Good Sound requires Good preamp?

R

rtmst3k

Member
Hi All,

I was speaking to a sound equipment dealer today and we were discussing the weak points in sound processing. I indicated that I had recently purchased a boom and the new Audio-Technica 4053b hypercardioid that would be used for indoor location sound. I was initially planning on using the boom mic wired (via XLR) directly to my Panasonic HMC-150 XLR inputs.

I tested the combination of 4053b and HMC-150 and it sounded really good, especially in the low end. The sound guy at the dealer told me the AT mic was definitely a professional quality mic but that the "preamp stage" of the HMC 150 probably isnt doing justice to the microphone. He suggested I come by the store and hear the difference between the AT4053b wired directly to the camera, and the 4053b wired into a SoundDevices 744t. for which he said the difference was like "night and day, and was mainly due to the preamp stage of the SoundDevices. He said their 702t would sound just as good as the 744t, but only records 2 channels.

Does anyone have any comparisons or sample video shot with good microphones wired directly to the camera vs. wired to something like a SoundDevices 702t? Can anyone verify that the sound directly to the camera is crap when compared to sound through a 7xx product. I noticed that SoundDevices also sells "just a preamp" for a lot less money which, if the preamp stage does matter, might be a less expensive way to achieve a professional sound.

Thanks!
Randy
 
The preamp is pretty critical, although how critical can sometimes be subjective...assuming, of course, that one is comparing preamps that are all good ones. Bad preamps add noise, distortion, and all manner of Bad Things. Jay Rose talks about this extensively in his book "Producing Great Sound for Film and Video," getting into the tech of why this is the case.

Sound Devices is one of the gold standards for location sound recording. They are truly phenomenal, for their price. For my ears, the qualities of pricier preamps aren't enough to make me want to spend more money.

As far as the camera preamps go, it depends on the camera. But think for a moment about the cost of an SD preamp and the cost of the camera, and that may tell you something. A great trick is still running the sound into the camera, but preamping it EXTERNALLY, and going into the camera as Line level, not mic level. This is how one gets better audio without recording double-system, which means you can just buy something simple (like the MM-1) or something more flexible (like the 302).

Personally, my rig is a Canon 7D, a Sound Devices 702, and a locker o' mics. I kind of have to record double system because the 7D sucks SO bad, worse than your HMC150 I'd wager. I also love the idea of being able to oversample the audio for more leeway and less aliasing as a result of potentially heavy processing. Much gear will come and go, but until I've got a burning need for timecode someday, that 702 is one of the gems of my gear closet - it's one of those rare high-cost, high-value purchases. Anything SD makes is solid and relied upon by pro's worldwide to great success.

Sound Devices isn't the only option, of course. Your ears and your wallet will lead you to the right solution.

I have no such tests to share, but I'd suggest maybe renting some SD kit or taking your camera to the store and asking for help making the test yourself. It'll be a great learning experience!
 
I have an HVX200, and I believe the HMC has comparable preamps. These are considered to be about as good as (prosumer) in camera preamps get. Good enough that using an SD mixer will improve the noise floor, but to my ears, not much else. I have a mix pre and have been plugging in directly a lot due to the minimal difference. This is especially true with high gain mics such as the AT 4073A. The in camera preamp can be turned to such a low level with this mic that it generates little noise.
 
Yes, regarding the reputation of Sound Devices, I've heard sound guys tell me that you can pay more money for a preamp than a Sound Devices (SD), but it won't sound any better.

I think the idea of going in at line-level than mic-level, I hadn't thought of that, but that may be what these guys at the audio store were suggesting by telling me that SD makes a "preamp-only" product. I'm not sure if my HMC-150 will accept line-in or not, I will have to check the manual. It's only got standard XLR inputs (2).

What alarmed me during the discussion is when I was told the difference between the camera preamp and an SD preamp was "night and day", really dramatic. Which really worried me about getting professional quality sound by just running the mic into the camera. I know I don't want any circuit hum or RF noise or any other kind of "noise" in the audio, and if my camera can guarantee that, maybe the camera will be enough - but if I'm just *ignorant* as to how good the sound COULD be, maybe I should invest in yet more hardware.

Thanks for the replies/comments,
Randy
 
Yep, the HMC-150 has a selectable line/mic level capability - I think I like the possibility of maybe lowering the noise level using an external preamp (like the SD), which according to the dealer is the same preamp circuitry used by the 702, 744, and 788.

