Need advice with passive transformer coloration

[Esppse]

I recently stumbled on the Lightning Boy 2020 passive transformer coloration box and was trying to see if I can cook up my own.

From the site, it says it uses a 1:1 high impedance audio transformer with a 0.5db insertion loss.

I found these:
https://www.hammfg.com/electronics/transformers/audio/142

and more expensively, this, but the insertion loss is not stated:
https://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-mb-ca.pdf

Which one would be appropriate for doing something like this? The Hammond has 3 variants with different frequency responses and turns counts.

And would I wire it like this? Found this picture on this forum, I think it's the Hudson Broadcast output, though I plan to use it passively:

https://postimg.cc/VrmGRWs8


And it I were to use it actively, can I just run a Super Hard ON boost in front of it and have a volume pot after to compensate to dial in coloration?

[garcho]

And it I were to use it actively...

Transformers are passive devices. If a transformer is used "actively" it's only because there's stuff before and after it. Whether that stuff is outboard or in the box doesn't matter to the transformer. I suspect simply running signal through a transformer isn't going to make you happy after the placebo effect wears off. I would dig deeper into your SHO idea.

[ElectricDruid]

I'd say if you're aiming to get colouration out of a transformer, you want the cheapest, lowest voltage, most hopeless transformer you can find. Anything that is *actually intended* to pass audio will have been designed to *eliminate* as much colouration as possible. Since that's exactly what you're after, those are exactly the parts you should avoid! Don't use good quality microphone coupling transformers or anything that might be found in a mixing desk - use the cheapest, most rubbish Radio Shack mini-transformer you can find. You'll get all the colour at a fraction of the volume and cost.

Consequently, I like the look of those Hammond transformers better than the Jensen ones - those say "FOR ULTRA-LOW NOISE AMPLIFIERS" which is not exactly what we're trying to do, is it?!? If you can find lower quality than the Hammond, go for it.

And yeah, drive it with a SHO - why not? You can dial up the volume going in, get a bit of distortion on the input, push the transformer, get a bit more, and dial the output back down if it's too loud (LOL - what a concept!). It's not a pure signal we're aiming to get here, so there's no need to be all hi-fi about it. Try it. Good stuff comes from experiments.

[PRR]

Add source impedance. Lets the transformer's faults shine out.

[Esppse]

I'd say if you're aiming to get colouration out of a transformer, you want the cheapest, lowest voltage, most hopeless transformer you can find. Anything that is *actually intended* to pass audio will have been designed to *eliminate* as much colouration as possible. Since that's exactly what you're after, those are exactly the parts you should avoid! Don't use good quality microphone coupling transformers or anything that might be found in a mixing desk - use the cheapest, most rubbish Radio Shack mini-transformer you can find. You'll get all the colour at a fraction of the volume and cost.

Consequently, I like the look of those Hammond transformers better than the Jensen ones - those say "FOR ULTRA-LOW NOISE AMPLIFIERS" which is not exactly what we're trying to do, is it?!? If you can find lower quality than the Hammond, go for it.

And yeah, drive it with a SHO - why not? You can dial up the volume going in, get a bit of distortion on the input, push the transformer, get a bit more, and dial the output back down if it's too loud (LOL - what a concept!). It's not a pure signal we're aiming to get here, so there's no need to be all hi-fi about it. Try it. Good stuff comes from experiments.

Would you have any recommendations for crappy transformers with color? I have some mouser xicon transformers too, been using those for varitones.

[Esppse]

Add source impedance. Lets the transformer's faults shine out.

Hey, how do I do this?

[merlinb]

Hey, how do I do this?

Just put a resistor in series with the primary.
https://www.diystompboxes.com/smfforum/index.php?topic=123985.5

[anotherjim]

Insertion loss spec may only be quoted for 1:1 transformers? these are for coupling purposes so any change it imparts can matter. If it's only one transformer in the path, even -3dB loss won't hurt much. Many DI boxes are passive with a single transformer.

This is a can of worms. You ask in pro-audio places for "transformer sound" and you will be directed to the expensive and near-perfect products that if used properly are transparent. They have no "sound". I suspect what is meant here is that they don't represent the all-solid-state sound that generally appeared in studios from the late 1970s.

Probably the most useful & affordable transformers are from brands like Xicon. These look like miniature AC mains transformers and have limited bandwidth and, apparently, some low-order harmonic distortion when pushed. Apart from a weak bass response, they suit guitar sound well. Published specs for these are minimal. Bandwidth and winding impedance is all you get.

You may also find modem transformers have their uses. Often listed as audio transformers (because modem comms is in the audio range) but by no means are they hi-fi.

Doesn't the effect of the primary series resistor have to be taken with the coupling capacitor making an LCR network? You get a boost bump at the low-pass turnover due to increased Q. Is this tool appropriate?
http://sim.okawa-denshi.jp/en/RLChikeisan.htm
You need to know the inductances, I found this on the web (anyone know the author?)

[amptramp]

Old-school transistor radios might be a good source.  You know, the ones you bought so you could harvest all the germanium transistors out of.  Their transformers are small and have limited range because you aren't going to get much range out of a three-inch speaker, so why pass the low frequencies at all?

[Esppse]

Ah thanks for all the information. I am going to get some Hammonds and also try to get a transistor radio for its transformer.

Another question, how does the transformer primary and secondary impedance affect tone? I will be getting a 142A, 142C, and 142D from Hawkelectronics, but they have a 25 minimum purchase.

What I noticed is the 3 transformers above have a 0.5 thd, while these here have 2%.

https://www.hammfg.com/electronics/transformers/audio/148

Which one of the driver versions would you pick? One of those should fill my minimum purchase threshold.

[teemuk]

If you find old-enough transistor radio with transformers then its going to provide as much as "transformer sound" you'll ever going to get. Which, unfortunately, will not be much to write home about.

If these circuits have any particular "tone" I would rather merit it to old low gain semiconductors, circuit topology and sparse magnitude of negative feedback.

No one made a fuzz about transformer sound when coupling and 70V system transformers were more commonplace components and widely used. In fact, wasn't that the era when transistor amps were actually reputed to sound horrible, if I recall right...?

I have experimented with aforementioned puny modem transformer and didn't get one to saturate or audibly distort with limited bandwidth of guitar and limited voltage range of typical solid-state "preamp" circuits. No, for obvious reasons I didn't experiment with frying the transformer with a SS power amp but maybe that would have done the trick. For a brief period that is.

Intentional impedance "mismatch" in coupling did create a somewhat resonant LC filter with a coupling capacitor but that's hardly "saturation", although - aside for spurious oscillations in particular impedance conditions -  it was only audible effect that transformer coupling ever provided.