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Author Topic: Are preamps for pu$$ies?  (Read 15758 times)

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Offline jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #30 on: July 16, 2008, 04:36:47 AM »
thanks for chiming in dan!


Offline eric.B

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Re: Are preamps for pu$$ies?
« Reply #31 on: July 16, 2008, 09:00:03 AM »
I also liked doug's old saying..  "what we need is a straight wire with gain!"


i dont really know much about the techno-babble, but doug oade once said, "the best pre-amp, is no pre-amp."

i was going to say this exactly (quoting Doug...who ironically makes a living making/moding preamps.  maybe he's just gutting our all in one boxes to the "no preamp MOD" )

We have a system that increasingly taxes work and subsidizes nonwork.  ~Milton Friedman

Offline Dede2002

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Re: Are preamps for pu$$ies?
« Reply #32 on: July 16, 2008, 10:00:48 AM »
Wow, even my brain is gonna explode from reading all of this. 


Mine too. Thanks everyone for the great posts. I've learned a lot ( and that's why I'm here in he first place  ;))
Mics..........................HLSC-1 and HLSO-MICRO
BB and Preamps........MM Micro bb / MM Custom Elite bb / Church 9100
                              
Recorders...................Edirol R-09 / Edirol R-09HR

Offline Gutbucket

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Re: Are preamps for pu$$ies?
« Reply #33 on: July 16, 2008, 11:27:57 AM »
Nothing to add, except thanks for the great discussion on a topic I often wonder about.. and still do.
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Offline Nick's Picks

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Re: Are preamps for pu$$ies?
« Reply #34 on: July 16, 2008, 03:13:04 PM »
I'll 2nd that.
+Ts
LMA recordings and what-not


Live music: hauling around a Marshall stack whose output will get squeezed through a single SM57, then mangled by a Guinness-soaked mixer and shoved through suspicious-smelling power amps into a pair of grungy cabinets whose best days were before they left the factory, all of which are under the control of an engineer who would much rather be at home watching television.

Offline jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #35 on: July 16, 2008, 04:21:32 PM »
nothing brings out the pros like some good old-fashioned name calling!

at this point, im still waiting to hear back from john siau on what mods we can do to 'open up' the input of the ad2k to lower levels. were talking about bypassing a resistor in the input section, or alternatively, a switch to a second resistor that would change the attenutation range of the front-panel knob. With no trim available, it would still need to be set conservatively, but if we can get the peaks up in the -20 to -12 range that would be better i think

to recap:
-to my ears, i cant hear additional audible noise when doing this
-we agree that there is adequate digital resolution to allow this, and a single normalization in soundforge has no negative effects
-ampification of the noise floor of the AD2K is the limiting factor, and appears to be minor, if audible at all.

tell ya what i'll do - I'll record both a high and VERY low level test recording with and without a pre this weekend, and we'll see if you guys can blind AB them

Offline WiFiJeff

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Re: Are preamps for pu$$ies?
« Reply #36 on: July 16, 2008, 04:26:42 PM »
i dont really know much about the techno-babble, but doug oade once said, "the best pre-amp, is no pre-amp."

Hell, yeah.  And while you're at it, get rid of those pesky mics and A/D distorters as well.  I just bought one of these:

http://cgi.ebay.com/Windup-Premium-Gramophone-Kit-by-Gakken-for-SP-EP-LP_W0QQitemZ140248973205QQihZ004QQcategoryZ1442QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

That's real analog sound for brave hearts.

Jeff

Offline jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #37 on: July 16, 2008, 04:32:47 PM »
that would go great with gutbucket's avatar


i dont really know much about the techno-babble, but doug oade once said, "the best pre-amp, is no pre-amp."

Hell, yeah.  And while you're at it, get rid of those pesky mics and A/D distorters as well.  I just bought one of these:

http://cgi.ebay.com/Windup-Premium-Gramophone-Kit-by-Gakken-for-SP-EP-LP_W0QQitemZ140248973205QQihZ004QQcategoryZ1442QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

That's real analog sound for brave hearts.

