[sdiy] Oberheim Xpander Multimode VCF Question

[Tom Wiltshire]

The best source is the Xpander Service Manual, which has some detail  
on the filter, including the basic equation:

http://www.synthi.se/oberheim/OberheimXpander-ServiceManual.pdf

If you've not seen this already, you should definitely have a look,  
Steven.

T.

On 11 Mar 2010, at 16:26, Jay Schwichtenberg wrote:

> Steven,
>
> Some where out on the net there is a lot of info on the filter.  
> Schematics
> and the modes that it supports.
>
> The Doepfer site has a clone with the db info.
> http://www.doepfer.de/home_e.htm
>
> Jay S.
>
>> -----Original Message-----
>> From: synth-diy-bounces at dropmix.xs4all.nl
>> [mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Steven Cook
>> Sent: Thursday, March 11, 2010 2:20 AM
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: [sdiy] Oberheim Xpander Multimode VCF Question
>>
>>
>> Hi,
>>
>> Is it possible to get a -24dB/oct allpass response out of an Oberheim
>> Xpander type of 4-pole filter arrangement? I've got the following for
>> an -18dB allpass, from a post by David G. Dixon...
>>
>> input + pole1*3 - pole2*6 + pole3*4
>>
>> Which seems to work fine (in software).
>>
>> Regards,
>>
>> Steven Cook.
>>
>> http://www.spcplugins.com/
>> +44(0)1271 867288
>>
>>
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>
>
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