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2m or 2.2M linear pots needed, small? PC mount?
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cslammy



Joined: Apr 27, 2018
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PostPosted: Thu Dec 27, 2018 4:33 pm    Post subject: 2m or 2.2M linear pots needed, small? PC mount? Reply with quote  Mark this post and the followings unread

I found some 2W panel mount honkers on ebay. They work, but are really big Razz

Linear or audio taper, audio preferred.

Anyone have any for sale? Trade? Know of a place to get some of these? PCB mount would be best. If not, panel mount will work.

Can't find them in the usual spots.

Thanks.

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Last edited by cslammy on Sat Jan 05, 2019 9:28 am; edited 1 time in total
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donpachi



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PostPosted: Thu Dec 27, 2018 10:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

I also could not find a small 2M pot. But the two sections of a stereo 1M pot can be chained in series as a workaround. What I used is this:
https://www.uk-electronic.de/onlineshop/product_info.php?products_id=3424&language=en
HTH
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cslammy



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PostPosted: Fri Dec 28, 2018 7:42 am    Post subject: Reply with quote  Mark this post and the followings unread

donpachi wrote:
I also could not find a small 2M pot. But the two sections of a stereo 1M pot can be chained in series as a workaround. What I used is this:
https://www.uk-electronic.de/onlineshop/product_info.php?products_id=3424&language=en
HTH



Interesting idea. How do you wire up the wipers? Use a SPDT switch to select between the 0 to 1M and the 1M to 2M wiper?

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donpachi



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PostPosted: Sat Dec 29, 2018 1:59 am    Post subject: Reply with quote  Mark this post and the followings unread

cslammy wrote:
How do you wire up the wipers? Use a SPDT switch to select between the 0 to 1M and the 1M to 2M wiper?


I did it the very simple way. For a single-gang pot, a variable resistor is usually achieved by wiring the low pin and the wiper.

Each pot section (A and B for dual pots) has three pins --- 1 is low, 2 is wiper, 3 is high. I chained the sections like this: A2 and B1 are connected with a wire. The rest of the circuit is connected to A1 and B2. The pot now acts as a zero to 2M resistor Cool

This trick will not work if you intend to use the pot as a voltage divider. But all circuits I encountered that ask for a 2M pot require the variable resistor configuration, e.g. some ADSR envelopes. So probably it will be fine.
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cslammy



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PostPosted: Sat Dec 29, 2018 10:08 am    Post subject: Reply with quote  Mark this post and the followings unread

donpachi wrote:
all circuits I encountered that ask for a 2M pot require the variable resistor configuration, e.g. some ADSR envelopes. So probably it will be fine.



Don You are right, this is for an ADSR and your idea is going to work just great! Thanks so much for helping me out on this one! Very Happy

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g.gabba



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PostPosted: Sat Dec 29, 2018 12:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

since tau=R*C,
an other workaround is to just increase the cap value,
which is usually easy-er to do

e.g. 1M/1µF shold act same as 100k/10µF

let me guess rene schmitz adsr?
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PHOBoS



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PostPosted: Sat Dec 29, 2018 1:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

g.gabba wrote:
since tau=R*C,
an other workaround is to just increase the cap value,
which is usually easy-er to do

e.g. 1M/1µF shold act same as 100k/10µF

That only works with a fixed rate. a 2M pot will give a much larger range than a 100K pot.
100K will give you more accuracy.

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cslammy



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PostPosted: Sat Dec 29, 2018 1:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes Rene ADSR.

I wanted to keep the RC curve cap as small as possible, thinking a small cap maximizes the real-world speed of a rapid attack. math wise it should sound the same (right?) but working with other ADSRs I have not always found that to be the case, at least to my ears.

I haven't A Bd the Rene-DSR circuit with both possibilities to see if I can hear a difference.

Once I get the 1M pots, different flavors are on their way from Mouser, I will A B them. I should be able to put a couple of Rene ADSRs side by side.

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PHOBoS



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PostPosted: Sat Dec 29, 2018 8:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

cslammy wrote:
I wanted to keep the RC curve cap as small as possible, thinking a small cap maximizes the real-world speed of a rapid attack. math wise it should sound the same (right?) but working with other ADSRs I have not always found that to be the case, at least to my ears.

Could be as a larger cap requires more current to flow to get to the same voltage as a smaller cap and if that current can't be supplied
fast enough it would take a bit longer. Just speculating though.

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g.gabba



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PostPosted: Sun Dec 30, 2018 1:41 am    Post subject: Reply with quote  Mark this post and the followings unread

this is, of course!, the case,
since our opamps are a limited source of current (ive had a look into the TL07x Datasheet, but couldnt find the exact value Crying or Very sad )

Once i tought one could replace the typical Attack-Diode with a transistor going to Supply, but ive never tested it, it works in the simulator

just some things:

if u are looking for very fast attacks, ur usually look for percussive-like sounds, means u dont have 10ns Attack and then 10s Decay --> so u could make it switchable (like in the yusynth ADSR)

an other idea is, if u need it fast: not to charge the Cap up to 2/3Supply, just charge it to say 1V, but i guess then you need a different design - not based on 555

concerning renes design, the Decay and the Release-discharge is realized with a diode which results in an issue which is described (and solved) here:
https://kassu2000.blogspot.com/2015/05/precision-adsr.html
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Grumble



