# Cali76 CBC confessions

Discussion in 'Effects [BG]' started by RichSnyder, Feb 25, 2021.

1. ### JKosSupporting Member

Oct 26, 2010
Torrance, CA
If hitting a low E produced only a sine wave at 41 Hz and the sidechain filter perfectly removed all signal below, say, 50 Hz, your statement would, indeed, be true.

However, that is far from a real bass signal. Any meaningful, real bass signal (like the output of your bass) contains significant energy above the root. And that energy will cause the compressor to reduce the gain across the spectrum.

The Cali76CB does not reduce the gain of a 100 Hz signal while not, at the same time, reduce the gain of a 20 Hz signal. It's not a multiband compressor.

Last edited: Mar 20, 2021
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2. ### frankzap

Apr 11, 2014
Bronx, New York
They say exactly what I am saying .

The frequencies filtered out of the sidechain are 20Hz (most filtered) to 350Hz (least filtered). Turning the HPF control clockwise reduces the amount of these frequencies that trigger the compressor
(this happens in the sidechain), making them (this "them" creates a bit of confusion, because they refer to what happens with these same frequencies in the actual working signal, otherwise they would contradict themselves, right? because something cannot be filtered out and end up louder at the same time in the same place) relatively louder than frequencies above 350Hz.

3. ### JKosSupporting Member

Oct 26, 2010
Torrance, CA
@frankzap ,
You're simply not understanding the connection between the sidechain filter, detector, gain reduction, and the "working signal." I'll try to use some scenarios to help.

Let us assume the sidechain filter is a perfect high pass filter at 50 Hz, the threshold is 0 dB, compression ratio is 10:1, and zero make up gain.

Scenario A: Sine wave at 41 Hz, 10 dB. The detector will detect nothing. The output is a 41 Hz sine wave at 10 dB.

Scenario B: Sine wave at 41 Hz, 10 dB, and 82 Hz, 5 dB. The detector will detect the 82 Hz, 5 dB signal as 5 dB above the threshold. Given a 10:1 ratio, that would cause a 4.5 dB gain reduction. The output will be a 41 Hz sine wave at 5.5 dB and an 82 Hz sine wave at 0.5 dB.

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4. ### frankzap

Apr 11, 2014
Bronx, New York
And this is where you make the mistake, because you don’t factor in the makeup gain, which will affect 41Hz as well. Do the math for 41Hz after you apply the general makeup gain to compensate for the compression at 82Hz. 41 Hz is not compressed, because the sidechain will decide that. It will end up at 10db x makeup gain.

5. ### RichSnyderGold Supporting MemberSupporting Member

Jun 19, 2003
I thought the entire signal is compressed or not, just that the triggering only looks at at portion of the signal.

6. ### frankzap

Apr 11, 2014
Bronx, New York
The hpf in the sidechain introduces a form of a time delay due to the difference in amplitude’s of low and high frequency spectrum. The signal is split and as long as the compression is not triggered by the filtered sidechain, the high-amplitude lows from the input pass uncompressed to the output (more correct proportionally compressed in the amount dictated by the hpf slope), and amplified by the makeup gain introduced to compensate the signal reduction set for the frequencies above the hpf.

7. ### JKosSupporting Member

Oct 26, 2010
Torrance, CA
Incorrect. The ENTIRE signal is reduced by the gain reduction amount then make up gain applied. If the gain reduction is 4.5 dB and the make up gain is 4.5 dB then BOTH the 41 Hz and 82 Hz signal will be the same at the output as at the input.

The 41 Hz signal will NOT be 10 dB plus make up gain in this scenario. It will be 10 dB - 4.5 dB + 4.5 dB = 10 dB.

Last edited: Mar 20, 2021
Derek Williams likes this.
8. ### frankzap

Apr 11, 2014
Bronx, New York

9. ### frankzap

Apr 11, 2014
Bronx, New York
Just for the fun of it, can you explain how the 41Hz is reduced since the detector won’t see it (hence the compressor is not yet triggered) while passing to the output and concomitantly amplified by the makeup gain?

10. ### JKosSupporting Member

Oct 26, 2010
Torrance, CA
Are you referring to scenario A or B?

11. ### frankzap

Apr 11, 2014
Bronx, New York
I am referring at both, since the makeup gain is set at +4.5db and remains unchanged.

12. ### JKosSupporting Member

Oct 26, 2010
Torrance, CA
@frankzap ,
In the non-real life scenario A, in which only a 41 Hz signal is present, output will be input level plus make up gain. You do understand that this is not a realistic scenario, right?

In scenario B, the detector will detect the 82 Hz, 5 dB signal as 5 dB above the threshold. Given a 10:1 compression ratio, that would cause a 4.5 dB gain reduction. Given the unfortunate choice of make up gain also being 4.5 dB, -4.5 dB plus 4.5 dB is 0 dB meaning the output is same as the input. Thus, the output will be a 41 Hz sine wave at 10 dB and an 82 Hz sine wave at 5 dB.

