Echo & Reverb Box




Introduction: Echo & Reverb Box

About: I've always liked pulling things apart - it's the putting back together again that I have some issues with!

This build is based around a great little reverb module you can get on eBay for under $5. I’ve used it now in a couple of projects (listed below) but this time I wanted to have a stand along reverb and echo effects box. You can use this in a whole bunch of different applications from a guitar pedal and Karaoke effects box to an effects module for DJ’s and synths.

I built mine primarily for my synths that I have been building over the last 18 months (check out my ible' page for the synth builds). Adding echo gives my bleeps and bloops a whole other dimension. I’ve also used it as a guitar pedal which produces a rich and beautiful sound. You could customise it even further to make it as a stand along guitar pedal very easily if you want to.

I brought 2 of these echo modules (I do each time I buy them, I usually kill one of them when I mess around with it!) as I’m starting to build a modular synth and I want to add a reverb and echo board to it.

Projects I've used this module in

Sound Bending Synth

Dub Siren Synth

Hackaday have also been nice enough to review this project. The article can be found here

Step 1: So What Can You Do With a Echo & Reverb Box?

What can't you do! Oh the things you can do!

- You can use it as a guitar pedal and play some nice, echoey tunes

- You can plug a mike into it (actually what it is advertised as) and be a karaoke superstar

- You can use it as a echo/delay effect on a modular synth

- You can use it for small beep boop type synths (you know the 555 timer types) to give them some awesome body and sound

- You can play music through it and get some funky beats and rhythms as the drums and voices echo

there are millions more but I've run out of room...

If you want to know more about the IC that is at the heart of this module - then check out this page on the PT2399 IC

Step 2: Parts & Tools


1. Reverb module – eBay (buy 2 in case one gets damaged)

2. 2 X 50K Potentiometers – eBay

3. 2 X Pot knobs - eBay

4. 2 X 3.5mm Jack inputs – eBay

5. 2 X 6.5mm Jack inputs – eBay

6. SPDT switch. I pulled mine out of some old electronics – eBay

7. Momentary switch – eBay

8. 3mm LED – eBay

9. 330R Resistor . Buy them in assortment lots- eBay

10. Case – eBay, Jcar (Australian electronics store)

11. You’ll also need a couple of 3.5mm male jacks which you can get from eBay

12. 9V battery holder – eBay

13. 9v Battery

14. Wires


1. Soldering Iron

2. Pliers

3. Screwdrivers and Phillips heads

4. Wires cutters

5. Drill

6. Hot Glue

Step 3: The Case

I used a case that I found at my local electronics store (I’ve added a link in the parts section) but it’s up to you want you want to use.


1. First thing is to decide how you want to lay out all of the parts. If you were making a guitar pedal you would probably place the knobs further back and use a 3PDT guitar pedal switch instead of the momentary one I used.

2. Once you are happy with how the parts are going to fit, unscrew the box and get ready to measure and drill some holes

Step 4: Drilling Holes for the Switches and Potentiometers

To ensure that holes were aligned I use a caliper to do all my measurements. You can use a ruler but make sure you follow the rule – measure twice, cut once. I have also recently brought myself some step drill bits. Can’t believe it has taken me this long to get some but they are awesome in making clean holes at the sizes you need.


1. First I measured where I wanted to add the potentiometers and drill these holes

2. Next I added a hole in the middle of the pot holes for the momentary switch

3. Drill a small hole for the LED. I added mine near the on/off SPDT switch.

3. Lastly I added a rectangular hole for my on/off SPDT switch. I pulled this switch out of something ages ago and I finally got around to using it.

Making a Rectangular Hole

4. To make a rectangular hole, first measure the switch and mark out on the box

5. Next, use a drill to make 2 holes inside the measured area. Don’t drill too close to the markings on the box, you want to give yourself some buffer

6. Cut away any plastic you can such as the small bit between the 2 drilled holes

7. Grab a flat file and start to remove the plastic.

8. Once you get a rectangular shape, try and push the switch in. You’ll probably have to remove more plastic before the switch will fit into place

Step 5: Adding the Switches and Potentiometers

Now you have a bunch of holes in your case, it’s time to add the auxiliary parts.


1. Secure the momentary push switch

2. Add the 2 potentiometers. They are the same value so it doesn’t matter which hole you add them to. You don’t have to add the counting scales to the potentiometer but they are handy.

