What THEY don't want YOU to know about PRE-AMPS!

MattinSTL

MattinSTL

Sound Modulator
Man oh man has it been a revealing couple of days. TIGEBA this is all YOUR fault!

Let's just say I got some new toys and skip further along in this thread... I gotta' DELETE some misinformation that I was beginning to propogate!

I'm sorry for that...

I'll post my little test at the end.:thumbsup:
 
Well...you're not really changing the mic characteristics (it has no idea what's going on after you plug it in).

But boosting the signal will...um...boost the signal. It'll also boost the mic's noise floor, but...it helps a LOT by pushing a stronger signal through the cable to the recording device.

Mic -> short cable -> preamp -> longer cable -> recording device, would be ideal, I think.

A long cable *to* the preamp will introduce a stronger cable-noise singal, too, sicne the preamp will amplify any noise produced frm the cable.
 
I know that it doesn't phycially change the characteristics of the mic... but the effect is much more then simply boosting the signal.

I'm hoping to get a bunch of replies like yours before I post clips.

I realize that my premise doesn't seem logical... and that there should be a simple explanation... but even with output levels equalized there's a big difference in the apparent proximity of a mic that's running through a pre or directly into the camera.

It sounds like one recording is gaining up the entire room AND the mic... and the other sounds like the mic is gaining up much more then the room is.

EDIT: Some mics seem to work like this more then others! Basically the input further along in this thread... from Ty and from Genjerdan... is the logical answer... sorry for posting prematurely... my "tests" do not fully support the results I predicted! I'll post a link at the end of this thread!:huh:
 
It shouldn't be doing any more than widening the S/N ratio. But that would have the effect of sharpening the edges of the bubble. The crappy sound is probably still there, but so far down into the noise floor that you can't hear it without blowing out your ears with the good sound inside the bubble.

The shape of the pattern for any given frequency should only be effected by the mechanical features of the mic, which won't be changed by outboard electronics.

Hmmm...unless...it might be changed by the impedance of the circuit connected. A better impedance match from a properly made preamp could affect the mic circuitry. It wouldn't have to "try so hard", and would be able to come closer to specs without struggling.

Just a raw cable, even a good one...the impedance is probably a bit ball-park...like 75 ohms +/- a tad. And (I think) it will also vary according to frequency.

Having a good match, and then boosting *that* signal...
 
I'm intrigued by your explanation.

Do you have a seperate pre-amp to compare the difference in the sound and character of a mic... I mean versus just running that same mic straight into the dvx?

If so I'd be curious to hear what you think of the difference if you make the comparison back to back.

Unfortunately there's no way to do this one directly A/B with one mic and a split signal. About the best I can do for a test like that is to use a pair of Oktava mics with one running to ch1 via mic-in and the other running to ch2 through the mixer/pre into ch2.

I don't know if that's scientific enough for some people who read this, but I don't have stock in any company so it's not like I'm trying to sell anyone on this idea... I'm just saying that if you listen to the difference it's really surprising. It's not that it makes the mic sound louder... I have the gain on the pre set so that I get the same number of reds on the DVX lcd... but it honestly sounds like I'm removing part of the room interraction and improving the clarity of the mic at the same time.

I have a few cardioids and hypers... all of which are modular mics... and in the past I didn't notice as much difference in the cardioids versus hypers either... there was always a difference... but now it seems like a completely different pattern... whereas before it sounded like a modification rather then a complete change.

Of course I always get excited when I feel like I discovered something (for myself I mean) and that's why I'd like to hear what everyone thinks... especially if they have a way to directly test this for themselves.
 
gee thanks mattin, i'd already decided a stand alone recorder would be a better investment than a mixer. so now i'll have to cough up another $1200. i hold you personally responsible for this. this is intolerable.
 
Hey I'm getting this same effect with the 671 alone... just running it mic-in.

The moddified 660 from oade is supposed to have much better pre-amps then the stock 671... so you might want to kick that option around also.

I don't know about the other stand-alone recorders... but so far it seems like the audio section of the dvx isn't as good as I thought it was... good? Yes. REALLY good? I don't think so anymore.

Good enough? Probably for many uses... but like I said before... I don't think it's a coincidence that the best audio you hear in any of the zombie flicks went through a mixer or was simply recorded seperately.
 
