Transformerless SM58

[antichef]

I have a Shure SM58 from which I removed the transformer, attaching the capsule leads directly to the XLR pins. This was my first mic mod ever, and it came out well, which was encouraging.

It sounds kind of cool; it's no SM7b, but it's nice to have around.

Here are my two related questions:

1) will phantom power now hurt the mic, since there's no transformer in between the current and the diaphragm?

2) should it be considered unsafe for live use? It occurs to me that one function of the transformer was to block DC in the event there was a mis-wiring, but obviously that won't happen now either.

 

[dgatwood]

I have a Shure SM58 from which I removed the transformer, attaching the capsule leads directly to the XLR pins. This was my first mic mod ever, and it came out well, which was encouraging.

It sounds kind of cool; it's no SM7b, but it's nice to have around.

Here are my two related questions:

1) will phantom power now hurt the mic, since there's no transformer in between the current and the diaphragm?

2) should it be considered unsafe for live use? It occurs to me that one function of the transformer was to block DC in the event there was a mis-wiring, but obviously that won't happen now either.

Yes and yes. You might consider replacing the transformer with a better one.

 

[lescro]

I have a Shure SM58 from which I removed the transformer, attaching the capsule leads directly to the XLR pins. This was my first mic mod ever, and it came out well, which was encouraging.

It sounds kind of cool; it's no SM7b, but it's nice to have around.

Here are my two related questions:

1) will phantom power now hurt the mic, since there's no transformer in between the current and the diaphragm?

2) should it be considered unsafe for live use? It occurs to me that one function of the transformer was to block DC in the event there was a mis-wiring, but obviously that won't happen now either.

1) NO.
If you wired the 2 wires from the moving coil to pins 2 and 3 of the XLR-3 male and wired the chassis of the microphone to pin 1 of the XLR-3 male. The phantom power is sent to the mic as such:
Pin 3 +48V
Pin 2 +48V
Pin 1 ground.

No current can flow through the moving coil as the potential difference across the wires is zero ie +48 minus +48 =0 volts

2) NO.
It is not unsafe.

 

[ecc83]

I can see that the mic is going to sound "different" sans transformer but since it has a turns ratio of about 1:4 you are loosing 12dB of signal dropping the sensitivity to a depressing -68dB you are almost certainly going to need a Cloudlifter type inline booster for anything other than a rip snorting amp or very loud rock vocalists.

As well as the voltage lift a mic transformer also plays a part in correcting the frequency response of the mic capsule when loaded by 'real world' inputs which, for a 57/58 if often said to be 600 Ohms but that figure is debated.
Input transformers of all sorts also play a big role in keeping RFI out. We have come a long way in proofing transformerless mic inputs but, in extreme cases, a transformer will be better.

Dave.

 

[RFR]

I can see that the mic is going to sound "different" sans transformer but since it has a turns ratio of about 1:4 you are loosing 12dB of signal dropping the sensitivity to a depressing -68dB you are almost certainly going to need a Cloudlifter type inline booster for anything other than a rip snorting amp or very loud rock vocalists.

As well as the voltage lift a mic transformer also plays a part in correcting the frequency response of the mic capsule when loaded by 'real world' inputs which, for a 57/58 if often said to be 600 Ohms but that figure is debated.
Input transformers of all sorts also play a big role in keeping RFI out. We have come a long way in proofing transformerless mic inputs but, in extreme cases, a transformer will be better.

Dave.

People much smarter than us designed the sm58, and that mic has a decades long positive track record.

It’s my opinion to leave well enough alone and to use it as intended.

 

[TalismanRich]

Dave, you just don't understand that any tweak that you do to a standard microphone will instantly improve it. Anyone can immediately hear the improvements, which probably can't be measured, and even if they measure worse, the measurements are wrong. Change the capsule, and it simply sounds better, swap a capacitor and the harshness instantly vanishes, reform the screen and the heavens part and the light shines through. Adding a transformer is only good if the manufacturer didn't use one in the first place!

Manufacturers ALWAYS use substandard crap so you must change things to make them better.

Its true... I read it on the internet!