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PostPosted: Sun Dec 30, 2018 11:47 am    Post subject: Reply with quote  Mark this post and the followings unread

You could also use an opamp with a fet based current source, that way you can increase the current beyond what the opamp can supply so the potmeter can have a smaller value while the capacitor can be increased.
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cslammy



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PostPosted: Sat Jan 05, 2019 10:36 am    Post subject: Reply with quote  Mark this post and the followings unread

To better understand all of this I built a Rene ADSR with 2M audio taper and 2.2uF/10uF cap. Post is here:

http://audiodiwhy.blogspot.com/2019/01/renaydsr-zen-and-art-of-tau.html

Favor: if someone who is good at EE can look at the middle of this post and check the math I'd be grateful. Be gentle please, it's my first time.

Thanks.

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g.gabba



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PostPosted: Sun Jan 06, 2019 7:05 am    Post subject: Reply with quote  Mark this post and the followings unread

congrats to the build cheers

some things:
the thing with tau, the rule say after 5*tau a cap is charged, that means it is then 97% charged,
if u take math a cap would never be charged 100%, a tiny tiny fraction would always be left - until we reach eternity Smile
if u are the electronic guy u could say ( like the best teacher in the world have said to me, once upon a time) if the last electron is on the disk - its on, there are no half electrons!


as i was building the yusynth adsr i also burned some 7555, they seems to be extremly sensible, i dont like them
here: http://electro-music.com/forum/topic-70684.html
JovianPyx describes very well the problem that normal 555 have, may u will need that information one day

can one adsr "sound" different to the other?
i would say only in the extrems, specialy if we go short`n`low,
short means what is the shortest attack time? that is quiet clear i guess, since people are even designing zero-attack-envelopes it is important to archieve a fast Attack for the ultimate percussion sound.

Low means: does decay goes to zero - and how fast it does (same with release- but imo it is not so important as for the decay)?
u can test it: set Sustain to zero and release to zero, u should have a AD Envelope now. But discharging with a standart diode results in an extended discharge time (view also the link ive postet earlier)
This often results in a audible effect when the gate goes low, as a workaround i used to open the release a bit to "soften it out", this effect u could even find in the stock ADSR of the https://vcvrack.com/
can you hear it too in your build?

Lin vs exp response Potis, imo especially in envelopes exp-pot making sense, cos the interesting things are happening fast, no-one is speaking about how nice slow his envelopes are, so with exp-response u can be very precise "in the beginning" means u can adjust very well between eg 1ms and 1,5ms, but u are going to be unprecise towards the end where it does not matter so much if u have 8000ms or 8200ms of release

altought it could handle math iam not in love, but i can remember that it was kind of interesting where the units are coming from, since tau is a time: where time is coming from if u calculate a resistor and a capacitor?
Then (once upon a time) the best teacher in the world used to say: there was a clever guy back then who had the same problem, so he decided to include time in capacity so the guys in the future (us) dont have to worry about that, since then capacity could be written as (A*s)/V
Smile


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g.gabba



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PostPosted: Sun Jan 06, 2019 8:52 am    Post subject: Reply with quote  Mark this post and the followings unread

even the bloody simulator can reproduce this behaviour Smile

on the left side my "normal" AD circuit, the decay discharge is realized with a transistor, is represented by the red graph

rigth side, same circuit but "modded" to discharge-over-diode-thru-opamp, is the blue graph

you can see very good first the deformation and may more important that it takes much longer to reach zero, in this example it couldnt even reach zero


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cslammy



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PostPosted: Mon Feb 04, 2019 1:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for all the advice and input.

I ended up building 3 Renay-DSRs using pretty much his stock design, and for my application--for this, trying to emulate 70's sounding synths, I think it sounds good.

Each has different realization of "tau", but all can be made to sound pretty much the same to my ears.

Here is my wrap up, including very basic sound samples.

https://audiodiwhy.blogspot.com/2019/02/renedsr-fastest-envelope-in-west.html

My next envelope projects: quad digital AD or D that will work with standard Expo VCA; gate modifier, and cloning the ADSR in the SH5. No idea when I will get to them Very Happy

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g.gabba



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PostPosted: Tue Feb 05, 2019 1:13 am    Post subject: Reply with quote  Mark this post and the followings unread

if you like to test "the probably fastest non zero attack envelope" --> tpfnzae

i would prepare the schematics for you Smile
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cslammy



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PostPosted: Tue Feb 05, 2019 7:28 am    Post subject: Reply with quote  Mark this post and the followings unread

g.gabba wrote:
if you like to test "the probably fastest non zero attack envelope" --> tpfnzae

i would prepare the schematics for you Smile


Sure gabba send em my way--I have a ton of things on my bench right now but I'll get to it!

Also: finished a couple of MS20 filter clones. Each is stuffed into a 1u Frac. I am happy with the results, I think they sound good. Happy to send you schems and gerbers, and I have a few extra PCBs. Requires x2 CA3080s OTAs though which can be a bit hard to find.

PM me if you are interested.

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g.gabba



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PostPosted: Tue Feb 05, 2019 10:23 am    Post subject: Reply with quote  Mark this post and the followings unread

will do so thumleft
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