MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

Scratchy pot on my Frequensteiner : (
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Scratchy pot on my Frequensteiner : (
rico loverde
Hey was curious if any one knows what size or a part number for the resonance potentiometer on the Livewire Frequensteiner. Mine is very scratchy...such a beautiful filter though. Wrote Livewire a week or two but no word back...

rico
wavecircle
Think it is like that by design. Mine and many others res pot is this way.
Adam-V
That is quite normal for that type of filter design. You could try putting a capacitor on the resonance pot in a similar fashion to what Ken has done with the CGS35 design if it really annoys you.

Cheers,
Adam-V
rico loverde
really? i mean this is really blatant when i move the knob. i love some dirt in my filter but this just doesnt seem right. ill try the cap thing. i also have the CGS synthcon filter and there is no noise on it (at least this crackly stuff that only happens when the knob is moved)...diff designs of the same filter i thought?

thanx for the help guys...
skweeegor
Apparently this is because of DC getting into the pot. Maybe the CGS Synthacons have a fix on the newer boards? The Elby Synthacon (which is based on the CGS layout iirc) has this issue as well.

Here's the thread with instructions for the Elby Synthacon; might be of some help:

http://electro-music.com/forum/post-246680.html
cluster
audio samples?
rico loverde
ill post one tomorrow for sure...
felix
It's not the pot, it's a side affect of the circuit design. Some units exhibit the behavior more than most, but it's something they all do (mine does it too). Replacing the pot will not change it.
rico loverde
well i guess im happy its not just mine...thank you for the help guys. even with the scratchy i still love this thing. the hp is just wonderful.
felix
rico loverde wrote:
well i guess im happy its not just mine...thank you for the help guys. even with the scratchy i still love this thing. the hp is just wonderful.

Yeah, it doesn't take long for you to get used to it. I too find it well worth the "blemish"... the Frequensteiner sounds so amazing.
rico loverde
heres a little audio of the scratchiness in action, just to be sure.

http://soundcloud.com/deadlover/frequensteiner-scratchy-pot

rico
richard
does it just crackle when you first use it and then it go away? = normal
or does it do it all the time = try deoxit and then get a new pot

I've had 2 and they both did the former - you just need to give it a pre-wiggle each time
rico loverde
it seems to do it always, anyone know the size and type of the pot for resonance?
Tim Stinchcombe
rico loverde wrote:
it seems to do it always, anyone know the size and type of the pot for resonance?
It's a 100k linear, but I doubt it will make much difference - if you search around this forum, and probably electro-music as well, you'll probably find a handful of threads with many people mentioning this problem, and you'll also probably find that as many people report changing the pot has little effect as those that say it does help.

A while back I looked into this, and if you Google 'scratchy pot' and 'DC', you are likely to find quite a lot of hifi-type forums where people discuss this problem in other contexts. If I remember correctly it is something to do with the DC level across a cap in the circuit somewhere, and effectively what you hear is the cap charge and discharge as the DC level changes (I hope this is correct - someone with better knowledge correct me please if it is not!), though just exactly how this happens I don't think I managed to establish, and this seems to explain why it only happens when you move the res pot, and not when it is static. (I thought I may have bookmarked some of the links, but alas, if I did, I cannot find them again!).

Tim

Edit: having just Googled a bit, it may be the DC through the pot that causes the noise, not a capacitor. This is one of those areas where you can find lots of info and opinion, but little decent technical explanation of just what exactly causes the noise. Dashed annoying!
rico loverde
Thanx Tim, I just wanted to be sure mine was doing the same as others, i was convinced it was but thought id post some audio to make certain.
felix
richard wrote:
does it just crackle when you first use it and then it go away? = normal
or does it do it all the time = try deoxit and then get a new pot

I've had 2 and they both did the former - you just need to give it a pre-wiggle each time

Mine is somewhat like the former, but it never goes away completely. If you sit there and "warm it up" like that, it will reduce, but it doesn't always go away completely.
Tim Stinchcombe
OK, I tracked down my notes (they were where I should have looked in the first place). So, this is the definitive "Your Frequen Steiner has a scratchy res pot, but it is due to the design and is not just your module" post. Unfortunately on re-reading these threads, I still haven't worked out whether it is a cap or the pot itself causing the noise, but one of the guitar effects threads says categorically that with the proper design knowledge it is possible to design around this issue and thus to not be afflicted by it (just a shame I still don't know the cause, and hence how to design around it will have to wait)...

