[IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

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L-1
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[IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by L-1 »

I made the new filter to replace the old Mutant VCF. Vactrol based 24dB LP HP.

All details please read on my site: http://l-1.su/MutantCureVCF.html


Module:

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Kit:

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OlivierWah
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Post by OlivierWah »

This one is really piece of art.

Very creamy, screamy resonance, a lot of character and insane harmonics at high resonance. And to finish a lot of possibilities with 1v/oct, 2 CV inputs + 1 CV to switch between modes.

Good work !
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Post by L-1 »

Thank you Oliver!

:bananaguitar:
derjip
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by derjip »

Hey, I'm currently building the Mutant Cure VCF. I had to switch to newer opamps, since OPA2604 are not available anymore. I decided to go with OPA1656 in cheap SOIC to DIP adapters (see attached photos). One question though: I could not find any instructions on how to calibrate the module with the trimmers. Did I miss that somewhere, or could you provide some insights?

Thanks a bunch,
Markus
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MoS-squared
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by MoS-squared »

From Aleksei:
"Calibrating is standard - v/oct and offset."
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by derjip »

Well okay that's what the silkscreen says :)
I can loosely think of (or google) a procedure how to calibrate V/Oct (get it into resonance and apply some voltage on 1 V/Oct input, measure output signal frequency, then add multiples of 1V and adjust the trimmer to get multiples of the frequencies and therefore - octaves).
I couldn't find anything about offset calibration, though. Also at Scott Stite's Website, the Mutant VCF design only has V/Oct but no offset trimmer.
If you could hint me to some useful resource, I'd be really grateful, since my search did not yield anything obvious. Sorry if I'm asking trivial stuff here, It's just that those topics are new to me and I'm a bit lost here.
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by derjip »

Okay, in case somebody else might also need this, I finally found something here, which I guess makes a lot of sense and can easily be applied to the module:

V/oct adjust
01) Repeat steps for frequency calibration but reconnect the CV keyboard
02) Depress low C (0 volts)
03) Adjust initial frequency slider and fine tune slider for 200Hz
04) Depress C three octaves higher and adjust 1V OCT trimmer for 1600Hz
05) Repeat step 2-4 until low C remains at 200Hz and C3 remains at 1600Hz

Output offset
01) Monitor VCF output with oscilloscope
02) Initial frequency, fine tune, and resonance slider – left
03) All input sliders down
04) Adjust OUTPUT OFFSET for minimum DC output. Movement of the initial frequency slider should not cause more than 1V deflection
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L-1
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by L-1 »

there is possible to trimm v/oct only approximately because of vactrols. Pitch flows a bit, so v/oct will be not precise.

You can just set frequency range from 16Hz to 16kHz and don't bother with v/oct.
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by derjip »

Ok cool, good to know, thanks!
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by muxbutter »

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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by muxbutter »

derjip wrote: Sat Nov 20, 2021 7:17 pm I decided to go with OPA1656 in cheap SOIC to DIP adapters (see attached photos).
How did the OPA1656 work out for you? I'm wary to buy OPA2604 from eBay...

Thanks in advance, take care!
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by derjip »

muxbutter wrote: Tue Mar 01, 2022 3:34 pm
derjip wrote: Sat Nov 20, 2021 7:17 pm I decided to go with OPA1656 in cheap SOIC to DIP adapters (see attached photos).
How did the OPA1656 work out for you? I'm wary to buy OPA2604 from eBay...

Thanks in advance, take care!
Sorry for the late reply. It works well and sounds really great. I don't have a reference to compare to though, can only say that it's one of my most favorite filter in my humble collection :)
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by L-1 »

Prices for OPA2604 on Ebay vary from less than $1 to $15 for one chip.

Probably all they are fake.

From the datasheet:
New circuit techniques and special laser trimming of dynamic
circuit performance yield very low harmonic distortion. The
result is an op amp with exceptional sound quality.

Do chinnese these technicues and laser trimming? Probably not. Ithink those OPA at Ebay are just repainted TL072.

Is possible to use some another dual opamp instead of OPA2604, and single opamp instead of OPA604. HiFi ones are preffered. It's a field for experiments.
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by MoS-squared »

muxbutter wrote: Tue Mar 01, 2022 3:34 pm I'm wary to buy OPA2604 from eBay...
I've been using opa2134s for builds, but SynthCube also lists having the opa2604 in stock...oddly they show a picture of an opa2134...
https://synthcube.com/cart/index.php?ro ... ct_id=7527
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by L-1 »

This is OPA2134 I bought from official source.
As you can see a circle near first pin is not flat, it's like a track from a ball.
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Re: [IN STOCK] L-1 MutantCure VCF -- Eurorack kit / module.

Post by fragletrollet »

I've used opa177 for 604 and lm4562 for 2604 with great success in my l1 mixers.

How does this compare to the old version, other than missing mode?
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