How accurate would a Bit Crush Emulator 2n5457 Trannie substitute have to be?

[Mojo Fandangle]

Hi peoples,

Haven't posted in a while. Been pulled out of retirement to for one last pedal build (sorta like Rambo), and wanna build my own too
A mate wants me to build a Bit Crusher.  I've decided on a Heliotrope Clone (part bit crush / ring mod + dist) analog BC emulator.

http://tagboardeffects.blogspot.com.au/2012/04/catalinbread-heliotrope.htm[/b]l]http://tagboardeffects.blogspot.com.au/2012/04/catalinbread-heliotrope.html

Question: How accurate would trannie specs for a bit crusher have to be?
I'm hoping maybe not too accurate because of the nature of the effect. Maybe something close will do yes / no?
And if so, what might be a good substitute for 2n5457 be?

Thanks in advance for any suggestions.