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Author Topic: Are preamps for pu$$ies?  (Read 20844 times)

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Offline sygdwm

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Re: Are preamps for pu$$ies?
« Reply #15 on: July 15, 2008, 04:19:09 PM »
i dont really know much about the techno-babble, but doug oade once said, "the best pre-amp, is no pre-amp."
mics: (4)akg c460b(a60,mk46,ck1x,ck1,ck2,ck3,ck61,ck63)
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And GODDAMN did I use ALOT of smilies in that post ;D 8) :smoking: :spin:
(P.S.: On a threaded discussion board like this one, there's no need to repeat someone's post when you reply to them; everyone can see all the messages in the thread.)

Online jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #16 on: July 15, 2008, 04:22:24 PM »
I dont know...., add a preamp and then see if its "no difference".


i did, i didnt hear one.

i was looking for a technical discussion on the digital theory of turning your music into bits in the lower range. in other words, in a 24-bit realm would an ADC digitize a waveform peaking at -30 db with the same resolution as one peaking at 0? by my understanding, a 24-bit recorder will have the same resolution as a 16-bit recorder when peaking at -48dB. That said, noise of the adc aside (which is lower than the mic anyway), i think i answered my own question.

Online jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #17 on: July 15, 2008, 04:24:53 PM »
please, please, somebody make me that sticker for my ad2k

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

Offline Nick's Picks

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Re: Are preamps for pu$$ies?
« Reply #18 on: July 15, 2008, 04:39:50 PM »
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" )

Offline Nick's Picks

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Re: Are preamps for pu$$ies?
« Reply #19 on: July 15, 2008, 04:40:22 PM »
interestingly enough....the KMD Neumanns come to mind.

Offline DATBRAD

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Re: Are preamps for pu$$ies?
« Reply #20 on: July 15, 2008, 05:17:43 PM »
I started using an outboard preamp at a time when very few open concert tapers did so, 1990. What I found then, and still content today, is that an outboard preamp can harness very loud sources better than any recorder where the mics are plugged directly into it.

So my personal experiences with the benefits of preamps does not deal with very quite and/or extremely dynamic sources where noise levels are a big consideration, as the OP seems to be concerned with.

Most all past portable DAT recorders, and most of today's wave/DSD file recorders, seem to operate best when they are fed a clean line level signal that falls within the normal line level ranges (-20 consumer/+10 professional). So, by placing an outboard preamp in the path to deliver a line level within the optimal range the recorders are designed to handle to my ears usually sounds better.

All the Sound Devices users I know personally, while willing to use the unit with mics straight in when a stripped down rig is required, they all swear by outboard preamps. I have heard comps between V2/V3 versus no preamp, Sonosax versus no preamp, Neve, PSP3, VMS, MP-2, etc.etc. and rarely have I been unable to pick out the difference between one of those preamps versus using no preamp at all.

I will not attempt to discuss the benefits of one brand against the others, since part of the art of taping is matching and tuning a rig based on how different mics and preamps sync together. Some are matches made in heaven, and others are downright ugly.

Bottom line, the original poster's joy in not using a preamp for HIS particular setup is great for HIM. If HE likes it for HIS recordings, that that is all that should matter to HIM. I think it's a waste of time to attempt to draw others into supporting a rationalization based on technical arguments.

To repeat Doug Oade's best and most famous quote, "trust your ears".





 
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Offline Dede2002

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Re: Are preamps for pu$$ies?
« Reply #21 on: July 15, 2008, 05:36:47 PM »
I started using an outboard preamp at a time when very few open concert tapers did so, 1990. What I found then, and still content today, is that an outboard preamp can harness very loud sources better than any recorder where the mics are plugged directly into it.

So my personal experiences with the benefits of preamps does not deal with very quite and/or extremely dynamic sources where noise levels are a big consideration, as the OP seems to be concerned with.

