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 Forum index » DIY Hardware and Software » YuSynth
ADSR Pots
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LetterBeacon



Joined: Mar 18, 2008
Posts: 454
Location: London, UK

PostPosted: Tue Jun 09, 2009 2:22 pm    Post subject: ADSR Pots
Subject description: To log or not to log....
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I can't get 1Meg log taper pots in the size that I need for my knobs (the Futurlec ones I use have a slightly shorter shaft length to the ones from Rapid), so I need to make a decision. Do I:

a) Use 1Meg linear pots
b) Use 1Meg linear pots and use a resistor to turn it into a reverse log pot

Which one will give me the best amount of control (although neither will be perfect)?

Thanks!
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yusynth



Joined: Nov 24, 2005
Posts: 1214
Location: France

PostPosted: Wed Jun 10, 2009 2:36 am    Post subject: Re: ADSR Pots
Subject description: To log or not to log....
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LetterBeacon wrote:
I can't get 1Meg log taper pots in the size that I need for my knobs (the Futurlec ones I use have a slightly shorter shaft length to the ones from Rapid), so I need to make a decision. Do I:

a) Use 1Meg linear pots
b) Use 1Meg linear pots and use a resistor to turn it into a reverse log pot

Which one will give me the best amount of control (although neither will be perfect)?

Thanks!


Why not using 1M log pots ? These are easily sourceable at other places than futurlec I think.
a) 1M lin is a very bad solution
b) you are not getting a reverse log curve as you write, but a log curve, which is fortunate because that is what you are actually looking for. By the way, you'll need a pot with a value bigger than 1M lin because the use of a taper resistor reduces the overal resistor : Rt = (Rpot + Rtapper)/(Rpot x Rtapper)

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Yves
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scriptstyle



Joined: Jan 22, 2008
Posts: 250
Location: nj

PostPosted: Wed Jun 10, 2009 7:54 am    Post subject: Reply with quote  Mark this post and the followings unread

a 5m lin pot and a 1.25m tapper should do the trick...
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LetterBeacon



Joined: Mar 18, 2008
Posts: 454
Location: London, UK

PostPosted: Wed Jun 10, 2009 11:41 am    Post subject: Re: ADSR Pots
Subject description: To log or not to log....
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yusynth wrote:
Why not using 1M log pots ? These are easily sourceable at other places than futurlec I think.

The pots from Futurlec seem to have a slightly smaller shaft than the ones I can get from elsewhere. Unfortunately the pots that I have designed the panel around require this slightly smaller shaft.

Quote:
b) you are not getting a reverse log curve as you write, but a log curve, which is fortunate because that is what you are actually looking for. By the way, you'll need a pot with a value bigger than 1M lin because the use of a taper resistor reduces the overal resistor : Rt = (Rpot + Rtapper)/(Rpot x Rtapper)

Thanks for that. I think I'm going to have to do some more reading!
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LetterBeacon



Joined: Mar 18, 2008
Posts: 454
Location: London, UK

PostPosted: Wed Jun 10, 2009 2:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

You'll have to bear with me here because I'm sure this is basic stuff, but I'm a bit confused!

In this article, near the bottom, it says the following:

The Secret Life Of Pots wrote:
In the two terminal connection, the resistance through the pot is what we're interested in, not the voltage divider ratio.

It turns out that the tapering trick works here, but only partially. If we want to make a reverse log tapering pot, we're in! However, there is no way to get a simulation of a log taper pot in the two terminal connection. For that we have to buy real audio taper pots.


On the ADSR module, all three log taper pots are two terminal connections. So how can I make a log taper pot if the pots in the circuit are two terminal connections?

Thanks for your patience!
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yusynth



Joined: Nov 24, 2005
Posts: 1214
Location: France

PostPosted: Thu Jun 11, 2009 9:53 am    Post subject: Re: ADSR Pots
Subject description: To log or not to log....
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LetterBeacon wrote:
yusynth wrote:
Why not using 1M log pots ? These are easily sourceable at other places than futurlec I think.

The pots from Futurlec seem to have a slightly smaller shaft than the ones I can get from elsewhere. Unfortunately the pots that I have designed the panel around require this slightly smaller shaft.!

Have thought of sawing them ?

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Yves
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yusynth



Joined: Nov 24, 2005
Posts: 1214
Location: France

PostPosted: Thu Jun 11, 2009 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

LetterBeacon wrote:
You'll have to bear with me here because I'm sure this is basic stuff, but I'm a bit confused!

In this article, near the bottom, it says the following:

The Secret Life Of Pots wrote:
In the two terminal connection, the resistance through the pot is what we're interested in, not the voltage divider ratio.

It turns out that the tapering trick works here, but only partially. If we want to make a reverse log tapering pot, we're in! However, there is no way to get a simulation of a log taper pot in the two terminal connection. For that we have to buy real audio taper pots.


OK then, take a lin pot and a resitor taper, and check what you eventually obtain ... Nothing replaces experimentation, and let us know what you get. Wink

Quote:
On the ADSR module, all three log taper pots are two terminal connections. So how can I make a log taper pot if the pots in the circuit are two terminal connections?


the resistor is to be connected in parallel with the two connectors.
Quote:
Thanks for your patience!

No problem, you're welcome.

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Yves
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