But I should probably go into their store and do some listening tests to see if it's really that much better than going directly to the camera.

Randy
 
Good sound requires a location mixer with good pre-amps, and not wiring it into the CAM's XLR. And recording it at higher than 48khz/16bit into something with really good DSPs. Also throwing away anything wireless (as it re-samples and digitizes the sound before it gets to where its recorded, wired is the way to go).

But mostly good sound can be achieved by good Mic placement, even if a $200 boom is wired direct into an HVX and a little of good dialog-edit post production mixing in protools.
 
I'm afraid the dealer salesman was trying to make some money and not necessarily giving you "sound" advice (maybe I intended the pun and maybe I didn't)

The quality of the mic preamp is 2-nd order AT BEST compared to choice of microphone(s) appropriate for the shot, and getting the mics in the optimal place for best performance.

Even more important is the fact that most video cameras (probably ALL of them) do NOT have separate line-level inputs. All line-level audio goes through a pad and then right into the same mic preamp as if you were using a mic directly. For this reason alone, I would take any advice from that salesman with a large quantity of skepticism.

If there really is some significant deficiency in the camera mic preamp, then you will hear it regardless of whether you are feeding mic level or line level. In fact by using an external mic preamp you will be ADDING noise and distortion because there is no preamp at any price that sounds as good as a straight wire.
 
Richard Crowley said:
I'm afraid the dealer salesman was trying to make some money and not necessarily giving you "sound" advice (maybe I intended the pun and maybe I didn't)

The quality of the mic preamp is 2-nd order AT BEST compared to choice of microphone(s) appropriate for the shot, and getting the mics in the optimal place for best performance.

Even more important is the fact that most video cameras (probably ALL of them) do NOT have separate line-level inputs. All line-level audio goes through a pad and then right into the same mic preamp as if you were using a mic directly. For this reason alone, I would take any advice from that salesman with a large quantity of skepticism.

If there really is some significant deficiency in the camera mic preamp, then you will hear it regardless of whether you are feeding mic level or line level. In fact by using an external mic preamp you will be ADDING noise and distortion because there is no preamp at any price that sounds as good as a straight wire.
Click to expand...

While on paper this sounds good (yes no amp = no noise), a straight mic level wire to a cam, compared to a good location mixer with pre (phantom +48) and there-after a balanced +4dbV send to a dedicated recording device and possibly a camera as a secondary (and for playback) - is what most people use now and days on location.

I would sit all day with the HVX if I had to try and get the dialog to measure V/u meters between -6dbV and -12dbV with the in camera built-in potentiometers and have that read out on its tiny LCD screen, while also focusing on framing, pulling focus and landing the fluid head on its mark, but why would one do that, if the end product is a film/video etc..

Also its basically a choice, use the built-in pre-amps in the camera to the cameras DSP or use a dedicated preamp to the cameras DSP (or hopefuly an external device).
Sending MIC level signal over a great distance, or sending line level signal over a great distance to the camera over the same gauge wire.

Your statement would hold 100% true in the RF world of radio and antenna transmission, where adding no gain is a benefit, just like in video image acquisition.
 
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DJDecay said:
...
Also its basically a choice, use the built-in pre-amps in the camera to the cameras DSP or use a dedicated preamp to the cameras DSP .
Click to expand...

Yes, I would agree IF (and that is a very big IF) you could bypass the camcorder mic preamp and go directly into the ADC. But that is NOT an option here unless you expect users to do sophisticated customization of the audio circuits in their camcorders. I think you'll agree that is unlikely in the extreme.

No question that an external mixer gives much better monitoring and control of levels,etc. But it also assumes a minimum 2-person sound crew (boom and mixer). And that also seems rather unlikely for the majority of people reading this forum.
 
Richard Crowley said:
Yes, I would agree IF (and that is a very big IF) you could bypass the camcorder mic preamp and go directly into the ADC. But that is NOT an option here unless you expect users to do sophisticated customization of the audio circuits in their camcorders. I think you'll agree that is unlikely in the extreme.

No question that an external mixer gives much better monitoring and control of levels,etc. But it also assumes a minimum 2-person sound crew (boom and mixer). And that also seems rather unlikely for the majority of people reading this forum.
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No argument here. Though I would take camcorders preamp running at minimum gain and a good preamp before it, vs. just the camcorders low-end pre amps running at high gain any day. Also there are some compressor and leveling circuits right before the ADC, that magically turn off in LINE mode.