Most all past portable DAT recorders, and most of today's wave/DSD file recorders, seem to operate best when they are fed a clean line level signal that falls within the normal line level ranges (-20 consumer/+10 professional). So, by placing an outboard preamp in the path to deliver a line level within the optimal range the recorders are designed to handle to my ears usually sounds better.

All the Sound Devices users I know personally, while willing to use the unit with mics straight in when a stripped down rig is required, they all swear by outboard preamps. I have heard comps between V2/V3 versus no preamp, Sonosax versus no preamp, Neve, PSP3, VMS, MP-2, etc.etc. and rarely have I been unable to pick out the difference between one of those preamps versus using no preamp at all.

I will not attempt to discuss the benefits of one brand against the others, since part of the art of taping is matching and tuning a rig based on how different mics and preamps sync together. Some are matches made in heaven, and others are downright ugly.

Bottom line, the original poster's joy in not using a preamp for HIS particular setup is great for HIM. If HE likes it for HIS recordings, that that is all that should matter to HIM. I think it's a waste of time to attempt to draw others into supporting a rationalization based on technical arguments.

To repeat Doug Oade's best and most famous quote, "trust your ears".





 

Very well said ;)
+T
Mics..........................SP-CMC-8, HLSC-1 and HLSO-MICRO
BB and Preamps........MM Micro bb / MM Custom Elite bb / Church 9100
                              
Recorders...................Tascam DR-100MKIII, Marantz PMD 620 MKII, Edirol R-09

Online jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #22 on: July 15, 2008, 05:41:29 PM »
thanks for the input, brad.

im not trying to justify or talk anyone out of their preamps, just trying to have a good tech discussion on why this may or may not be acceptable.

as for your example, i would say that a preamp is absolutely essential for recording to 16-bit recorders as you describe

the theory here is that the super low noise of the ad2k and the 24 bit theoretical noise floor allows you to skip the pre. while some may consider this 'skimping', if i can save the cost of a pre and the weight and power in the field and not hear a difference , thats enough for me

i just got off the phone with John Siau (designer of the AD2K, who graciously took time to support a legacy product). what he explained to me is that  noise is cumulative and is slightly higher than the level of  the loudest noise. something along the lines of youve got two levels of noise, one (i think he said 18db) lower than the other. the combined effect of this noise willl be 1 dB higher than the loudest one. so that said, the post-normalized noise floor of the ad2k is NOT totally masked by the noise of the mics. But realistically, to me, and increase of 1db of low level noise is essentially inaudible.

Hes looking at the schematics of that unit to see if we could mod the unit to more closely match the output of the cmr mics.
i think if i could get it to peak at -12 vs. -25-35 dB that would be a win-win


I started using an outboard preamp at a time when very few open concert tapers did so, 1990. What I found then, and still content today, is that an outboard preamp can harness very loud sources better than any recorder where the mics are plugged directly into it.

So my personal experiences with the benefits of preamps does not deal with very quite and/or extremely dynamic sources where noise levels are a big consideration, as the OP seems to be concerned with.

Most all past portable DAT recorders, and most of today's wave/DSD file recorders, seem to operate best when they are fed a clean line level signal that falls within the normal line level ranges (-20 consumer/+10 professional). So, by placing an outboard preamp in the path to deliver a line level within the optimal range the recorders are designed to handle to my ears usually sounds better.

All the Sound Devices users I know personally, while willing to use the unit with mics straight in when a stripped down rig is required, they all swear by outboard preamps. I have heard comps between V2/V3 versus no preamp, Sonosax versus no preamp, Neve, PSP3, VMS, MP-2, etc.etc. and rarely have I been unable to pick out the difference between one of those preamps versus using no preamp at all.

I will not attempt to discuss the benefits of one brand against the others, since part of the art of taping is matching and tuning a rig based on how different mics and preamps sync together. Some are matches made in heaven, and others are downright ugly.

