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[IN STOCK] L-1 Quad VC EQ. Eurorack. (Mouser cart p.4)
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2, 3, 4, 5  Next [all]
Author [IN STOCK] L-1 Quad VC EQ. Eurorack. (Mouser cart p.4)
L-1
Now is time for announces. I too decided not to break away from the team.

I'm working now on the Quad VC Equalizer/Resonator. Already finished simulation works.

Your comments/critique are welcome.

I used as reference 'Digitally-Controllable Audio filters and Equalizers' paper of Gary K. Herbert and Fred Floru.
http://www.thatcorp.com/datashts/AES13-031_Digitally_Controllable_Audi o_Filters.pdf

The device has four identical bands with BP filters. Also first band is switchable to HP mode and fourth band to LP to make low and high shelves. Also each band is switchable to boost or cut modes.

Every parameter has voltage control, also I plan master CV ins for all bands.

Controls are:

FREQUENCY is peak frequency of a band. Range is 10 octaves. V/oct responce and initial frequency are trimmable with trimpots. CV range is 0...10V.

BANDWIDTH range is from 2 octaves to 0.06 octave at 3dB point. CV range is -5....5V.

LEVEL range is 14dB. CV range is 0...5V.

LM4040 precise voltage source for all offset voltages.

Temperature compensation.

Filters are based on hi-end quality THAT2180 chips. VCA for resonance gain (level control) is discrete.

Chips used:

8 x THAT2180
2 x THAT300
3 x TL074 (for CV)
12 x dual opamps for audio. I will use OPA2604 but TL072 possible.

24HP Eurorack.




Here are simulation plots:

BANDWIDTH

from -5V to 5V CV in 1V steps. Level CV is 5V. Freq CV is 5V.

Simulation is made for 5V amplitude modular input signal level (14dB).

I didn't changed level for cut mode but for boost mode I decreased level from 14 to 0 dB to have headroom for boosting.

cut:



boost:





LEVEL

From 0 to 5V CV in 0.5V steps. Bandwidth CV is -5V. Freq CV is 5V.

cut:



boost:





FREQUENCY

From 0 to 10V CV. Bandwidth CV is -5V. Level CV is 5V.




I expect a bit of selfoscillation on high frequencies for thin bandwidth.
This is plots for 3 last volts of frequency and 3 last volts of bandwidth.




LOW AND HIGH SHELVES

They are not shelvig filters really but HP for low self and LP for high shelf.
So if we want to cut low freq, we need to swith in boost position.
We can very effectively cut (or boost) low (or high) freqencies. Bandwidth setting changes slope in this case.
On the plots bandwidth setted to min, middle, max (-5V, 0V, 5V). Freq setted to min for low shelf, to max for high shelf.










TEMPERATURE COMPENSATION.

I made temperature compensation for the filters, it affects to frequency and bandwidth.
But I didn't made tempco for level. It makes 1dB loss from 25 to 75 °C. I think it's not so important.

Plots for 25, 50, 75 °C.

Without tempco:




With tempco:

Dogma
before I explode Alex how long till production?

I cant wait to show off my L1 rack....bring on the ADSR and now this!
horstronic
Awesome!
albmoya
Impressive. Good job!
jules
I know that you don't have anymore space on your panel (and it's already big), but individual outs for the bands would be cool. Maybe leave some easy to access jumpers/connectors at the back of the PCB.
albmoya
Quote:
I know that you don't have anymore space on your panel (and it's already big), but individual outs for the bands would be cool. Maybe leave some easy to access jumpers/connectors at the back of the PCB.

+1
It would be cool applause
L-1
albmoya wrote:
Quote:
I know that you don't have anymore space on your panel (and it's already big), but individual outs for the bands would be cool. Maybe leave some easy to access jumpers/connectors at the back of the PCB.

+1
It would be cool applause



It's not so easy really. To have cut mode, bands must be connected in series.
So individual out of each band must be normalled to individual in of next band. An expander is impossible.
I'm thinking to make bipolar CV for level. Negative voltage will make cut, positive - boost. It allows to avoid boost-cut switches and to place individual in-outs for each band at these places. I think it must work but will make the module more complex and expensive. It means worst sales for me...
But it will allow to make interesting modulations..
So, I have what to think hmmm.....

I'm thinking about CD4066 electronic switches..

albmoya
Do you mean something like the "Band" and "Notch" outputs on the Cwejman RES-4? That would be nice, too.
synthdiy
Nice work @L-1. I've shared it to synthdiy subreddit.
jules
Bipolar CV control to go from cut to boost is a great idea.

Then your next module will then be a joystick so you can plug CV level cut/boost on the Y axis, and bandwidth CV control on the X axis.
(Or you make a theremin to control of these 2 parameters).
I guarantee some happy customers.
L-1
albmoya wrote:
Do you mean something like the "Band" and "Notch" outputs on the Cwejman RES-4? That would be nice, too.



Boost mode = "band".

Cut mode = "notch".

Just same phenomenon called differently.


jules wrote:
Bipolar CV control to go from cut to boost is a great idea.


OK, will work on it.
cranleigh
Absolute definite build for me! the poor man's res-4!
Rockin' Banana! Rockin' Banana! Rockin' Banana!
sonicwarrior
cranleigh wrote:
the poor man's res-4!

I hope it pings as well.
synchromesh
Looks fantastic! The banana jack conversion might be a bit tight, but that's fine...
CLee
Nice work, looks really interesting.
fluxmonkey
very nice, i have a few eq's in various formats, but none w/ VC.

having the bandwidth control going from wide (fully counterclockwise) to narrow (clockwise) seems backwards to me... no big thang, just saying
L-1
fluxmonkey wrote:
very nice, i have a few eq's in various formats, but none w/ VC.

having the bandwidth control going from wide (fully counterclockwise) to narrow (clockwise) seems backwards to me... no big thang, just saying


OK will make backwards, it's possible.
CLee
L-1 wrote:
fluxmonkey wrote:
very nice, i have a few eq's in various formats, but none w/ VC.

having the bandwidth control going from wide (fully counterclockwise) to narrow (clockwise) seems backwards to me... no big thang, just saying


OK will make backwards, it's possible.


Makes sense to me. Its like the Q control on an eq
Kashyyyk
i want the first serial number the 0001 love
ben_hex
Looks great, having Shelves, the Serge Res EQ and Ladik E-110 I'm an EQ in the rack fan smile
Reality Checkpoint
Any update on this?
L-1
Now I spent all money on VCADSR and PSU + Busboard projects.
PSU + Busboards will be full kits, include transformers.
So this VCEQ will be autumn project.
Reality Checkpoint
L-1 wrote:
Now I spent all money on VCADSR and PSU + Busboard projects.
PSU + Busboards will be full kits, include transformers.
So this VCEQ will be autumn project.


Roll on the autumn!!
Paradigm X
man sooner or later im going to have to give up and go eurorack. these no wiring projects look so easy. And theres actually a fair bit of wiggle room for the knobs, which is my usual complaint about euro.

Looks awesome smile

Great feature set, switchable HP/LP/BP on the end two bands is great!

Cheers
Funky40
personally i would add a bypass switch on such a module.
....i see there some tiny space left on the left side of the out jack.
Any FX module and any filter should have a bypass switch.
.......makes experimenting around ALOTS faster !.....and patching and jamming more flexible.

i also would add some vertical lines on the bottom row of jacks for better distinguishing between the four filter units and their jacks.

i know, it would take a little away of the symmetrical optics. at least a switch more.
personally i rate functionality much higher than optics wink...but thats me lol
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