[sdiy] Moog ladder theory questions

[Tim Ressel]

Dear cheater^2,

If you are talking about the transistors in the ladder itself, I don't think the beta is critical. The transistors are being used not for their amplification quality but for their ability to change AC impedance in relation to their collector current. I believe other transistor qualities, like noise, are much more important. I'm toying with the idea of making an ARP ladder phasor which uses 28 transistors in a ladder configuration similar to the Moog ladder filter. The MAT04 transistor quad is looking attractive for its low noise. With 28 transistors, noise is a real issue.

Of course, the sonic quality of the filter is affected bt transistor choice as well. But you cannot determine that from a data sheet. BTW the choice of capacitor type will affect sound quality as much as transistor choice.

--Tim (had $0.02 to spare) Ressel

--- On Wed, 1/14/09, cheater cheater <cheater00 at gmail.com> wrote:

> From: cheater cheater <cheater00 at gmail.com>
> Subject: [sdiy] Moog ladder theory questions
> To: synth-diy at dropmix.xs4all.nl
> Date: Wednesday, January 14, 2009, 3:29 AM
> Hi guys,
> I'm reading up on the moog ladder.
> What beta do the transistors used in the moog vcf normally
> have?
> I bet there's a difference between the case of
> 'original instruments
> of lore' and 'nowadays', so let's consider
> both options.
> 
> Cheers
> Damian
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