Bottom line, the original poster's joy in not using a preamp for HIS particular setup is great for HIM. If HE likes it for HIS recordings, that that is all that should matter to HIM. I think it's a waste of time to attempt to draw others into supporting a rationalization based on technical arguments.

To repeat Doug Oade's best and most famous quote, "trust your ears".





 
« Last Edit: July 15, 2008, 05:50:59 PM by jerryfreak »

Offline Nick's Picks

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Re: Are preamps for pu$$ies?
« Reply #23 on: July 15, 2008, 05:57:13 PM »
well...I guess if it ain't broke....., FUCK WITH IT MORE !
my new motto.
:)

Online jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #24 on: July 15, 2008, 06:28:40 PM »
Thanks MS!

ok, that said, im currently using it as a 0dBFS =+14 dBV device, would i assume EIN = 117 dB at that setting. it appears the nature of the mod we want to do will decrease the attenuation, making it a 0dBFS=-0 dBV or 0dBFS=-10 dBV device. Perhaps this is why they say in the manual "Sensitivities greater than +14 dBu have not been included since they would compromise the
dynamic range of the AD2402-96."

so basically if we go from +14dBV to 0dBV, we are going to take the dynamic range from 117-14 = 103 dBA (or alternatively 93 dBA at 0 dBFS = -10dBV) .

as for dither im talking about in the course of the final product in 16 bit, i wouldnt dither a 24bit file just to do it. the dynamic range of a 24-bit waveform is self dithering on all real-world equipment


This is largely correct, except for a couple of points, one minor and one major.

First, the major point:  a 117dB dynamic range on an A/D converter does NOT equate to equivalent input noise of -117dBA.  That's the difference between 0dBFS on the converter and its noise floor.  If the converter is say 0dBFS = +8dBV (a -10dBV nominal device, perhaps), then the noise floor is at -109dBA.

That means if you don't amplify the mic signal, then the converter noise will dominate.  More accurately, as you note in your last post, the noise will sum and the result will be about 3dB of extra noise in this case.

It gets worse if you're using a +4dBu A/D, it might have 0dBFS at +16dBV (+18dBu), that means your converter noise now lives at -101dBA, so you need much more gain to offset that.  If we use the figures in your post, that's +27dB (although I think it's more like +19dB; noise power sums, not noise voltage).

Further, I would suspect that could be a bit dangerous for people who don't have converters with 117dBA dynamic range, who see this conclusion and think "Hey I don't need a preamp either!"  With a quiet mic on a quiet source, they could suffer from audible converter noise in that case.  So the conclusion on whether or not to use a preamp is going to depend on the rest of the taper's gear.

But will any of that ever be noticed at a loud show?  Probably not.  That's because the acoustic noise level could be high enough that none of these electronic noise sources matter.


Now, the minor point is about dither and quantization distortion.  First, you can't dither after conversion (or truncation), dither must be added to the signal before conversion.  If you dither a signal that already has quantization distortion, then you just get noise + distortion.  When quantization distortion exists, it is at a MUCH higher level than the nominal dynamic range of the converter system.

Having said that, all existing 24 bit converters are sufficiently noisy to self-dither any signal at any level (unless we are talking about a digitally-generated signal that does not have dither; perhaps a synth).  So you need only worry about converter noise, not quantization distortion.

If you are talking about quantization distortion upon truncation to 16 bit, well then that couldn't exist if you dithered the normalized 24 bit signal first, but as you have already noted, the noise floor of the recording would be high enough to self-dither.



Offline Krispy D

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Re: Are preamps for pu$$ies?
« Reply #25 on: July 15, 2008, 06:51:28 PM »
well...I guess if it ain't broke....., FUCK WITH IT MORE !
my new motto.
:)
qft
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Online jerryfreak

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Re: Are preamps for pu$$ies?
« Reply #26 on: July 15, 2008, 06:59:24 PM »
qft

ha! i finally looked up that acronym. for a lng time now,i thought it meant 'quit f$#^kin talking!'.

kinda changes the context of message board discussions!

