Passive ring modulator trick

[markusw]

Hi,

during my Ring Stinger revengineering I found the passive ring modulator to be slightly modified from the standard schem :



By carefully adjusting the 100k trim pot it's possible to almost completely get rid of the carrier breaking through.

Just thought it might be of interest also for other designs involving the 2-transformer setup.

Any further comments on the usefulness of this trick would be highly appreciated.

BTW, the LT-44 has 20k and 1k impedance prim and sec as well as 660 and 80 ohm prim and sec serial resistance, respectively.

Markus

Sorry for the massive schem. When I reduce the size the lines tend to disappear. Don't found the right way to export schems from LTSpice.

[Tim Escobedo]

Interesting idea. A few years ago, a guy on the SDIY list offered some similar ideas using trimmers. In that realm, the diode ring mod seems generally passed over, however, because of the usual problems. I don't know if any of the other gurus on the list ever tried the idea.

Using a monolithic schottky diode chip helps with matching the diodes. But balancing the transformers out is a whole other costly ballgame. This seems worth a try.

[markusw]

BTW, it's interesting that Lovetone added this trim pot without altering the layout simply by soldering the pot directly to the diodes. It seems that this modification was done on a later series of the Ring Stinger.
I think it's a really cool idea, you can watch the carrier break through disappear on the scope while adjusting the pot.

I used 1N34 diodes that were within 1 mV volatge drop when measured with my DMM. For the LT-44s I chose 2 out of six that had relatively similar DC resistances. However, they were far from being really matched.  If I got it right it should be possible to compensated for both, not perfectly matched diodes and transformers. Please correct me if I'm wrong.

Markus

[jmusser]

I knew that transformer sounded familiar. It's the Maplin HX82D that's used in the John Hollis Titan Boost. I must not have the proper program to read the GEO text and schematic for the Titan Boost, but I believe there is a Mouser equivalent for people in the U.S. on that page, for those who are interested.

[jmusser]

Finally got to the Titan Boost at GEO here at work. The 42TM006 Mouser transformer is the one to use if you don't have access to the Maplin HX82D (AKA Eagle LT-44).

[soggybag]

While we're on the topic of ring mods and the Titan Boost. I have had the idea that the titan boost might make a good ring mod by adding a second transformer? I was also thinking it might be interesting to use signal going into the first transformer as the carrier for an octave efect?

[soggybag]

While we're on the topic of ring mods and the Titan Boost. I have had the idea that the titan boost might make a good ring mod by adding a second transformer? I was also thinking it might be interesting to use signal going into the first transformer as the carrier for an octave efect?