Choosing a preamp, based on the microphone

[bennychico11]

A recent thread got me thinking...

How many people base the preamp they buy off of the microphone they use? It's generally recommended to compare the impedance on both preamp (input) and microphone (output) that you plan on using together. The theory is that an incorrect mismatch can cause havoc on your audio messing with the microphone frequency response...in other words, acting like a big EQ to the incoming signal.
The recommended input impedance of the preamp is 10x the amount of the microphone's output. This is a reason why some manufacturers are putting variable impedance knobs on their preamps.
Do people pay attention to this? Or is the actual sound of the preamp more important than how it messes with your audio?

Or is it both? When people sit there and complain about certain preamps and how they sound...are they giving a biased opinion because there happened to be an impedance mismatch between mic and preamp they listened to? Or are the electronic savvy people out there that can tell me the impedance causes only a slight difference in the resulting signal?

-B

 

[littledog]

I've never done that, but that's because I use a lot of different microphones. I usually buy a preamp because it does certain things well, much as I would buy a microphone for the same reasons.

For example:

clean and pristine
warm and colored
lots of headroom
good with really soft sources
good with really loud sources
has built-in eq
sounds good on a particular instrument
sounds good on a particular voice
portable (for live recording)
other useful features (lightpipe, built in converters, submixing ability, etc.)

 

[Blue Groove]

well...

It would be important if you only plan on buying a couple of pres and a couple of mics, but I think too many people change their gear regularly by adding and changing as funds allow, to balance it all. It's a good idea, but why limit the sound of a neve 1073 to a mic or two in your possesion? If every pre could change impedance, it might work out.

 

[SouthSIDE Glen]

How many people base the preamp they buy off of the microphone they use? It's generally recommended to compare the impedance on both preamp (input) and microphone (output) that you plan on using together. The theory is that an incorrect mismatch can cause havoc on your audio messing with the microphone frequency response...in other words, acting like a big EQ to the incoming signal.
...
Do people pay attention to this? Or is the actual sound of the preamp more important than how it messes with your audio?

Or is it both? When people sit there and complain about certain preamps and how they sound...are they giving a biased opinion because there happened to be an impedance mismatch between mic and preamp they listened to? Or are the electronic savvy people out there that can tell me the impedance causes only a slight difference in the resulting signal?

In response to the first question, I'd say that the experienced engineers with the budget certainly often take that into account. I think that for many of us that don't have that luxury probably just choose preamps based on best reputation for the price.

But you bring up an important point, Benny. There are many A-list engineers that I've read that consider the mic/preamp combo to be a single coupled system where one cannot seperate one from the other. Mic X may sound "better" for a certain task than mic Y when used with preamp A, but with preamp B they may consider the difference to be negligable or possible even that the reverse is true. Also, with some mics and applications, a "better" pre is not necessarily the "right" pre for the desired sound.

It's much like the way one has to consider their monitors and their environment as a coupled system, it's extremely difficult to accurately talk about the response character of a given type of monitor without considering the room it's in and it's position within the room.

It's not entirely a matter of impedance matching; every pre does have it's own coloration even when impedances match. Plus there can be differences in the quality of the phantom power supply between preamps which can affect the sound/performance of condensors differently. However, I have played with - just as one example - an ART DPS II with the variable impedance; while the variable impedance capability does not mean one can dial in the sound of a GML preamp just because one can match it's impedance, the variable impedance can definitely allow one to dial in different tones from a single microphone, which is a fantastic angle of flexibility to have, IMHO.

G.

 

[Fletcher]

I think you're getting a little too "waka waka" about the technical stuff... the bottom line is that if it sounds good then it is good... impedance matches or mismatches be damned.

Most modern microphones, especially condenser microphones don't really care all that much about the input impedance of a mic-pre. Other microphones with transformer based outputs like SM-57's [and SM-7b's], many ribbon mics [but not the Royer R-122 with active electronics] will care about the input impedance of a mic pre... but that will really only come into play if you have a selection of pre's from which you can choose and play mix and match to achieve the sound you desire to fit with the overall tone and texture of what you're recording.

Make sense?

 

[bennychico11]

Thanks for the resposnes
And I understand you totally, Fletcher. Real world aspects prevent many people from being able to mix and match preamps/microphones. I was just wondering how many people actually DO keep in mind which microphones they are using when buying the preamp. And wondering if anyone hears negative coloration in preamps that don't match the microphone's output impedance with a 10:1 ratio....or does anyone notice positive effects of not matching.

