Ringmod transformers

[Dave Halliday]

>     About 20 years ago I made a pair of such ring mods, literally just 
>     grabbing a few unknown transformers I had lying about from old 
>     transistor radios. The ring mods worked fine. Of note, if the 
>     transformers are mismatched, you will get different harmonic 
>     distribution depending which of the two inputs you use as the 
>     modulating signal.  I'd pick transformers with at least 1k impedance 
>     for their coils. In other words, don't use 8ohm speaker transformers. 
>     Ken.

>> I am about to attempt the ringmod circuit that Kevin Lightner has 
>>posted on his site.. (Starting with the tough ones..=)) Anyway, it 
>>requires 2 driver transformers, and the part listed (Stancor A-4713) 
>>apparently does not exist anymore.(?) The schematic states that "many 
>>small driver transformers will work", but neglects to mention anything 
>>about specs, etc. For those of you who have built this/know what I mean, 
>>does "many" mean "any" small driver transformer, or is there a certain 
>>type (EI-19/24?) or spec concerning resistance/impedance/mW output which 
>>I need to match?
>>
>> Jason



Hmmm...  If you had a transformer with several taps, you could turn 
this bug into a feature and bring these out to a rotary switch on the 
front panel...


Also, I haven't seen the circuit in question but since diodes have a 
specific voltage drop across them, I was wondering about a small 
battery for a bias - make it a little more linear.  You could also use 
a CMOS invertor chip as an oscillator and then parallel the other 
invertors to get extra current to drive an isolation transformer but 
this would require power to the module.
--- Via Silver Xpress V4.4 [Reg]