3. Add the SPDT switch. My switch didn’t lock into place so I used some hot glue to secure it

4. Add the LED and superglue it into place if necessary

5. I added another SPDT toggle switch later on which isn’t shown here. The toggle switch allows you to change from having the echo always on to having off until you hit the red momentary switch.

Step 6: Adding the Audio Inputs to the Case

Next thing to do is to add the audio jack inputs into the case. I decided to add 2 different sizes, one for 3.5mm jacks like you use on your headphones and some 6.5mm (1/4”) jacks like the ones you use on your guitar. This makes the echo & reverb box more versatile and open.


1. First you will need to add 4 holes into the side section of the case. Measure, mark and drill the holes for each of the jack inputs.

2. Secure each of the jack inputs into place using the small nuts that come with them

3. One lot of the jack inputs will be “audio in” and the other lot will be “audio out”. You need to connect a 3.5mm and a6.5mm jack together for each audio in and audio out.

4. I’ve added an image of a male jack input which shows how a male jack connects to the points inside a female jack insert. The tip and first ring are left and right and the last ring is ground.

Step 7: Making Sure Everything Fits Ok

I know that it might be self-evident but I’ve failed to do this before and had some major issues. Once you have everything attached to the case, place the components inside it like the battery and the module and make sure everything fits ok. For a large case I did still have to mod the battery holder slightly in order for everything to fit.

The main problem I had was the large on/off switch which I placed top, middle of the case. It hit the top of the battery (just) and I had to make a small mod in order for everything to fit.

Once you are happy then it’s time to start adding a bunch of wires to the module

Step 8: Modding the Module

The module only comes with reverb. You need to remove a resistor to control echo as well. You might need to remove the potentiometer attached to the module as well. It will depend on what type of case you use and where you want to place the pots.


1. First, locate the R27 resistor. It is labelled R27 and is near 3 small solder points. Those 3 solder points are where you will add the 2nd pot.

2. To remove the SMD resistor you can just use an exacto knife and cut it away. Do it carefully though as you don’t want to damage any of the other components

3. If you do have to remove the pot on the board then I suggest you use a pair of wire cutters and cut it off. The reason being, the solder pads are very fragile and if you try and de-solder the pot you might rip them off (I’ve done it a couple times before). Easier to just destroy the pot and cut it away then take the chance.

4. You’re board is now ready to get a bunch of wires solder to it

Step 9: Wiring the Module

Now it’s time to solder some wires to the module. I like to use computer ribbon when I do this as it’s thin, easy to use and I get it for free from my local e-waste. Always make sure that the wire is longer then you need it. You can always trim later but having to extend is a pain.


1. Solder wires to the “+” and “-“ IN Solder points on the module

2. Solder wires to the “+” and “-“ OUT Solder points on the module

3. You will also need to add wires for the potentiometers. Add a little solder to each of the solder points and connect 3 wires to each one

4. You can add the power wires later so don’t worry about them for the moment

Step 10: Connecting All of the Components

Now onto the fun bit! It’s time to connect all those wires to the pots, jacks and switches. I have make a schematic of how I connected the input jacks together and also how to wire everything up including the switches. Those with sharp eyes may have noticed that I have only included 1 switch in the schematic and my build has 2. That’s because you only really need one switch which is an on-off-on one. I used an on-off one to start with and later decided to change the build which meant adding an on-off-on switch.


1. When connecting the wires from the module to the auxiliary parts, it’s important that you are able to do the following:

a. get to the module easily in-case you have to make changes

b. ensure that the wires are long enough so when you are soldering them to the auxiliary parts, the top section of the case can sit flat.

c. Take your time and carefully solder each wire into place

2. Once you have everything connected, it’s time to give it a test. Plug in a jack to the input jack and plug the other end into your phone

3. Add another jack to the output jack and plug this into a speaker

4. Play some music and you should here it reverb and echo through the speaker. If you don’t hear anything, try the following:

a. Turn g the pots full one way then the other.

b. Remove the battery from the holder and add it back in again

c. Check your wiring on the jacks. Note that the 6.5mm input jack has 2 solder points for the tip. Only use one of these when attaching to the 3.5mm input jack and module.

d. Check all of your connections again and make sure that they are correct.

