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Different 8 hp Doepfer filter for my A-188-2 BBD
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Author Different 8 hp Doepfer filter for my A-188-2 BBD
natureclubcassettes
Hello all- kind of specific question here so bear with me.

I am looking to replace my A-108 filter for my A-188-2. It is just a few hp too big and I want to fit the A-151 in my processing rack.

I am specifically looking to replace it with another Doepfer filter in 8 hp, but there are a number of options. I mostly use the filter to get rid of clock noise at lower delay rates and was wondering which 8 hp Doepfer filter would work best for this. In another thread it was mentioned (by one of the Intellijel/Cylonix guys?) that 2-pole filters are best for this...

I am not looking to get a different delay, although I know the 188-2 is huge, nor am I looking to change any other aspects of my rack (in my sig) at the moment.

Thank you!!
Rigo
The Doepfer manual for the A-188-1 states that the more poles the better for filtering clock noise, and the A-188-2 has more clock noise. So the A-101-6 Six Stage Opto FET VCF is 8HP, with six 6dB stages. Don't know if you will like the behaviour though hihi
natureclubcassettes
hmmm, interesting.... thank you for the suggestion and the different information regarding poles. The 101-6 lacks the multiple CV ins that the 12_ filters have, though, and the FB in/out would likely not be useful in my rack (already using the filter as the external FB in for the 188-2).
natureclubcassettes
So really I'm looking at these ones:

A-120 24db Transistor Ladder
A-105 SSM 24db
A-102 Diode
A-122 24db Oberheim/CEM
A-103 18db 303-style

I had the Wasp and was not fond of it beyond using it to totally abuse audio. Not interested in the SEM filter. Leaning towards the 105/122 due to it's slightly more sophisticated CV ins.

Thanks!
Blairio
Rigo wrote:
The Doepfer manual for the A-188-1 states that the more poles the better for filtering clock noise, and the A-188-2 has more clock noise. So the A-101-6 Six Stage Opto FET VCF is 8HP, with six 6dB stages. Don't know if you will like the behaviour though hihi


Yes, the more stages (and hence the steeper the slope) the better. I used an A108 for filtering clock noise from my A188-1. I had the module set for a 48db slope, via configuring the jumpers on the main circuit board - the manual tells you how to do this.
natureclubcassettes
[quote="Blairio"]
Rigo wrote:
Yes, the more stages (and hence the steeper the slope) the better


Just to be clear, the stages in a BBD are not what I am asking about. I am asking about the number of filter poles for the external filter, not the taps (stages) of the BBD. I realize that you can achieve longer delays with more BBD stages and that at lower delay rates the clock noise is more pronounced.

I suppose I am really asking about the different filter responses when being used in the ext fb in loop for the 188-2, in which case I am asking about slope response....
Monotremata
[quote="natureclubcassettes"]
Blairio wrote:
Rigo wrote:
Yes, the more stages (and hence the steeper the slope) the better


Just to be clear, the stages in a BBD are not what I am asking about. I am asking about the number of filter poles for the external filter, not the taps (stages) of the BBD. I realize that you can achieve longer delays with more BBD stages and that at lower delay rates the clock noise is more pronounced.

I suppose I am really asking about the different filter responses when being used in the ext fb in loop for the 188-2, in which case I am asking about slope response....


The filter slope/cutoff/response is exactly what they were describing, not the BBD stages.. Poles/Stages, same thing..
Blicken Synths
The A-122 was the first filter i ever got (along with the A-120) 6 years ago and it still gets used all the time. CV control over the resonance it definitely a bonus over the A-120
natureclubcassettes
ok, so what I had read in a different post regarding a 2-pole being better than a 4-pole in a BBD ext fb in loop is wrong then (i.e. a 12db is does a better job rounding off clock noise while still retaining as much as possible of the original signal/BBD mix)?