Offline Krispy D

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Re: Are preamps for pu$$ies?
« Reply #27 on: July 15, 2008, 07:05:03 PM »
quoted for TRUTH!
Peluso CEMC6, ck4/ck21
Oktava MC012
Sony ECM260f
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canare star quads
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You cannot strengthen the weak by weakening the strong. You cannot help the wage-earner by pulling down the wage-payer. You cannot help the poor by destroying the rich. You cannot help men permanently by doing for them what they could and should do for themselves.
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Offline tunanotaphish

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Re: Are preamps for pu$$ies?
« Reply #28 on: July 16, 2008, 03:25:37 AM »
Wow, even my brain is gonna explode from reading all of this.  Greetings to all I haven't seen in a long time.
Going to give this one a cursory glance, don't have time to respond to every detail of the very fine discussion here.... but....

First, I'd be inclined to believe that there will simply be inherent differences in coloration attributable purely to different impedances between the output of a preamp at line level vs. the pure mic level output.

Second, as someone already said here, (sorry, too lazy to quote, so I'm gonna paraphrase) using a preamp will in most cases improve signal to noise ratio at the A/D.  The quieter the material, the worse the signal to noise ratio.  Noise being not just self noise from the mic and analog stage in the A/D, but also quantization noise from the A/D process.

Third thought, the best way to prevent any further noise from being added to the signal and still amplify the signal is to use bit shifting (e.g. some software... I think samplitude has a 2x volume function).  Any sample value multiplied by exactly 2 will not generate a mantissa, and therefore, will not create additional noise.  Amplification through bit shifting would be the only way to preserve the effect of dither and noise shaping once applied.  Of course, in using this method, how close you can get to 0dBFS would depend on how close your loudest peak is to -6.02dBFS.

Fourth, I usually consider it simply like this.  You really only have about 25dB extra headroom with the AD2K over the best 16 bit A/D.  So -48dBFS is only in theory the same as 16bit at 0dBFS in terms of S/N ratio.  In practice, it's probably closer to -24dBFS being about the same.  Granted, when comparing differences down to this level, you'd also have to consider the differences in color of *all* frequences over the dynamic range for any given analog stage.  I believe most specs center their S/N ratios, etc... around a 1kHz tone.  As such, every analog component's self noise will have it's own unique FFT.  The degree to which the noise signature with a preamp or without a preamp is complementary to the live source is purely up to the listener.  In other words, the differences in self noise will impart a coloration to low level sounds.  It is possible that cumulative (i.e. greater than the loudest noise, as John Siau puts it) noise dithers the sound better to your ear one way over another for your recording, much in the same way that white noise dither would sound different than "pinker" noise.

Bottom line, practically, I'd say, if you were willing to carry a Benchmark AD2402-96 to a show, you should be willing to carry a Grace Lunatec V3 to the show instead, and kill two birds with one stone.

I still love that V2->AD2402-96 combo, and for anyone curious, for 2 track live recordings (as infrequently as I do them these days), I still use the DAARWIN-24 Sony picturebook with the VXPocket, Win2K, and that Pre/AD combo.  The combo continues to do exactly what it was designed to do 8 years ago, no reason to mess with a good thing.  A solid state disk sure would be nice though.  ;-)  For the multitrack Hot Tuna shows, well, that's a whole other ball o' wax.  Gotta love the Alesis HD24-XR for that.

(no, I don't read this board regularly at all.... too busy coding stock trading formulas these days. ;-)
 jerryfreak roped me in on this thread.  Somewhere along the line I also created two ID's here as well.  And so it goes...)

Cheers, and keep up the quality discussion.  Mmmmmmmmmmmmmore bits please.

Dan Heend
High Fidelity Microsystems
HFM Studios
www.hottunatunes.com



Offline muj

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Re: Are preamps for pu$$ies?
« Reply #29 on: July 16, 2008, 03:58:55 AM »

 

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