Janky Tape Echo

An open source, DIY tape echo effect for guitars, vocals, and synthesisers.

Real tape echo

This isn't a digital emulation, but instead a real magnetic tape echo that uses cassette heads and magnetic tape for lots of warm, crunchy, warbly echo. Add a lo-fi cassette vibe to your sound.

Indifferent Engine - Janky Tape Echo
Indifferent Engine cassette echo

Made from readily available parts

The primary design principle is to enable the project to be built by as many people as possible, as easily as possible. All parts are selected to be easy to source online.

3D printed

Designed to be printed on any home FDM 3D Printer with a print area of 160mm x 150mm x 50mm or bigger using PLA, ABS or PETG filaments.

Janky Tape Echo code

Digital control

The motor controller is driven digitally by an Arduino Nano board. This allows for modulating the motor control signal for added warbles, flutters and wow using simple software.

Fully open source

​Want to make your own improvements and upgrades?


The design is fully open source, including all source CAD for Fusion 360, Eagle schematic files, Arduino code and PCB gerbers. We also provide PCB blanks that have the jacks and potentiometers in the correct places to fit the 3D printed parts, so that you can easily make your own board layouts.


Make the design better and share it with the world. 

Licensed under GNU Public License v3.0

Indifferent Engine - Janky Tape Echo CAD
Tape Cassette


  • Cheap and relatively easy to fix yourself to keep it running. Break something? Print more parts at home!

  • Uses readily available cassette machine parts that can be found online. There are also no exotic electronic or hardware parts - we try to use easy-to-find parts like TL072 op-amps rather than discrete transistors that are becoming rare.

  • Uses simple cassette tape for making replacement tape loops

  • The design is free and open source. We will sell PCBs on our merch store to make it easier for you to build and so that you can support the band. But, you don't even have to source a PCB from us - gerbers are provided for you to take to any PCB manufacturer - or to make your own boards at home.

  • Customisable. Want to make your own modifications? Perhaps add stereo, or an expression pedal or extra switches and potentiometers? It's entirely open source, so go right ahead. We even provide PCB blanks to make it easy for you to make your own customised boards.

  • 3D printed parts can be printed in PLA filament for easy home printing. All parts are also designed to print without supports.

  • Pre-printed kits will be available from our merch store, making it possible for you to build a tape echo, even if you don't have a 3D printer.


  • Not as reliable as commercially available devices. Expect to have to change tape loops and perform maintenance yourself.

  • Requires a 3D printer. Any reasonable home FDM printer will do, but is a big expense if you don't already have access to one. Pre-printed kits will be available in limited numbers.

  • It's big, for a stompbox. If you want something smaller, simpler and more dependable for your pedalboard then there are great commercial, digital pedals available that get a really good approximation of the tape sound.

  • It's really janky. Really. This isn't a clean sounding echo - it has a lo-fi, noisy cassette vibe. Even at minimum-jank this thing adds a lot of warble and character.

  • Complicated to build. It's not often that a DIY stompbox requires not just electronics, but software, 3D printing, moving parts and redundant magnetic tape media. There are a lot of challenges to making a working, reliable device. But, it is a lot of fun and we provide a video walk-through.

  • If you don't get a kit from us, then it requires some light CAD work. Heads are all different dimensions and so you will need to make some small "adapters" to fit your heads. Don't worry, it's easier than it sounds and there is an instruction video on how to do this with the free software TinkerCad. If you're new to CAD this will be an easy introduction to designing your own parts.

  • Parts are selected to be easy to find and use and the design is kept as simple as possible. This means that in a lot of ways performance isn't optimal - you can get better sound quality and performance but that would make it harder for other people to copy. The electronics would be more complicated with a higher part count, using more discrete or exotic parts. Likewise, If we used a higher quality tape machine then it would be harder for people to find that exact machine.

  • No direct support is offered by us. We provide videos to show how to build the device and provide PCBs and kits for sale, so that you don't have to  make or source your own parts, but beyond that, you're on your own. If something we've sold you is faulty, then we will of course address that, but we won't help you debug your rats nest of wiring or dodgy soldering job.

  • Not for commercial use. If we catch you selling these devices we will find you and force you to come to one of our floor shows where we can full-throat scream right in your sad little face.

Broken Cassette Tape
Indifferent Engine @ Club85 for Feral Promotions

Have a listen

Indifferent Engine @ Club 85

Download - Coming Soon!

All the project files - including 3D printing STLs, Fusion 360 CADs , PCB files and schematics - will be available from our GitHub page soon. Well. Soon-ish.

Pre-order Kits and PCBs

Pre-order for both kits and PCBs will be opening soon. Keep an eye on our social stuff, or sign-up to our mailing list to get notified.


Frequently asked questions

Where do I find everything I need?