didn't mean to ruffle any feathers; it's just that I was asking about a subject in which the term stages meant two different things (poles/BBD taps).
Blicken Synths
the A-121-2 looks pretty mental. Would give you plenty of options
natureclubcassettes
Ya, saw that one... not sure that I would use high pass and notch for this, though, and I have a fxdf in another case for band pass fun. thanks though!

still leaning towards 105/122 at this point
Blairio
[quote="Monotremata"]
natureclubcassettes wrote:
Blairio wrote:
Rigo wrote:
Yes, the more stages (and hence the steeper the slope) the better


Just to be clear, the stages in a BBD are not what I am asking about. I am asking about the number of filter poles for the external filter, not the taps (stages) of the BBD. I realize that you can achieve longer delays with more BBD stages and that at lower delay rates the clock noise is more pronounced.

I suppose I am really asking about the different filter responses when being used in the ext fb in loop for the 188-2, in which case I am asking about slope response....


The filter slope/cutoff/response is exactly what they were describing, not the BBD stages.. Poles/Stages, same thing..


Apologies, I caused this confusion. Putting the verbiage of poles/stages to one side, the steeper the Low Pass Filter slope, the better it will be for aggressive filtering out of clock artefacts. 48db is as steep as the A-108 can go.
natureclubcassettes
No worries! And to reiterate, I am looking to get a different filter than the 108.

It's a fine filter, just a smidge too big.

On the 108 I typically use the 24db or 12db output in the 188-2 external feedback. Somehow the 48db sounds less full to me.

Loved the 188-2 since I first saw it on Raul's World of Synths, ha. It was one of my first modules back in the day (2013), as was the 108. Different times!
Jumbuktu
I would get the TB-303 18db (3-pole). The SEM filter is nice as well, and useful for other things.

The diode and Wasp filters have 'character' that isn't really what you need.

I would keep the A108 though. It's my favourite Doepfer filter, and I think you will regret it if you let it go, even if you have to keep it in a box outside your rack until you feel the need to put it back in.
natureclubcassettes
Jumbuktu wrote:
I would get the TB-303 18db (3-pole). The SEM filter is nice as well, and useful for other things.


Cool! Have you used either in a feedback path with a BBD module? I haven't heard much from the 18db filter, what do you like about it (beside the obvious, ha).

I'm not really interested in the SEM one, but was in the SSM. Had the Wasp, and totally agree. I don't plan on getting rid of the 108, it's just a little too wide and I'm not using it to it's full capacity.
helix
Blairio wrote:
Rigo wrote:
The Doepfer manual for the A-188-1 states that the more poles the better for filtering clock noise, and the A-188-2 has more clock noise. So the A-101-6 Six Stage Opto FET VCF is 8HP, with six 6dB stages. Don't know if you will like the behaviour though hihi


Yes, the more stages (and hence the steeper the slope) the better. I used an A108 for filtering clock noise from my A188-1. I had the module set for a 48db slope, via configuring the jumpers on the main circuit board - the manual tells you how to do this.


It has a 48dB output as standard..
natureclubcassettes
helix wrote:
Blairio wrote:
Rigo wrote:
The Doepfer manual for the A-188-1 states that the more poles the better for filtering clock noise, and the A-188-2 has more clock noise. So the A-101-6 Six Stage Opto FET VCF is 8HP, with six 6dB stages. Don't know if you will like the behaviour though hihi


Yes, the more stages (and hence the steeper the slope) the better. I used an A108 for filtering clock noise from my A188-1. I had the module set for a 48db slope, via configuring the jumpers on the main circuit board - the manual tells you how to do this.


It has a 48dB output as standard..


Yep, it has outputs for 6/12/24/48/band pass right on the panel, one of the reasons it's a great filter (also why it is bigger than the one's I'm asking about)
Blairio
natureclubcassettes wrote:
helix wrote:
Blairio wrote:
Rigo wrote:
The Doepfer manual for the A-188-1 states that the more poles the better for filtering clock noise, and the A-188-2 has more clock noise. So the A-101-6 Six Stage Opto FET VCF is 8HP, with six 6dB stages. Don't know if you will like the behaviour though hihi


Yes, the more stages (and hence the steeper the slope) the better. I used an A108 for filtering clock noise from my A188-1. I had the module set for a 48db slope, via configuring the jumpers on the main circuit board - the manual tells you how to do this.


