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Based on a pair of PT2399 chips The Jellyfish is a double delay with modulation options capable of a wide variety of sounds. Analog passive filters, CV inputs, two LFOs, infinite feedback switch, xdelay function, “dry” and “wet” controls, pseudo-stereo (1 in-2 outs) or mono mixed sound makes this delay machine a versatile tool for your live set or your studio. From simple delay lines to crazy modulated stereo sounds.



Front Panel Controls:

VELO: Frequency of the LFO. It can go from 0,33 to 3,12 Hz and modulates the time parameter of the delay.

DEPTH: Quantity of modulation applied to the time parameter. It goes from 0 or no modulation to full wave modulation. It works on the LFOs and the CV inputs.

WAVE: This switch changes between square or triangle waves of the LFO. These are not exact square and triangle waves. It have some imperfections giving its own character to the machine. Square and triangle waves have different amplitudes also.

TIME: The main function of the delay. It controls the delay time and varies from 27 to 570msg. With this times the PT2399 are going through its capabilities. So on longer times you will notice some noise and distortion of the sound.

FINE: This pot also controls the delay time but only a 10% of the main pot do. It is very useful when you want to be very precise or when using the two delay lines at once, providing nice surf stereo expanding sound.

FEEDBACK: It sends the output of the delay again to its input causing repetition. It varies from 0 (one delay) to infinite. To more repetitions, more distortion and filtering are added to the sound.

INFINTE: When this switch is activated and the feedback pot set at its maximum position the repetion never stops. This makes that the level increases at every step.

DRY & WET: Mix input and effect signals to the output. Note that this pots are not are the same level when clockwise. The effect level amplifies the signal while the DRY have a gain of 1. If you want a gain of 1 on the effect turn the pot at 3 o’clock.

XDELAY: When activated this switch sends the output of the delay line 1 to the input of the delay line 2 and viceversa. This tool is used for create interesting double delay lines. It’s necessary to turn on the feedback pot of the secundary delay line to activate this feature. The feedback pot acts as a level of the 2nd delay.

PARALLEL: When it’s off this switch sends the delay line 1 to out 1 and the delay line 2 to out 2. When it’s on sends the 2 delay lines to the output 1.

BYPASS: Turns on and off the effect. When off the input goes directly to outs 1 and 2 through a buffer.

Rear Panel Controls:

CV INPUTS: this inputs modulates the time parameter of the delay. When plugged it deactivates the LFO. It accept positive DC signals. Too loud line signal can distort the chip input.

OUT 1: Output signal of the delay line 1.

OUT2: Output signal of the delay line 2.

IN: Input signal. It accepts line, synth and instrument levels.

DC 9V: Accepts 9V DC center negative. The machines consumes 60mA, use a power supply with 100-200mA.

General Specs:

CASE: Aluminum black painted.

DIMENSIONS: 188x120x33 mm

WEIGHT: 687 gr.



The signal goes through a buffer (an amp with a gain of 1) and feed the two delay chips and filters. At the output the signal is mixed with the buffered original signal and then send to the outputs. Every LFO is sent to its delay line. The Xdelay switch combines the two delays. The parallel switch sends the signal of delay 2 to out 2 or 1. The bypass switch activates or deactivates the effect.




Input is feed to IC3D buffer inverting the signal. C35 and C36 decouple the signal and send it to the delays respective parts. The signal is also buffered with a non-inverting configuration for send it directly to the output via the bypass switch.

The Jellyfish Schematic

The delays

** The two delays lines are identical so we will center in part 1. **

The signal comes from the buffer (1) and passes through a series of passive low-pass filters before entering in to the internal stages of the chip via the pin16. R11-C11 and R23-C50 forms this two firsts filters. R23 is normally used as a trimmer in the PCB for adjust the cut-off frequency.

The delayed signal comes from pin 12 of the chip, and then is filtered two more times via R5-C9 and R44-C51. R44 is another trimmer. The signal is sent again into the second internal LPF and passes through the last 2 filters: R3-C51 and R31-C29. C31 acts as decoupling capacitor sending the delayed sound to P5, “feedback”, and  P6, “wet,” pots.

From the P5  the signal passes through S7, the “xdelay” function. When S7 is low the signal goes directly to SW2, “infinite” switch, and then passes to R13 and R15 resistors, a combination of resistors and trimmers. This trimmers are used to adjust the maximum repeats when P5 is fully clockwise. From this point the signal goes again to the second filter of the beginning of the chain, the R23-C50 filter. This means that P5 controls the amount of repetitions and with every repetition the signal is filtered again.

When S7 is high the delayed signal goes to SW4, “infinte” switch of the second delay, entering into it and then returning again to delay 1 via S7 switch. This means that the delayed signal is delayed a second time before entering again into the circuit.

From P6 the signal is mixed with the buffered (1) original signal (through P7) via the inverting IC3A op-amp. Then the signal goes directly to OUT1.

From the second delay line SW6, “parallel” switch,  sends the signal to IC3A, mixing it with the delay line 1, or to IC3B, sending it to output 2.

From the other side P3 and P4 control the amount of the delay time. These 2 pots ara connected to ground via Q1, a JFET that acts as a variable resistor depending on the incoming voltage from the “LFO” path. Due to its configuration, the signal voltage from the LFO and CV must be positive.

The LFOs

A square wave is generated using an Schmitt Trigger,  from the hex inverter CD4016. IC4-1, P1, R25 and C27 forms a very simple circuit that generates the wave. This is not a pure square wave but is very useful for this purpose. Q3 and R27 forms the triangle wave. Waves are selected via SW1 and goes to P2, “depth”pot, adjusting the amount of signal that goes to Q1. Between S1 and P2 there is he CV in formed by a switched jack that disconnects the LFO when plugged.



