which is generated when the stick hits the drum skin. In the case of the lower-tuned oscillator, C11, R22, and R24 shape the ~2mS square pulse from the trigger stage, giving it a sharp transient and exponential decay. As specified, C11, with a value of 1nF, adds very little “click” to the output; increasing the value of the capacitor will increase the “clickiness” of your snare. Replacing C11 with a 10nF – 15nF component should give your snare more snap.
White Noise Generator & Swing Type VCA
Filtered white noise is used to simulate the sound of the snare wires vibrating against the lower skin of the drum. The source of this noise in the TR-808 is a reverse-biased NPN transistor, often a 2SC828 in the original design and a 2N3904 in ours. Q8 is reverse-biased, which breaks down the base-emitter junction and generates avalanche noise. C20 and R37 form a lowpass filter, AC coupling the raw noise signal to U2C, which acts as a buffer between the transistor and the VCA section. Roland describes this VCA configuration as a swing-type VCA.
The transistor Q7 is configured as a high-gain amplifier, amplifying the raw noise signal. The amplifier’s output is via Q7’s collector, which sources current from the Noise Envelope. As such, Q7 is modulating the envelope with the noise. To look at it another way, when the envelope is at its peak, the current available to the amplifier is high, and so is its gain. As the envelope decays towards 0V, the current available to Q7 decreases, limiting the available gain. Either way, the amplitude of the noise signal follows the shape of the envelope and, given the crudeness of the circuit, is also distorted in a sonically helpful way.
Noise Envelope
The noise envelope is an equally simple and effective circuit. The trigger pulse is scaled by the voltage divider formed by RV3 ( the Snappy control ) and R32. The greater the voltage across RV3 ( turned clockwise ), the more Q6 will conduct during the trigger pulse. While Q6 is conducting, the current available to the Noise VCA is high, so the noise signal has a high gain. The onset of the gain is shaped/slowed by the charging of C16 — we can think of C16 as setting the envelope’s attack. C15 is also charged for the ~2mS duration of the trigger pulse. When the trigger pulse subsides, Q6 is cut off, and C15 will begin discharging via Q7, gradually reducing the current available to the VCA and, thus, the noise signal’s gain. C15 sets the decay of the envelope generator. D3 needs around 0.7V to conduct, so it ensures the VCA can be entirely shut off even if the envelope doesn’t fully reach 0V, which may be the case due to general noise in the circuit.
Noise Filter
The output of the noise VCA is shaped by a Sallen Key high-pass filter. This is a 2-pole filter with a corner frequency of ~2466Hz. Again, this is a little lower than the original TR-808 snare, which sets the corner frequency at 2749Hz. Swap C12 and C13 for 1.8nF parts if you’d like to try the original spec.
Output Stage
U2A is configured as a summing amplifier and combines the output of the high and low oscillators ( mixed via RV2 ) and filtered noise. R38 provides sufficient gain to deliver a nominal 10V peak-to-peak output, while RV1 allows us to adjust that gain. C4 acts as a first-order lowpass filter with a corner frequency of ~10KHz to roll off some of the high-frequency noise.
Bill of Materials
We’ll build the Eurorack 808 Snare using the 8HP Eurorack Prototype kit. The kit contains a Eurorack Solderable Breadboard and Eurorack Control Deck, a pre-drilled Eurorack panel, and the pin headers used to connect them. The Eurorack breadboard provides power to our module, and the Eurorack Control Deck makes mounting controls a breeze.
The 8HP Eurorack Prototype kit, jacks, and pots required for this module are available from the N8 Synth store. The remaining components are widely available and relatively inexpensive. If you are just getting started building modular synths, stock up on these components, as they are ubiquitous in the schematics you’ll find online.