It has a 48dB output as standard..


Yep, it has outputs for 6/12/24/48/band pass right on the panel, one of the reasons it's a great filter (also why it is bigger than the one's I'm asking about)


Ah, I see. I no longer have my A108, and was quoting from memory. Chapter 6 of the A108 user manual details the output options available at the 4 front panel outputs:

www.doepfer.de/a100_man/a108_man.pdf

They include: 18db, 30db, 36db and 42db, in addition to the front panel defaults.
Monotremata
Hmm if its a seriously steep filter you're looking for, I probably wouldn't go with the A-105. I have it and LOVE it (its my #1 along with the Wasp) but its your standard 24db filter, and if you're looking to surgically remove noise, its probably not the best. The SEM is a 12db filter so its going to be an even 'broader' cutoff slope.

I wouldn't necessarily call the CV ins 'sophisticated' on those either.. Its got the same CV inputs every other filter does.. 1V/oct cutoff, regular cutoff, resonance.. The SSM is exactly the same as the Wasp and SEM, except those two left out the resonance CV because there's a Bandpass out on those two..
letitbleep
i think a 2-pole filter works better in the feedback path. the signal remains better articulated as it feeds back. and if you go SEM you can optionally use band or high pass in the path, which can be nice.

a 4-pole filter should work better ~after~ the mix output on the delay for finely cutting off those noisy top frequencies. of the doepfer 4-poles, it's really a matter of taste. i sometimes use the tip top z2040 (similar to the doepfer ssm) after the doepfer delay for this and it works as it should, doesn't impart tons of character in this application.
Navs
The tip I got from Paul from Schneiders years ago to filter BBD clock noise was to use a tracking notch filter, not low pass.
GNSDG
Navs wrote:
The tip I got from Paul from Schneiders years ago to filter BBD clock noise was to use a tracking notch filter, not low pass.


That's really interesting. I use an A-188-1d extensively, and at longer delay times the clock noise is just a pitch (makes sense, I guess it's basically an oscillator?). Not seems like it would work well for that.

I tend to use mine as a delay, but not as a typical, get-your-cleanest-possible-analog-delay. I tend to just slap a filter on the Mix output; usually it's a 1-in, multiple out multi-mode so that I can use a LP out as my delay sound and the HP out as a sort of weird noise source for modulation, hats & cymbals. Right now I'm using the 106-6 for this, which is a sick filter. I have also used the 120 at times, and used to use the A-121 (kind of boring which is actually great for this application, but wanted more of a compromise like the 106).

All that to say, although my use case is different from OP's (Mix out, not feedback path), I have found that the best filter really depends on your use. If you're not going to push the 188 to extreme settings, a 12db/oct filter can be nice and letting a little clock noise through on the high end just sounds fine. If I'm going to go crazy with CV'ing the 188 and want the filter cutoff to track the time (I guess the 188-2 doesn't do this but I'm sure you could figure out a workaround), steeper the better--the 4L out on the 106-6 is great to get rid of pretty aggressive clock noise at longer delay times.

And as always, gain staging is extremely important in this application.

I would really just experiment with the A-108's 12 and 24 db outs before you sell it and see which you like better. (Incidentally, if you do sell, I may have a buyer for you! DM if you're interested!)
Shledge
The A-188-1 is not the best delay, if you only want a delay to be... a delay. It's deliberately made for experimental purposes.
GNSDG
Shledge wrote:
The A-188-1 is not the best delay, if you only want a delay to be... a delay. It's deliberately made for experimental purposes.


Oh, 100%. That's why it's great!
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