[sdiy] SVF High Pass Mode not Cutting Off

[Neil Johnson]

On 30/10/2011 14:39, rob at emulatorarchive.com wrote:
> Hi
> David is right, although the solution appears more dramatic than
> matching to 0.1%. The circuit I am attempting is a Roland 703 SVF.

Is this the circuit?

http://fa.utfs.org/diy/roland_filters/SYSTEM700_703abc.jpg

If so then...

 > The schematic is slighly odd in
> that the LP and BP signals are not feedback independently, so I will try
> changing this - maybe a mistake in the original schematic.

No that looks fine.  The oddity, if you will, is that the feedback is 
around the second integrator, not the first as is usually the case.

 > However I am
> on the right track thanks to David and the list. I have the same issue
> with an ARP2500 UAF, which I will try and fix next weekend, this could
> well be a matching issue on the first Op Amp.

Are you using 1% resistors, or 5%?

Cheers,
Neil
-- 
www.njohnson.co.uk