pendragon-andyh/juno60

Analysis of Roland Juno60 sound

Juno60

Introduction

This project aims to analyse the sound of Roland's Juno 60 synthesizor with the eventual aim of recreating its distinctive sounds using the Web Audio API.

I decomposed the Juno 60 into the following functional areas so that I can analyse each in isolation:

• DCO - Sawtooth, PWM, Sub oscillator, Noise, Mix down
• Envelope - Attack, Decay, Release, PWM modulation, LPF modulation
• Filter - VCF, HPF
• Chorus
• TBC

Testing

The test plan is documented here. Most of my analysis was carried-out using the brilliant Sonic Visualiser software.

Resources

I found the following resources helpful for understanding the analogue synths.

• URLs for Juno 60
• URLs for Juno 106 - has almost identical sound engine.
• Books
• Web Audio API

Any mistakes and misinterpretations are entirely my fault.

Licensing

Copyright (c) 2015 Andy Harman and Pendragon Software Limited.

Released under the MIT license. Please feel free to reuse the techniques developed in this project in your own projects.

juno60's Issues

Chorus rate

Firstly, thanks for creating this repo. I am building a chorus plugin inspired by the Juno chorus and your analysis is very helpful.

It looks like you may have miscalculated the rate of Chorus II? (I haven't checked Chorus I+II)

In your analysis you show the rate as 2Hz, but your PWM Chorus 2 wav file looks like the LFO is completing a cycle approximately every 1.15 seconds, which corresponds to a rate of ~0.86Hz:

1/1.15 = 0.869 cycles per second

I have seen the figure of 0.86Hz mentioned on a forum someplace, which corresponds to that calculation.

And while I have your attention... :D Are you able to explain to me how you calculated the min and max delay times? I have found zero information about the LFO depth of the Juno chorus other than your analysis, so I am very keen to understand how you arrived at those figures.

EDIT: Ignore my last question. I can see that the offset of the delay is visible in the waveforms, so I assume that it is just a matter of measuring the points at which the offset is greatest and smallest.

Chorus I+II mod rate appears wrong

Hi, the LFO rating at 15.175 Hz seems very suspicious.
We are making a Juno chorus and we have used your sound samples as a reference.

It has current source available and there is experimentation in our repository.

This is a rapid analysis of your 1+2 saw sample, and we deduce a completely different mod rate.
Prior to this analysis, I have deduced from a ear a similar rate, and the ~15 Hz value seemed to absurdly fast to be believable.

Link to analysis:
jpcima/rc-effect-playground#2 (comment)