CrossOver Filter

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CrossOver Filter

Post by BugBrand » Mon Jun 23, 2014 2:49 am

Here's the first word..

Two filters in one box - nice arrangement, I think.

This is a picture of the only existing prototype which now isn't even in my possession - could only loan it out yesterday as the 1st production batch is underway already!

Main thrust was SERIES filtering where the Highpass out of the first State-Variable Filter feeds the input of the 2nd SV-Filter. Thus you get a MID-band from the 2nd filter's Lowpass output.

Block diagram will hopefully clarify!

Image

Image

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Post by a100user » Mon Jun 23, 2014 4:57 am

Hot damn, ready already :D

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Post by BugBrand » Mon Jun 23, 2014 6:47 am

Image

Hopefully this block diagram can help explain somewhat.

Input Preamp - clean with gain up to 20dB

Two independent or chained 12dB/Oct State Variable Filters with resonance (Q) to self-oscillation.
Each filter covers the full audio spectrum 20-20kHz and has Low/Band/High-pass outputs though not all of these are accessible on the standalone module (there is a 1FW expander for modular users which presents ALL + extra CV and audio ins)

The filters can be run in Series or Parallel:
Series - the High output of Filt1 feeds the input of Filt2.
Parallel - both filters get the buffered input signal. In this mode the first filter is purely a Low-Pass, while the 2nd has separate Low/High outputs.
I was initially just going to have Series but it proved easy to add the mode switch.

The Filters are, of course, voltage controlled, scaled to 1V/Oct (haven't confirmed tracking range - imagine 5+ octaves tight tracking) - each one has an FM input (banana) and polarizing depth control. The Int/Ext switches are a weird bonus -> I took the BandPass output from each filter and that feeds the Int switch position for some audio cross-modulation - it can get very gnarly and chaotic, especially with high resonance.

The three outputs bands each have a polarity switch (centre-off for quick signal muting) so you can experiment with phase inversion/cancelling before an output level control and buffer.
The Low and Mid outputs are normalised to the High section so if nothing is plugged into either then the signal flows on to mix at High.

I found this quite powerful - you can either mix in mono from the High output, adjusting the different bands OR perhaps take each output to a different mixer channel & try panning (headphone space out). I'd been keen to start bringing some more stereo action to my setups and while this is obviously just MONO in, the 3 outputs gives some new fun powers.

Release date & price TBC - as mentioned, production is underway, but this always takes some time.

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Post by BugBrand » Mon Jun 23, 2014 6:57 am

PS - here's an old recording during proto-times. Good on headphones for head-spin panning.

http://www.bugbrand.co.uk/audio/Crossover2__16Apr14.mp3

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Post by a100user » Mon Jun 23, 2014 7:07 am

Any indication on pricing yet Tom?

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Post by BugBrand » Mon Jun 23, 2014 7:09 am

Probably a nudge above the PT Delay but below the DRM1.

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Post by Gringo Starr » Tue Jun 24, 2014 2:21 pm

Is there any chance in the future that you will do a run of these that are designed to flow easier with Bugbrand modular systems? Banana-fied and uncased basically?

Btw, no offense to your vision and creation. I'm always a bit hesitant to ask things like this to the designers. I feel like that would be like someone hearing my song and saying "any chance in the future that you'll change the chord progression of the verse?".

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Post by BugBrand » Wed Jun 25, 2014 4:25 am

The 1FW Expander will open things up for modular users and won't be available as Standalone as I don't have 4FW cases.

The expander gives individual filter inputs (designed for standard +/-5V audio signals as in the modular), individual Low/Band/High-pass responses for each filter, and a 1V/Oct CV input for each filter.

Pics once I've built the first one.

You know I've had to make a choice to move from the previous modular work, but I'm also generally trying to design in expansion possibilities to new designs.

Edit - to clarify - I will not be doing these new designs with bananas instead of 1/4" jacks. The work flow for me is more studio based rather than pure modular. Audio routing on jacks and modulation on banana. (yeah, don't say Buchlalala)

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Post by 101010oxo » Wed Jun 25, 2014 5:02 am

BugBrand wrote:Image

Hopefully this block diagram can help explain somewhat.
So, if I am setting this to parallel MID and LOW are both LP outputs from two different (but identical) filters?
Image

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Post by BugBrand » Wed Jun 25, 2014 5:40 am

Yup - may be useful in some instances - it was a simple addition so I figured to go with it - useful too with the Expander panel.

