[sdiy] Moog ladder filter 904a

[Terry]

According to the Moog 904A spec sheet:

Pos.1) 1Hz to 5 kHz
Pos.2) 4Hz to 20kHz
Pos.3) 16Hz to 80kHz

At the first position, there is a wall at around 5 kHz. No matter how much  
CV applied the filter only opens so far, easiest to observe with white  
noise. If the schematic is correct that would be the large 1.2uF cap set.
Pos.2 would be the middle ground with the .3uF set.



Have a Moog 902A Band Pass Adapter I'm trying/experimenting with right  
now. Someone recently auctioned one off on Ebay. There were enough photos  
of the board to try and reverse engineer. Works in conjunction with the  
902 VCA. Always wondered what that other Moog filter sounded like.


> In the following circuitv there is a 3 way switch
> that selects the VCF freq 'range' (3 capacitors set choices)..
>
> http://www.freeinfosociety.com/media/images/4145.jpg
>
> Which capacitors set would provide full freq range sweep ?
>
> C1: 1.2uF
> C2: 0.3uF
> C3: 0.075uF
>
> I would quess C1 1.2uF
>
> Any clues ?
>
> J-Pierre
>
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