A note about capacitors
The voltage rating of the ceramic capacitors is not critical. We’ve specified 50V as this is a typical value for the cheap bulk capacitor kits you’ll find on Amazon and the like, but any voltage rating greater than 25V will work. As described above, the capacitors related to the two oscillators, noise envelope, and filter, shape the sound. Ideally, these should have a low tolerance to be as close to the specified values as possible if you want the maths to work.
| Type | Refs | Value | Qty | Notes | Add To Cart |
|---|---|---|---|---|---|
| 8HP 2x5 Eurorack Prototype Kit | 1 | Includes Eurorack Breadboard, 8HP Control Deck, 8HP Panel, 40-pin headers (PH1 & PH2), and 2x8 power header. | |||
| Jack Socket | J1, J2, J3 | PJ-3001F | 3 | PJ-3001F | |
| IC | U1 | TL072 | 1 | DIP8 Operational Amplifier | |
| IC | U2 | TL074 | 1 | DIP14 Operational Amplifier | |
| Hardware | 1 | DIP8 IC socket for U1 | |||
| Hardware | 1 | DIP14 IC socket for U2 | |||
| Potentiometer | RV1 | A100K | 1 | Alpha-RV901F Style Round Shaft | |
| Potentiometer | RV2 | B100K | 1 | Alpha-RV901F Style Round Shaft | |
| Potentiometer | RV3 | B10K | 1 | Alpha-RV901F Style Round Shaft | |
| Potentiometer | RV4 | B10K | 1 | Alpha-RV09 Style | |
| Hardware | Level Knob | Davies 1900H Clone Orange Round Shaft | 1 | Davies 1900H | |
| Hardware | Tone Knob, Snappy Knob | Davies 1900H Clone White Round Shaft | 2 | Davies 1900H | |
| Capacitor | C27, C28 | 10uF ±20% 25V | 2 | Radial Electrolytic 5x11mm | |
| Capacitor | C17 | 22nF ±5% 50V | 1 | Polyester Mylar Film Capacitor | |
| Capacitor | C3, C9 | 47nF ±20% 50V | 2 | Multilayer Ceramic 4mm | |
| Capacitor | C18, C19 | 4.7nF ±5% 50V | 2 | Polyester Mylar Film Capacitor | |
| Capacitor | C11 | 1nF ±5% 50V | 1 | Polyester Mylar Film Capacitor | |
| Capacitor | C25, C26, C21, C22, C16, C24, C23 | 100nF ±20% 50V | 7 | Multilayer Ceramic 4mm | |
| Capacitor | C5, C10, C14 | 10nF ±20% 50V | 3 | Multilayer Ceramic 4mm | |
| Capacitor | C4 | 200pF ±20% 50V | 1 | Multilayer Ceramic 4mm | |
| Capacitor | C6 | 1nF ±20% 50V | 1 | Multilayer Ceramic 4mm | |
| Capacitor | C20 | 1uF ±20% 50V | 1 | Multilayer Ceramic 4mm | |
| Capacitor | C15 | 2.2uF ±20% 50V | 1 | Multilayer Ceramic 4mm | |
| Capacitor | C12, C13 | 2.2nF ±5% 50V | 2 | Polyester Mylar Film Capacitor | |
| Capacitor | C2, C1 | 6.8nF ±5% 50V | 2 | Polyester Mylar Film Capacitor | |
| Capacitor | C7, C8 | 33nF ±5% 50V | 2 | Polyester Mylar Film Capacitor | |
| Diode | D1, D2, D3 | 1N4148 | 3 | Switching Diode, 300mA 100V | |
| Resistor | R30, R33 | 15K | 2 | Metal Film 1/4W | |
| Resistor | R35 | 1M | 1 | Metal Film 1/4W | |
| Resistor | R18, R3, R16, R14, R4 | 47K | 5 | Metal Film 1/4W | |
| Resistor | R38 | 470 | 1 | Metal Film 1/4W | |
| Resistor | R12, R23, R29 | 33K | 3 | Metal Film 1/4W | |
| Resistor | R31, R27 | 20K | 2 | Metal Film 1/4W | |
| Resistor | R32, R28, R13, R26 | 1K | 4 | Metal Film 1/4W | |
| Resistor | R7 | 220R | 1 | Metal Film 1/4W | |
| Resistor | R2 | 3K | 1 | Metal Film 1/4W | |
| Resistor | R5 | 8K2 | 1 | Metal Film 1/4W | |
| Resistor | R34 | 2M | 1 | Metal Film 1/4W | |
| Resistor | R8, R6, R21, R20, R37, R22 | 100K | 6 | Metal Film 1/4W | |
| Resistor | R25 | 43K | 1 | Metal Film 1/4W | |
| Resistor | R19, R24 | 680R | 2 | Metal Film 1/4W | |
| Resistor | R9, R15, R11, R10 | 10K | 4 | Metal Film 1/4W | |
| Resistor | R17 | 820K | 1 | Metal Film 1/4W | |
| Resistor | R36 | 100R | 1 | Metal Film 1/4W | |
| Resistor | R1 | 1M2 | 1 | Metal Film 1/4W | |
| Transistor | Q3, Q1 | 2N3906 | 2 | PNP Transistor | |
| Transistor | Q2, Q4, Q6, Q7, Q8, Q5 | 2N3904 | 6 | NPN Transistor |
Constructing the Eurorack 808 Snare
Building the breadboard 808 Snare circuit
Our 808 Snare circuit is built on an N8 Eurorack breadboard. The layout is the same as a sprung breadboard, so if you’ve used one before, you should feel right at home. The product page provides a diagram of the layout and connections and an overview of the breadboard’s design and features.
