Dumb Question...What exactly is a pre amp?

G

Gorilla King

Well-known member
I'm trying to learn more about capturing quality audio for my next film and while I'm very familiar with the term preamp, frankly I just don't know what it is or what it does. Could someone elaborate on this for me ? Thanks.
 
Most audio equipment inputs and outputs signals at a standard level called "line level" (actually there are 2 standards, one "professional line level" and one "consumer line level"). Microphones output a signal much weaker than line level. A preamplifier takes a mic level signal and increases it to line level. It also usually has variable gain which allows you to adjust the signal to exactly the level you want, since combinations of different sources and microphones and situations produce different mic signal levels.
 
So the bottom line is it allows you to capture richer audio with less distortion and static noise? Or am I just not getting it?
 
Gorilla King said:
So the bottom line is it allows you to capture richer audio with less distortion and static noise? Or am I just not getting it?
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It allows you to capture "richer audio", but the less distortion and static noise parts are more up to you than the preamp. Some pre's will cut that stuff out and help with filtration, but good mic techniques will help much more. Using the shortest, highest quality XLR cable, keeping your cables in good condition, and mic positioning and/or isolation will help a lot to get rid of those problems.

Mic pre's are indispensible tools, and can add huge production value to your work. They can help you craft a tone and sound that may be difficult to create later in post work.
 
Any recommendation for a 500-1000 dollar pre amp (I don't have any clue what they cost so I'm just throwing out a number). I'm not shooting until Spring 2007, but I'm trying to determine what equipment I'll need so I can get it and start working with it. I'm going to have to train someone to do sound work and so simpler is probably better but at the same time I do want great quality audio.

Oh yeah, my mic is an ME66k if that has any relevance.

Also, would it be best to use a wireless transmitter and record sound into the camera or to buy something like that Marantz 660 (I think that's the number). I just don't want to be wired to my sound guy. I didn't know any better on my my last movie and it really affected my sound quality du to awkward mic angles and proximity to the actors. Fortunatley that was just a film I made with friends a couple years ago, but this one is the real deal.

Oh and I should have mentioned this earlier, but this is an Adventure movie that'll be shot in the mountains of Colorado so I need equipment well suited for long days outdoors and fast paced shooting.
 
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There's a lot of info out there on this kind of equipment, but I'll take a quick stab at it. Usually for location recording, the mic pres are built into your recorder or mixer. In the music biz you can get standalone mic pres, but most likely, thats not what you want.

Sound Devices makes has a great line of equipment. I'd either get their MixPre (2 channel mic pre/mixer - $600) or the 302 (3 channels + other goodies - $1200). They also make a 1 channel mic pre + headphone amp (so you can hear what you are doing) for around $300 - I think. Go to sounddevices.com for more info and check the prices at bhphoto.com

As far as recording to camera or separate recorder. Recording to a separate recorder (double system) will most like result in better sound since the recorder is of better quality than your camera's audio section. This doesn't mean using someone's ipod to record dialogue. Check out the Sound Devices recorders ($$$ but nice), the Tascam flash recorder, and maybe the Marantz or Fostex (haven't heard them). Doing this will create extra work for you since you will have to sync the sound to your video in your editor. This is easier than it sounds, but something to keep in mind. If you do it, make sure you use a slate!

Even if you do double system, I would recommend you still run a mic cable from your recorder to the camera to have a backup. That makes syncing sound a bit easier since you have a reference on camera. It also makes watching dailies easier since there is some sound on tape.

If you find that the cable between camera and sound man is compromising mic position, get longer cables.

As far as wireless to the camera, I would recommend 1 of 2 things:
1) if you don't have an external recorder and are only recording to camera, then use a hardwire connection.
2) if you insist on having a wireless connection to the camera, at least have an external sound recorder running as backup.

If you do either of the two things above, when you get a dropout or noise on your wireless connection, you won't lose your audio. Have some kind of recording device connected to you mixer via hardwire, be it the camera or your external recorder.

I just shot a 30 min short with a Sound Devices 722 and a boom mic, all wired up to the camera. Syncing the raw footage (about 3 hours worth) with the sound from the 722 took about 2 hours. It was the first time I'd done it and it was pretty easy. Sounds great and the 50' of cable connecting me to the camera wasn't a big deal.