 

[Random dude]

15 years later............

 

[rob aylestone]

I sold some of the mics I reviewed and really hated, or were even faulty. It’s fun when the buyers tell you what they’ve done to them and made them wonderful. The nasty sounding capsule is still in there!

 

[drtechno]

I have a Shure SM58 from which I removed the transformer, attaching the capsule leads directly to the XLR pins. This was my first mic mod ever, and it came out well, which was encouraging.

It sounds kind of cool; it's no SM7b, but it's nice to have around.

Here are my two related questions:

1) will phantom power now hurt the mic, since there's no transformer in between the current and the diaphragm?

2) should it be considered unsafe for live use? It occurs to me that one function of the transformer was to block DC in the event there was a mis-wiring, but obviously that won't happen now either.

So basically what you did is turn it into a PG58 which is the same thing without a mic transformer.
Nothing is going to happen when you put a dynamic mic on phantom. Because the circuit is across pins 2&3 on a dynamic mic and pin 1 is just shielding.
Its going to be the same on stage as a PG58.
The only design issues with their capsules is source resistance, so you might want to play with putting a 470-1K resistor across the mic output (pins 2&3) if you want to play with mid-range boosting.

 

[drtechno]

Manufacturers ALWAYS use substandard crap so you must change things to make them better.

Its common for a lot of mass produced corporate stuff. The only problem with shure mics are design based. The SM7 for it to be correct, it needs a dynamic mic step up transformer added. (Which was the common mod way before those cloudlifters were invented. Which the cloudlifter adds noise and another stage to the circuit) The other dynamic mic capsules, have poor source resistance stability which I shared the shunt resistor mod in post number 9.

 

[ecc83]

"So basically what you did is turn it into a PG58 which is the same thing without a mic transformer."
Not really because the PG58 uses a 300 Ohm capsule and has a sensitivity of -53dBV/Pa (2.2mV) which is slightly hotter than the specc' usually given for the SM58.
I would also expect the higher impedance of the capsule to cause some response differences and the PG to be slightly more sensitive to pre amp loading?

Dave.

 

[rob aylestone]

If you do this you end up with a 58 that no longer sounds like all the other 58s. If that works for you, it's a useful extra tool in the mic box. I've fiddled with genuine and fake 57's - and created some monsters and some gems. If I put a real one on a snare drum (as I usually do) and it sounds a bit dull, or too cutting - I know exactly which one to swap it for. (two have labels - dull and bright).

 

[drtechno]

If you do this you end up with a 58 that no longer sounds like all the other 58s. If that works for you, it's a useful extra tool in the mic box. I've fiddled with genuine and fake 57's - and created some monsters and some gems. If I put a real one on a snare drum (as I usually do) and it sounds a bit dull, or too cutting - I know exactly which one to swap it for. (two have labels - dull and bright).

SM58 and SM57 are really low quality mics that became a standard for live people because most music stores carried them back in the day before internet. They are poor performers for recording and now these days there are better mics to use for live too. Termination resistor mods, I do in mic cables and use a different color cord than the standard black one so I know its one with a resistor across pins 2&3 on the male connector.

For the extra $20-$30, a Telefunken Dynamic beats them every time. Of course the Sennheiser, which is actually made by Neumann is better too.

The mic I like to use on a snare is a Beyerdynamic TG D58c because it sounds better. But for a dynamic snare mic, a telefunken M80-sh is better than all other dynamic snare mics I have tried.

 

[Folkcafe]

SM58 and SM57 are really low quality mics that became a standard for live people because most music stores carried them back in the day before internet. They are poor performers for recording and now these days there are better mics to use for live too. Termination resistor mods, I do in mic cables and use a different color cord than the standard black one so I know its one with a resistor across pins 2&3 on the male connector.

For the extra $20-$30, a Telefunken Dynamic beats them every time. Of course the Sennheiser, which is actually made by Neumann is better too.

The mic I like to use on a snare is a Beyerdynamic TG D58c because it sounds better. But for a dynamic snare mic, a telefunken M80-sh is better than all other dynamic snare mics I have tried.

