SM57 impedance cable mod, 48v OK?

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Bthiemann80

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I have a SM57 that I run with a XLR cable using the impedance mod (resistor soldered between pins 2 and 3 on a XLR cable to lower impedance of the mic). The mic is not actually modded, just the cable but I was wondering if running phantom 48v power could mess it up somehow.
 
No, it will make no difference to its use with spook juice.

But! WTF is the raison d' behind the mod? There is a bit of a fashion for proving alternative loadings on pre amps but most of those run HIGHER than the common 1-2kOhms, some as high as 10k. Some of the cognoscenti have commented that there IS a change in sound quality but it is subtle and mostly of use with ribbons.

What is the value of the shunt resistor? The 57 is a pretty low sensitivity mic to start with, seems daft to me to chuck even a dB of signal away?

Aha! Is the idea that the mic was originally designed to "see" 600 Ohms? If that is the case peeps should not cheap out and should buy a 1:1.8 traff!

Dave.
 
No damage. The power is ON 2 and 3 so no current would flow across the resister.
 
It's kind of credible . . . . but he don't half rabbit on. Where's the executive summary?

Frankly, it may work, but why bother?

If a microphone is not doing what you want it to do, why not get one that does? If I'm recording something and I think it sounds too dull with the microphone I'm using. I'll swap to a brighter mike. I do have more than one, and so would anyone who does stuff this a lot. That's what a mike locker is for.
 
Yes, the absence of a conclusions paragraph is annoying.
Then the article has the stamp of "scientificallity" but since there is not double blind test or tabulated results he could have told us the subjective results in 1/10th the verbage!

One technical error/assumption. Valve mic pre amps did NOT as a rule leave the transformer secondary unloaded and I task everyone to find me same? All the schematics I could find had grid leaks or/an a CR Zobel network across the first grid. Most networks are a series CR circuit but the Gates pre uses 220k in parallel with 1nF and the latter has a reactance of 159k at 1kHz and of course progressively less at higher frequencies.

So, in the words of The Men? IMHO "Busted"!

Dave.
 
I was curious enough to do a simple test. I placed an SM58 5" in front of one of my monitors and recorded some pink noise. I then connected in the impedance mod and recorded the same pink noise without changing anything else. Took both files into Rx. The recording with the mod was 15db lower.
I adjusted this in Rx (+15db) to make the levels match. I then captured each file in the spectrum analyzer and made an overlay in photoshop.
The attached image is the overlay. The blue trace is the signal without the mod. Gold is with. test overlay.webp
 
WoW! 15dB! That is a hell of a lot of signal to make up. Shoots my calculation into the trees never mind long grass! The OPZ of the mic must be a lot higher than 150 Ohms at high frequencies.

Hmm, as "louder" in a crude A/B test almost always comes out as "better" so I would aver, "quieter" could be equated with "smoother"?

But why bugger about? If you want smooth but "airy" as someone said, just grab a decent SDC!

Dave.
 
Yeah, ok. I see your points but looking at it from the other side - If your preamp had an impedance change option you'd use it, almost certainly, right?
You'd learn that you like your sm57 better on setting A and your NT1a better on setting B?

So if you're DIY handy and interested, what's really different about making an XLR barrel to do the same job.

I'm only intrigued by this thread because I've hated my re20 for years (on my voice) and never used it, and recently discovered that what I hate is the sound of the re20 through one particular preamp.
Now, this is a very clean high gain low noise preamp - I'm not hearing 'character'..... It has no identifying tone that I'm aware of, but I can tell you from a mile away which pre the re20 is plugged into.

Through preamp A you'd swear someone had eqd a very tight boost around 1.5k, whereas through another (equally clean) preamp the re20 sounds great.


Now, the re20 is known and recognised - A lot of people want that sound, so now I'm wondering if I should be investigating mic and input impedance.
 
Why does this forum appear to want to discourage someone from trying something. What better way to learn what something does than actually trying it? The lack of willingness to experiment and try things is what's wrong with a lot of the younger generation, they rely too much on needing someone else telling them how to do things. Look at some of the newb questions that show up here and you scratch your head with wonder how they'll survive in life without someone holding their hand for guidance.
Kudos to darscuzlo for his lab experiment!! :)
 
arcaxis said:
Why does this forum appear to want to discourage someone from trying something. What better way to learn what something does than actually trying it? The lack of willingness to experiment and try things is what's wrong with a lot of the younger generation, they rely too much on needing someone else telling them how to do things. Look at some of the newb questions that show up here and you scratch your head with wonder how they'll survive in life without someone holding their hand for guidance.
Kudos to darscuzlo for his lab experiment!! :)
Click to expand...

That's the second reason I'm intrigued.
I understand pointing out negatives (signal reduction in this case) but it kinda sounded like there's zero merit to this idea at all.
Surely there is?

arcaxis said:
The lack of willingness to experiment and try things is what's wrong with a lot of the younger generation, they rely too much on needing someone else telling them how to do things.
Click to expand...

As a 30 year old I feel very lucky to have narrowly escaped this. Attitudes amongst people my age seem to range drastically!
I'm very glad of my 'old fashioned' attitudes and values.
 
arcaxis said:
Why does this forum appear to want to discourage someone from trying something. What better way to learn what something does than actually trying it? The lack of willingness to experiment and try things is what's wrong with a lot of the younger generation, they rely too much on needing someone else telling them how to do things. Look at some of the newb questions that show up here and you scratch your head with wonder how they'll survive in life without someone holding their hand for guidance.
Click to expand...
Amen.
 
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