what value range would you consider high primary inductance?Depends on what you plan to feed it into but generally high primary inductance, low leakage inductance and low inter-winding capacitance preferably achieved with a Farady screen all housed in mu metal.
Cheers
Ian
Cheers
Ian
The SM58 has an impedance of 300 ohms. With a 1:4 xfmr, it turns into 4.8 kohms.Apart from size and humbucking or not, what should be the ideal characteristics of a 1:4 step up to boost a voice coil to modern mic input?
Primary inductance is what limits LF response so you want it to be high enough not to load the microphone at the lowest frequency of interest. As Abbey has said, an SM58 has an approximate impedance of 300 ohms. If you want the response to be no more than 3dB down at 20Hz then the reactive impedance of the primary (2 x PI x f x L) needs to be at least 300 ohms. This means L must be at least 300 / (2 x PI x f) = 2.4 Henries. In practice, good quality microphone transformers will have a primary inductance of 6 Henries or more which will have a 3dB point at close to 8Hz.what value range would you consider high primary inductance?
I've always read that the SM58 capsule has an impedance of 60 ohms. If that's the case, putting a 1:4 xfmr would result in 960 ohms, which is quite high and may result in altered response.I am referring to the voice coil of the mic.
I want to substitute the internal transformer.
800The tranny in there is 1:4 I think. I can measure it.
SM58 used to have a dual impedance model for 50 ohm inputs as well. What does that translate to as source impedance?
Ah, so I was misinformed.AMI has the T58 replacement transformer for Shures, they say the capsule coil impedance is 10 - 20 ohms (or that's what the tranny is for at least)
A standard 1:4 xfmr would have a nominal secondary imedance of 2400-3200 ohms. If you connect it to a standard mic preamp with a nominal impedance of 150-200 ohms, which actual input impedance is about 1500-2000 ohms, there would be about 3-6dB loss.So, would a normal 1:4 mic preamp step-up work, or would the low source impedance affect performance negatively?
The frequency response may be a little more extended, at both HF and LF, but the overall noise factor may be poorer. It depends on the quality of the mic pre. If it is very quiet, the booster will be noisier.Say we dumped the internal transformer in a 58 , instead used a 48v powered fet inline 20db booster ,would we end up better or worse into the nominal 3kohm mic input ?
the original makes the mic sound distorted. I didn't try loading it with a 600 ohm resistor, which some people say makes the transformer sound better. I hadn't thought about loading it, before I removed the transformer, but I'm not sure that would help.Was there a reason you needed to replace the original Max or are you just chasing better performance
Are you sure about distortion? The SM58 is known for its aggressive frequency response, that helps it cut through a busy live rig, but tends to emphasize nasals and fricative, in a way that may be perceived sa distortion. The SM58 is not a studio mic.the original makes the mic sound distorted.
Loading takes off some of the high midrange but will not turn it in a contender for a Sennheise 441 or even an SM7.I didn't try loading it with a 600 ohm resistor, which some people say makes the transformer sound better. I hadn't thought about loading it, before I removed the transformer, but I'm not sure that would help.
That's what many people think, and what has made it a staple of any live situation...To me it sounds crappy.
It may be the case, not everybody would agree. It will never be a good mic for picking up acoustic instruments, transformer or not.Without transformer it sounds a lot more usable to me.
Considering the cost a a new decent xfmr, you'd be better off buying a good specialized mic.So I thought maybe a different TX would improve the situation.
True, for the money AMI wants for a SM58 style transformer, you can almost get a used Beyer M201.Considering the cost a a new decent xfmr, you'd be better off buying a good specialized mic.
Are you sure about distortion? The SM58 is known for its aggressive frequency response, that helps it cut through a busy live rig, but tends to emphasize nasals and fricative, in a way that may be perceived sa distortion. The SM58 is not a studio mic.
Loading takes off some of the high midrange but will not turn it in a contender for a Sennheise 441 or even an SM7.
That's what many people think, and what has made it a staple of any live situation...
It may be the case, not everybody would agree. It will never be a good mic for picking up acoustic instruments, transformer or not.
But you may want to check your mic against another 58; maybe yours is defective?
Considering the cost a a new decent xfmr, you'd be better off buying a good specialized mic.
Enter your email address to join: