Tag Archive for swell effect

Project Ryu Lagger Guitar Pedal Take 3

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LM13600 LM13700 slow attack pedal

Hello dear readers,


It has been a quiet period but a very busy period, very active and very fruitful. I will be launching the projectryu.com site soon with tons of free resources for the audio hobbyist.


Getting back to the title of this post, i would like to present a few improvements and a concrete design as a pedal unit.  If you don’t remember about the Lagger project let me put the links below in case you want to check it out.

Project Ryu Lagger – Guitar Effect

Project Ryu Lagger Guitar Pedal Take 2


As a quick summary, Project Ryu Lagger is  a guitar effect pedal that slows down the attack of the guitar (or any instrument for that matter) just like an automated volume pedal.

It does this with a VCA (Voltage Controlled Amplifier), based on the LM13600/LM13700. The fade in envelope is created with a ramp voltage generator that controls the VCA and this generator is triggered by a digital circuit created with a Microchip PI18F1320 MCU.

The digital signal conversion and rectification is explained in a previous article, please read it at the link below:

Analog to Digital Signal Rectification


The new version i will present today was adapted as a real pedal with a 3 pole footswitch.

Another change was in the ramp generator replacing the 100k potentiometer with a 10k one since the other two pots in the circuit are 10k. This last change also implies changing some capacitor values. Please refer to the new schematics below:

Project Ryu Lagger Schematics

I am pretty satisfied with this pedal so i have created the PCB for this circuit. The PCB gerber files and the MCU firmware is available for free as usual to subscribers in the next newsletters. If you are not a subscriber yet please register in the form to the right.

Slow attack pedal PCB Project Ryu Lagger

Some things to consider if you plan to design your own PCB is good shield of the LM13600/13700 input pins. It is good to surround it with ground plane like below:

pch shield LM13600 LM13700

You can find the PCB artwork below:

Project Ryu Lagger PCB Art

With the new modifications on the ramp generator circuit the min – max values for attack control is 0.1s and about 1.4s. Below is the ramp waveform measured, this is actually the control voltage of the VCA:

1. full counter clockwise attack pot setting:

Horizontal resolution: 50ms/div

Project Ryu Lagger control voltage

2. full clockwise attack pot setting:

Horizontal resolution: 200ms/div

Project Ryu Lagger LM13700 control voltage

Below is a screenshot that shows the triggering of the ramp generator, the red trace is the input signal:

Project Ryu Lagger LM13600 LM13700 swell pedal

As you can see modifying the attack control will adjust the length of the fade in effect. The trigger control adjust the input level above which the ramp generator is triggered. This is to prevent noisy pickups or other pedals used in front of the Lagger to trigger the effect.

The level control adjusts output gain from between +6dB to a max of +24dB so it is capable of a high amount of gain. In the measurement below voltage gain is 14 with an output voltage of 3.6V peak to peak (yellow trace). As you can see there is a bit of saturation happening.

Project Ryu Lagger Measurement


Bellow are two videos showing signal traces using sine waves at 1kHz, one video triggering the effect manually and the other with the effect triggered by the input signal.

Project Ryu Lagger is one of my favorite pedals, i really like this effect and the latest version allows for a great deal of control for the guitarist in sustaining the effect or muting by simply applying muting effects with the palm for example.

Project Ryu Lagger Guitar Pedal

Project Ryu Lagger Guitar Pedal

Project Ryu Lagger Guitar Pedal


For DIY-ers this project is of moderate complexity but you can subscribe or comment here and i will try to offer any assistance i can. Remember to read the Disclaimer though.

Here is the parts list for this project:

Quantity: References Value
3 C1, C8, C15 4.7u
2 C2, C3 22p
1 C4 10u
1 C5 100u
2 C6, C7 33u
1 C9 4700u
1 C10 10u
2 C11, C12 1000u
5 C13, C14, C16-C18 100n
2 R1, R21 2k
13 R2, R6-R12, R15, R22, R23, R26, R28 10k
1 R3 22k
1 R4 3.3k
4 R5, R29, R31, R32 2.2k
3 R13, R14, R24 100k
1 R18 1k
1 R19 470
2 R20, R25 200
1 R27 5.6k
1 R33 1M
1 U1 LM13700
1 U2 PIC18F1320
1 U3 78L05
1 U4 79L05
2 U5, U6 TL071
2 Q1, Q2 BC549
1 Q3 BC559
2 D1, D2 1N4001
1 D5 LED
1 J3 3 pole foot switch
3 POT1-POT3 10k
1 RV1 1k
1 X1 20Mhz Crystal

I hope you enjoyed reading this article as much as i enjoyed building this pedal and hope to hear from you. To the subscribers, the newsletter will be sent in a few days with Gerber files for PCB and MCU firmware and a couple more details about this construction.


Here are 2 sample sounds of the effect played by one of my guitarist friends:


Thank you for your visit.