Most of the threads I found are from the Yahoo 'cgs_synth' group, with respect to Ken Stone's Cat Girl Synth CGS35 module, which is the Synthacon filter, whilst I believe the Frequen Steiner is the Synthasystem filter (but the circuits are extremely similar, with only the number of diodes being different, and a small difference in the feedback method). I've quoted some of the posts for those who aren't in the group.

Thread: synthacon level and resonance control questions
Quote:
ok so i went out and bought a new pot just to drop in in case the pot i had was bad. seemed it was. i dropped it in and still its scratchy.
Followed by:
Quote:
One known cause of scratchiness showing with pots is if there is a DC signal involved. I don't know if the following will help or be a total failure, but try placing a 10uF electro in series with the pot to block any DC component.

A later thread: Synthacon: The case of the scratchy res pot
Quote:
my Synthacon has a scratchy res pot, very noticeable in lowpass mod, i have tried adding a 10uf cap in series with the pot which gets rid of the scratchy pot, but also the sound. I have replaced the pot 4 times..

A little later, talking about the circuit's simularity to guitar effects unit
Quote:
Another quirk of the original is that there is a DC voltage across the volume control, which also serves as the collector load resistor. This means that it will inevitably scratch and crackle whenever the control is moved even if you use high-collar conductive plastic pots.
That quote is evidently from this document.

A suggested fix (for the CGS35):
Quote:
The fix is to replace the pot with a resistor or two and then isolate the pot from the collector current with a cap. That really does defeat the design, however. The idea was to set up the transistor gain how you want through the collector (with the pot) rather than simply throttling the output.

That apparently it can be seen to be DC causing it (I must try this):
Quote:
Do me a favor and watch the output on a scope while you turn the knob. My problem with my CGS steiner filter sounds like a "scratchy pot" to the ear, but is pretty obviously due to some kind of DC component when you look at it on a scope. Could be inherent in the original design.

And again: Scratchy Synthacon Res pot question and poll
Quote:
The third one is on the way but before that I need to solve I problem I'm having. Turning the Resonance pot produces a scratchy noise. I think this is a common problem others have had, too. I'm under the impression that this is DC through the pot. I've tried wiring a cap in a variety of ways with no luck.
...
I have tried swapping pots (all Alphas, though).

And again: Scratchy Synthacon Res pot question and poll
Quote:
Check back post from about a month ago, seems everyone has this problem. Not due to bad pots but DC getting into the pot. I've tried a couple of fixes posted on the board and nothing has worked.

And another suggested fix
Quote:
The solution that supposedly works is to wire the 1k pot outer terminals into the circuit instead of an outer and the wiper. One then adds a capacitor between the wiper and one end. The result is that the DC passes through the 1k as required, and the wiper only ever sees AC.
Unfortunately there is no follow up from anybody saying whether this actually works or not!

And this thread entitled: Treble Boosters-Do They Typically Make a "Dirty Pot" Noise When Adjusting the Boost? contains posts saying it can be designed around, and that it is a cap actually causing the noise.

I would love to know more technically on the cause and the supposed cure, but it looks like it will have to wait until my knowledge catches up!

Tim
rico loverde
wow! thanx Tim. cool info
MUFF WIGGLER Forum Index -> Eurorack Modules  
Page 1 of 1
Powered by phpBB © phpBB Group