Throbbing Balls - LFO modulated dual filter with video demo

Stompboxes circuits published in magazines, books or on DIY electronics websites.

Throbbing Balls - LFO modulated dual filter with video demo

Postby Nocentelli » 06 Aug 2017, 14:13

Essentially a mash-up of the twin filters from the EHX Bassballs, modulated by the LFO from the Tremulus Lune and mixed with inverted dry signal to give a mix/effect depth control:


Link


Video is long, as it goes through all the controls (L-R = Fast/slow switch + Spacing (both side-mounted), Shape, Rate, Ramp, Range, Depth, Filter Blend, Mix, Filter-shift switch (side mounted)). EHX SuperEgo synth engine is used for most of the video to provide a sustained pad sound to mess with, and I switched on a sub-octaver (Pearl OC-07) around 9m30 to provide some sub bass for the wubwubwub.

throbbing balls schematic_nocentelli.bmp
You do not have the required permissions to view the files attached to this post.
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.

For this message the author Nocentelli has received thanks: 4
Manfred (06 Aug 2017, 18:44), mirosol (11 Aug 2017, 16:30), moidphotos (08 Aug 2017, 00:07), uncleboko (06 Aug 2017, 14:28)
User avatar
Nocentelli
Tube Twister
 
Posts: 2027
Joined: 09 Apr 2009, 08:06
Location: Leeds, UK
Has thanked: 770 times
Have thanks: 770 times

Re: Throbbing Balls - LFO modulated dual filter with video d

Postby lapsteelman » 07 Aug 2017, 16:49

Looks like a cool circuit.. should there be a feedback resistor on IC2B?
(Formerly fjp1975)
User avatar
lapsteelman
 
Posts: 7
Joined: 03 Jan 2013, 19:39
Has thanked: 2 times
Have thanks: 0 time

Re: Throbbing Balls - LFO modulated dual filter with video d

Postby moidphotos » 08 Aug 2017, 00:07

That sounds excellent Nocentelli, thanks for posting it! Do you mind me asking a (probably daft) question? Do the points marked va, vb and vc all connect to each other? To the power line marked va anyway, or do they connect elsewhere?
moidphotos
 
Posts: 5
Joined: 20 Sep 2014, 19:34
Has thanked: 1 time
Have thanks: 1 time

Re: Throbbing Balls - LFO modulated dual filter with video d

Postby Nocentelli » 08 Aug 2017, 01:12

lapsteelman wrote:Looks like a cool circuit.. should there be a feedback resistor on IC2B?


Good spot! Yes, believe I have a 22k in there. I tried a 33k but I think it was a bit much. 25k or 50k trimmer might be a good idea.

moidphotos wrote:That sounds excellent Nocentelli, thanks for posting it! Do you mind me asking a (probably daft) question? Do the points marked va, vb and vc all connect to each other? To the power line marked va anyway, or do they connect elsewhere?


Thanks, I like it. The vref question is a good one... I drew the schem to represent exactly what I have on the breadboard right now, each 1/2 supply (a, b, c) is separate. I feel sure I could use fewer, or even one single vref (not LFO, though) and was planning to try either a rail splitter. regulator type thing or even a buffered vref - I'm not too keen on adding another opamp, though. If you're breadboarding it, maybe try it with just the 47k pair supplying input buffer, IC1+2.

I'm away for a few days, but I intend to keep tinkering with it
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.
User avatar
Nocentelli
Tube Twister
 
Posts: 2027
Joined: 09 Apr 2009, 08:06
Location: Leeds, UK
Has thanked: 770 times
Have thanks: 770 times