As with any PCB construction, we want to build low to high, starting with the wires and then adding components in reverse order of height. Beginning with the lower-profile components makes our life easier by giving us more room to manoeuvre without the taller parts getting in the way. This design has several longer wires, which may be easier to route after the other components have been positioned, as indicated below.
1. First up, we add the shorter wires indicated in the “step 1” diagram. Strip around 3mm of insulation from each end of the wire and feed the conductor through the appropriate holes. It can be helpful to work in sections and use masking tape to hold several wires in place before flipping the breadboard for soldering. The pink and orange wires around C7 & C8 will run between and around the capacitors. Depending on the size of the capacitors you have chosen, it may be easier to add these after the caps are mounted.
2. With the wires in place, solder in the two DIL chip holders. It is good practice to solder one pin first and check that the part is flat on the board before soldering the other pins.
3. Add the flat resistors to the breadboard, for example, R35, R19, R26 etc.
4. Add the remaining resistors and the three diodes.
5. Capacitors. Solder in the small ones and then the big ones! The two electrolytic caps, C27 & C28, are polarized, so make sure to mount them with the correct orientation.
6. Important: Q8 is the reverse-biased noise-generating transistor, the schematic shows that pin three is not connected. Cut off pin three ( the collector ) of one of the 2N3904 NPN transistors and then mount this transistor in the Q8 position.
7. Now add the other seven transistors. Remember that Q1 and Q3 are PNP devices while the others are NPN, and check their correct orientation.
8. Solder in the 2×8 pin header (PH1), our power connector. The power connector can be mounted on either side of the breadboard, but we mount it on the front (component side) for an 8HP module like this.
9. Solder the single-row, 90-degree, 40-pin male header to the left edge connector since we are using an 8HP Eurorack Control Deck, the pin header is mounted on the breadboard’s rear (non-component side).
10. With the components in place, we now tackle the longer wires indicated in the “step 2” diagram to complete the breadboard.
Top Tip: It can be tough to strip the insulation from the short wires, like the ones connecting the power rails to the TL072 op-amp. Instead of stripping 3mm of insulation from each end, remove 6mm from one end of the wire and then cut the wire to length. You should then be able to slide the short piece of insulation along the conductor, leaving 3mm at each end.
The 808 Snare Control Deck
N8 Eurorack Control Decks have logical front and rear sides. The front has screen-printed boxes indicating where pots, jacks, and switches are mounted, while the rear doesn’t have these boxes. Components can be mounted on either the front or the rear.
For this 808 Snare module, we mount our jack sockets and pots on the front of the Control Deck, the side with screen-printed boxes, and add a number of wires to the rear.
Check out these guides for further details on mounting components on your Control Deck.
Important: The wires on the rear of the Control Deck should be added first.
1. On the rear of the Control Deck, position the short (black) wires connecting the “d-bus” to the spare horizontal C pad of each JPS cell, where a 3.5mm jack socket (J1-J3) will be mounted. These are JPS7, JPS9 & JPS10. Flip the control deck over to solder these wires in place from the front.
