[sdiy] Buffering Busses?

[Dave Kendall]

Thanks Harry.

Mystery laid to rest. VCO3D input buffers it is then......

Cheers,

Dave


on 29/12/05 4:10, harrybissell at harrybissell at prodigy.net wrote:

> The VCO3d has a 'bug' (feature).
> 
> In the original Moog design, the CV inputs were permanently connected
> so the impedance into the VCO never varied.
> 
> In a modular system, going from open circuit to 100K (the input resistor)
> will throw the pitch off everytime a connection is made.
> 
> The design does NOT have a true summing junction, its 100K and 100ohms.
> Close, no cigar.
> 
> I added an opamp voltage follower to each input. Now connecting the CVs
> does not change the impedance at the pseudo-summer.
> 
> It was late in the design when I found the trouble. Buffers were the easy way
> out at that point.
> 
> H^) harry