You can also download it here.


Before you start to assemble the Jellyfish be sure that you have the following list of material:

- The Jellyfish PCB
- The components listed in the BOM (Bill of Materials) – The Jellyfish case or any other case that you like
- Soldering iron
- Solder
- Cutters

- Soldering skills! This is nothing that you can buy, so if you don’t know how to solder check out some tutorial. Just type “how to solder” in your search engine and you will find thousands of tutorials. It is also recomended to start with a smaller project like the WSG from MFOS.


ATTENTION!: continue at your own risk. We’re not responsible for any problem ocurred in this stage of the process. This includes any injuries and accidents like electric shocks, fires, burns, etc. You’re advised.

Take your time soldering all the components and triple-check every value. Saving 1/2 hour here can result in an error that will take you days to fix. Go step by step and you will easly succeed.
Prisa mata amigo



Start soldering the resistors to the PCB. Follow the BOM to check out which value corresponds to every label. Start with the 1K resistors R37 and R38. Put it in place, solder and cut. Continue with the 1K2 resistors and so.


Do NOT solder R23, R29, R44 and R46. These are filter resistors. You will solder 4 trimmers here later. Only if you know what are you doing solder the resistors that you consider. Check the schematic for reference.

IC sockets

Time to solder the sockets now. Notice that the sockets for the PT2399 are 16 pin type, and the ones for CD40106 and TL074 are 14 pin type.

Put the 4 sockets in place and turn the PCB trying to maintain the sockets in place. Using a plastic or a wood sheet will help. Solder the 4 sockets.


Capacitors and diode

Start with the film capacitors. Like with the resistors follow the BOM and solder by groups. Start with the 10nf C9, C10, C49, C50, C51, C52, C53. Solder it and continue with the next ones.


Continue with the ceramic caps and the 1N4001 diode. Take in mind that the diode is polarized. Do not solder C34.


Now solder de electrolitic capacitors.


This capacitors are polarized. The long leg of the capacitor should go to the “+” symbol of the PCB. Just like this:

electro polarity

Transistors and voltage regulator

Now solder the 6 transistors and the voltage regulator. Transistors are temperature sensitive and too much heating time can destroy it. The use of pliers here pressing gently to body of the transistor is a good way to dissipate the heat of the solder. You will need an extra hand (or tool).



Solder now the 14 potentiometers. Push carefully until the base of the potentiometer is touching the PCB. It is very important for all the pots to be straight and perpendicular to the board. If not you might find some trouble later.

It is a good idea to all the potentiometers first, and then solder it.



Like the potentiometers, switches must be installed and soldered straight and parallel. Solder it to the board.



Solder the leds now. You have to use the led spacers and put every led trough its spacer before solder it to the board. Note that the leds are polarized. The short leg must go where the line cuts the circle.



You can solder the trimmers to the upper side of the board, but is better to do it to the other side. This way you can calibrate the machine without disassembly the case every time.

Solder 13B, 14B, 15B and 16B. You can see that it are already soldered in the picture.


Before soldering R23, R29, R44 and R46 you need to adapt the trimmers, as only 2 legs are used. Cut one of the legs, as in the picture, and solder to the board.


Now is time to wiring. You can see that the ICs are mounted in the sockets.


Before wiring and if you don’t want to use the CV inputs you need to solder a bridge between the 2 holes of “CV1″ an “CV2″. If you want to use the CV inputs, which is recommended, just jump this step.


For the wiring follow this diagram:


Important on wiring:

- You could connect the ground to the switch of the “IN” jack. Doing it you will prevent noise when nothing is plugged in. Don’t do the same with the outputs.

- Twist thight the power wires and keep it short. This way you will prevent noise.

- The wiring diagram for the power jack is for a power supply with +9V at the ring and ground at the tip. If your power supply is diferent, reverse the wiring here.

- It is recomended to solder the power cables on the top side of the board and rest on the bottom side. Wiring will be easy later.

- The best way for wiring is:

1. solder the wires to the board,

2. assemble the board and the case without screwing,

3. assemble the connectors to the case and

4. solder the wires to the connectors.

You can now screw the nuts of the switches, turn on the machine and test it.

Before turning it on check that the “time” pot is not at its minimum position. It will cause malfunction to the chip.


If everything is ok you can assemble the knobs. You don’t need to screw the pot nuts. With the switches the machine is well fixed to the case. If you want to do it don’t screw too hard or you will bend the PCB.

Congratulations! You’ve finished the Jellyfish! You need to calibrate it now.


C34 appears to be soldered in some of the last pictures. If you don’t know what are you doing leave it empty.



You can also download it here.


- Start with the 4 upper trimmers (ch1).

- Connect a source of sound to the input.

- Turn “FDBCKA” & “FDBCKB” somewhere between 12 and 3 o’clock.

- Turn the “Feedback” pot until you can listen 3 or 4 repetitions.

- Adjust the filter trimmers to your taste. I like to leave it around 1 – 2 o’clock, just pointing the upper-right corner.

- Use a short sound as a source now.

- Switch down the “Infinite” switch and adjust the “feedback” pot to max.

- Turn the trimmer ”FDBCKA” until the repetitions are very long but it fade out finally. Try different “Time” positions.

- Switch up the “Infinite” switch.

- Turn the trimmer ”FDBCKB” until the repetitions never stop. Don’t cross too much this point or the delay will become too crazy.

- Repeat for channel 2.


The BOM (Bill of Materials). Here.

The PCB etching files. Here. Remember to flip before print when necessary.

The case template. Here.