We are using the d-bus to create a common ground on the Control Deck, saving space on the Breadboard for our core circuit.
2. The schematic shows that Pin 1 of RV4 is also grounded. Pin 1 corresponds to the A pads of JPS8. To make this connection on the rear of the Control Deck, connect a black wire from JPS8’s vertical A pad to the “d-bus.”
3. The tip (T) of J2 is connected to the switch of J1 (TN). We can make this connection on the rear of the Control Deck by connecting JPS7’s horizontal B pad to JPS9’s Horizontal A pad. The yellow wire on the diagram.
4. Connect the vertical B and C pads of JPS1 on the rear of the Control Deck, again soldering from the front. This is the short pink wire on the diagram.
5. Take a moment, make coffee, and check that all the wires on the rear of the Control Deck match the diagram. They can be corrected after the pots and jack sockets are added, but you’ll save time if they are correct before they are added.
8. Dry-fit the potentiometers on the front of the Control Deck. If the pots have metal support tabs on their top and bottom edges, they should be tucked under the body, as illustrated here.
9. Dry fit the jacks on the front side of the Control Deck. If in doubt, check out this guide for correctly positioning jacks on the Control Deck.
10. Attach the pre-drilled Eurorack panel using the hex nuts provided with the jacks and pots, checking that the jacks are centred in the holes and that each component is seated on the Control Deck.
11. Leaving the panel attached, flip the Control Deck over and solder the pots and jacks into position from the rear. The trigger input jack (J2) needs its switch pin connected to ground. We achieve this by connecting the switch and ground pins of JPS9 on the rear of the Control Deck with a solder blob.
12. Remove the panel, position the 40-pin female header on the rear and solder it into place from the front. If needed, hold it in place with masking tape. Solder a pin at either end and check it is perpendicular before soldering the other pads.
13. Connect the finished Control Deck to the Breadboard using the pin headers.
14. Insert the TL072 and TL074 op-amps in their sockets, being careful to orient them correctly.
Testing, Testing, check one two.
Before you power up your snare for the first time, you should do some basic tests. While not extensive, these help keep the magic smoke in the components where it belongs.
Visual inspection
- Compare your module to the diagrams and schematic on this page. Do all the components and wires look like they are in the right place? Anything missing?
- Inspect the solder side of the Eurorack Breadboard and Control Deck.
- Are any of the pads shorted by solder splashes or untrimmed component leads?
- Are all the component leads soldered?
- Have solder bridges indicated on the diagrams been made?
Continuity
We want to ensure there is no continuity between +12v, ground and -12v rails. We’ll do this using a multimeter.
Put your multimeter in continuity test mode, then, with your module unpowered, check the continuity between the following points on the circuit:
- Connect one of the multimeter’s test leads to the +12V rail and the other to ground. There should be no continuity
- Connect one of the multimeter’s test leads to the -12V rail and the other to ground. There should be no continuity
- Connect one of the multimeter’s test leads to the -12V rail and the other to +12V. There should be no continuity
Power Up
If your new module passed the continuity tests and visual inspection, it’s time to power it up. If you have a bench power supply, it is good practice to use it for the first power up of a DIY synth module so that it is a minimum safe distance from your other modules.
The Eurorack power connector format is sadly a little open to interpretation, and many a module has lost its life to the specification’s vagueries.
N8 Eurorack prototype boards follow the most common convention. A white stripe is printed next to the -12V end of the power connector. Typically this is where the red stripe of the power cable should be aligned. BUT not every manufacturer follows this convention, and this is a DIY synth tutorial, so chances are you made your cables, right?
Always check that your power supply is supplying -12V at the red stripe before connecting power to your synth module and that the red stripe is connected to the -12V pin on the module.
Making your 808 Snare look beautiful
The final step is to make your shiny new DIY 808 Snare look the part next to those expensive commercial Eurorack modules. The good news is you can do this with nothing fancier than an inkjet printer and some sticky-back plastic.
We have a complete guide to making labels for Eurorack panels here. If orange and black are your thing, you can download our finished label, ready for printing.
Download the N808S label template.
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