EQ - but the boost & cut frequencies are different

The BH Range bass amps from TC Electronic have an EQ system I have fallen in love with.

The 4 (or 3) tone knobs target different frequencies depending on if they are boosting or cutting. This is perfect for bass. E.g you might boost higher-lows to add oompf but cut lower-lows to reduce rumble.

Here’s how TC map it on the 550 and 800.

Bass 50 Hz @ Gain -24 to 0 dB; 80 Hz @ Gain 0 to +24 dB
Low Mids 200 Hz @ Gain -24 to 0 dB; 160 Hz @ Gain 0 to +24 dB
High Mids 630 Hz @ Gain -24 to 0 dB; 800 Hz @ Gain 0 to +24 dB
Treble 1800 Hz @ Gain -24 to 0 dB; 4000 Hz @ Gain 0 to +24 dB

Does anyone know if there is an existing plug-in (or combination) that can achieve this — using a single knob for each?

If one doesn’t exist, would anyone be interested in making one? I think a 3 knob version would be great for dwarf and a 4 would be ideal for the Duo X!


I tried to make your pedalboard. It is possible to use the CV pedals to emulate the behaviour you are looking for. By setting up 4 CV knobs and connecting each one with a -1 multiplier we get the signals for each gain-value. Then you need to give each signal a name with the “Manage CV Ports” button. Then we can map each frequency gain to its signal, like we do when we assign a knob for it.

Here is the testboard i made for this ( made for my ModDuo, but i hope it works for you too ).
It’s not a real beauty, more a proof of concept and the Q values of the frequency bands need to be adjusted. If you find a useful sweetspot for yourself maybe tell me about it. I really like the idea and I’ll try to make it work for my own bass setup. :slight_smile:


Hey @CharlyRebell, thanks for giving it a try!

I’m in the queue for a dwarf, so will test it when it arrives. Or if I get impatient I will try and recreate it on the sandbox :sweat_smile:

I really appreciate you taking a look, fingers crossed!


Thanks @CharlyRebell for sharing the pedalboard. Will give it a try myself. :smiley:

Speaking theoretically, I would assume a parametric EQ could to that as well. You could set the frequencies you want to either cut or boost, and also adjust the Q factor as needed. This one from x42 seems to do that, though max cut/boost is 18dB:

(If I get a chance, I’ll try to build one such pedalboard myself and report back. Sorry, Summer vacation with kids at home do not boost productivity…)


Thanks @QuestionMarc, in your example how would that work when ‘bass’ is mapped to a single actuator on the MOD?

Where I find this most useful is quick adjustments on function gigs, where it would be common to not have enough time for even a sound check :sweat_smile:

EDIT: My original post was wrong. I’ll try to build a model for that and, if I manage to get it going, I’ll post back.

Thank you!

The bit I am struggling with is making the cut frequency different to boost. I wonder if logic in CV is possible like

If boost freq = 80
Else if cut freq = 50

Hope you can crack it!

Hi @QuestionMarc
Yes, the parametric X42 EQ was also my first try, but i wasn’t able to set the frequency bands as specified by danmh.


I was able to build an emulation, hope you like it. Thanks @CharlyRebell for laying out the basic concept, it helped a lot.

TC Electronics BH550 EQ Section Emulation

Basically it employs a CV Range Divider to split the control voltage into 2 zones, 0 to 5 and 5 to 10V. The lower range controls the cut and the other the boost. One EQ does the cutting at the frequencies stated above, and the other does the boost.

The CV Range Divider goes from -10 to 10V. It must be set to MINIMUM=0 and MAXIMUM=5 – which corresponds to the “within range” cable – and everything else will be sent to the “out of range” cable. On the plugin side it must be set to respond to Unipolar positive (0 to 10V). Another important detail is to use the “sample and hold” setting, otherwise once out of range the value resets to 0.

Then the frequency for cutting (and its Q factor) are set within each EQ.

This pedalboard has 4 gain knobs, mapped to Duo X’s rotary encoders 1-4. You might need to change that for the Dwarf and Duo. I’ve used x42’s parametric EQ, it has 4 more controls available (plus overal gain).

I’m sure there might be a more elegant way of doing this, but this is as far as I can go. Please check it out and post back what you think and/or improvements.


Very neat! Thank you all!

Very smart using only 2 EQs this way. I probably would have ended up with 8 :sweat_smile:

Looking forward to trying it out in the coming months :bowing_man:


Very nice work! Now I also see, that i misunderstood the bahaviour you were looking for. :sweat_smile:
I will give it a try for sure!


Really nice! Thank you so much for sharing this with us :slight_smile:

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