WIGGLING 'LITE' IN GUEST MODE

[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]

[L-1]

[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]

[cranleigh]

Absolute definite build for me! the poor man's res-4!

[sonicwarrior]

[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]

[CLee]

[Kashyyyk]

i want the first serial number the 0001

[ben_hex]

Looks great, having Shelves, the Serge Res EQ and Ladik E-110 I'm an EQ in the rack fan

[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]

[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

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 ...but thats me