Source Audio C4 Modular Synth Pedal

rsmith601

Vendor
Messages
6,192
I have reconstructed 1 of the ones I sent on the offline Spectrum editor. I have also reconstructed another that @jibreel thought he’d converted but it seems something went awry. I can’t see anything in the other two that shouldn’t work so I’ll reconstruct those too.

I’ll PM you with screenshots and the values written in for ease of programming.
Awesome! Thanks.
 

bassbrad

Member
Messages
21
Some folks asked for this. I will improve the formatting later.

ENVELOPES IN THE C4

8/19/19

The Source Audio C4 Synth pedal has two envelope followers available. They both have the same capabilities, but their control parameters may be set differently. Input 1 or input 2 may serve as the input signal to either. An envelope follower uses its audio input signal to output a representation of how loud the audio is at the moment. Louder signals get a higher output level from the envelope follower.

Since the audio signal goes both positive and negative, we first take the absolute value of the audio; negative values are replaced by the same number, but made positive. A certain amount of smoothing is necessary, because the input signal will repeatedly go to zero, but at a rate which we don't perceive as a level change, since it is happening too fast for us to hear like that. Deliberately introducing a slower than necessary smoothing will cause the output to move more slowly than the actual audio signal changes. Different smoothing rates for attack (a rising output) and decay (a falling output) permit more control over the final response.

Whereas a typical synthesizer has a controllable release time on its envelopes (which begins when one takes their hand off a keyboard note), we have the problem that the guitar sound is over when a note is through. A synthesizer oscillator would still be running, but the pitch detector output tends to lose it as a note is dying away, so the synth oscillator is also not reliably available after note end. So our final release times are always quite short.

We also offer ADSR type envelopes (attack – decay – sustain – release). The attack segment begins when an attack threshold level is exceeded. When the envelope level gets to 1.0 (full scale ON), the decay segment takes over, dropping until the sustain level is reached. When the input gets below a release threshold, we go into a (fast, as always) release segment. These threshold levels are fixed. One more reason to do the Input Gain Calibration procedure, to make sure your guitar signal is in the proper range, for the fixed thresholds.

All of these possible envelope controls are not brought out to the user interface. This is partly due to trying to save bits in the preset data (and if you had asked me 50 years ago whether saving bits would still be a thing in 2019, I would have laughed), and also to keep the complexity down. Reasonable people may disagree that boiling down a lot of controls into only a few, with a selection of envelope types, is really simpler. But that's the way it is.

The Envelope Type definitions:

Atk_lo Atk_hi Dec_lo Dec_hi Fast_atk ADSR Sustain

0 ADSR Adj A/D 0.2 1.0 0.2 0.6 N/A YES 0.0

Both A and D are controlled by the Speed control. With Speed = 0 (full counterclockwise), we use an Attack control value of 0.2. When Speed = 1.0 (full clockwise), the Attack control is 1.0.

1 Fast A, Adj D 0.7 0.7 0.2 0.85 0.05 NO N/A

The Attack control is fixed at 0.7.

2 Wide 1, Adj A/D 0.0 1.0 0.2 0.6 0.03 NO N/A

3 Swell 0.0 0.4 0.0 0.2 0.02 NO N/A

Slowest attack.

4 Wide 2, Adj A/D 0.0 1.0 0.5 0.8 0.07 NO N/A

Same Attack range, but Decay is faster than #2.

5 Snappy 0.6 1.0 0.4 0.75 0.15 NO N/A

Fast.

6 ADSR Fast A, Adj D 0.9 1.0 0.1 0.55 N/A YES 0.0

7 ADSR Adj A/D 0.0 1.0 0.2 0.5 N/A YES 0.0

8 ADSR 4 0.9 1.0 0.1 0.55 N/A YES 0.2

Same as #6, but with a Sustain level of .2.

9 ADSR 5 0.0 1.0 0.2 0.5 N/A YES 0.2

Same as #7, but with a Sustain level of .2.

10 ADSR Slow A, Fast D 0.0 0.5 0.55 0.55 N/A YES 0.0

13 Fastest A, Adj D 1.0 1.0 0.2 0.8 0.5 NO N/A

The Speed control goes from 0.0 to 1.0, for both Attack and Decay times. This is translated to the following range of what are called "time constants". (After one time constant, a decaying signal has dropped to 36.8% (or -8.7 dB) from its starting value.)

Speed Time Constant

1.0 .65 msec

0.75 6.5 msec

0.5 65 msec

0.25 650 msec

0.0 6.5 sec

The Fast-Attack number controls exactly how fast the initial attack can rise. 1.0 is instantaneous; 0.5 is the fastest used. Most are considerably slower. The ADSR envelopes do not use this control.

Sustain is the ADSR sustain level. Most are 0.0, with two at 0.2.
Thank you I guess or, or was this some sort of Monday engineer's rant or am I supposed to apologize for asking? Go away kiddo, because I said so dammit! ;-) I do honestly understand and appreciate what an engineering challenge and accomplishment it is to have created such an AH-F-ing-Mazing a pedal as the C4 and thank the heavens every day for Bill Chidlaw and the SA crew for this tool I waited 40 years for. I don't really feel any better informed about what the Envelope types do or don't do and I want to Grok this incredible beast.
 