I've never had a chance to play with some of the variable impedance preamps, but I'd be curious to know how much a difference it gives between settings. An ideal preamp would be a single wire with a gain knob on it that gives no EQ change to the incoming sound...which of course can't happen...but can the frequency changes of the sound be minimized simply by being aware of the impedance of both devices?

But yes, I agree, the end sound is what's important.

 

[Middleman]

I think the basis for the myth of matching a mic to a preamp falls around matching say a tube mic to a tube preamp, or vice versa, as being a wrong approach. Sometimes yes, a tube mic and a tube preamp come off a little too warm or fuzzy sounding. Sometimes no, depending on the mic and preamp.

I think the only consensus lies in a few tried and true matches like say a Neumann U47 into a Neve 1073 or 1084 then into an LA2A/1176. Seems a lot of people like that sound or something very similar. Although this chain can be breathtaking at times, there are other possibilities waiting to be explored and yes, as mentioned above, let your ears be the judge.

Preamps provide a range of sound with emphasis in certain frequencies, as well clarity and transient response. The same is true of mics. Discovering what works, although at times costly, is kind of what keeps me interested in the whole recording thing. Its a science experiment!!
!!

 

[Robert D]

From the Tampa owners manual....

"The Input Impedance Selector
On some microphones, such as vintage or tube mics, you will want to
match the TAMPA’s input impedance to the output impedance of the
microphone. On others, such as modern solid-state FET mics, the input
impedance can be set to 10x the microphone’s output impedance or more.
TAMPA’s Input Impedance selector is designed to optimize performance
with different microphones.
For vintage (older tube or ribbon mics) or modern tube mics, check the
output impedance listed in the microphone’s documentation, then set the
INPUT IMPEDANCE selector to the closest setting. If in doubt, try the 300
Ohm or 600 Ohm setting.
For a FET mic (solid-state), start with the 2400 Ohm setting. For any mic,
some experimentation might be in order.You may achieve varied results
from alternate impedance settings, and the effect that you hear in tonal
quality may be a desirable one."

While I'm pretty well versed on impedance matching, I tend to view the impedance selector knob as more of a tone selector knob. If a mismatch gives me a tone I want, I'll go with it.

 

[littledog]

An ideal preamp would be a single wire with a gain knob on it that gives no EQ change to the incoming sound...which of course can't happen...but can the frequency changes of the sound be minimized simply by being aware of the impedance of both devices?

That's not always the case in all situations. Reproducing exact reality is often the goal, especially in classical recording, but often the goal is creating something that is "better" than the reality.

 

[SouthSIDE Glen]

I think the only consensus lies in a few tried and true matches

Agreed. While different mic/pre combos do give different results, if you asked 10 engineers to rate the "quality" of the different matchups, you'd probably get 10 different answers. Just as with microphone choice alone or monitor choice, "better" is highly subjective.

But the differences are there. How much is caused by the impedance mismatch vs. the puwer supply (when applicable) or just the coloration of the preamp design overall I couldn't rightly say. But I can tell you that the difference between an SM57 and a Rode NT2 (just to pull some models out of a hat) is different when run through a Tascam preamp than it is when those ideantical mics are run through an ART preamp (again just pulling brands out of a hat.) Four different mic/pre combinations yielding four different sounds.

Planning for that, though, like Benny is asking about, would require extensive experience with a variety of mic/pre combos, the critical enviironment and hearlig skills to ID and catalog those differences, and well as a budget large flexible enough to be able to afford to match preamps with our mic lockers the way Imelda Marcos matched shoes with purses. I doubt there are very many who frequent this forum with the wherewithall in all three categories to make much of an extensive practice out of doing that.

Not to mention that if I'm using a quality microphone though a half-way decent - certianly more than an entery-level - preamp, if I can't get an enjoyable sound out of it without having to go to a rack of different preamps, perhaps I should stop looking at my gear and concentrating on my technique.

Preamps provide a range of sound with emphasis in certain frequencies, as well clarity and transient response. The same is true of mics.

This illustrates greatly why the mic/pre pairing is indeed important. It's the serial linkage of two different response curves that yeilds a hybrid curve out the back. Some preamp colorations work better with one kind of mic than they do with another.

Benny, re your specific question on variable impedance, I have limited experience with that. I have worked with the ART DPS II and with a larger, older pre who's make and model I frankly don't recall (this was a while ago, and all the sessions start to blur after a while). My impression is that the variable impedance can indeed give you subtle but important color control over your mic in, but that there is no guarantee that my matching one impedance to another - either matching the mic or matching a different pre's specs - is going to yield a standard, predictable sound.

YMMV IMHO and all that jazz.

G.