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Re: DIY Fun With Transformers
dboomer #3053983 07/13/20 03:53 PM
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Originally Posted by dboomer
I think you have to remember these transformers were designed NOT to color the sound. So while they contribute some non-linearity that is easily measurable they shouldn’t change the audible results much if at all.

That's what I said early on in this discussion, but there seems to be folklore on the net that there's some magic to the distortion when a transformer begins to saturate. Actually, I think that "saturate" is a much-misued term in these parts, but it's one that's become accepted so I guess we have to live with it. Saturation of the core - where it just can't take any more magnetism - does take a lot of poop. A couple of mic-to-line transformers I found around here needed to be driven upwards of +25 dBu before the linearity curve - the (ideally) straight line plot of input to output level - began to look like the start of a compressor's "knee" curve. And there are other electrical characteristics of a transformer that can cause distortion besides core saturation.

There's lots of other things between a mic and an output that cause distortion that people love, and while transformers are well known contributors to the "tube" sound, in circuitry where a transformer is the best design choice, for solid state circuitry, a transformer is often a designer's or manufacturer's choice for a combination of excellent common mode noise rejection and marketing. In truth, these days the THAT chips do CMRR better than coils of wire, and cost less. And of course nothing says "marketing" like "fully Class A," but in order to get that in a mic preamp these days you need to go to something like a Jensen 990 module (Radial makes a preamp with that) to achieve it.

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Re: DIY Fun With Transformers
dboomer #3053997 07/13/20 05:40 PM
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Originally Posted by dboomer
I think you have to remember these transformers were designed NOT to color the sound. So while they contribute some non-linearity that is easily measurable they shouldn’t change the audible results much if at all.

Now you could design a system that purposely drives the snot out of them. Or you could just get a fuzz box wink.

The less sane you are about driving them, the easier it is to saturate the core smile But I think an important point is that the distortion is inversely proportional to frequency, which is why my preferred transformer abuse is with bass. Also, the distortion caused by hysteresis, which doesn't depend on excessive levels, is also in the low frequencies. I don't hear much difference in mids on up. For example, the average transformer doesn't do much with voice, as far as I can hear; if someone wants to use a transformer to change the vocal quality, they'll probably be disappointed.

Re: DIY Fun With Transformers
Anderton #3054038 07/13/20 09:08 PM
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Originally Posted by Anderton
Originally Posted by dboomer
I think you have to remember these transformers were designed NOT to color the sound. So while they contribute some non-linearity that is easily measurable they shouldn’t change the audible results much if at all.

Now you could design a system that purposely drives the snot out of them. Or you could just get a fuzz box wink.

The less sane you are about driving them, the easier it is to saturate the core smile But I think an important point is that the distortion is inversely proportional to frequency, which is why my preferred transformer abuse is with bass. Also, the distortion caused by hysteresis, which doesn't depend on excessive levels, is also in the low frequencies. I don't hear much difference in mids on up. For example, the average transformer doesn't do much with voice, as far as I can hear; if someone wants to use a transformer to change the vocal quality, they'll probably be disappointed.

Curiosity - what transformer are you using and is it just the transformer or is there a circuit with other components?

A couple posts back I mention that it seemed like there was some compression, this is because running straight in with the bass and the same setting on the BTC - bass cranked and treble attenuated slightly - and it was super bassy (as we would expect). Using the transformer(s) it sounded more "even" with the bass attenuated a bit and the trebles audible but not to the point of revealing my less than perfect bass technique.

I looked inside the Whirlwind IMP 2 and there are two 1/4" TS jacks, 1 XLR male output jack, a transformer and a ground switch. The Radio Shack DI has a schematic drawing on the label, just the jacks and a transformer. I am assuming those bore the brunt of the bass and BTC since they were next in the signal chain.

Now I need to dig around and see what other cables I have, I remember seeing an XLR to 1/4" TS cable that I need to try to get the bass and BTC to go directly to the Beyer. Otherwise I can't really tell much as to what it sounds like. I may have to change the XLR plug, depending on if male or female. I have the parts.

If that is feeble I'll suspect that the Beyer really wants to see a microphone or similar load at the primary instead of whatever is coming out of the BTC (or the bass, which I will also try).

While I am by no means sane, this isn't exactly like running with scissors - "You could put out an eye!!!!!." laugh


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Re: DIY Fun With Transformers
KuruPrionz #3054137 07/14/20 01:24 PM
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Originally Posted by KuruPrionz
I think it is time to ship the transformer project box to Mike Rivers and see what he comes up with. It is certain that he will observe some unseemly soldering technique in the build.

Bring it on. While I don't think we're going to find anything in the way of "saturation," there are, as I've said, plenty of other effects that transformers can cause, including just plain ol' frequency response rolloff and resonance due to inductance and capacitance that are unavoidable when making a transformer from coils of wire/

Re: DIY Fun With Transformers
Mike Rivers #3054216 07/14/20 08:52 PM
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I'll try to get it out this week, will keep you posted.

I am here to learn, what is the better word if "saturation" is not satisfactory?


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Re: DIY Fun With Transformers
KuruPrionz #3054219 07/14/20 09:36 PM
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Originally Posted by KuruPrionz
I am here to learn, what is the better word if "saturation" is not satisfactory?

For my two cents, there's nothing wrong with "distortion." But let's see how much and what kind. I suspect that as input level goes up, the first we'll see is second harmonics, then as the level increases further, higher order harmonics will be added to the mix.
Hysteresis, I believe, is, in essence, slew rate distortion, which translates to intermodulation distortion.

Take your pick, or some of everything.

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