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Tweaking componant for finishing touches
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Tweaking componant for finishing touches
kevin0
Hi all,

Just wondering if there are any resources on tweaking components for better sonics? Swapping components and such?

I've read that Cwejman sounds so good because he hand-finishes/tunes/sets-up all of his modules, so I imagine he is doing this by ear? I guess he knows the modules inside out.

Does anybody have any resources for tweaking components in VCFs, VCOs etc?
mskala
Usually superstitious nonsense, so you are unlikely to find any instructions for it that actually work.
kevin0
I mean tweaking the values of components, not replacing parts with rare parts.

Changing values of certain things can change the sound, it seems strange to call this superstitious.
forestcaver
Datasheets and maths. eg for the Curtis chips and clones tell you the expected currents and voltages to achieve which frequencies. Maths will let you calculate the filter cutoff and slope as well as resonance response. An oscilloscope and multimeter will let you check this....
SphericalSound
The Cwejman LFOs are the best sounding LFOs. Sure

hihi
mskala
kevin0 wrote:
I mean tweaking the values of components, not replacing parts with rare parts.

Changing values of certain things can change the sound, it seems strange to call this superstitious.


Oh, I misunderstood. There are a lot of bad ideas going around for swapping in supposedly "upgraded" types of parts - especially in audio circuits - without understanding the purposes they serve and with no beneficial effect, and I was trying to warn against that common mistake.

HOWEVER, even though modifying a circuit with different component values can certainly make a difference to its sound, any such modification would depend entirely on the circuit. There's unlikely to be any kind of general advice for it that would apply to more than one specific product, beyond just saying "Learn circuit design yourself and then make design changes if you want to." And I'm sure that making design changes on a per-unit basis is not something Cwejman or other well-regarded manufacturers do. More likely he just does careful quality control and adjustment to make sure each module is working according to its specifications, the same specifications for each unit - as many people in the business do, including myself.

In general, if a different component value would sound better, then the original designer would have used that value. Changing component values from the designer's selections only makes sense if you really believe that the original designer made a mistake (sadly possible and I'm resisting the temptation to name names here) and you know better than they did; or if you are trying to achieve a different goal from the original design (like "change this filter to run in a different frequency range"). In either case you're not far off from just designing a new circuit of your own.

I've written a couple of recent Web log entries on choosing component values and designing for adjustment; those may be of some interest, but they do focus primarily on the initial design. Swapping values in an existing design is not really a thing very often.
kevin0
mskala wrote:
"Learn circuit design yourself and then make design changes if you want to."


The answer I was afraid of! That entry you wrote is a great help though, thanks!

forestcaver wrote:
Maths will let you calculate the filter cutoff and slope as well as resonance response. An oscilloscope and multimeter will let you check this


Filters are the main thing I want to play with! Do people ever adjust componenet values by ear?
KSS
kevin0 wrote:
Filters are the main thing I want to play with! Do people ever adjust component values by ear?

Sure, it can be done, and some will do it. That is the core belief and desire of so-called circuit-bending. But please don't dismiss what mskala just said. You can take what he wrote to the bank, because he's given a gold star answer.

Don;t be that guy who gets a new module and immediately starts fkg with it internally.

So how does a non electronics guru handle this? By adjusting the voltages into the filter. Both audio and CV. Level, offset, range are all available to you without changing any components. They are voltage controlled filters after all. Only after failing the goal in this would it make sense to try and adjust components. But that doesn't mean just hook up a cv and audio source and go through the motions so you can get back to tweaking parts. Think about all the different ways you can control that audio voltage and cv voltage into the filter to get the result you want. There is often far more available in a good design to begin with than many ever see, because study and actual planned effort are not taken toweards the goal of truly exploring the limits of a VCF.
NV
Swapping components per individual module isn't practical for production, and I would argue indicates design flaws rather than perfection. Some components with wide tolerances or specific needs can be matched pre-production, but again that's time and expense. I don't think an engineer would be satisfied with either.

Multi-turn pots can be used to fine tune circuits, such as adjusting a sine output where component tolerances can lead to differences between circuits. In many cases you can get as close as needed without external adjustment, but it requires work and precision components to nail down. Which isn't cutting corners, it's refinement.

I have respect for Cwejman and certainly he designs quality modules, but the reason his products are so rare and expensive is because he chooses to offer them that way. The companies releasing thousands of modules have streamlined their process so they can manage those numbers. I'm sure if many of the most popular designs were marketed at twice the price they still would sell, but those modules are popular because the designer's goal was to make them accessible. I think that too is a sign of excellent design.
synthetek
I have seen a prototype from a big manufacture that had way more pots and trimmers than the finished product, those were used to adjust values and once everything was how they wanted it those extra pots and trimmers were replaced by components with the values they determined to work/sound the best and the final product didn't have all the extra options.
sduck
Beware. There is a certain filter that is regarded as magical as it was originally designed (I have one, it is). Alas, the designer sold the design to another person, who made some changes to the design. Someone sent me one of the new ones to fix, and I fixed it, although I noticed it had none of the magical qualities that I associated with this filter. I reached out to the new owner of the design, who said that changed it slightly to get a more "acid" quality in the resonance, and so that there was less "dead space" in the freq knob travel. Those little changes completely ruined the filter - it still didn't sound like he wanted it to, and it didn't sound like it used to, it was just a generic low pass filter. This filter design has since been resold to another party, who I believe has changed it back to the original specs.
Repeater
For learning about filter designs, you may want to consider Don Lancaster's Active Filter Cookbook. It covers and compares many basic filter types, the effects that component substitutions can have in these circuits and why you might want to try them. You can learn a lot by trying basic recipes on a breadboard and experimenting with substitutions.

Keep in mind that not everything you'll read about filters has to do with music, synthesizers or even sound. It is rare to dream up a circuit in your head or just do some math and have it sound interesting as a circuit without tinkering a bit. Some resources that link filter design and sonic potential are various articles in Electronotes and Delton Horn's books. Those also cover voltage control in depth, which is not a common subject in engineering texts.

Ultimately, no one can tell you how to design circuits that will sound interesting to you. You have to use your ears for that. thumbs up
ixtern
There are the cases when swapping part may get better results (not necessary better sound) than original design. But usually it is connected with a higher price.
For example: in pitch control voltage paths TL072/TL074 are often used. They are today parts of medium quality in general (although very good for the price) - low input currents but not so small input offset voltage and offset voltage temperature drift. Replacing them with such chips like LT1057/LT1058 or OPA2134 may result in better accuracy and temp stability. But for a price.

Second example: TL072/074 used as a comparator to produce pulse wave in some designs may behave poorly. Replacing it with better ones (better slew rate) like OPA2134 or even TL052 may get better pulse wave (although for me old cheap LM311 is still the best for the pulse).
EATyourGUITAR
if the cwej wants to put each and every module on the bench to tweak all the trim pots personally then that would also explain why people report such excellent quality and sound. it does not surprise me. I am happy that people are building good stuff. this is a similar story with guitars and guitar pedals. plug in, turn on, check everything before you sell it off.
kevin0
Repeater wrote:
For learning about filter designs, you may want to consider Don Lancaster's Active Filter Cookbook.


Hot tip! Thank you Dead Banana

Ditto to Ixtern
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