If you have the money for a 722 (or a 702t) I would highly recommend it for 1 or 2 mic dramatic work. For 3 or 4 mic dramatic (low budget) work I'd get a Sound Devices 442 mixer and 744t recorder. If you are trying to keep it cheaper than that, get a 302 or a MixPre and go right to camera. I'd also recommend a looking at your mic options; Audio technica makes some great shotguns and picking up an Oktava hyper is worthwhile. Again, check out the really long threads in this section to see what has been said about mics and other important bits.
 
Is the only difference between the 722 nd the 702 that the 702 only records to compact flash?

I'm trying to figure this out here....So the mic would connect into the Mix Pre and then another XLR cable would run from that into the 702? Do I have that right?

Regarding the Mic you mentioned, the Oktava, how does it compare with the Sennheiser ME66k? I'm thinking about using two mic's on certain scenes and first off I was wondering if one was significantly better than the other and if not would they have a similar tonal quality?
 
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First question you have to ask yourself is if you want to record your audio double system or not? If you do go double system, then you will need a small mixer, usually will have a built-in pre, and a sound recorder. I personally like the Marantz stuff, but those are a little higher in price, but great quality.

If you attach the mic to the cam, you will obviously need XLR cable, but remember this, the longer the cable the worse the quality. XLR cable is very sensitive to long lengths, and has more chance picking up distortion, etc... Now, this may not be a huge problem in the mountains since there isn't much radio wave type stuff going on, but still...

http://www.sweetwater.com/store/detail/PMD660/
 
Oh wow, that price on the Marantz is much more reasonable. Granted if the 702 was a huge leap over it I'd be willing to stretch my funds a bit to get it ,but I'll need to do some more reasearch on it all.

I definatley need to have my sound guy be completely independant of me. I may have him go a quarter of a mile away on some shots and I'm sure a quarter mile of XLR cable wouldn't be the best idea.

By the way, what do you mean by double system? Sorry, I'm new to all of this audio stuff.

Also, is there a huge difference between 16-bit and 24 bit recording or is it more or less negligable?
 
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Gorilla King said:
Is the only difference between the 722 nd the 702 that the 702 only records to compact flash?
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yes. The 702t also records timecode, but no hard drive. If you are doing indie projects where you are in control, then no timecode is fine - it just means a little extra time in post.

Gorilla King said:
I'm trying to figure this out here....So the mic would connect into the Mix Pre and then another XLR cable would run from that into the 702? Do I have that right?
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yes. However, the 722/702 has 2 really nice mic pres. 70db of gain and really quiet. It also has better metering than the Mixpre. If you aren't doing professional work (meaning you are getting paid to do a job in a minimum of time), I would think that JUST the 702 or 722 would fit the bill fine. If you are doing professional work, the time saved by the extra features and interface of a location mixer like the 302 might save your butt.

Gorilla King said:
Regarding the Mic you mentioned, the Oktava, how does it compare with the Sennheiser ME66k? I'm thinking about using two mic's on certain scenes and first off I was wondering if one was significantly better than the other and if not would they have a similar tonal quality?
Click to expand...

Read the mic threads that populate this board. Short answer - a hyper is good indoors, a shotgun is good outdoors. You probably want one (or more) of each. I'm "getting by" right now with a hyper and a shotgun, and will probably add another cheaper hyper and shotgun as a backup/2nd mic shortly.

For the kind of low budget indie stuff (1 camera) we are doing, working mostly with a close group of people, one mic hasn't proven to be problem. I don't aspire to do reality TV, so I can get away with not having 8 wireless, 2 booms, a 10 track recorder, and 3 cameras that need wireless feeds.

RE your new questions:
Double system sound is recording audio on a stand alone recorder and video/film on the camera.

The 7 series recorders from Sound Devices are really nice. I'm sure the other recorders mentioned are nice too, but I feel like the 7 series is a step up in build quality. Personally, for the price, the Tascam HD-P2 sounds like a lot of bang for the buck. I can vouch for the mic pres built into the 722. I can't do the same for the other cheaper recorders. If you end up with a $1000 mixer and a $600 recorder, I'd just go with the 722 to begin with.

