Question on a Mod: SM57

kfowler8 · Post by **kfowler8** » Sun Dec 20, 2015 4:05 pm

I'm trying out the TapeOp mod on the SM57. Essentially removing the transformer. I wanted to try it out first before I decide to remove it permanently. So I unscrewed the capsule and soldered a mic cable directly to the capsule leads therefor bypassing the transformer. (See attached pic)

To test it I ran one xlr cable to he bottom of the mic which goes through the transformer (for stock sound) and another cable as mentioned above soldered directly to the capsule.

As expected, the signal from the mod line running directly to the capsule was about 13 dbs lower. What I was surprised to find is there was no audible difference between using the transformer and bypassing it. Sonically they sounded the same.

So my question is could the transformer still be impacting the line that's directly connected to the module?

Thanks for your help![/img]

floid · Post by **floid** » Sun Dec 20, 2015 4:53 pm

I can't see the pic.
Is the "direct" xlr wired parallel to the transformer?
Are both outputs being recorded, with level matching for A/B comparison?
What type of source material?

A.David.MacKinnon · Post by **A.David.MacKinnon** » Sun Dec 20, 2015 5:12 pm

kfowler8 wrote:I'm trying out the TapeOp mod on the SM57. Essentially removing the transformer. I wanted to try it out first before I decide to remove it permanently. So I unscrewed the capsule and soldered a mic cable directly to the capsule leads therefor bypassing the transformer. (See attached pic)

To test it I ran one xlr cable to he bottom of the mic which goes through the transformer (for stock sound) and another cable as mentioned above soldered directly to the capsule.

As expected, the signal from the mod line running directly to the capsule was about 13 dbs lower. What I was surprised to find is there was no audible difference between using the transformer and bypassing it. Sonically they sounded the same.

So my question is could the transformer still be impacting the line that's directly connected to the module?

Thanks for your help![/img]

i can't see the pic either but it sounds like you're running out of the transformer and out of the capsule at the same time (am I right?). If that's the case I wouldn't be surprised if there is something funky going on and you're not hearing a true representation of each option.
Try recording a bit through the xfrormer and then disconnect it and record a bit wired direct to the capsule.

kfowler8 · Post by **kfowler8** » Sun Dec 20, 2015 5:56 pm

A.David.MacKinnon wrote: i can't see the pic either but it sounds like you're running out of the transformer and out of the capsule at the same time (am I right?). If that's the case I wouldn't be surprised if there is something funky going on and you're not hearing a true representation of each option.
Try recording a bit through the xfrormer and then disconnect it and record a bit wired direct to the capsule.

Yes, you've got the right idea. So both are running at the same time into two different pre-amps. I've adjusted the gains to so their equal. I'm wondering if I'm getting an effect similar to a tone pot on a guitar. Similar to how a cap filters out a frequency. I wonder if the transformer is doing the same. Or it could be that there's just not much of a difference between the two other than volume.

You can probably see a pic here: http://www.mylespaul.com/forums/recordi ... ost7428228

kfowler8 · Post by **kfowler8** » Sun Dec 20, 2015 6:07 pm

This should help. Here's the test results. The first mic you hear for each section is the stock SM57, second is the modded SM57, and third is a Pyle PDMIC78 (SM57 clone). I adjusted gain for each track to get he same volume level.

Sections are: Snare, Kick Drum, Guitar Amp, Acoustic Guitar, Voice

I'm not hearing much of a difference between the stock and modded SM57.

https://soundcloud.com/kfowler8/sm57-mod-main-file

What do you think?

Drone · Post by **Drone** » Mon Dec 21, 2015 4:47 pm

If you haven't disconnected the transformer, it's still in circuit and loading the capsule. Even if you don't remove it, you have to at least disconect it.

kfowler8 · Post by **kfowler8** » Mon Dec 21, 2015 5:01 pm

Drone wrote:If you haven't disconnected the transformer, it's still in circuit and loading the capsule. Even if you don't remove it, you have to at least disconect it.

Yeah you're right. I spoke to someone else and he said the same thing. I've unsold were the capsule and am now going to retest every thing

Drone · Post by **Drone** » Mon Dec 21, 2015 5:44 pm

One other quick observation, and this I'm not sure about.

Does having the cavity behind the capsule unscrewed also affect the sound of the mic? Just thinking of those 90 degree bend 57's.

kfowler8 · Post by **kfowler8** » Mon Dec 21, 2015 7:35 pm

Drone wrote:One other quick observation, and this I'm not sure about.

Does having the cavity behind the capsule unscrewed also affect the sound of the mic? Just thinking of those 90 degree bend 57's.

Interesting question. I have no idea. Off hand I don't think so. It sounds like a standard 57 with it unscrewed.

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