[sdiy] Oberheim Xpander Res fail

[Tom Wiltshire]

Hi Csaba,

They mean that the cutoff frequency is set for the note E9 or E5. There's no definite standard for which 'E' is 'E0' so it isn't totally obvious which frequency they mean by E5 or E9, but the basic idea is that you set the filter to the highest frequency, and then check that it oscillates by turning the resonance voltage to maximum (since it is, apparently, most difficult to achieve resonance at the high frequencies on this synth - not the case with all filter designs). It's then adjusted by changing the frequency to E5 and then reducing the resonance voltage until the point at which it *doesn't* resonate any more, and then turning it up again until it does. This Res CV is then regarded as the 'oscillation break point'. 

I expect that the oscillation break point for the filter resonance actually varies a bit across the range, but they didn't bother checking in several places across the range. Instead, they did it once in the middle - E5. Presumably the break point doesn't vary much and this is good enough.

HTH,
Tom




On 14 Jan 2012, at 17:12, Csaba Zvekan wrote:

> OK I replaced tons of 4051's and 4053's and 4016's on the voice board just to find out that it still refuses to tune the "Res". After further investigating the problem It seems my problem is not around the voice board rather around the 5V generation of my DAC. So I'm trying to figure out what really is going on when "Res" is pressed and what components are involved after the Software is " .. .set for E9 and it's resonance control is at maximum (5Volts) " taken from the device manual page 22.
> So I believe this is not even happening . How do I trouble shoot this "…E9" and where is this ???
> And later it goes into "…frequency is set for E5 …"  ??? where and what is that.  
> If I know what and where those lines are I'm getting closer.
> 
> Any help greatly appreciated 
> 
> Csaba