5. At the last minute, I added an external power input jack. Up to you if you want to do this or not. It allows me to plug it into the wall and bypass the battery

That's it! You can now add echo and reverb to any audio source! Have fun and if you do make one, post a couple images in the comments section.

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Question 1 year ago

I am confused about the Momentary switch in the circuit:
It is described as turning the Echo on when you hold in the switch - which is useful.
But the wiring diagram shows it as allowing the positive current from the battery to flow to the circuit board - to me, it appears to be acting as an on-off switch for the entire unit.
Am I missing something? I would appreciate an explanation of where I am going wrong.

Thank you in advance,



Question 2 years ago

Hello, I had an idea that I thought might be neat and wanted to hear your thoughts on it. Planning on building a couple synths for myself and either building this module or integrating it, however I was also thinking of building a little guitar pedal as a present for my girlfriend, but I don't have any knowledge about guitars whatsoever so forgive me if this sounds dumb.

I came across this Fuzz Pedal and I was wondering wether it would be possible to kill two birds with one stone and build one box containing both circuits and having just the one Input and Output terminal. Then I would add a SPDT switch for each module either switching it on or bypassing it if I didn't want to use the effect.
Firstly: Would that even work/would it sound any good? Also would it be better leading the reverbed signal into the distorion circuit or vice versa, or does this not matter? Secondly: Would I still need all the pots or could I combine the functions, say, by using dual gang pots instead? What exactly do the pots in this build do anyway?

Any thoughts, tips, tricks, ideas or insights of any nature much appreciated. Thank you!


Answer 2 years ago

Been thinking more about that, and I came to the conclusion that It might make more sense anyway to just build both pedals and then they can be chained together like that. Would make everything easier when playing and you could switch between effects more seemlessly. I knew that idea would be dumb haha!


Answer 2 years ago

Building a 2 in 1 pedal won't be an issue. you can even power it from the same 9v battery or power source. You just have to have 2 SPDT stomp switches like used in the Fuzz pedal 'ible and wire them up to each of the circuits. I would do a little research on how best to wire those switches up as it can be a little complicated. If you are asking whether you could use both circuits at the same time then yes you could. Would it sound any good? I have no idea! It could be amazing or make your ears bleed - you'll prob just have to try it to see if it will work or not.
I'd also use separate pots as well - it's only 4 in total so not too many. would also give you more control if you wanted to use both at the same time.


2 years ago

Check out the YouTube vid, Moog circuit bend challenge winner (2019 I think) the guy hacks an Omnichord musical toy, he adds this module, he adds a B100k pot to the echo (or delay time) pads and an extra A100k pot connecting pin 3 to the outer pin of C15 and the middle pin to the middle pin of the stock issue pot on the the module (the wet/dry mix knob) it extends the delay time massively which gets noisey on this ic. I've built a few, one had 2 crashing into each other. Chaotic industrial delays which can be coaxed into latching on to a signal and repeating it for hours.


Reply 2 years ago

Thanks for letting me know about this! Just watched the winning circuit bend winners entry. Going to have to play around some more with the PT2399 module now and see what else I can get out of it.


Reply 2 years ago

I'll share a couple of my favourite bends with you. When wiring in the Delay time pot try shorting it with a switch or push button to get it to glitch, you can coax the classic 70's Dub trick, of banging the top of a spring reverb unit. You can also wire a switch or button to bypass the Feedback pot, using upto 20k resistor inline, to get a boost effect, happy bending


2 years ago


Ive just built one of these as a foot pedal but at the moment, I cant seem to hear any echo or Reverb - do you have any more information on wiring up the pots and is there any info available on the module and how to test it is working OK?



Reply 2 years ago

Sorry for the late reply. Have you tried disconnecting and then reconnecting the battery? I know it sounds simple but I have had to do this in the past on one of them and this seemed to work.

have you also removed R27 from the board? I have found that the traces around the pots can be a little weak as well. If one of them is broken it won't work and you might have to try again


3 years ago

You mention an LED and 330R resistor; I'd guess they're in series with the power, but I don't see where it says so.


Reply 3 years ago

Yep you got it. Just connect ground to the battery and positive to the switch and have the LED and resistor in series.


3 years ago

This is amazing, can't wait to build it, but what interested me the most was the mention of the 555 synth. Might build one of those with this built in.


Reply 3 years ago

Yeah I really love this little module. It heaps of fun to play around with. Good luck with the 555 synth as well.