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

single passive attenuator for idiots
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2  Next [all]
Author single passive attenuator for idiots
Cybananna
I want to make a few of these. I want just a simple single passive attenuator for audio or CV attenuation. I found some stuff on the Doepfer website that appears to be what I want, that is extremely simple. Am I correct that you just wire an input jack and an output jack to a pot (like a 50k log for example)?

Is it really that easy? no other resistors needed? hyper
thermionicjunky
Yes, it's that easy.
Cybananna
thanks for the reply! w00t
DGTom
Thanks from this DIY idiot to both of you, thats exactally what I was looking for!
governor blacksnake
Cybananna wrote:
I want to make a few of these. I want just a simple single passive attenuator for audio or CV attenuation. I found some stuff on the Doepfer website that appears to be what I want, that is extremely simple. Am I correct that you just wire an input jack and an output jack to a pot (like a 50k log for example)?

Is it really that easy? no other resistors needed? hyper


input jack to one side, output to middle, ground to the other side
fluxmonkey
Cybananna
Thanks again everyone for all the good info. I've done several Blacet kits and am stepping more into DIY, starting with a simple utility box. A few passive attens, mults, and some 1/8 to 1/4 conversion jacks.

gotta start somewhere right! hihi
fonik
if you add a 10k resistor from the 100k potentiometers wiper to ground you can modifiy a linear potentiometer to act like an logarithmic one. that's quite nice for audio, i use it for control voltages, too.
http://www.elby-designs.com/documents/tailoringpotentionometers.pdf
http://www.mindspring.com/~clist/PotGraph.html
felix
fonik wrote:
if you add a 10k resistor from the 100k potentiometers wiper to ground you can modifiy a linear potentiometer to act like an logarithmic one. that's quite nice for audio, i use it for control voltages, too.
http://www.elby-designs.com/documents/tailoringpotentionometers.pdf
http://www.mindspring.com/~clist/PotGraph.html

Wow, hot tip!!! Of all the basic books and sites I've read, none of them have ever mentioned such a thing. Very cool to know.

Does the same apply to other size pots? Is it simply a 1:10 ratio? For example, a 1k resistor on a 10k pot?
fonik
felix wrote:
Does the same apply to other size pots? Is it simply a 1:10 ratio? For example, a 1k resistor on a 10k pot?

certainly, it does. grin
A Dingleberry Monstrosity
welcome to freshman electrical engineering Guinness ftw!
slow_riot
will a passive attenuator work in both directions? or just input... attenuate... output ?
10011001
thank you everybody thumbs up
daverj
slow_riot wrote:
will a passive attenuator work in both directions? or just input... attenuate... output ?


What do you mean by "both directions"?

You can't connect an attenuator in reverse. If you connect the output of a module into the output of an attenuator then when you turn the attenuator down you will short circuit the module's output to ground.
slow_riot
yep that's how I meant, should have enagaged my brain and looked harder before asking the question! the answer is pretty obvious now you mention in.
intellijel
fonik wrote:
if you add a 10k resistor from the 100k potentiometers wiper to ground you can modifiy a linear potentiometer to act like an logarithmic one. that's quite nice for audio, i use it for control voltages, too.
http://www.elby-designs.com/documents/tailoringpotentionometers.pdf
http://www.mindspring.com/~clist/PotGraph.html


this is exactly what I did on the Intellijel uATT module. There is a jumper to select whether this resistor from the wiper to ground is connected.

Good article here:
http://www.geofex.com/article_folders/potsecrets/potscret.htm
GeoffC
Thanks for those links.

However I think I will click on the link to "potsecret.htm" from home, not here at work.

d'oh!

Geoff
Just me
You might want to look at these.

ersatzplanet
On our passive Slide pot modules (Synthwerks SP-1P) we also add a 1K resistor in line between the wiper of the pot and its jack. This prevents a total short from ever happening. Just as a safety measure. The SP-1P has the other legs of the pot normalized to ground though to act as a attenuator. The added resistor keeps the wiper from ever producing a direct short to any modules down stream.
-James
nuketifromorbit
I've got a broken rolls line mixer I want to salvage pots from. Anyway the pots in the mixer are 100k and I'm guessing stereo since they have six connectors rather than three. Can I still use these to build passive attenuators?
jimboburgess
nuketifromorbit wrote:
I've got a broken rolls line mixer I want to salvage pots from. Anyway the pots in the mixer are 100k and I'm guessing stereo since they have six connectors rather than three. Can I still use these to build passive attenuators?


yup, just use only one side on the pots
21hertz
I'm trying to make my own attenuators for CV purposes.
I have tried three different pots, Alpha A50k, B50k and B100k.

NONE of them goes down to zero, if connect a LFO (0-10v) the pots only attenuates by maybe 25-50% when having the pot full CCW.

I have read somewhere that 50k or 100k should be fine. I don't get why 50k och 100k works for other people. I suspect that I have to get a 500k to make this work. Any insights?
PWM
21hertz the problem doesn't lie in the overall resistance of the potentiometer. When connected properly there should be no resistance between CCW and W when the pot is turned all the way CCW.
Try measuring your pots.
ersatzplanet
The important thing in the passive attenuation is the connection to Ground. Without that connection, the pot's resistance will probably not be enough for the level of signals in a modular. I find the Doepfer DIY page is a good resource for simple circuits like these. Here is what he suggest for an attenuator.



The important bit is as you can see, the output is shorted to ground when fully attenuated. The input of the connected module will have protection resistors so don't worry (to be safe you can add a 1k resistor after the pot). With this circuit, there is no way signal will pass.
PWM
ersatzplanet wrote:
The important thing in the passive attenuation is the connection to Ground. Without that connection, the pot's resistance will probably not be enough for the level of signals in a modular. I find the Doepfer DIY page is a good resource for simple circuits like these. Here is what he suggest for an attenuator.



The important bit is as you can see, the output is shorted to ground when fully attenuated. The input of the connected module will have protection resistors so don't worry (to be safe you can add a 1k resistor after the pot). With this circuit, there is no way signal will pass.



What I was trying to explain done properly...
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2  Next [all]
Page 1 of 2
Powered by phpBB © phpBB Group