Here is my Time Machine.
An homemade stereo cassette tape echo
It took me 5 month to build. I had to start electronic from the very begining, and I think I’ve made every possible mistake before making this thing working.


Thanks everyone for your very encouraging comments, I really appreciate it !

A lot of you guys ask if I sell it or plan to build new machines. Answer is no, sorry.
Portable Marantz are getting rare and expansive, and often need to be serviced. And I’m not an expert for that. It would cost you a lot of money for an old machine that would fails who knows when.

Anyway, this guy here seems to work very well and is selling cassette echoes.

For those asking for tutorial or schematics : I won’t make a step by step tutorial, but I can give you pointers.
I invented nothing, I just modified a very old diy project and tried to make it stick to my needs.

– This project is called Echo Matic. You’ll find everything you need on google.

– I use a 3-head stereo Marantz recorder (PMD430). Rather hard to find at a good price, put I was lucky and got one for 70 €. You’ll also need the service manual to understand how different circuits of the recorder works.

– I added an active EQ I found on a very good French site. Here it is :

– Motor speed : I replaced the internal speed trim pot of the recorder with a 20k linear pot and wires.

– You have two Chinese VU meters I found on eBay. I just plugged them same as the old ones and I changed the settings with the internal trim pots of the recorder.

– Stereo ? I always have trouble to explain that part… The cassette deck itself is stereo. In the echomatic project you will find a description about how to wire your recorder inputs and outputs to use both tracks for doubling the delay time. This principle can be used to achieve a ping pong delay effect.

Signal goes like that : guitar – echomatic in – ecomatic send – recorder input 1 (left track of the tape) – output 1 (left track from the tape play back head = delayed signal)

At this point you have two options :

1) take output 1 and wire it to your echomatic return. You have a mono delay
2) Take output 1 and route it directly to input 2. Then take output 2 and wire it to the echomatic’s return.
It’s not stereo yet but your delay sound (the wet signal) is now recorded on 2 tape tracks. The echo is twice longer and it’s very useful to fix the fidelity lost related to low motor speed.

If you choose option 2, all you need to do now for stereo is to plug wires (along with the wiring I just describe) on your two recorder outputs and solder them on two nice RCA or jack outputs.

After that I used a 4DPD switch to select option 1 (mono, single delay) or option two (double delay time and stereo outputs).

– In my machine I put CV and gate inputs to control tape speed with an external device.
CV input is directly plugged in the motor speed pot. Gate is achieved with a MOSFET transistor.
Tutorial here

– I also built a pwm motor controller so I can choose with a switch between the Marantz motor speed circuit and the one I’ve made. I thought it would have made the motor more stable. Actually, the Marantz circuit is better, so I use the pwm when I want unstable wobbly sounds.
You have a lot of pwm circuit online, choose one with a cutting frequency above the earring frequencies (20 hz – 15 khz basically) Otherwise you’ll end with a very annoying buzz in your sound.

– Power supply : You have now at least 4 circuit to feed with electricity. Your recorder (4,5 V), the echo matic circuit (9V) and the EQ (15V). I bought a 16V wallwart power supply and voltage regulators, LM7805, LM7809 etc. along with radiators fixed on a metal plate to spread the heat of all this lost power.

Tutorial here

– The box where everything fits is an old Mexican wooden cigar box I found on « le bon coin » the French version of craigslist. The inside is shielded with aluminium tape and connected to ground. It’s very tight down there, and it’s actually a very big mess.
I’ve made a terrible mistake and chose to use stiff wire… Don’t do that. Please. Never. I spend my time re-soldering cables because they just break.

That’s it. If you have questions, like precise questions, just ask 😉

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