Audio Proz Service and Sales

About Audio Transformers

(Educational)

Jun 17th, 2016

Concerning transformer use. Interesting, wonderful but brutally simple transformer designs, in many vintage products do create a nice, slightly “warm” sonic color but there are modern products which can do the same sound trick but without the high expense and use of rare parts. First be aware of the +24dbm maximum operating level (transformers or sound state) used in real pro signal level designs do not mate perfectly with “semi pro” equipment designed to operate at at +14dbm 10k load levels. In most cases pro equipment has no special circuitry beyond basic designs but simply plays louder and can interface 600 -Ω matching transformation to +24dbm. +24dbm operation is mostly about overcoming cable noise (hum, static, RFI, etc) and long wire resistances between patch bays etc. But I think if you are also asking for mic transformers, you can find modern transformers which are just as good or better and very cheap. The real problem is building a good hum shielding can (which I do) is critical! Many new mic transformers are simply excellent, almost too good! Winding techniques have improved to a point of near perfection.

Mic transformer sound character is really defined by in and out loading impedance’s and size type of transformer core material, which can dramatically effect frequency response and saturation in extreme lows and highs limits of design criteria occur. Indeed the correct “Zobel” loading impedance filters circuits connected at input or output) and can optimize (or not!) a transformers total spec (bandwidth, dynamic range, etc). I like vintage things, excellent built quality, etc but correctly selected comparable, properly impedance chosen modern transformers can be about the same. In fact the most popular modification I have been doing is installing a specially prepared transformer, with Zobel circuit, in an A.R.T. preamp with a variable control “loading” circuit and whoa! Best of all options because it allows the widest opportunity to “tune in” the sonic character desired. Such a circuit can do thick, full, bight, warm, or whatever with virtually any mic. A circuit installed into a compressor can do a similar trick. Remember also that most vintage mics have transformer outputs, so the ability to optimize this old device with another old device with transformer can get very opinionated. Old devices usually (but not always) like transformer loading at next stage device. In fact the greatest irony is cheaper transformers with less dynamic head room are often preferable as it sonically creates a little soft limiting, maybe thicker bass (more 2nd and 3rd harmonies generated). However as a rule most transformers loose real deep (impulse response) bass by the losses in the coil to coil winding, but exaggerate mid bass 60 to 120 Hz region because the manufacturers long ago felt this was the acceptable bandwidth requirements in that era. That’s why transformers can sound “plump” or thick vs modern transformers which can go to 30 Hz no problem. Irony is most older mics will never go that low with truly significant output. Many inexpensive moder mics can and indeed have more extreme low frequency capability with their modern transformers in them. Such designs are so clean, they almost seem without character and consequently different mic positioning and gain construction at preamp require new thinking.

In the final analysis the next important question to ask... How well do your speakers reproduce such subtleties and qualify these effect. As an overview when selecting mics or preamps we must keep in mind the users philisophical agenda. Some sound engineers want mics with character but preamps and processing super clean, others want the opposite; super clean mics, character in the processing. Personally I think there is more versatility in the second option because having quality of full bandwidth signal with low noise mic to start with will capture more signal clearly. Now the signal can transform or be EQ, compress etc. to fit into the mix. Obviously if the mic has fidelity limitations then important timbre and dynamics forever lost, but I do recommend certain old or new mics which can sound just right for a particular instrument. We all know some cheap sounding dynamic mics can be perfect for drum recording or modern $200 large conductor or mics can be really nice on vocals. The debate now is how careful placement of mics can be done to accomadate the charater of a transformed preamp. Ultimately I debate the high cost of many products which have many basic design inside but fancy name marketing on the outside. My efforts persue the more clever and inexpensive products in any era, which can do the magic.

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