Ring modulator help

[Dr.EM]

Hello. I'm planning on building this very simple circuit:

**broken link removed**

I have made a few before like this, but I wanted to know if there was a more suitable transformer as my current setup seems to be quite noisy in terms of allowing the original signals into the line.

I am using the LT700 audio transformer rated as 1.2k CT - 3.2 ohm.
I wanted to know whether the LT44 would be more suitable, with a rating of 1k CT - 20k. If niether are ideal, please give any suggestions! Thanks!

 

[Nigel Goodwin]

I am using the LT700 audio transformer rated as 1.2k CT - 3.2 ohm.
I wanted to know whether the LT44 would be more suitable, with a rating of 1k CT - 20k. If niether are ideal, please give any suggestions! Thanks!

The circuit in the link specifies 'driver transformers', which the LT44 is, the LT700 is an output transformer.

I suspect neither will give great cancellation of the original inputs though, as they are not designed for that purpose - the tapped windings really need to be wound together, using two strands of wire at the same time.

 

[Dr.EM]

Thanks for your help! By the tap, do you mean it would be more ideal to have a 1+1=1+1 configuration, whereby each 1 represents an individual coil, and I could then wind the ones i needed together, rather than them being internally wired.

 

[Nigel Goodwin]

Thanks for your help! By the tap, do you mean it would be more ideal to have a 1+1=1+1 configuration, whereby each 1 represents an individual coil, and I could then wind the ones i needed together, rather than them being internally wired.

One side of the transformer is a single winding (two wires) the other side has three wires, and can be considered as either two windings joined together, or as a single winding with a centre tap.

For maximum rejection the two halves of the centre tapped winding should be 100% identical, obviously 100% can never be achieved. But a good way to get better performance is to wind the two halves of the winding simultaneously, this is known as bifilar winding. By winding the two wires together they are as well matched as possible.

 

[Sebi]

Off topic, but i'm just curious why appeared in all forums the ohm as link, and when click on it, made a page up....

 

[Dr.EM]

Thanks Nigel, I understand you completely now. I probably won't do this, as i'm kind of new to it, but if I wanted to wind my own transformer, would a ferrite ring make a good core? Using that of course would form a toroidal type transformer, which I don't know if is ideal. Also, what sort of number of tuns would be needed, I want a good transfer ratio, but I have no way of winding quickly.

 

[Nigel Goodwin]

Thanks Nigel, I understand you completely now. I probably won't do this, as i'm kind of new to it, but if I wanted to wind my own transformer, would a ferrite ring make a good core? Using that of course would form a toroidal type transformer, which I don't know if is ideal. Also, what sort of number of tuns would be needed, I want a good transfer ratio, but I have no way of winding quickly.

I'm not a transformer expert, but, as far as I know, ferrite rings aren't suitable for audio purposes - more for RF frequencies.

Whereas at high RF frequencies a transformer would only require a few turns, at audio frequencies you would need a LOT of turns - you certainly wouldn't want to wind a LOT of turns on a torodial core :lol:

Have you considered using an electronic method of ring modulation?, it's basically a double balanced mixer - they are commonly used in radio amateur equipment to generate a double-sideband signal (DSB), before filtering it to leave a single-sideband signal (SSB). Some of the IC solutions would probably work OK at audio frequencies.

 

[Dr.EM]

That was what I was originally intending to do. I saw the double balanced modulator chip and wondered if I could use it some way to make a ring mod circuit. While I searching for a scematic, I found the passive ring mod, and decided to try it out. I think my best bet is to try the LT44 and see what happens. The final circuit shall have 2 transistorised push-pull oscillators for the X in (with a passive filter), and the Y in will be an external source. Should make a funky effect if I get it all working, prototypes are working, but are not perfect.