[sdiy] Cooking pots

[electronicpresskit]

> On Tue, Sep 13, 2011 at 3:29 AM, Paul Perry <pfperry at melbpc.org.au> wrote:

Thanks Paul!

>> Erik Dower - who started this thread - appears to be havign some trouble
>> posting to the list. He's asked me to send this for him:
>> 
>> Erik:
>> "I thought about filing off the material but I'm not sure how good of a
>> solution it is to open up a quad bourns sealed pot.  I've never attempted
>> such a thing but it seems perhaps as messy as my proposal?
> 
> I don't think filing would be a good idea due to the noise that would
> produce the
> scratches and the possibility of multiple cuts to the track.
> Burning is definitely a bad idea because the extra carbonization will
> surely reduce
> the total resistance

it's been a while since I flamed a pot, but if I remember correctly, burning away the conductive material increases resistance as there is less conductive material.

> not to mention the weird nonlinearity would
> experiment the wiper
> trying to slide in a (new) totally irregular terrain.

yeah, not sure how to get a controlled/even burn.

>> The pot is in a feedback path of an opamp in one band of an EQ.  The band
>> goes from -infinity to +6db with center detent @ 0db, and the goal is to get
>> more gain out of it.  Here's the schemo:
>> http://www.muffwiggler.com/forum/userpix/1370_screen_shot_20110911_at_92828_pm_1.png
> 
> Increasing the pot value would probably increase the gain range of
> last opamp but
> the filter characteristics would be deteriorated, unless you
> recalculate the value of
> the passive network to accomodate the new pot, in wich case you will end up with
> a filter of exactly same characteristics of the one you already have
> with no mod at all.
> 
> Sorry for the bad news.
> 
> Fabio

Thanks very much for your response!

I'm not after a pristine sparkly EQ here so deteriorated characteristics could be ok as long as it still basically works.  I've been able to get the middle two bands of this EQ (a different design) to work at +/-30db and it's easily enough to get clipping, but it's a pleasing effect in the right circumstance.

So I'd still very much welcome any ideas on how to boost the gain without losing center detent = 0db.

epk