The effect of preamp impedance on an sm57

[mickrich]

I don't know if this has come up here before.
Preamp impedance will vary the response of a dynamic or ribbon mic (more than a condenser) by "damping" the diaphragm.
A lower impedance dampens more.
See this for more details:
http://www.recordingmag.com/resources/resourceDetail/266.html

In short, a lower impedance will lessen the presence peak and roll off highs and give more mids. High impedance sounds a bit more scooped.
I prefer low impedance with the 57.
This test is using the 300 and 1200 Ohm options on my DON NV73 Neve 1073 clone.
Go to the soundcloud page and click download at the bottom of the files and it will download 44/16 wav files.
How much of a difference you will hear will depend on your ears and the quality of your monitoring.
There is zero post processing on the guitars.
Looking forward to opinions.
Thanks to Lasse and Mago for the DI pack used in this test.

300 Ohms


1200 Ohms

 

[wishtheend]

I like the 1200 one, it's got a bit more heft in the low-mids to it which I dig. Both are usable, but if impedance gets you closer without eq then yeah totally worth it.

 

[Manicompression]

I can't listen to the files atm but ever since I got some non interface preamps I've been loving experimenting with the impedance knob. I'm surprised this hasn't made its way onto more top of the line interfaces yet.

 

[mickrich]

I can't listen to the files atm but ever since I got some non interface preamps I've been loving experimenting with the impedance knob. I'm surprised this hasn't made its way onto more top of the line interfaces yet.

Proper impedance variance is done by tapping the transformer.
Variable impedance on non transformer pres uses resistors.
I have been researching this the past couple of days and saw a piece about this.
Can't remember where the article was.
Apparently similar results but not exactly the same.

 

[mickrich]

I like the 1200 one, it's got a bit more heft in the low-mids to it which I dig. Both are usable, but if impedance gets you closer without eq then yeah totally worth it.

The 300 is missing a bit of low mid hump for sure.
It's also missing the 4K resonance and a lot of high fizz.
If I were to EQ the 1200 in a mix, it would start to sound like the 300 so you are exactly right in saying it gets closer to the sound I want with less processing.

 

[JeffTD]

1200Ω has a more open characteristic I'm digging on this one, which is surprising since I've previously always preferred 300Ω on 57s when I've shot it out. I'm not sure the difference is still noticable once the drums/bass kick in, but I think initially I would've decided to go with 1200Ω + eq over the 300Ω.

 

[captainboom]

Another vote for the 1200Ω.

 

[mickrich]

Thanks for the replies.
Really interesting that people are preferring the 1200 so far.
BTW, the Don NV73 is just superb.
My APIs are relegated to snare drum now (where they excel)
These clips are with output down 6db and input gain driven to hit -12DBFS.
The saturation with this pre makes everything I put through it larger than life.
I have also been using it at line level for printing mixes.

 

[Fagulhakc]

+1 for the 1200!

 

[mickrich]

I'm tracking guitars today and, again, I prefer the 300 Ohm setting.