mic pre noise rating

[JTC111]

What does this stuff really mean?

Noise: -90dB @ 22Hz to 22KHz

And how much of a difference is really noticeable between a unit rated at -90 and a unit rated at -129?

[Robert D]

Some of the really coveted vintage mic pres, even some modern ones, are not so great in the noise specs department, so for most apps it's not the most important thing in the world..... great sound is. But some applications requiring either high gain (ribbon mics and Large diaphram dynamics) or dealing with low level passages (classical recordings) need really good noise specs.
The AMS Neve 1073 re-issue specs out at -83db, and we're talking about a $3700 preamp, so -90db isn't a reason not to buy a pre, it's just one thing to consider amoung many variables. Also, remember that noise is cumulative in a multi-track recording. If a less than stellar noise spec pre is used on everything, it tends to build up. Also, if it will be used on, say rock vocals, that's different than if it's going to be used on a grand piano fading to black.

[MOFO Pro]

For comparison... the best analogue tape decks could provide was about 80... This spec won't make or break a purchasing decision, but should be considered...

Robert pretty much hit it right on the nose

[JTC111]

Originally Posted by Robert D

Also, if it will be used on, say rock vocals, that's different than if it's going to be used on a grand piano fading to black.

You had me feeling really confident... until I read that last line. I'm going to be using it for acoustic guitar and vocals with very little instrumentation. Should it become a slightly bigger concern in that case?

[Kevin Deschwazi]

What pres are you looking at?

You'd have to spend pretty unwisely or be extremely limited with your budget to buy any modern preamp with self noise levels that are going to hamper your recordings. Especially if you steer clear of "Coloured" pres containing transformers and valves (as a general rule anyway).

The ubiquitous DMP-3 has a SNR of -120dB and low THD to boot. If you want clean on a budget that would be a fine choice. Gobs of gain for quiet sources/distance micing too.

There are other "straight wire with gain" designs (which tend to be clean, low noise/distortion), if you have more to spend there are more options of course.

[JTC111]

Originally Posted by Kevin Deschwazi

What pres are you looking at?

You'd have to spend pretty unwisely or be extremely limited with your budget to buy any modern preamp with self noise levels that are going to hamper your recordings. Especially if you steer clear of "Coloured" pres containing transformers and valves (as a general rule anyway).

The ubiquitous DMP-3 has a SNR of -120dB and low THD to boot. If you want clean on a budget that would be a fine choice. Gobs of gain for quiet sources/distance micing too.

There are other "straight wire with gain" designs (which tend to be clean, low noise/distortion), if you have more to spend there are more options of course.

The pres I'm looking at are:
John Hardy M2 (-129)
A Designs MP-2A (-128)
Demeter VTMP-2C (-125)
Phoenix Audio DRS-2 (-90)
Wunder Audio PAFOUR (don't know yet)

I put the noise levels in parenthesis if I could find them. I'm thinking, from what I've read here, that it might be something I should consider in this decision, but I don't know how much weight to give it for the application I want it for: acoustic guitar and vocals without much instrumentation.

[mixsit]

Just to toss this in for a 'relative check; Look how those numbers compare to the s/n levels of the condensor mics we're apt to be using.

[mshilarious]

It's not just a question of what you are recording, but also what microphone you are using. Preamp noise specs are usually listed as equivalent input noise. That means if the noise rating is -90dBV (it must also have a reference, the "V" in this case means 1V, another possibility is "u" which is 2dB higher at the same voltage), that would be like using a microphone with -30dBV/Pa sensitivity, and a 34dBV noise rating.

That would be a noisy microphone, on par with very small cardioid lapel-type mics, so you might feel that -90dBV is an undesirable noise rating for a preamp, and truthfully in a modern preamp it is. To avoid that problem, you'd need to have a hot enough mic and source to get your signal far above the noise. That probably means no ribbon mics for anything except guitar amps or drums, for example.

But first be sure that the noise ratings are really and truly comparable. There are a few other ways to state a noise measurement, although it befuddles me why any manufacturer would punish their specs by quoting them in such a manner. Another concern is weighting; noise specs are often listed using A-weighting (which personally I feel is appropriate), but other manufacturers might cite unweighted noise readings, which is like a 6 or 8dB penalty.

Another question is what gain the manufacturer measured noise, and how that affects the preamp's noise rating. You might have noticed that some preamps get suddenly noisier at the top of their gain range. Others don't, and will show similar noise at any gain setting. If you are concerned about preamp noise, that probably means you are concerned about high gain settings, so that is the relevant statistic to know.

[JTC111]

Originally Posted by mshilarious

It's not just a question of what you are recording, but also what microphone you are using. Preamp noise specs are usually listed as equivalent input noise. That means if the noise rating is -90dBV (it must also have a reference, the "V" in this case means 1V, another possibility is "u" which is 2dB higher at the same voltage), that would be like using a microphone with -30dBV/Pa sensitivity, and a 34dBV noise rating.

That would be a noisy microphone, on par with very small cardioid lapel-type mics, so you might feel that -90dBV is an undesirable noise rating for a preamp, and truthfully in a modern preamp it is. To avoid that problem, you'd need to have a hot enough mic and source to get your signal far above the noise. That probably means no ribbon mics for anything except guitar amps or drums, for example.

But first be sure that the noise ratings are really and truly comparable. There are a few other ways to state a noise measurement, although it befuddles me why any manufacturer would punish their specs by quoting them in such a manner. Another concern is weighting; noise specs are often listed using A-weighting (which personally I feel is appropriate), but other manufacturers might cite unweighted noise readings, which is like a 6 or 8dB penalty.

Another question is what gain the manufacturer measured noise, and how that affects the preamp's noise rating. You might have noticed that some preamps get suddenly noisier at the top of their gain range. Others don't, and will show similar noise at any gain setting. If you are concerned about preamp noise, that probably means you are concerned about high gain settings, so that is the relevant statistic to know.

I had to read that about 15 times just to wrap my brain around the simpliest parts. But I get what you're saying and I probably will be better off if go with a lower noise pre. I think the A Designs MP-2A is the front runner for me right now (despite the fact that it's butt ugly).