[sdiy] Passive Ring Modulator

[>>>marjan<<<]

Theo wrote:
> 
> Is only the forward drop of interest here?
> Germanium diodes kind of "smoothly" come to conductance.
> The Scotty diodes you suggest switch quite abruptly.
> Seems to me the smooth switching behavior of the germanium diodes would be
> better for the "sound" of the ring modulator.


Only reason to use Ge over Si 'cause Si needs over +-0.7V signal
input to work and there's no premp to amplify your signal - 
the whole point of this rm is that it doesn't need power.
Ge diodes have much lower treshold, but more problems.

You want all 4 diodes matched very well. Ge stuff is hard to 
match, and even when matched much more prone to temp variations
of parameters ie they won't stay matched.

I've made my version a while ago - used two xformers from
the _same_ old radio (there are several of them inside
color coded - use the same color). I think they are 600 ohms
or something like that. You can buy new in that shack thing
suppliers, they are used for old wah-wah 500uF coil replacemnts.

For diodes - used 3046. Added small (100nF) caps in i/o
paths. Works but needs high input. 
Rather simple project on samall piece of perfboard.

No need for specific xformer types or diodes. 
You can build much better rm but you'll need power supply...


--



marjan


me    : Marjan Urekar
e-mail: urekar.m at eunet.yu
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