[sdiy] Interpreting four-pole-w-feedback circuits

Dave Manley dlmanley at sonic.net
Thu Mar 6 22:35:36 CET 2008

Aaron Lanterman wrote:

> Curious... what is up with the extra transistors in ARP's ladders? On 
> the 4034 and 4035 they're labeled Z3A and Z4A. Wait - there's another 
> odd one, Z2A. I don't think I've seen any other ladders like that.

In the CA3086 the A and B sections are a diff pair, with pin 3 the 
common emitter, so one of them can't be used in the ladder.  Z3A and Z4A 
are just hooked up as diodes, and I don't think they really do anything 
given the DC voltages in the ladder.  Is this just a way to tie the 
unused sections off?

Z2A is diode connected as well, but is it doing anything?  The anode DC 
voltage is ~1.5V, not sure what the cathode voltage is.


More information about the Synth-diy mailing list