B*inger 914 ffb hacking and modding brainstorming

[Hlp]

So after comparing different routes including building a inductor based FFB moog clone from J Haibles pcb, i bucked out for now, ordering the B FFB for 102,-eur and want to hack away what i can. Thats fun too.

I want an FFB for the formant Filtering Quality and heavy ringing resonances. Most clones are much too tame for that. Of course feedback to itself is needed but i would like to mess with the parts in the signal part and wonder

1)if anyone have hints about what caps are actually in the tone shaping path here. I am thinking about replacing with some vintage stuff even if its just for the non-linearities.

2. i can wire jacks to pots for independent outs of the bands and if there is a way to not have all bands out but lets say odd and even or other groups. Like for example, if i take a jack to the last filter band, will i have another all-out but simply pre HPF?

3)if i would like to add a crossfader like on the AJH model, how would one wire that up exactly?

Here is a pcb shot, besides the smd resistors it looks pretty hackable.

Ultimate goal is shimmering uneven harmonic content by resonance drive for organic shaping of sounds, think formant filtering adding voice like overtones and harmonics.

The pic is from amysynths.co.uk and there is a hint „ One potential modification is to improve the accuracy of the lower filter bands by adding capacitors on the rear of the PCB, but this is not an option for the upper frequency bands.“

I am not sure how to add, if he is talking about parallel, i forgot the tech term but thats a typical EQ thing to add a high quality low value cap to a generic one for filtering

[Hlp]

Does someone have a clue if, instead of a more common breakout per band, an input per band is possible?

[JaggedNZ]

This might help:
http://yusynth.net/Modular/EN/BANK/index.html

You could potentially modify the HF filters by stacking SMD caps. Would require steady hands.
And yes, you should be able to Tap individual filters from the potentiometers, but you might want to buffer them.

[Hlp]

Yup watching the yu sites but most is over my head techwise.

If you mean bypass caps, afaik the caps are all tht and only the resistors smd?
Or i dont spot them.

Any idea about the other way around, making inputs to the some bands in order to pass certain sources only through lets say last few bands and other sources through the full array?

Anything to bring up non-linearity and resonance?

[Hlp]

So have this thing apart now, putting potis on wire for space and want to add a feedback pcb and some things to the faceplate.

What could be modded for sound sweetening (it does sound good) and maybe higher ringing/resonance? Some vintage caps? I wont touch the smd parts and the tht had to be cutted too difficult to desolder that stuff. I tried

[kbit]

If you really want to make purposeful modifications you’re best bet is to find a schematic for this circuit and do your best to reverse engineer what components could be doing what (no guarantee this circuit is exactly the same as any schematic you may find).

Replacing whatever you can find with it’s vintage counterpart is not automatically going to give you desirable results. & be gentle with your desoldering efforts because you could easily find yourself with an unusable circuit.

[Hlp]

Sure i hope i did not cut a trace allready.

The signal flow is pretty obvious w/o shematic. Left and right Radial caps should be in the Lp/Hp the signal is going through everything, every filter stage consiting of box-cap-opamp circuit wich i better not touch.

I just wonder if there are hacks to introduce non-linearities and more ringing

One pretty basic question. Can i move the power header from bottom to top and remount without screwing up polarity? As far as i can see i wont be able to keep the same pin connections

[grey]

If you cut a new notch with a dremel, you can, but you’ll want to make sure it’s clear which way you are suppose to orient the plug. You could also just ditch a shrouded header altogether. Header pins will do. You can also track down those headers with the red plastic if you want to get fancy. Or just use some nail polish or a paint pen. Anything that is clear to you about how to orient the cable!

[Hlp]

Not sure what you mean. If i mirror the header either with header or pins i dont see how i could keep the same pin to cable connections when attaching an euro cable. They will be flipped. Attacking with a dremel seems too much i think. Gonna live with the 1 cm then.