24bit vs 16 bit: 24bit lets you run your levels more conservatively and still capture higher quality than 16bit. You can run (correct me if I'm wrong) at around -48db on the meter and have equivalent quality as 16 bit. That's a lot of headroom for louder sounds. One thing to keep an eye out for is that some of the analog front ends of the 24 bit recorders don't actually give a noise floor low enough to make recording 24 bit worthwhile. Sure, you can record 24 bit with them, but they are noisy enough that you might as well have done 16bit.

What kind of camera are you recording to? You best bet is probably just to get a nice little mixer (mixpre or 302) and record to the camera.

If you are really a quarter mile away from the actors at times, are you shots going to be framed such that you can actually see their mouths? If not, you can always record ambience and dub in the voices later - it's not like you have to match lip movements...
 
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Gorilla King said:
I definatley need to have my sound guy be completely independant of me. I may have him go a quarter of a mile away on some shots and I'm sure a quarter mile of XLR cable wouldn't be the best idea.
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If your camera is a 1/4 mile from your subject (ie, long vista shot with tiny people walking thru it) you don't need audio for that scene. Record it later :thumbsup: Rule of thumb: if you don't see their lips moving, location dialog can be recorded after take ala "wild lines".

Double system is where you record audio separately while also recording to the camera (double recording).

24 bit is a big difference but when you look at your audio chain, there are plenty of other things to invest money in before moving up from 16 to 24 bit (better mics, better preamps, better wireless, etc. Sell your ME66 and get a better shotgun before investing into a 24bit recorder. The ME66 is junk (IMHO).

Lastly, you want both a hyper and shotgun (indoors/outdoors) mic to get good sound. Do a bit of reading around the forums to get yourself up to speed on these terms. Start with the stickies.
 
Gorilla King said:
I definatley need to have my sound guy be completely independant of me. I may have him go a quarter of a mile away on some shots and I'm sure a quarter mile of XLR cable wouldn't be the best idea.
Click to expand...

2 other quick things: I'd rather trust a quarter mile of mic cable then a wireless at the same distance. Especially if you have mic->short cable->micpre->long quarter mile of cable->recorder. Boosting up your levels before you do a long run of cable is a good thing.

Also, you might be best served by hiring a sound guy who has the equipment.
 
Ahh glad to know the thing about the having the shotgun and the hyper cardioid mics. I'll definatley read those stickies to get up to pace on things. I think I will sell my ME66K on ebay. it looks like I can get around 350 for it which isn't too bad.

With reagrds to the production, no it definatley won't be a "proffesional" production. I'm doing it because I'm passionate about it and I love it. I've been making movies for a decade now ever since I was 13 and I'm just going all out on this one to make something that people hopefully will actually want to watch.

I hope to have a HVX 200 (maybe an A by the time I shoot!). Right now my only camera is an XL1 but it's old and has some dead pixels now. I'm going to sell it on ebay most likely.

I like the idea of having headroom for louder sounds. That was a problem with my last movie. I was just using one of those Beachtek XLR adapters and there were many many instances of the sound just peaking and breaking up.


Good point on the 1/4 mile thing. I wasn't thinking. still though, I would prefer not to have my sound guy tethered to me. If I were on a tripod most of the time that'd be fine but once I hit act two in the script I'll be using far more dynamic camera motion and I don't want to risk any accidents. On my last movie the sound guy was tethered and he started walking away and yanked my camera down onto a hardwood floor while I was talking with the actors.

My next question was going to be asking for mic recommendations but I'm sure it's already on here somewhere so I'll go have a look.
 
Just so you all know, after reading what you all have posted and the sticky I got a little over excited and bought up a silver Oktava. I'm also in the process of getting my ME66k up on ebay so I can buy a MKH 416 instead. Man this is exciting!
 
Are you talking about the Audio Technica mic Tex? I'll have to actually hear some sound samples. Like I said I've been using the ME66k and I've been dissapointed with how flat the sound is. I definatley want that warm sound so whatever can do that well I'd definatley like to check out.

And thanks Yankee! I've been reading through the sticky and there is a TON of great information on there!
 
The AT4073a sounds nothing like the thin ME66. It has much more of a neutral tone, slightly to the warmer bass/mid side of the MKH416. It does not have as tight as a pattern as the 4073a, but it is the best >$1000 shotgun available.

-Jeremy
 
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