Joachim Verghese has a nice page about ARP filter modules:
http://www.netcontrol.fi/~jocke/arptech/JH.
> I do hear they make a good product, but I agree about the prices. What's
even
> worse is they are the only place around making replacement submodules for
the
> old ARP stuff. If you happen to need a replacement ladder VCF for your
2600
> (like I do, because a previous owner had replaced it with a CEM 3320), it
> will cost you $250 for their Bluemeanie VCF submodule alone! It would seem
> that there is a clear market for unpopulated PCBs to fill this need --
maybe
> Tony, or Harry (or someone) will take the hint.