[sdiy] MS-20 tempco (was Model D service)

[Adam Inglis]

Hz - per - volt synths don’t need tempcos, do they?

I have no experience with the MS-20 but I do have a Korg 700 from a few years earlier. It never needs re-tuning.


> On 9 May 2017, at 11:53 AM, matt holland <matt at mattholland.org> wrote:
> 
> ebers moll equation: Ic = Is*e^(Vbe/Vt -1)
> 
> a single transistor itself is an exponential converter. the second transistor in the common two transistor expo converter compensates for the complicated temperature dependance hidden in the Is term (Is goes away to the extent that the two transistors are identical). the tempco resistor compensates for the less severe effect of the temperature dependance hidden in the Vt term. gory details of the equation terms can be found in your nearest device physics textbook.
> 
> 
> 
> On Mon, May 8, 2017 at 5:36 PM, Tony K <weplar at gmail.com <mailto:weplar at gmail.com>> wrote:
> Hello, those so-called special Rx's are 0.1% or precision resistors , the ones with the circle around the resistor symbol.
> 
> When we recorded I always had to tweak the Master Tune as time went on. I never bothered adding one either. In mono synths it's not critical , the exponential pair handles the biggest part of the temp drift - forget the equation offhand.
> 
>  Just referring to my notes , it's been a while.
> 
> TK
> 
> > On May 8, 2017, at 7:48 PM, Declare Update <declareupdate at gmail.com <mailto:declareupdate at gmail.com>> wrote:
> >
> > wait a second... no tempcos in the MS-20? what's with all the special resistor symbols in the schematic? and how does that super common and known-to-be-temp-dependent expo converter not need compensation?
> >
> > Chris
> >
> >> On May 7, 2017, at 4:14 PM, Michael E Caloroso <mec.forumreader at gmail.com <mailto:mec.forumreader at gmail.com>> wrote:
> >>
> >> That's the one...
> >>
> >> MC
> >>
> >>> Anyway, I think Michael E C was referring to this posting of his:
> >>> http://search.retrosynth.com/ah/search/lookit.cgi?-v9901.2166 <http://search.retrosynth.com/ah/search/lookit.cgi?-v9901.2166>
> >>
> >>
> >>>> On 5/7/17, Michael Zacherl <sdiy-mz01 at blauwurf.info <mailto:sdiy-mz01 at blauwurf.info>> wrote:
> >>>>
> >>>>> On 7.May 2017, at 19:48 , Michael Zacherl <sdiy-mz01 at blauwurf.info <mailto:sdiy-mz01 at blauwurf.info>> wrote:
> >>>>>
> >>>>> On 7.May 2017, at 19:04 , Quincas Moreira <quincas at gmail.com <mailto:quincas at gmail.com>> wrote:
> >>>>>
> >>>>> Michael, thanks for saving me frustration, I will refer to your
> >>>>> instructions.
> >>>>
> >>>> uhm .. I didn’t do anything -
> >>>
> >>>
> >>> whoops  *blushes* … the other Michael.
> >>>
> >>> Anyway, I think Michael E C was referring to this posting of his:
> >>> http://search.retrosynth.com/ah/search/lookit.cgi?-v9901.2166 <http://search.retrosynth.com/ah/search/lookit.cgi?-v9901.2166>
> >>>
> >>> sorry, Michael E C, Michael.
> >>>
> >>>
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