Jeff

Offline live2496

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Re: Are preamps for pu$$ies?
« Reply #38 on: July 16, 2008, 04:39:38 PM »
just wondering about your thoughts on this.

My new rig doesnt have a pre, and it sounds great to my ears (MK4v>CMR>battery box>AD2K)

normalizing once in soundforge at about about +25 - +30 dB doesnt seem to hurt the sound at all.

While minimalist, this is actually my new 'open' rig. I'd love love love to find a super small, super low noise floor stealth AD to eschew the gain stage entirely while stealthing. Whose got time to check levels when you're watching your back? the only good small AD of fthe top of my head is the sbm-1, but its only 16bit, and wouldnt have the headroom to pull this off.

i was hoping to get some feedback on this setup from the more electrically inclined. as to any major disadvantages with regard to headroom, dynamics, etc.

it seems with an AD capable of a clean -117db, and a mic with a noise floor of -75 to -80, id never be limited.

check it out. AD2K was set to its highest input level (+14 dB, minimum attenuation):

http://www.sendspace.com/file/uzt783

One reason why there is a trim control on mixers is to adjust the gain so that you get the best signal to noise ratio. It's all about proper gain staging. Some preamps have a variable impedance. Matching the impedence allows for a better signal transfer between the mic and the destination circuit.
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Offline Gutbucket

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Re: Are preamps for pu$$ies?
« Reply #39 on: July 16, 2008, 05:00:28 PM »
Hell, yeah.  And while you're at it, get rid of those pesky mics and A/D distorters as well.  I just bought one of these:

http://cgi.ebay.com/Windup-Premium-Gramophone-Kit-by-Gakken-for-SP-EP-LP_W0QQitemZ140248973205QQihZ004QQcategoryZ1442QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

That's real analog sound for brave hearts.

Jeff

Oh yeah. No pesky electronics at all.  I love how it records on CD's.. by scratching in an analog groove!  Just wind up the clock spring and point the horn.  You gonna thread the base for a lightstand mount?

that would go great with gutbucket's avatar

Yup. I run two of 'em in a giant kangol cap.
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Offline jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #40 on: July 16, 2008, 07:47:51 PM »
Heres what John Siau had to say. Note his comments are for the CMC6, the CMR have a very slightly higher noise spec, so it seems with the mod hes talking about, the noise level of the AD would be comparable to that of the mic, and more importantly inaudible in all real world field recording environments

        mk4+cmc6, sensitivity = 13 mV/Pa, max SPL = 132 dB, EIN = 24 dB CCIR/ 15 dB A weighted
        mk4+cmr, sensitivity = 8 mV/Pa, max SPL = 130 dB, EIN = 29 dB CCIR/ 18 dB A weighted

John's comments:

Jamie,
Your analysis is basically on track but has some errors that are
throwing the final numbers off a bit.

I am including my microphone data spread sheet which already has the
MK4V+CMC6 combination.  This shows a self noise of 14 dB SPL and given
the sensitivity of the microphone this means that the noise at the
microphone output is -115.5 dBu.  The AD2402 has a signal to noise ratio
of 117 dB and a maximum sensitivity of 0 dBFS at +14 dBu.  This means
that the equivalent input noise of the AD2402 is +14 dBu-117dB = 103
dBu. The self noise of your microphone (measured at its output) is
actually 12.3 dB lower than the equivalent input noise of the AD2402.
In a perfectly quiet room the AD2402 would add about 12 dB of noise to
your recording.  Obviously the noise level in a live venue exceeds 14 dB
SPL even when nobody is in the room.  If the noise in the room measured
14+12.3=26.3 dB SPL the AD2402 would add 3 dB of noise to your
recording.  At a room noise level of 32.3 dB SPL the AD2402 will only
add 1 dB of noise.  Your system is working because you are recording in
a noisy environment.  In a quiet studio you would benefit from a
microphone preamplifier.