Ah you meant dremel a notch to the header, sorry. But still left/right will be flipped and there are precise traces to certain pins

[wheelersounds]

Not sure what your background in circuit design is, apologies if this is stuff you already know… gotta be honest I only know enough to be dangerous. But I guess one could approach it a bit like circuit bending, no?

The Serge FFB has really excellent ringing possibilities and different outputs (“comb” but really just alternating bands). The CGS version on Elby has a schematic (which I’ve also posted here) and a comparison between the two might be helpful…?

You could look at this very informative Rane webpage with overviews of all kinds of different EQ types. The API EQ (figure 18) has Proportional Q, so the bandwidth narrows as you turn up the gain. Might be a simple wire bridge, or a totally different circuit…

[Hlp]

Yes i think thats a good track and dont worry i am more dangerous to myself.
I precisely went with the moog layout vs serge, dunno if its the choosen frequency bands or what, but i enjoy the silky smooth response of the ffb more then the resEQ not sure why, still want more ringing eheh. I will study the shematics, hacking the filtering caps probably makes the most difference. I think about adding in different kinds of caps not for any pro result put for non linearities maybe even happy accidents. Didnt get this thing as an mastering eq obviously.

[wheelersounds]

Yeah, when I built my first Peter Blasser paper circuit I remember trying some vintage mylar caps and getting crazy results compared to polyester. And I remember reading about the original ResEQ caps being polystyrene and that making a difference (smoother maybe?). I think Mylar and polystyrene are also much more susceptible to temperature fluctuations.
Maybe you can temporarily install header sockets so you can swap out different cap types and see what happens? Or solder wires to the bottom of the connections and work on a breadboard?

Re: your power header question, you should be able to! According to multiple sources there it L/R symmetry on these connections. You just have to also flip the connector horizontally, not vertically. I would write “+” on the board or use red sharpie/nail polish like @grey said, and also def check it with a meter.

[Hlp]

A right 10 pin is symetric i got that mixed up, thanks.

A cap header hah thats over the top. But never heared of mylar, was looking at pio ones

[Hlp]

Another basic Q, on the board the pots are common 3 piin mounted + ears.
I just realised every first (left) connection goes nowhere, both sides of the board, every pot.

I assume that actually does go nowhere not even grounding and wont have to be connected when doing pot on wire?

[wheelersounds]

It depends on the board, sometimes there is a hidden layer inside that carries either 5v or ground. Best bet is to plug the thing into power and test it with a meter.

[Hlp]

I can not recomend desoldering power headers and resolder pins to beginners. That was a nightmare and took ages, looks like a graveyard from a stephen king novelle but i think it worked. Will have to find out wich pin of the audio ins/out is tip and sleeve and solder all pots on wire before i know this thing even still works. Fingers crossed

[kbit]

What’s your desoldering method?

[Hlp]

The desolder gun couldnt deal with the pre-reflowed behringer solder, its super hard to get out. Braid was used for cleaning up but to make actual holes for the new pins (shoving through didnt work) i had to kind of melt them in with a small iron. Anyway the damage is done and i just hope it will work as is. One issue is, the copper holes of some of the pins got quite busted in this process and its not so easy to make conductive again / make solder stick. Usualy i am not too bad soldering but headers are my nightmare…

[kbit]

Yeah hopefully everything is ok, or at least easy enough to add jumpers. Desoldering can be such a pain even with the best equipment. I’ve had some instances where I had to reflow some joints 3 times just to remove the solder clean. Lead free solder doesn’t make it any easier… a tube of flux can be a lifesaver if you try to do more stuff like this in the future (assuming you didn’t already use some). Do you have a vacuum pump or a handheld solder sucker?

[Hlp]

Its a sucker with a spring back mechanism.

Building diy i feel okay with, but desoldering is bad bad bad. I allready had to wiggle of all 14 pots. No way to get them off board otherwise. So yes i just hope i didnt kill it. Will know soon.

Does anyone understand the funny in / out markings so i at least know i have tip to hot and sleeve connected correct when testing for life / sound?