The project has not yet released. Follow us on social places or sign-up to the mailing list to get notified when it launches. Once it does, everything will be available on our GitHub page. This includes 3D printer files, software, instructions, bill of materials, source CAD files and schematics. If you want to help support us by buying a PCB directly from us then look out for the PCB pre-order, which will be opening soon. You can source PCBs yourself using the gerber files included on our GitHub, but by buying from us you'll be helping the band do more stupid projects and play more messy shows.

​Do you sell assembled pedals?

No. We only build these for ourselves and - occasionally - for musicians we have played with or that we respect. Please don't contact us asking us to build you one. We're not hyper-libertarian capitalist gangster pirates, so we currently have no plans to sell completed tape echo pedals. Maybe in the future when we're hard up for cash.

Do you sell kits?

Yes, we plan to do this. However, we will likely not be offering kits that include the electronic components, at least not at first - you will have to find these yourself from a local supplier. A full bill of materials will be available to help you find what you need. Luckily it doesn't use any unusual parts - you shouldn't have any problem finding the components you need.

Why don't you sell these assembled?

A number of reasons. These devices are not up to what we would consider commercial quality - they're made from 3D printed PLA plastic and as such are not built to particularly tight tolerances. Commercial machines would need to ideally be made from metal, or at the very least injection moulded plastic - both of which are much more expensive and complicated. They also take some tuning to get the tape loop working reliably. As a DIY device it makes good sense - if you can build this thing then you can easily repair and service it and so if you smash it to bits at a show you can get it working again without too much trouble - just print yourself some new parts. But, if it's a commercial device then we'd have to price in you sending it back to us to repair it and service it. That would mean it wouldn't be economically viable when compared to what's already available on the market. Even more of a problem is the time commitment - we are first and foremost a DIY punk band. We do these sorts of projects to use in our art and also to make a little money to keep the band going. We make almost no money from our music or selling T-Shirts, so by selling PCBs that are easy to make and to ship we are trying to make a bit of cash to keep the band going - and maybe to fund some interesting "installation" shows. We also want to focus on recording music and playing shows, so we don't have time to manufacture and service these in any kind of numbers.  If you want something you can just buy at a reasonable price right now that includes warranty and manufacturer support, go check out the T-Rex Replicator Jr. Yea, it doesn't look as cool - and won't get you as much DIY-punk respect - but we have one in our studio and can confirm it sounds great. We used a replicator extensively on the Canis EP.

Can I build these to sell?

No.  I mean yea if you wanna build one or two for your mates, if you're grabbing the boards and/or kits from us then it's all good. But don't setup a little criminal empire hocking these things. Essentially, don't be a dick.

Can I sell these in kit form?

No. However, if you're a kit shop and would like a license to do this please contact us to discuss.

Can I release my own modified version?

Yes - however, you must release it as sources and you cannot charge money for it. This is a requirement of the GNU Public License. Support the open source community, you scallywag.

Where can I find build instructions?

Build instructions will be via video on our YouTube channel. There's also a PDF file included in the package that provides some step-by-step instructions. The videos are useful to actually see what you need to do, though, so I recommend you watch those as you go.

How much does the janky tape echo cost to build?

That depends. If you already own all the tools needed and are building from scratch (not using one of our kits) then we estimate that you can build a tape echo for between £130 and £170 UK pounds. However, there are a number of ways you can save money compared to how we build - for example by cutting and drilling the acrylic window yourself, using cheaper filaments for your printer or simply sourcing cheaper electronics. If you buy a kit from us then it's going to cost a fair bit more, because it takes a lot of labour on our end to create the kits. We haven't set firm prices yet for kits.

I'm having trouble with my build, where can I get help?

We don't offer support so please don't contact us for this. Of course if you suspect a board or kit we've sold you is faulty then get in touch - however, this is very unlikely. If you're having trouble it's almost certainly that you've made a mistake somewhere. Here's a quick checklist of things you can test to make sure you haven't made a simple mistake.

  1. Check your tape machine is turned up on the original tape machine PCB. There's a small volume control on the original tape machine next to the headphone jack - that needs to be turned up or you'll get no repeats. With kits we have already set this and glued it in place.

  2. Check all wiring. Check all wiring is connected to the correct places. Check your guitar and amp are connected, powered on and turned up. Check you're using the correct power supply - 12V DC center negative rated to at least 1A. Check the control board is connected correctly.

  3. Check voltages with a multimeter. Check you get 12V coming in at the DC jack. Check the outputs of all three voltage regulators are kicking out the expected voltages - if not it's likely the regulator pinout is incorrect.

  4. Check your Bias Oscillator is working. We show you how to do this with a cheap, pocket oscilloscope in the instructional videos.

  5. Did you make the ground link? There's two little pads called GND_LNK. If you don't connect these together, then nothing is gonna work.

