White Noise Studio, Winterswijk

How to do the SM57 transformerless mod – Tutorial

Hi,
This is a tutorial on how to do the ”SM57 transformerless” mod.

With this mod you’ll remove the transformer of a ‘Shure SM57 which will open up the sound and will give a little bass boost.
I have already done such a  mod with our SM58 microphones and it works great.
Here’s a video where you can see how it’s all done.
Below the video we’ll continue with the explanation.

 

Play Video

Good reasons to do the SM57 transformer mod:

  • It opens up the sound
  • The low end increases
  • The bleed of other instruments in the SM57 will be better mixable , so it’s easier to fit in the mix.

The disadvantage is that the output of the SM57 is a bit lower, so you need a preamp with good clean gain.
Of course, if your SM57 is always on the hot side, this can actually be a benefit.

To start with the mod, first you have to screw open the SM57. Do it carefully, otherwise you could easily snap the wires in the microphone and we want to remove them ordently.
Desolder the 2 wires at the capsule side.

Then you unscrew the XLR chassis part at the bottom of the SM57, pull it out and unsolder the contacts.

Now you’re left with the bottom chassis part of the SM57 with only the glued in transformer inside. We now have to remove this glue to pull out the transformer. And you do that by heating the glue.

Pot o’ water: 

The best way to do that is to put the bottom chassis part in a pot of hot water. That will niceley melt the glue, after which you can pull out the transformer.
Of course, only put the chassis part with the transformer in the water, not the capsule.
You could damage the capsule.

From experience, I recommend you put the bottom chassis part in a plastic bag, and put that in the water. The glue can get out and stain the pot. It’s difficult to remove. Of course, if you have an old pot and don’t mind it getting dirty, don’t use a plastic bag.


I also recommend to not boil the water. The glue melts below the boiling point of water and the coating of the SM57 could get loose if you keep it too long in too hot water.
Check from time to time if the glue is melting, and after it’s melting and somewhat liquid, pull out the transformer.

SM57 resoldering:

Cut of a piece of wire which fits. You need 2 cores / wires. Solder it to the A and B connector on the capsule. Remember which wire goes to which connector.

Then pull the wire(s) through the hole in the bottom chassis part.
Resolder the XLR chassis part to this wire.

  • Pin 2 of the XLR goes to the A connector of the capsule.
  • Pin 3 of the XLR goes to the B connector of the capsule.


If you’re done soldering, put the XLR chassis part back in the microphone and tighten the screw.

Tighten the SM57 and that’s that.
Congratulations!
You have your SM57 transformerless mod.

This is an easy way to have more flavours of SM57 for no extra cost.
The mod will sound more open with a bass boost and an original SM57 will have a presence boost.
Different sounds for different purposes.
To check out some sound examples, check the video!

Please subscribe to video channel and until the next blog!

Bye!

Marlon