I've been messing around with transformer winding in a (failed) attempt at getting transformer ring as an audio effect.
Guitar pedal-type thing.
From reading & searches, transformer ring would happen in poorly-designed or poorly-wound transformers.
I felt I was qualified to do both; but so far the output sounds the same as the input.
Tried several configurations but obviously not the right one.
I was wondering if someone could point me in the right direction.
Search results bring up folks who already have the ring & wish to get rid of it.
It may or not be a good audio effect, but it's been fun to mess with despite lack of success. at least my winding skill have gone up a bit.

 

Any inductor or transformer will ring. That's how we test for shorted windings.
"shorted winding tester" would be a possible Google search.

The trick is to hit them with a pulse and listen for the results. The windings must be unloaded...without a significant load resistor. That means you listen with a high impedance amplifier. It also means the way the excitation pulse arrived must get out of the way instantly so it doesn't load the input side. You adjust the natural frequency with capacitance. This immediately poses a problem. How do you get a ring to sound melodic when it only has one frequency? That's why digital signal processing was invented. You can't make church organ chimes with only one frequency.

I don't have a circuit for this, but that's the basic principles.

 

Any inductor or transformer will ring. That's how we test for shorted windings.
"shorted winding tester" would be a possible Google search.

The trick is to hit them with a pulse and listen for the results. The windings must be unloaded...without a significant load resistor. That means you listen with a high impedance amplifier. It also means the way the excitation pulse arrived must get out of the way instantly so it doesn't load the input side. You adjust the natural frequency with capacitance. This immediately poses a problem. How do you get a ring to sound melodic when it only has one frequency? That's why digital signal processing was invented. You can't make church organ chimes with only one frequency.

I don't have a circuit for this, but that's the basic principles.

The DSE shorted turn tester for horizontal output transformers, schematic was floating freely on the web.

 

It appears my terminology is wrong.
I have read of harmonics in audio signal caused by oversaturation of transformer cores.
That is what I was referring to. Apparently that is not the same thing as transformer ring.
Perhaps a bit more reading is in order to be able to ask the right question.

 

Inductor Ring Tester.
BlueRingTester.

 

It appears my terminology is wrong.
I have read of harmonics in audio signal caused by oversaturation of transformer cores.
That is what I was referring to. Apparently that is not the same thing as transformer ring.
Perhaps a bit more reading is in order to be able to ask the right question.

The easiest route for generating harmonics is diode clipping, there's a whole industry devoted to germanium diodes because of their "favourable" knee curve. You can also experiment easily for different effects with assymetric clipping.

If you really do need to do it with inductors - ferrite cores saturate more readily than laminated iron. You have to scrutinise the datasheets, some ferrite cores are ground as pre-gapped which raises the saturation threshold. You need the cores that are designed to be used with added packing to create a gap - and not add any.

 

I have read of harmonics in audio signal caused by oversaturation of transformer cores.

Well, yeah, you can do that. Harmonics are fashionable in vacuum tube amplifiers and some jfet amplifiers. If you're going to saturate a transformer, the first thing you have to know is the power rating of the transformer and which amplifier you're going to use that can overload it. Hint, it won't happen at the same amount of power for all the frequencies.

Got a clue now?

 

Got a clue:
Yes, but barely.
I've done a fine job of it with multiple stages of jfet preamps.
Not so thrilled about the sound of diode clipping.
Just thought I'd try it with transformers.
Never know your limitations without a little experimenting (translation: repeated failure).
Thanks to both of you for advice. I believe I am at least pointed in the right direction now.

 

I would like to see some of your distorting jfet circuits.

Another hint: If you run a DC current through a transformer winding, it takes the core closer to its saturation level, but only in one direction. If that's useful to you, Bingo. You have a new tool to work with.

 

...If you run a DC current through a transformer winding, it takes the core closer to its saturation level, but only in one direction...

A nice strong magnet will do the same thing but control of effect is more of a problem.

 

re:I would like to see some of your distorting jfet circuits
A really nice one is http://www.till.com/articles/GuitarPreamp/ with the Bypass R2 with a large value electrolytic capacitor for more gain option
Do it 3 times with a cut trimmer between stages. Roll off some highs if you must.

My favorite & installed in one of my guitars is:
http://www.runoffgroove.com/thor.html physical config needs to be kicked around a bit to fit inside a guitar.

The Thor is awesome. Both circuits pass the "open D" test without breaking-up when set at ballistic.
These things need to be done gently to avoid the "wasp in a soda can" sound you tend to get from diode clipping.
Unless, of course, you want that sound.