Hey Matt,
so let's hear the diff! Post them clips, will ya? ;-)
Would be interested in hearing what the MIXPRE can do, as we need a mixer/preamp. We're running an unmodified 660 with pretty crappy preamps, so we need something that can feed it, or a DVX.
 
MattinSTL said:
I'm intrigued by your explanation.

Do you have a seperate pre-amp to compare the difference in the sound and character of a mic... I mean versus just running that same mic straight into the dvx?
Click to expand...

Nope. :( Or should I say Not yet. :)

What you could try, if the preamp will let you, is do a unity gain test. Don't have the preamp boost the signal at all, just pass it through.

That'll tell ya if the effect is due to the preamp's circuits (in which case the effect will probably still be there, since they'll be active even if not amplifying), or just from sending a cleaner boosted signal down the wire (in which case it should sound like it does running straight into the DVX).

Of ocurse, if there's no difference, and it's better either way, it might still be the impedance thing... Trying different cables might show that up. Brands, lengths, condition.
 
:angry: Matt: stop playing with your avatar, and post them clips!

:grin: :grin: :thumbup:
 
Hey while I'm playing with my avatar I'm ALSO trying to figure out how to easily drag and drop files off this damn thing! WinXP said "unknown hardware" and the disc that came with this thing just has bootlegged Eminem songs on it (just kidding)... seriously I can't figure out how to make this damn thing work as simply as my digi-cam.

I have SPDIF in on my comp but the point is DRAG AND DROP convenience!

I'm working on it! I have to leave for work in about 00:30:00... so if I can't figure it out before then you'll have to wait. D'oh!
 
Ouch!
No worries, of course. Many thanks for the efforts, and I'll be looking forward to when you get it uploaded.
 
Okay I pushed it to the last second... now I gotta' get ready to go... I can pop the CF card into my printer (which has a reader) and I got the files on my computer... but they sound like ****. Clearly I'm doing something wrong... there is a random crackly hiss with the dialog... not like I hear when I play it back on the unit itself. I've got an Audigy2 which is supposed to handle 24/96... but that might be the problem... SoundForge and Acid Pro both refused to even SEE the files... it would let me drag them or try to open them but then nothing.

I'll put up a comparison like Tigeba did the last time... but I'll post some small pics to show the setup... and somebody will probably think I'm still fudging up the test somehow... but that's okay. It's not a subtle thing... unless you thought Tigeba's previous test was subtle. Obviously I didn't or I wouldn't have lost my mind shortly thereafter.

Damn I wish my comp room was padded.
 
Tigeba! What are you doing "out"? Man you really shoved a thorn in my paw when you posted those tests!

Hey I also got an FP-24 which is just a MixPre, but the meters are all green instead of red leds from 0db on. Why in the hell they didn't adapt that as well I'll NEVER know... but I'm finding that you only want to light 2 greens anyway and flicker the third... or else you're pushing the input of whatever you're feeding.

Oh yeah, Tigeba... why doesn't anyone mention the UPFRONT sound that pre-amps impart on the mics connected? Remember when I said the mic you used sounded like a different mic on the good setup? Well I'm finding that to be the case with this stuff also... the mic sounds SO MUCH BETTER... it's like Christmas all over again... even the MIC is like new again... When I first got a good mic for the DVX I was fascinated by how my own voice sounded... and that got old pretty quick... but I've only got that feeling two other times... the second was when I heard my voice through a studio tube mic... and then again NOW that I hear the mics I already have through the FP-24. To my ears it honestly sounds as if it's "magically" closing the distance to the mic... a mic that's 2 feet away sounds no more then 23"... okay seriously a mic at 2.5' away sounds 6-12" away. That's pretty cool... booming is gonna' be a lot more fun like this!

EDIT: Please take the above paragraph with a grain of salt... I think the quality improvement is directly related to the pre-amp improvement and that there IS NO MAGIC happening... as I put it. The logical (and certainly correct) explanation is a better match of the pre-amp and mic. Should I delete this thread? I think it still has some redeeming value... but I wouldn't mind deleting it either!
 
My only experience in comparing preamps was critically listening to the difference between the factory ones on a Midas XL200 and the Avalon's and it is night and day. Good preamps add "life" to otherwise "lifeless" sounding mics. I can't put my finger on what it is exactly. I think they capture the subtleties of even ordered harmonics better or something...

