I removed a transformer from a Shure mic with a HiZ output. Pretty straightforward connection to dynamic capsule and output connector. Figuring all transformers found within a microphone are for the purpose of HiZ output, I ordered a handful or "SM58 microphone replacement transformers"...
Only to find out that even the LowZ balanced output of such is <drum roll> transformer coupled.
Why is this? The capsule winding cant drive the few hundred ohm load directly? The transformer's BH curve and FR factors into the SM58 microphone's sound?
Now I have a few useless mic transformers, as I was expecting them to output a high Z level and they do not. More like 20 Ohms to 200... I'm trying to adapt low Z sources to ordinary HiZ guitar pickup levels and a transformer is a very convenient way to go. No pop when removing the 1/4" plug, no battery to eventually die.
Only to find out that even the LowZ balanced output of such is <drum roll> transformer coupled.
Why is this? The capsule winding cant drive the few hundred ohm load directly? The transformer's BH curve and FR factors into the SM58 microphone's sound?
Now I have a few useless mic transformers, as I was expecting them to output a high Z level and they do not. More like 20 Ohms to 200... I'm trying to adapt low Z sources to ordinary HiZ guitar pickup levels and a transformer is a very convenient way to go. No pop when removing the 1/4" plug, no battery to eventually die.
Are you measuring DC on those transformers to get 20 to 200 ohms? You need to measure impedance at about 1K AC instead.
Yes, I am and forgot to mention. The actual HiZ transformers I have measure 1.8k to 4.5k DC on the HiZ side. I have 6-7 in various configurations. Some are too valuable to destroy for the transformer inside; better to sell on epay and buy the correct part, which I see ranges from about $12 to $30, shipped. The expense is fine, but the time to have it in hand is more of a pain...
Avoid measuring microphone transformers or phono cartridges or tape heads with a ohm meter. It is possible to magnetize them and cause poor performance. Wondering if it is possible to de magnetize them with some AC signal at least.
The SM-58 capsule DCR is only ~12 ohms, so the step up increases the voltage, and gets the impedance up to the "low impedance" 300-600 ohm range (~150 ohms actual), and increases the signal to noise ratio.
The transformer saturation when you scream into the mic is also part of the SM58 microphone's sound.
Shure did make a transformerless mic for a brief time with the SM-78, but that faded out of production quickly- a transformer works better with a wide variety of console's input impedance, and the transformer saturation was missed.
The SM-78 "matte suede" finish, available in multiple colors, turned to a dirty grey after a short time, that killed the deal for those who preferred their cleaner sound.
The 10/1 ratio of the transformers you bought should be similar to direct box transformers, though may not handle the voltage as well, you get what you pay for, specs and Mu metal shields that can match a Jensen usually cost more:
hi, I got a few replacement SM57/8 transformers, they are a bit bigger than originals. I wander is it possible to use those core to wind a ribbon mic transformer? And what number of primary turns are optimal? I might even wind foil primary, or is it overkill?
Its not possible to magnetise the transformer if the core material is 80% nickel as this material has very low remanance. 49% nickel isnt too bad
either. I do it all the time without problems to check winding continuity.