  6. I get dry signal but no echo. Check that the magnetic tape loop is the correct way around. Cassette tape is only ferrous-coated on one side, so make sure that side is facing the heads. Also make sure your playback head is engaged by clicking it down onto the tape. Check your tape machine's headphone output is turned up on the little fader on the original tape machine PCB. Check the oscillator works. Check all wiring. If all else fails, follow the schematic in the Eagle schematic and PCB files and use an audio probe to trace where the problem is.

  7. The motor runs but the reel doesn't move. Don't forget to engage your playback head by clicking it down into place. Check the transport drive belt hasn't come loose. Check the transport is running the correct direction - it has auto-reverse so might be running the wrong way. If this is the case you can change the direction with a small round button on the top of the transport - press the button while the transport is running with the head engaged.

  8. I get a low quality, quiet or crackly echo. This is most likely due to the tape being mis-aligned with the record head or the tension of the tape loop being wrong. You need to adjust your record head mounting to make sure that you're getting a clean but not-too-tight contact with the tape. Watch the build instructions video, specifically the section that deals with making tape loops. Alternatively, this can be due to a malfunctioning bias oscillator, so get out the oscilloscope and check the oscillator is working as you expect. If you've been running the machine for a while you may simply have worn out the tape loop - tape loops wear out over time due to the physical stress of being run through the machine as well as the ferrous coating being damaged by the heads writing and erasing the tape over and over. Might be time for a new loop!

  9. The machine runs fine for a short while and then the tape loop shreds/jams. This is most likely due to the wrong tension in your loop, or simply using cheap tape. Watch the section of the build instructions that deals with making tape loops. In short, you need to make sure the write head is brushing against the tape cleanly but not too much or too little. Too much and the tape will tend to jam, and the tape will stretch, wear or even shred. Too little and you'll get lower quality or intermittent echo. Currently tension is adjusted in two ways - firstly by the length of the tape loop. Shorter loops will be tighter, longer loops will have some slack. The other way is to adjust the head adapter to move the head closer/further from the tape. I make my loops the same length each time and then for a given machine I move the head closer/further by adjusting the position of the head mounting holes on the adapter until I find just the right spot. Also make sure you're using felt contact pads with your heads and again that they're not applying too much or too little pressure. Another potential cause could be that your tape path isn't "clean" and so the tape is catching on something. This could be edges of your reels, maybe a misaligned head or a bit of 3D printed plastic that needs sanding down. 3D printing parts is not the most accurate way to manufacture something - the tolerances are quite low due to part shrinkage and depending on how well tuned your machine is. So make sure your parts fit together cleanly and you remove any little nodules of plastic that the tape might be rubbing on. Last useful tip - make sure you use high quality tape. Cassette tape is not all created equal and you generally want to use the thickest tape you can find - watch the instructions video for more on that. Also check that your steel rods are as vertical as possible - I once had 3D parts that didn't print as cleanly as usual and so the rod mounting holes were a little too wide. This resulted in the rods not being vertical but leaning off to the side a little. This caused the tape to precess up and down the rods, wearing against the plastic surfaces as they went and eventually they tangled or shredded. You can always use a little glue in the mounting hole to hold the rods if that helps - just remember you to only glue one end as you need to be able to remove the top plastic part in order to replace the tape loop in the future! Keep in mind tape loops will wear out eventually - if you've been running the machine a lot then at some point you will have to replace the loop. All part of the joy of a real tape echo!

  10. My parts won't 3d print cleanly. All parts are designed to be easy to print on a home 3D printer - these parts shouldn't be challenging to print if you have a bit of printing experience. Everything will print in PLA and no supports are needed. Check your parts are oriented correctly on the bed - that the correct surface is facing down. I tend to print with 60% infill and a reasonably large layer height (I use 0.32mm). Most printing problems are due to the tuning of your printer - make sure the bed is level. Almost all problems beginners have are a bed being not levelled quite right. Make sure you're using good hot-end and bed temperatures for your filament - these are different for different filaments so experiment a bit. Make sure the gantry is aligned and your extruder is working correctly and e-steps are configured correctly. Make sure the nozzle isn't worn out or clogged. Make sure belt tensions are right. For the small parts like the reel clamps you can add a brim when slicing in order to prevent them warping.

  11. My tape transport makes a horrible clicking, crunching sound when I start the motor. Your motor is wired backwards - switch the red and black wires around where they connect to the echo PCB.

  12. Auto-reverse keeps kicking in and /or the tape runs the wrong way. If you follow the build instructions I show you how to permanently disable the auto-reverse feature on these tape machines. However, if auto-reverse is kicking in it's because your tape loop is jamming - I suggest disabling it, but also you may need to work on your tape-loop-making skills and adjust your head positions. In order to change the direction the transport runs, there's a small round button on the top left of the transport that will change the machine direction - the machine has to be running with the playback head engaged for that to work.