Preamps do make a difference, but other than Avalon's or Brent Avirell's I don't think they're worth the trouble, personally. Hope this helps, even though I don't know what I'm talking about...
 
Good preamps really do make a huge difference, as you have noticed :) I would say that the preamp is probably at least 25% of the sound, and possibly more depending on the situation. I think you don't see that much discussion about the sound of various preamps here because this is mostly a board about video production. Roll over to gearslutz.com and you can see more discussion about the lowly preamp than you thought was possible.

The leap from crappy preamp to decent preamp is far bigger than from decent to high-end in terms of end results. Once you get to a certain level, it is more about different flavors of preamp. My experience is mostly recording music, and for that application, it is pretty common to mix it up with lots of different preamps, as it tends to make things easier to mix in the end.
 
tigeba said:
The leap from crappy preamp to decent preamp is far bigger than from decent to high-end in terms of end results.
Click to expand...

True statement that, and one that can be applied to MANY other areas also. Question is, in your definition and by your estimation, are the DVX's preamps "crappy" or "decent"?
:undecided
 
Aaaaahaha!:grin: Yeah Tigeba... are they crappy or decent... c'mon now... and think about it... you don't want to start a war!

Hey vidled... Nobody was more in love with the DVX audio section then me... NOBODY. Just ask someone who thinks the DVX pre-amps are perfect... "How many mics have you bought to try out with your DVX?" I'll be surprised if anyone else on this entire board has bought as many mics as I have! Why would I buy SO many mics? I constantly did these little "showdowns" between similar mics... just so I could tell myself that I got the best mic to capture the perfection of the DVX audio. I did this for YEARS because I was so convinced of the quality of the cam's pre-amps.

Well I won't say the DVX pre-amps are crappy... not by a long shot... but have you heard Tigeba's shoot-out?:huh: I just heard that about a month ago I guess... and now read this thread. For me the difference was stunning. I had no idea there was still that much room for improvement. But the thing that ISN'T apparent in Tigeba's test... and I don't know why... is the anamoly that I'm talking about here. I think Tigeba probably equalized levels and stuff like that... in order to make the test sound fair... but the gist is that the upgraded pre-amp not only makes the mic sound much better... it also works like a tractor beam for the sound you're trying to record. The effect is not subtle... it's not that it simply makes the mic more sensitive... causing you to simply turn it down to equalize levels... it audibly isolates any given mic more then without the pre.

As soon as I get my 671 sorted I'll post some clips with it... but later today (after work) I'll at least put something up that shows a DVX with just a mic and then with the FP24 (mixpre) factored in. Like I said, it's not that you gain a few db of improved SN... it's that you gain a totally new level of control over the room.

As I started this thread... I keep coming back to the fact that this is one of the biggest challenges of good video sound... getting control over the acoustic space... so why on earth that single fact isn't mentioned as part of any pre-amp thread, I'll NEVER know. I feel like I wasted a couple years by not having this information sooner! People would just say that such and such pre-amp sounds good... but I thought the DVX sounded good. Had somebody mentioned this other trait of a seperate pre-amp it wouldn't have taken me so long to get one.

Okay all this considered... I gotta' post the clips later today. Since I also got a good recorder at the same time I need to be sure of the total effect if you just get a pre and run it line in... I already played with this and I remember it still being a major improvement... but I'll post the clips and you can make whatever you want of it.

EDIT: Please forgive me for my early enthusiasm on the pre-amp... this is an easily explained QUALITY difference and perhaps a better match of pre-amp and mic... Please pay attention to my yellow notes!:happy:
 
Many thanks, Matt.
Your audio "endeavors" are much appreciated by many here, I'm sure. They certainly are by me. Heck, we can't ALL go and try all those mics you have! :shocked: :thumbsup: :grin:
Coincidentally I have a NON-modified 660, which means any preamp we get, I will at least try and take through the 660's line in; although to be honest, I was already impressed with its quality as is, but there's always room for improvement of course.
Audio is one of the things that weighs much more on a video production than many think. I put it at right at 50% of the experience. There's a reason why the audio crew is so important on a shoot. And I agree with you 100% that more effort should [often] be made to improve the audio.

Also another side note: I read you were getting a Microtrack? Just read that its 48V phantom power is only 30V. Not an issue with many mics, but it IS with some. FWIW.
 
You must log in or register to reply here.
Back
Top