Here are some easy rules-of-thumb for adding noise sources:

1) Two equal amplitude noise sources added will degrade the SNR by 3 dB.
2) If a new noise source is added that is 6 dB lower than the existing
noise, the resulting noise will increase by 1 dB.
3) If the noise sources differ by more than 6 dB, the quieter source can
be ignored.
4) Use RMS calculations for summing noise sources when you need exact
numbers.

The above assume random noise and no correlation between the two noise
sources.  This is usually the case with microphones and electronics, but
be careful about room noise because it is often not random when the room
is empty.  On the other hand, the random rustle of a crowd can approach
white noise under certain conditions.

Another interesting and useful rule of thumb:
The human ear can detect a tone that is 30 dB lower than the ambient
noise level.  I frequently demonstrate this is the lab.  What this means
is that a TPDF dithered 16-bit signal with an SNR of 93 dB can audibly
reproduce a signal that is recorded at -123 dB FS. 

FFT analyzers can easily resolve signals that are 50 dB or more below
the noise floor.  Our ears have about the same resolving ability as a 4k
to 8k point FFT - this is amazing.  In the lab we have the luxury of
using 64k FFT analyzers so that we can analyze distortion signals that
are too small to be heard.  Every time the number of points is doubled,
the resolution of an FFT analysis increases by 3 dB (sound familiar? -
see rule of thumb #1 above).

Here is a modification that will boost the input sensitivity of the
AD2402 by 8.2 dB (making the self noise of the AD2402 only 4.1 dB higher
than the microphone self noise - please note that the signal to noise
ratio of the AD2402 will still be 117 dB).  With this modification the
AD2402 will only add about 1 dB of noise to your microphones in the
quietest studio.

Modification to increase sensitivity of AD2402 by 8.2 dB:

Each of the input attenuators has a 5.62K Ohm and a 649 Ohm resistor.
There are 4 of each.  If you swap the position of the 649 and 5.62k
resistors, the +14 dBu switch position will become a +5.7 dBu switch
position (meaning that 0dBFS = 5.7 dBu).  All other switch positions
will remain unchanged.
<snip>
« Last Edit: July 16, 2008, 07:50:31 PM by jerryfreak »

Offline jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #41 on: July 16, 2008, 08:12:44 PM »
as a point of reference: Dr. Booty (LOL) says a library is 30 dB

http://home.new.rr.com/trumpetb/audio/dBexamp.html



I find his analysis excellent.  There's your answer right there, more succinctly than I have said it.


sounds like a go.

Offline live2496

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Re: Are preamps for pu$$ies?
« Reply #42 on: July 16, 2008, 10:35:12 PM »
Got a chance to listen tonight. I must say the recording quality sounds really good.  :)
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Offline jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #43 on: July 17, 2008, 02:26:51 AM »
thanks. that was in a corner of a small bar room, far from optimum conditions. just goes to show how forgiving the schoeps are.

Got a chance to listen tonight. I must say the recording quality sounds really good.  :)

Offline waltmon

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Re: Are preamps for pu$$ies?
« Reply #44 on: August 21, 2008, 10:03:18 AM »
Well I can't take it quite as technical as some of the posters on this thread, but my rule of thumb has always been as close to 0 db without going over.

    I am always looking to attain the best result with the least post recording processing. Before I went to 722 and finally 744T, I ran 140's/50's > v-2 > ad2k+ > HHB PDR1000.

It took some experimenting to finally get the AD2K+ dialed in.  In general, the best performance out of the ad2k comes when you run it on the warm side. You want to see plenty of activity in your level meters peaking at yellow and keeping away from red. The yellow light means something to the effect of full digital signal without saturation ( which would be red)

   I apologize for the lack of technical speak, but I love the AD2K...I'd run it in front of my 744T in a second , but I've been trying to scale down the sze of my already over full gear-slut bag   >:D
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