Klas wrote:
>Thanks Rob, obviously you have thought a lot about this.
>
>But still:
>
>I have recordings of atmos only, distant birds and perhaps a woodpecker
>coming in nearby every 45 sec or so.
>The mic is a Telinga MPS1 with a self noise around 6 dbA.
>
>Still, with only 6dbA noise - the noise I hear is mic noise, not Tascam DA=
P1
>preamp noise.
At what record level? "10" no pad? One of the factors that makes the
DA-P1 harder to compare is its gain structure is possibly very
different:
http://www.xs4all.nl/~fjkraan/digaud/dap1/MicrophoneCircuit.html
.
As you may recall from a discussion we had a year or so ago, I had a
chance to compare mkh-20->mp-2->bal line in of DA-P1, gain at "6.5"
--to-- mkh-20->DAP1 mic pre in. I found the mp-2/bal line
combination to be quieter. I should do another test with the NT-1A's.
As for clearing the air about whether external pres really are better
than most internal mic pre's in terms of noise (and all of the
factors involved), I'd guess that side by side field tests would
leave the least amount of dust Using manuf specs, there's a large
range in the amount of noise generated and gain provided by both
internal and external pres- even among the better pro units. But the
same info is also very sketchy if you wanted to rank them. I thought
Equivalent Input Noise (EIN) is supposed to be measured at full gain,
but Sound Devices says, "50% gain or higher," Portadisk doesn't say
what gain level their EIN number is measured at and Tascam is nearly
mute about what their mic preamps specs are. Sony and Sharp provide
no info I could find. By specs alone, the MP-2 looks to be the
quietest pres among these. Recorder line input tends to spec
considerably better than mic input in terms of signal to noise. If we
bring mic sensitivity into the equation-- this spec is measured as
the voltage generated at a certain (loud) level-- not the actual
output at low sound levels. Its likely that sensitivity (signal
output) is not linear-- in other words, some mics probably kick out
a proportionately higher signals at low sound levels. I know my
MBHO's, with pronounced low end response have much more sensitivity
than they are spec'd at under low sound levels-- for certain sounds.
In these matters, maybe it is what we can judge and enjoy over the
speakers? Maybe we could set-up a low sound level test at the
Recordist camp out this May and crank up all of our pres with all
possible combinations of mics and play over a high quality system at
matched levels and take a listen. We are hoping to have a cabin with
good playback this year.
>When using EM23, the omni with a self noise around 14 dbA, what I hear is =
of
>course mic noise, not preamp noise, using a simple and inexpensive
>Sharp MD...?
I've heard your EM-23's and agree they are ~14dB(a) self noise.Do you
remember the gain setting on the MD mic pre, max? My self noise mic
pre guidelines are for low sound level recording through the MD mic
pre-- I use these because that's the reality recordists face when
recording remote ambience, when their systems are at their worst.
Best,
Rob D.
>
>"Sound quality" is another issue here, - whether using a preamp and line
>input "sounds better" or not.
>The only thing I would like to be cleared out (finally, if possible) is if
>there is any facts supporting that there is better noisefigures to gain, a=
nd
>how this relates to output voltage of the microphone and it's self noise.
>
>Like - using a MKH20 (10 dbA) - is there a lower noise with a good preamp
>than directly into the Tascam or HHB??
>
>Klas.
>
>At 14:43 2004-02-13 -0600, you wrote:
>> wrote:
>>>All: This preamp question comes up now and then.
>>>
>>>Has anyone really investigated how bad the mic inputs are of different M=
D's
>>>and DAT's?
>>>Has anyone tested how sensitive a microphone must be, (output voltage) t=
o
>>>run over the noise of the standard MD mic amps??
>>>
>>>My little idea is that there is not much use of preamps (to improve nois=
e
> >>level) as most microphones today have either enough output voltage or =
make
>>>so much self-noise that a preamp won't help.
>>>
>>>So: What is the advantage spending lots of money on a preamp and how do =
you
>>>know that for sure??
>>
>>
>>Don't you think that most folks who are talking about noise are
>>trying to record soft sounds? With your dish and a nearby healthy
>>bird at 30 yards, your Portadisk mic pre gain must be well below max.
>>Going the extra mile to lower noise comes from people interested in
>>recordings where the local acoustics are part of the image. For
>>their surround projects, my students are moving mics away from sound
>>sources to capture more of the space-- a very different practice than
>>trying to isolate all sounds except junk "presence" tracks of 20
>>years ago. Of course, this is not a new desire or technique, but it
>>is much more common and people have modest budgets. The MD mic pre is
>>the weakest link. There are mics with high output, 6 to 18dB(A) self
>>noise, the ability to record in high humidity and wind for $200.
>>
>>Some numbers that have proven to be very useful estimates for us are:
>>
>>Consumer MD mic pres with the gain set at maximum have an equivalent
>>self noise of 20-25dB(A).The Walkman DAT's are in the same
>>neighborhood.
>>
>>Tascam DA-P1 with the mic gain set at maximum has an equivalent self
>>noise of 12-14db(A). Based on comments on this list and others, the
>>Portadisk mic pre at full gain might be around 10-12dB(A) but I've
>>never had one to compare.
>>
>>The MP-2 has a self noise of about 4-5dB(A)
>>
>>The Audio Buddy Mic Pre has an equivalent self noise of about
>>12-14dB(A) when the gain is set to max.
>>
>>Bob Cain (micbuilders llst) derived one or two of these numbers, I've
>>ear-tested them with many mics and have found them pretty accurate in
>>determining whether an investment is likely to lower noise. Being
>>able to use the line input of an MD recorder is itself a big
>>advantage. Even a 25dB(A) mic will sound a bit cleaner using a $300
>>Mic pre like the Edirol UA-5. A mic with 18dB(A) self noise through a
>>decent pre will sound considerably cleaner. Some of us use pres in
>>the 5-12dB(A) range to better enjoy the low noise of great mics-- and
>>that is why somone would consider a $700 mic pre for an MD recorder.
>>It's a bit overkill, and it seems odd, but there aren't too many
>>alternatives.
>>
>>Many of the lower cost and better mic pres have maximum gain in the
>>neighborhood of 45-55dB which means 10-15dB less gain than the folks
>>cranking their MP-2's to the max. In quiet settings, that's huge.
>>I've been trying to get the DC power and phantom power issues solved
>>with the Audio Buddy which is a very decent sounding $90 pre with
>>60dB of gain. That would fill a big void with the $200 low noise mic.
>>
>>
>>>And for which microphones??
>>
>>It would take quite a bit calculation to put all the mics and pres on
>>one standard because, as you point out, its not just noise but mic
>>output/sensitivity too. We'd also need apples and apples numbers for
>>the pres and the -10dB line inputs.
>>
>>As a ballpark guide, the Rode NT-3 seems to consistently ou-tperform
>>the MT-90 mic pre. This mic has 17 dB(A) self noise and 12 mV/Pa
>>sensitivity. In theory, there's no point in spending more on a mic
>>that specs better than this without considering a better recorder or
>>a mic pre. When you consider that many nature recordists and natural
>>space recordists find their way to an ECM-MS957 stereo with 25 dB(A)
>>self-noise with and considerably lower sensitivity or DIY Panasonic
>>WM-61a capsules with 32 dB(A), its easy to see why people start
>>imagining what another few hundred could do,.. For me, a $90 portable
>>pre with 12d(A) self noise would mean students would have much
>>better access to low noise recording rigs.
>>
> >Rob D.
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