  13. My bias oscillator doesn't work or isn't stable. Make sure you've used the correct voltage rating for all capacitors. If in doubt, use 100V rated capacitors. Make sure your transistors are the correct type and match the pin-out expected by the PCB. Never run the circuit without the erase head attached - this can cause the transistors to overheat and die. Very occasionally, I come across an erase head that just doesn't want to work with the oscillator. If all else fails, try a different erase head and see if it sorts the problem.

  14. My computer can't upload code to the Arduino Nano. Make sure the USB cable you're using is a data cable. Some USB cables are power only - often called charging cables. You need a data cable to transfer data to the Arduino. Always blame the USB cable first. Make sure you have the correct board type, processor and port selected under the Tools menu. After that, check you have a genuine Arduino Nano - there are many clones and fakes around. Keep an eye on the console at the bottom of the Arduino IDE for errors, warnings or info that might indicate what the problem is. If you've made modifications to the code, make sure the code actually compiles.

Where can I find tape heads?

Check E-bay, AliExpress, BangGood etc. Failing that - buy a broken second hand cassette machine and take the heads out of that. You'll need a read head, write head and erase head. If you're building the big, 4-head machine you'll need an extra read head. Read and write heads are generally interchangeable. Erase heads are specifically designed for that purpose. You will only find erase heads in tape players that have a recording function. You need an active erase head - not one of those little tiny passive magnet ones. Please don't destroy a perfectly good, working tape machine to just harvest the heads - there's loads of broken ones out there that can be recycled. The majority of broken machines are due to mechanical issues and so the heads are almost certainly going to be fine - maybe just give them a clean with some isopropanol.

Can I base my echo around a different tape machine than the one specified in the bill of materials?

In theory yes - but you would need to do some CAD work to make the 3D printed parts fit your machine. How extensive that would be depends on the machine you're trying to use. There's a rumour that these new tape machines that we use are based around the only transport that's still manufactured new. If that's true, then it means if you buy a brand new (not NOS) machine, then it will have this transport in. So maybe it doesn't matter unless you want to use a vintage machine?

Why didn't you design this to use cassettes rather than a tape loop?

There's no simple way to include 3 heads when using a standard C cassette. Cassettes have 3 openings along the top to interface with the machine, but one of these would be used by the pinch roller that drives the tape through the machine. This would mean you wouldn't get any erase functionality and would have to continually switch (and manually erase) the tapes between uses. If this isn't a problem for you then you could rework the design to take cassettes reasonably easily - provided you can do the CAD work.

Why didn't you board-mount the remote-switching jack?

Because we hit the maximum board size for the free version of Eagle. We're too poor to buy an Eagle subscription, but also want to keep the project "free" to develop - if we keep the board size under the maximum size for the free version then anyone can develop new designs without needing a subscription. We provide PCB blanks that only has the jacks and pots on (so that the jacks and controls are in the correct place to mount on the 3D printed parts) for you to experiment with your own layout and own modified electronics.

Are you continuing to develop improvements yourselves?

Yes. We're also developing other crazy ideas, so give us a follow.

I'd like to make my own modifications, any ideas on what cool things I could add?

Yep, there's loads of scope to make modifications. You could make two devices and connect the Arduinos together over serial so that they can synchronise their motor speeds. Then you have a stereo tape machine - one for left, one for right. But why not just use one machine - as cassettes support stereo - I hear you ask? Well, because this way the left and right machines will run at slightly different speeds due to subtle variations in motor speed and will thus create a really cool stereo chorus effect. You could even add a control to increase the variation in motor speed between the 2 devices to widen the chorusing effect. Maybe make the 2 machines into one 3U rack-mount case for your studio? Why not add a dry-kill switch to get only the repeats for use in the studio. We provide extra pads on the PCB next to the Arduino (and also on the control board) to access ADC channels for adding controls - so, why not add some simple switches or extra potentiometers to change the janky-ness behaviour on the front panel? Or perhaps push the guitar signal into an ADC channel on the Arduino and use it to create an envelope follower that adjusts the delay time based on what you play? Or add an external expression pedal jack via ADC? Try allowing the user to use multiple read (or write) heads at the same time for interesting rhythmic effects. Why not reuse parts of the design to make a simple cassette-synth? Or any crazy cassette based thing you can imagine.

How can I support the project?

Everything is open-source so feel free to contribute design improvements. Just keep in mind that the core principles are to keep the electronics and hardware simple and easy to source. However, there are lots of ways to improve this design while sticking to those principles so have at it!

How can I support the project if I don't know anything about electronics or CAD or whatever?

Just support the band - we will make more weird stuff and share it with you. Support us by listening to our music and then share it with your mates. Or come to a show and let us scream at you! Stick around after if you want to chat. Or simply buy a T-Shirt, you filthy animal!