This is where the old guy tells stories from "back in the day".

We were recording a three-night concert series with a group that did lush vocal harmonies. One of the singer's was just getting over a cold and her unusually deep voice was, let's say, extra burly. We had a few days for set up and rehearsals and swapped out a lot of vocal mics and did test recordings. Corporate studio with a deep mic closet. We emptied it of every mic that could be used as a vocal mic, trying to tame that extra grit. In the end what sat perfectly in the mix for that voice and style was an SM57.

Not sure the label, "low quality" applies. Both are very robust. I did years of FOH and its advantage is universality. It's rare when you can't make it work. I produced an open mic night for years. I'd have a singer I've never worked with get them dialed in while they introduced themselves and tuned their guitar.

So what about this definition of quality? I remember when the Neumann KMS105 came out. It seemed every folk artist I worked with picked one up hoping it would be magic. For many, it was completely the wrong microphone. Don't get me wrong, great mic, on the right voice. I traveled with a variety of microphones when I did live sound. SM58, Beta 58, OM5, OM6, Beta 87. SM58 was on most of the technical riders. My use of it had nothing to do with it being sold at the local music mart. Even as a small sound company, I spent thousands on microphones. Live guys buy what works. There were plenty of other mics available throughout the 70's and on. It is ubiquitous for a number of reasons but the primary one is it suited the need without fuss.

With microphones, better is both subjective and objective based on source, style and intent.

 

[drtechno]

With microphones, better is both subjective and objective based on source, style and intent.

I can relate to that as I try different mics on someone when I record them. When I do live sound, most of the time I have to settle with what the PA guy sat out. But on my personal PA, I use sennhieser mics because they work well in the untreated spaces I end up setting it up.

 

[Papanate]

SM58 and SM57 are really low quality mics t

They are not ‘Low Quality’ - SM57s and SM58s have a sound that people have found useful for 60 years.

For the extra $20-$30, a Telefunken Dynamic beats them every time. Of course the Sennheiser, which is actually made by Neumann is better too.

Telefunken Dynamics? Which ones? The M80 and M81 are good mics - but they are also $250 - which when you are buying 30 or 40 adds up -
and that aside not everyone likes the Telefunken sound - even though it’s not much different that the SM58 - it’s just HyperCardiod.

The mic I like to use on a snare is a Beyerdynamic TG D58c because it sounds better. But for a dynamic snare mic, a telefunken M80-sh is better than all other dynamic snare mics I have tried.

Which means you like the Telefunken or BeyerDynamic - it doesn’t mean it’s better - it only means you like them.

 

[drtechno]

They are not ‘Low Quality’ - SM57s and SM58s have a sound that people have found useful for 60 years.

I find this a hive mind mentality than anything. Especially when I let an artist taste test different mics on stage and most notice how much of a POS they truly are, so most end up with something not a SM58 by their choice.

 

[rob aylestone]

I'm a little unsure what part of their sound is 'bad'? I quite like Sennheisers - not so much the 835 head, but 845,855 and 865 are nice - but I'd happily swap an 845 for a 58 and the 865 for a 86? It's a tweak of EQ between them. I'm happy you don't like them, but 58s sound perfectly fine. I rarely go with artist preference unless they're really skilful in the audio field. most are not. In their IEMs or decent wedges, they hear extra LF or HF, but tonal stuff like swapping a Shure for Senn? Not convinced.

 

[TalismanRich]

I have several e835s and a 935. I've also got the Shures, but I really like the Sennheisers for PA vocal work. I bought Shure first because that's what everyone used around here in years gone by. Then I tried the Senn, and I was sold.

I have a friend from Missouri that feels the same way. When I pulled out the 835s and 935s while setting up the PA, he said he agreed with my choice.

 

[Track Rat]

I have a MD441 and about a dozen 57's, some 545's, and a couple of 58's. A couple of EV PL-80's. I even pulled a transformer out of one of the 57's that I've used on guitar cabs and snare. That's neither here nor there. 57's & 58's are around for a reason. They work and they work very well. They are NOT bad mics. Geezus.