Funksandwich

Member
Messages
17
Is there a way to set the presets so they are unaffected by the physical knobs? I use a DMC to shuffle through and it would be great to not have to adjust the controls
 

rsmith601

Vendor
Messages
6,192
Is there a way to set the presets so they are unaffected by the physical knobs? I use a DMC to shuffle through and it would be great to not have to adjust the controls
I believe this is called "preset mode" and it can be configured in the app and editor hardware settings. You might want to see the manual about this. I forget!!
 

rsmith601

Vendor
Messages
6,192
Thank you I guess or, or was this some sort of Monday engineer's rant or am I supposed to apologize for asking? Go away kiddo, because I said so dammit! ;-) I do honestly understand and appreciate what an engineering challenge and accomplishment it is to have created such an AH-F-ing-Mazing a pedal as the C4 and thank the heavens every day for Bill Chidlaw and the SA crew for this tool I waited 40 years for. I don't really feel any better informed about what the Envelope types do or don't do and I want to Grok this incredible beast.
The formatting is a mess and makes that one section really hard to read. I am working on this.
 

bassbrad

Member
Messages
21

Quatschmacher

Member
Messages
452
@rsmith601 there seems to be a bug in the iOS app. Every time I try to preview a patch via a soundcloud clip with headphones plugged in, the next patch that loads has the sound coming out of the speak instead and I have to unplug and put in the headphones again to switch back.

Also, the search function in the “library” tab doesn’t seem to be working. Are your servers overloaded?
 

rsmith601

Vendor
Messages
6,192
@rsmith601 there seems to be a bug in the iOS app. Every time I try to preview a patch via a soundcloud clip with headphones plugged in, the next patch that loads has the sound coming out of the speak instead and I have to unplug and put in the headphones again to switch back.

Also, the search function in the “library” tab doesn’t seem to be working. Are your servers overloaded?
The search function on my Android works perfectly. Anyone else having trouble searching with your library on iOS?

Audio preview works fine for me on Android and Windows.

Making sure that preset preview works across all platforms and devices perfectly on YouTube and SoundCloud is beyond the scope of our offering. These are sound development tools for an audience or a few thousand skilled users and not a million person audience consumer audio listening tool.

If there is some kind of serious issue impacting multiple platforms, we need to know.
 

rsmith601

Vendor
Messages
6,192
Some folks asked for this. I will improve the formatting later.

ENVELOPES IN THE C4

8/19/19

The Source Audio C4 Synth pedal has two envelope followers available. They both have the same capabilities, but their control parameters may be set differently. Input 1 or input 2 may serve as the input signal to either. An envelope follower uses its audio input signal to output a representation of how loud the audio is at the moment. Louder signals get a higher output level from the envelope follower.

Since the audio signal goes both positive and negative, we first take the absolute value of the audio; negative values are replaced by the same number, but made positive. A certain amount of smoothing is necessary, because the input signal will repeatedly go to zero, but at a rate which we don't perceive as a level change, since it is happening too fast for us to hear like that. Deliberately introducing a slower than necessary smoothing will cause the output to move more slowly than the actual audio signal changes. Different smoothing rates for attack (a rising output) and decay (a falling output) permit more control over the final response.

Whereas a typical synthesizer has a controllable release time on its envelopes (which begins when one takes their hand off a keyboard note), we have the problem that the guitar sound is over when a note is through. A synthesizer oscillator would still be running, but the pitch detector output tends to lose it as a note is dying away, so the synth oscillator is also not reliably available after note end. So our final release times are always quite short.

We also offer ADSR type envelopes (attack – decay – sustain – release). The attack segment begins when an attack threshold level is exceeded. When the envelope level gets to 1.0 (full scale ON), the decay segment takes over, dropping until the sustain level is reached. When the input gets below a release threshold, we go into a (fast, as always) release segment. These threshold levels are fixed. One more reason to do the Input Gain Calibration procedure, to make sure your guitar signal is in the proper range, for the fixed thresholds.

All of these possible envelope controls are not brought out to the user interface. This is partly due to trying to save bits in the preset data (and if you had asked me 50 years ago whether saving bits would still be a thing in 2019, I would have laughed), and also to keep the complexity down. Reasonable people may disagree that boiling down a lot of controls into only a few, with a selection of envelope types, is really simpler. But that's the way it is.

The Envelope Type definitions:

The Speed control goes from 0.0 to 1.0, for both Attack and Decay times. This is translated to the following range of what are called "time constants". (After one time constant, a decaying signal has dropped to 36.8% (or -8.7 dB) from its starting value.)


The Fast-Attack number controls exactly how fast the initial attack can rise. 1.0 is instantaneous; 0.5 is the fastest used. Most are considerably slower. The ADSR envelopes do not use this control.

Sustain is the ADSR sustain level. Most are 0.0, with two at 0.2.
@bassbrad New formatting makes this much more useful!!!
 