One thing I played with recently was using the Parallel mode with LOW going to centre, then MID and HIGH being panned (hard panned or less so). As you sweep the Cutoff2 the pan position will alter --- interesting to me is how you can pretty much maintain the percieved fidelity of the full audio band, while sending it into stereo weirdyness. (though wondering how vinyl mastering engineers will take all this...)

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Post by 101010oxo » Wed Jun 25, 2014 6:46 am

BugBrand wrote:Yup - may be useful in some instances - it was a simple addition so I figured to go with it [...]
Don't get me wrong - I quite like the design! :tu:
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Post by BugBrand » Fri Jun 27, 2014 4:29 am

Here's the Expander.
Super simple - passive - just connects to headers on the main module.

In essence you then have two completely independent SV-Filters.
You could, for example, patch up a 24dB/Oct LowPass or HighPass (must try this actually!) - just use in parallel mode.

Image

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Post by tron23 » Sat Jun 28, 2014 2:29 pm

:love: Too promising design, I have to save some money! :party:

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Post by Gringo Starr » Sun Jun 29, 2014 10:24 pm

Aha! So this will be available uncased. Coolio!

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Post by soup » Fri Jul 04, 2014 7:30 pm

This looks so good.

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Post by 101010oxo » Mon Jul 14, 2014 8:04 am

I quite like the soundcloud demos :tu:
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Post by BugBrand » Mon Jul 14, 2014 8:14 am

Here we go then!

[soundcloud url="https://api.soundcloud.com/tracks/158640672" params="auto_play=false&hide_related=false&show_comments=true&show_user=true&show_reposts=false&visual=true" width="100%" height="450" iframe="true" /]
Running through the bands of the BugBrand CrossOverFilter.

Clean signal loop to begin then Low, Mid and High Bands - for each band, begin with no resonance, then turn it up and also show some gentle Frequency Self-Modulation.
The final bit has the bands mixed together (all positive phase)
Downloadable as .wav


[soundcloud url="https://api.soundcloud.com/tracks/158641195" params="color=ff5500&inverse=false&auto_play=false" width="100%" height="20" iframe="false" /]
Demo of the BugBrand CrossOverFilter taking the 3 Band outputs to separately panned channels - LOW to left, MID to middle, HIGH to right.
Try to listen with headphones! Clean-ish processing beginnings (sweeping with no/low resonance) before becoming more experimental - phase inversion of MID band - Frequency Self-Modulation - then no-input Self-Oscillation tones at the end.

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Post by BugBrand » Mon Jul 14, 2014 11:55 am

Here's another::
[soundcloud url="https://api.soundcloud.com/tracks/158649223" params="auto_play=false&hide_related=false&show_comments=true&show_user=true&show_reposts=false&visual=true" width="100%" height="450" iframe="true" /]
The CrossOver Filter processing a pattern on the Korg Volca Beats.
Playful modulations - some clocked external modulations & Frequency Self-Modulation
Downloadable as .wav

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Post by a100user » Tue Jul 15, 2014 2:55 am

Sounds very nice indeed Tom

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Post by tron23 » Tue Jul 15, 2014 2:56 am

Is this the future sound of acid? :party:

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Post by otoskope » Tue Jul 15, 2014 10:56 am

Truly a beautiful set of demos, Tom. Very nice. Can't wait!
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Post by BugBrand » Tue Jul 15, 2014 11:43 am

Thanks!

One more while I was testing boxes.. I've already been using the little MiniBrute for checking the 1V/Oct tuning of the filters, but I thought I'd try 'ping-ing' the filters with the keyboard's Gate output - I used to do that with the modular (PRC3A SV-Filter). Works quite nicely (though would prefer Trigger rather than Gate)

[soundcloud url="https://api.soundcloud.com/tracks/158822685" params="auto_play=false&hide_related=false&show_comments=true&show_user=true&show_reposts=false&visual=true" width="100%" height="450" iframe="true" /]

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Post by shady smiles » Tue Jul 15, 2014 12:56 pm

Great demos Tom. Love the pings.

Can't wait! :banana:

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Post by Ginko » Tue Jul 15, 2014 2:23 pm

I thought I would also prefer a banana only version as I am using a bunch of small bananafied devices in some work - then i realised that I wouldn't be able to use the effect with any device other than those :hihi:

Looks great!

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Post by otoskope » Wed Jul 16, 2014 3:38 am

Completely OT, but inspired by your ping demo above, Tom, I did this little noodle as a little night excercise, all bug modular, based on gate-pinged SV filters:

viewtopic.php?p=1616617#1616617
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