Re: Throbbing Balls - LFO modulated dual filter with video d

Postby moidphotos » 09 Aug 2017, 00:54

Thanks, so I'd need to make sure I have multiple versions of the power section of the circuit (top right in your schematic) to supply each of the va, vb and vc areas (3 for the vc's, 2 for the vb's, I can't see a connecting point for va now) - but I could tie the two 47 input buffers' CV points together to connect to their own power section. I won't be able to breadboard this for a while; mine is full of a traced circuit that is undergoing a lot of extra experimentation... but as soon as it is free I'll need to look at this; you've got some great sounds in that demo, especially around 4min56 onwards - how much of that part is a super ego? I have a super ego myself, and I could see myself enjoying putting it into this pedal.
moidphotos
 
Posts: 5
Joined: 20 Sep 2014, 19:34
Has thanked: 1 time
Have thanks: 1 time

Re: Throbbing Balls - LFO modulated dual filter with video d

Postby Nocentelli » 09 Aug 2017, 20:35

moidphotos wrote:Thanks, so I'd need to make sure I have multiple versions of the power section of the circuit (top right in your schematic) to supply each of the va, vb and vc areas (3 for the vc's, 2 for the vb's, I can't see a connecting point for va now) - but I could tie the two 47 input buffers' CV points together to connect to their own power section.


No: Va is the filtered +9v supply that comes from the 100r/100u on the right: This same voltage point is connected to all points with the upwards arrow, including opamp pin 8s and the top of the three voltage dividers. There are only three physical voltage dividers (a pair of 33k, a pair of 47k and a pair of 1M resistors. I used Vb and Vc to denote points that shared the same Vref (IC1 uses he vref from the 47K||47k, whilst IC2 and the mix pot use the Vref from the 1M||M pair). I will try running ALL points of a single 47k pair and see how that works out, probably in the next few days.

moidphotos wrote:...you've got some great sounds in that demo, especially around 4min56 onwards - how much of that part is a super ego? I have a super ego myself, and I could see myself enjoying putting it into this pedal.


I have the superego on the auto setting with the speed almost maxed which increases the sustain of the note played to infinite. Without any other effects applied this setting appears to make the sustained note subtly change slowly over the duration of the note - I think it might just be getting slightly louder which interacts with the fairly crude but effective dual filter.
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.
User avatar
Nocentelli
Tube Twister
 
Posts: 2027
Joined: 09 Apr 2009, 08:06
Location: Leeds, UK
Has thanked: 770 times
Have thanks: 770 times

Re: Throbbing Balls - LFO modulated dual filter with video d

Postby Nocentelli » 11 Aug 2017, 18:00

I tried just using a single 47k||47k divider to supply all the vref points and it worked fine: I then stuck in a TLE2426 rail splitter i had kicking about (cool little transistor package regulator that kicks out a steady 4.5v from a 9v supply) and that also works fine, so that is probably what I will use in my build when I box it to save a bit of space on the board.

Whilst I was fiddling, I tried to improve the depth/range control I have over the CV and came up with the arrangement shown below on this updated version 1.1, with a series resistance control for the range alongside voltage divider depth pot - Works MUCH better, and allows a far greater range of CV pulse widths and depths to be dialled in.

throbbingballs2_nocentelli.bmp
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.
User avatar
Nocentelli
Tube Twister
 
Posts: 2027
Joined: 09 Apr 2009, 08:06
Location: Leeds, UK
Has thanked: 770 times
Have thanks: 770 times

Re: Throbbing Balls - LFO modulated dual filter with video d

Postby Nocentelli » 12 Aug 2017, 14:11

Here is the most recent iteration, with two LEDs: The small red is just for status and tempo display, the big yellow one tracks the depth as well (much more satisfying, but goes almost imperceptibly dim at very low depths, hence the red one for confirmation it is on).

throbbingballs3_nocentelli.bmp



Link
You do not have the required permissions to view the files attached to this post.
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.

For this message the author Nocentelli has received thanks:
mirosol (12 Aug 2017, 15:54)
User avatar
Nocentelli
Tube Twister
 
Posts: 2027
Joined: 09 Apr 2009, 08:06
Location: Leeds, UK
Has thanked: 770 times
Have thanks: 770 times


Return to DIY Stompbox designs

Who is online

Users browsing this forum: No registered users and 8 guests