Quatschmacher

Member
Messages
452
I’ve finally got a soundcloud account and have recorded and uploaded clips for many of my patches.

It seems that TGP has the same embedding problem that TB has so here’s a link to the basschat page where I’ve successfully uploaded the whole playlist of patches, I’ll add to it as I write more and record clips:
https://www.basschat.co.uk/topic/335905-source-audio-c4-synth-pedal/?do=findComment&comment=3823790

For anyone downloading my patches, I’d strongly recommend getting an expression pedal as most have some kind of morphing assigned to expression (external, via the hub). If you have a Source Audio expression pedal then you’ll need edit the patches to select that in the external control section.

I’m thinking about getting a Hot Hand too so there may be more craziness to come. Watch this space.
 
Last edited:

Auger64

Member
Messages
94
While having the C4 plugged into the hub, I am seeing intermittent rapid blinking of the ALT function LED. There seems to be no rhyme or reason for this and it doesn't seem to affect the sound of the pedal. The main LED also went to a red AND green solid mode at one point. This DID require me to unplug and plug the unit back in. Anyone else have this issue?

I am using the supplied power supply.
 

rsmith601

Vendor
Messages
6,192
While having the C4 plugged into the hub, I am seeing intermittent rapid blinking of the ALT function LED. There seems to be no rhyme or reason for this and it doesn't seem to affect the sound of the pedal. The main LED also went to a red AND green solid mode at one point. This DID require me to unplug and plug the unit back in. Anyone else have this issue?

I am using the supplied power supply.
That sounds like the calibration mode. It is covered in the manual. This is to ensure your input level is at the ideal setting for the envelope and such.
 

Auger64

Member
Messages
94
That sounds like the calibration mode. It is covered in the manual. This is to ensure your input level is at the ideal setting for the envelope and such.
I don't think that's it, Roger. It's only happening if I have a Hub cable in...and I'm not touching the controls on the pedal. Besides, I thought that was the MAIN LED not the ALT function LED.
 

rsmith601

Vendor
Messages
6,192
I don't think that's it, Roger. It's only happening if I have a Hub cable in...and I'm not touching the controls on the pedal. Besides, I thought that was the MAIN LED not the ALT function LED.
You are right. I just checked. The manual:
o INPUT CALIBRATION FUNCTION: We have provided a unique Input Calibration Function to assure that you are getting the best possible interaction between your instrument and the C4. The Calibration process is as follows: 1. Turn the INPUT knob all the way down. 2. Continuously pluck your instrument at your average plucking velocity. 3. Slowly turn up the INPUT knob up until the center LED starts flashing red. This flashing indicates that you have reached the optimum INPUT level. Leave the knob where it is – the process is complete

I will investigate.
 

rsmith601

Vendor
Messages
6,192
While having the C4 plugged into the hub, I am seeing intermittent rapid blinking of the ALT function LED. There seems to be no rhyme or reason for this and it doesn't seem to affect the sound of the pedal. The main LED also went to a red AND green solid mode at one point. This DID require me to unplug and plug the unit back in. Anyone else have this issue?

I am using the supplied power supply.
What’s the MIDI source? IS there an expression pedal connected somewhere?

Might be some stray CCs sneaking through.
 

Gibs210

Member
Messages
8,233
I don't think that's it, Roger. It's only happening if I have a Hub cable in...and I'm not touching the controls on the pedal. Besides, I thought that was the MAIN LED not the ALT function LED.
You are right. I just checked. The manual:
o INPUT CALIBRATION FUNCTION: We have provided a unique Input Calibration Function to assure that you are getting the best possible interaction between your instrument and the C4. The Calibration process is as follows: 1. Turn the INPUT knob all the way down. 2. Continuously pluck your instrument at your average plucking velocity. 3. Slowly turn up the INPUT knob up until the center LED starts flashing red. This flashing indicates that you have reached the optimum INPUT level. Leave the knob where it is – the process is complete

I will investigate.
Make sure you have the external switch option disabled in the editor, it will mess with the pedal when it’s actually connected to the hub.
 

Quatschmacher

Member
Messages
452
@RSmith I’ve had another instance of the “likes” all disappearing from patches when editing info. This time, all the patches to which I added sound clips have had the likes reset to 0 in the “community” tab. I wonder if it’s either the “edit” or the “save” command which is causing this or indeed simply just any edit made after the preset has been initially uploaded. If people are searching for most popular patches it’s going to get in the way of that.
 

Auger64

Member
Messages
94
What’s the MIDI source? IS there an expression pedal connected somewhere?

Might be some stray CCs sneaking through.
Make sure you have the external switch option disabled in the editor, it will mess with the pedal when it’s actually connected to the hub.
I'm running out of the Soleman into the Hub. There is no expression pedal at the moment as I unplugged the one I was using (I'm getting a new mini one)... Hmm? Wonder if that's it? The cable is still plugged into the Hub... BUT none of my 4 other SA pedals are having these issues so that's probably not it.

Gibs5000 I will check later when I get home that the ext. switch option is disabled.
 




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