13. ### frankzap

Apr 11, 2014
Bronx, New York
Once the makeup gain is hard set with a knob it is real for any scenario. If the makeup gain is not used, you end up using the compressor as a nice attenuator for the frequencies not affected by the behavior dictated by the sidechain filter.

You contradict yourself. Just above you state “The output will be a 41 Hz sine wave at 5.5 dB and an 82 Hz sine wave at 0.5 dB.”

You are still wrong in your interpretation of how a compressor with a sidechain filter behaves, because in this new statement “Thus, the output will be a 41 Hz sine wave at 10 dB and an 82 Hz sine wave at 5 dB.” you don’t factor in the sidechain filter behavior, which this discussion was all about. In this one you state your compressor capriciously behaves like a buffer for the 41Hz and as a compressor for the 82Hz, arbitrarily taking out the makup gain stage AND the sidechain filter for the “buffer behavior” and introducing again the makeup gain for the “compression behavior” while still leaving out the sidechain filter influence... all these at the same time.

I’ll stop here.

Last edited: Mar 21, 2021
14. ### JKosSupporting Member

Oct 26, 2010
Torrance, CA
The first numbers were before you wanted make up gain included.
Do you agree with the following statements which describe how a compressor with a sidechain filter works?
A) The sidechain filter is not in the audio path from input to output.
B) Gain reduction as determined by the detector is applied equally across the spectrum.
C) Make up gain is applied equally across the spectrum.
Incorrect interpretation. Both are reduced by the gain reduction and then increased by the make up gain. Having the calculated gain reduction and make up gain be the same was a very poor choice for the illustration. My bad.

Let's try this again. Please specify some arbitrary numbers for the following.

1) Frequency A at amplitude x
2) Frequency B at amplitude y
3) Threshold
4) Compression ratio
5) Make up gain

We will assume the following.
1) The sidechain filter is a perfect HPF
2) Frequency A is below the HPF cutoff frequency
3) Frequency B is above the HPF cutoff frequency
4) Hard knee compression

I will write out all the math for you.

Last edited: Mar 21, 2021
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15. ### JKosSupporting Member

Oct 26, 2010
Torrance, CA
Let's try a different example.
1) Frequency A at amplitude 4.1 dB
2) Frequency B at amplitude 7.5 dB
3) Threshold of 0 dB
4) Compression ratio of 5:1
5) Make up gain if 2 dB

Gain reduction = (Freq B amplitude - Threshold)/ratio = (7.5 dB - 0 dB)/5 = 7.5 dB/5 = 1.5 dB

Output level = Input level - Gain reduction + Make up gain = Input level - 1.5 dB + 2 dB = Input level + 0.5 dB

Freq A output level = Freq A input level + 0.5 dB = 4.1 dB + 0.5 dB = 4.6 dB

Freq B output level = Freq B input level + 0.5 dB = 7.5 dB + 0.5 dB = 8.0 dB

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16. ### frankzap

Apr 11, 2014
Bronx, New York
You don't seem to understand that frequencies bellow the scf are not affected by compression but are affected by the makeup gain, ending up amplified at the output. Consequently, frequencies above the scf are affected by both, gain reduction AND makeup gain at the same time, ending up at the same level at the output (provided that makeup gain exactly compensate for the gain reduction). And now, I'll definitely stop.

17. ### Derek Williams

May 14, 2020
Milton Keynes, UK
A compressor sidechain is just an alternate signal that the compressor uses to decide how much to compress the entire audio signal. I’ve never heard of a sidechain that will decide which frequencies get compressed. Some compressors could have a separate sidechain loop where you could run an EQ to help put emphasis on the frequencies that you want to control the compressor. You could even have a completely unrelated signal coming in (like a kick drum) that causes the bass to duck out.

So no, the Cali76 Compact Bass doesn’t compress different frequencies differently, it isn’t a multiband compressor. And if it was, I’d want the opposite behaviour. I like a heavily compressed low end, and more dynamics in the high end.

RichSnyder likes this.
18. ### revd

Apr 11, 2020
It does compress different frequencies differently if you use the the HPF sidechain.

From the manual :

"With the HPF control dialled in, the compression ratio effectively becomes frequency dependent".

It compresses the higher frequencies more.

19. ### RichSnyderGold Supporting MemberSupporting Member

Jun 19, 2003
Screw it, I'm getting a Cali76 TX

20. ### revd

Apr 11, 2020
"The low strings come back to life, adopting an extra weightiness, power and dynamic response, while the higher strings are strictly controlled, preventing slapped and popped notes from leaping out of the mix."

Compresses higher frequencies more, according to the manual.

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