since everyone is always asking

[para]

here is a simple resonant analog low pass filter. possibly the simplest there is? i'm not giving out values though.

UPDATED so re-download it




love,
steven

[caress]

no values!  where's the fun in that?  

[para]

thats precisely the fun


no silver platters from me. i had to figure out the whole res scheme on my own. you can't find this shit anywhere



steven

[caress]

just a single silver spoonful...a single opamp, yes?

[para]

actually there is a slightly different version here that will work with just about any opamp. 072 4558 5532 whatever. the one above is only for a single supply opa. i forgot to mention that

http://thesquarewaveparade.com/brdlayot.html

the mimeo is there too



steven

[expanoncolin]

Dual gang pots are a cop-out

Some theory here: http://experimentalistsanonymous.com/di ... filter.pdf

-Colin

[para]

so are OTA's and vactrols and anything other then dual OPA's according to you  

simplicity is all that matters where the parasites are concerned

and please don't make me feel like a dick about not posting the values. if this weren't an active design for me i'd be a little more forthcoming. its not like you see every manufacturer just giving out their designs. some do, yes, and i have more on the way but this one is so simple and was a huge triumph for me personally. as simple as it is, it answered a million questions.


steven

[para]

where did you find that datasheet colin?


steven

[expanoncolin]

so are OTA's and vactrols and anything other then dual OPA's according to you  

simplicity is all that matters where the parasites are concerned

and please don't make me feel like a dick about not posting the values. if this weren't an active design for me i'd be a little more forthcoming. its not like you see every manufacturer just giving out their designs. some do, yes, and i have more on the way but this one is so simple and was a huge triumph for me personally. as simple as it is, it answered a million questions.


steven

No no, OTA's are not cop-outs...  I like things that can easily be voltage controlled, and are not special purpose (H11F3's contradict that though).  Dual gang pots and vactrols are special purpose to me.  It is a strange bias I know, but I guess it stems from building stuff...  I can't use dual gang in the pedals I am making production because of the way the pots are mounted.  I can't use vactrols because my resistance ranges vary so much.  These sort of quirks that are caused by me trying to automate my designs normally end up in me using twice as many ICs as needed, but hey.  Just bias on my part most DIYers wouldn't have to pay attention to.

http://www.national.com/apnotes/

You shouldn't feel like a dick posting component values.  9 times out of 10 I will change most values in a circuit I see elsewhere.

-Colin

[para]

you were talking shit about OTA's in filters but i guess that was the sound of the res people seem to get

the vactols in production now are all pretty close, you just use a trimmer and do a little cal before you ship them out. the stuff in the PS's are nos btw. and the main point for using them is the simplicity and the SOUND. vactrols just sound so fucking good. period and i'd rather work with a vactrol over an OTA any day. but i will always end up having to use OTA's for certain tasks.

dual pots are almost exactly the same as single, just add 1mm to the bottom dim.

some are bulky, but some are great.


"9 times out of 10 I will change most values in a circuit I see elsewhere. " me too, but people bitch if you don’t do the work for them. and no i’m not talking about you caress


steven

[expanoncolin]

you were talking shit about OTA's in filters but i guess that was the sound of the res people seem to get

the vactols in production now are all pretty close, you just use a trimmer and do a little cal before you ship them out. the stuff in the PS's are nos btw. and the main point for using them is the simplicity and the SOUND. vactrols just sound so fucking good. period and i'd rather work with a vactrol over an OTA any day. but i will always end up having to use OTA's for certain tasks.

dual pots are almost exactly the same as single, just add 1mm to the bottom dim.

some are bulky, but some are great.


"9 times out of 10 I will change most values in a circuit I see elsewhere. " me too, but people bitch if you don’t do the work for them. and no i’m not talking about you caress


steven

I wasn't talking shit about the OTA so much as the yucky clipping of the standard sallen key OTA VCF.  I use OTAs all over the place though, as VCA's, VCO's, VCF's...  Like I've said though, I have steered clear of vactrols because of the range and taper limitations, and that I used to think they were all NOS (thanks for showing me they weren't though).

I don't mount my pots right angle, there are no holes, the leads are soldered directly to pads on the board.  So dual gang would require a second circuit board.

-Colin

[para]

where are you finding right angle pots?


steven

[para]

hey caress i posted this somewhere else, maybe it will help---


set yourself some easy limits to allow you to experiment with the more important values. like the input DC cap should be around 104 or whatever you like to use, the first resistor to ground can be 100k, the two cutoff pots can be temporarily replaced with 100k resistors so you don’t have to worry about matching two separate pots for now if you don't have a dual, and the res pot can be like a 100k or whatever until you get the last resistor and cap values decided. then once they are set you figure out your final pot values and test the caps for range and your finished.

UPDATED for stupidity !!!



steven

[expanoncolin]

where are you finding right angle pots?


steven

They aren't right angle pots, they are the pots from futurlec.  The tabs aren't bent, they are mounted on the board directly...  the board is parallel to the tabs.  The shaft is perpendicular to the board.

-Colin

[para]

you just have the tabs slid over the edge of the board? interesting. how’s it working out for you? that never even crossed my mind to do that. nice!

so now you can use pcb mounted switches and leds and stuff too and still not have to pay like $3 a pot. but are all of your passives and semi’s on the other side of the board? i may have to steal that. but i'm pretty happy with the other idea i stole from you of having a little pcb just for the pots and then a ribbon to the board that is jack mounted. it worked out fantastically well. but i need to start using IDC's for the ribbons, trimming and soldering those bitches takes longer then the passives. no joke. next batch IDC

heres the new DG




steven