[sdiy] Trimmers

[George Hearn]

The Oberheim XPander appears to have a mere 6 trimmers total for its 6
Voices!  It 'Autotunes' its oscillator pitch and scale, VCF pitch and scale,
it even auto-calibrates its own resonance controls for the VCFs so all the
voices break into resonance at the same point on the dial.  It's quite an
achievement I think.  This is a design that doesn't use pots or DACs or
digital pots but circumvents the need for trimming entirely..  bravo to
them.  G 

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Nate Reeves
Sent: 28 February 2009 17:05
To: Synth-DIY DIY
Subject: Re: [sdiy] Trimmers

yes its surprising as i thought the SCI 6 trak had a "self tune" mode

as does the oberheim matrix 6!

those were more recent i guess than the poly6!

cheers

nate


On Feb 28, 2009, at 11:46 AM, Tim Ressel wrote:

> The modern solution, from a manufacturing standpoint, is to use  
> either DACs or digital pots to make the adjustments. A test station  
> puts the instrument through a set of tests exercising various  
> functions and determining the values for the DACs/pots.
>
> Of course this adds cost to each unit. Sometimes it is cheaper to  
> pay a worker to make the adjustments. In this case the test station  
> facilitates the adjustments by showing a clear indication of which  
> direction to turn the pot and when the adjustment is correct.
>
> I like the solution where the thing adjusts itself. Imagine a VCO  
> that could apply its own precise voltage and measure its own  
> frequency. Or even better: a VCO that can measure the input voltage  
> precisely and adjust itself on the fly all the time.
>
> --TimR
>
>
> --- On Sat, 2/28/09, Tom Wiltshire <tom at electricdruid.net> wrote:
>
>> From: Tom Wiltshire <tom at electricdruid.net>
>> Subject: [sdiy] Trimmers
>> To: "synth-diy DIY" <synth-diy at dropmix.xs4all.nl>
>> Date: Saturday, February 28, 2009, 7:43 AM
>> The Korg Poly6 voice board has 50 trimmers for six
>> single-osc voices. There are seven per voice (osc, filter,
>> vca and env all have trimmers) plus 8 more for the overall
>> stuff.
>>
>> It's amazing that this was ever considered viable. The
>> amount of time it must have taken to tune each instrument
>> before it left the factory must have cost them a fortune.
>> Elimination of these kind of trims from a design must be an
>> important part of modern design for manufacture.
>>
>> No real point to this, beyond that startling initial
>> statisitic. 50! Blew my mind!
>>
>> T.
>>
>>
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