But a minimum 2 person crew is how I typically roll, someone does need to hold the boom pole (no I'm not lugging a mast around with me) :-). My sound goes to the CAM and to another recorder running at 24bit/96khz.
 
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Richard Crowley said:
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No question that an external mixer gives much better monitoring and control of levels,etc. But it also assumes a minimum 2-person sound crew (boom and mixer). And that also seems rather unlikely for the majority of people reading this forum.
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Boom and mixer can be combined into one person, ENG sound guys swinging a boom while wearing a mixer and a couple or four radios on their person are not uncommon, though they are busier than a one-armed paper-hanger on the shoot. But trying to combine boom, mixer, and camera into one person, maybe replacing the boomer with a mic stand, like many forum posters seem to want to do, is well nigh impossible if you want any of it to come off properly.

The amazing thing about a one-man band is not the beauty and artistry of the music he makes.
 
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If Only

If Only

DJDecay said:
No argument here. Though I would take camcorders preamp running at minimum gain and a good preamp before it, vs. just the camcorders low-end pre amps running at high gain any day. Also there are some compressor and leveling circuits right before the ADC, that magically turn off in LINE mode.

But a minimum 2 person crew is how I typically roll, someone does need to hold the boom pole (no I'm not lugging a mast around with me) :-). My sound goes to the CAM and to another recorder running at 24bit/96khz.
Click to expand...

I wish that they actually reduced the gain of the mic preamp circuit. But from all the camcorder schematics I've studied, they take the simple approach of throwing an H-pad in front of the preamp, so you haven't really gained anything (pun not necessarily intended.)

I can see 24-bit to allow more headroom for unexpected peaks. When I do multi-channel audio recording, I use 24-bit for that reason. But why 96K sampling? That is 4x the Nyquist rate for anything you can record out in the Real World. Unless you are making videos for dogs? :happy:
 
I can vouch for the huge difference in using a Sound Devices mixer or recorder with a high end mic. It is a WORLD of difference. I have a sanken cs3e. it's a $1500 condenser mic.
The sound of it going into a sound devices 702t or even the little mixpre is a about one billion and a half times better than going directly into the dvx100 or hvx200. Record to an extenal device and stay wired, not wireless.
 
Richard Crowley said:
I wish that they actually reduced the gain of the mic preamp circuit. But from all the camcorder schematics I've studied, they take the simple approach of throwing an H-pad in front of the preamp, so you haven't really gained anything (pun not necessarily intended.)

I can see 24-bit to allow more headroom for unexpected peaks. When I do multi-channel audio recording, I use 24-bit for that reason. But why 96K sampling? That is 4x the Nyquist rate for anything you can record out in the Real World. Unless you are making videos for dogs? :happy:
Click to expand...

At 96khz I can paint out certain waveforms during dialogue track edit, with much higher precision than at 48. Its sort of like retouching a photo and then scaling it down for the web. Noise reduction algorithms work better against a more defined noise pattern at 96khz vs. 48khz. More samples, more zero crossings, more fluid dialogue edit.

The 24 bit part is not for headroom, the bits go backwards into the virtual noise-floor. @ 16bits anything below -48dbv is less defined than at 24. (32 unfortunately is not structured that way and uses floats instead of ints to store samples).

Now the interesting part is why would you not record at the highest sample and bit-rate possible on location?

If the difference is only in the amount of cheap $20 SD/Compact flash cards you use? It can always be down-sampled/dithered after.

P.S. I have the Panasonic HVX200 Circuit layout, I'll take a look to see what they do with the XLR plugs. I know the pots are directly wired via a 16pin cable outside of the ribbon cable business, so they're not "virtual".
 
Blackout said:
I can vouch for the huge difference in using a Sound Devices mixer or recorder with a high end mic. It is a WORLD of difference. I have a sanken cs3e. it's a $1500 condenser mic.
The sound of it going into a sound devices 702t or even the little mixpre is a about one billion and a half times better than going directly into the dvx100 or hvx200. Record to an extenal device and stay wired, not wireless.
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I could not agree more. This is the way everyone does it, it sounds good, editors, dialog-editors and mixers are happy, audience happy etc... easy to use on the set, etc.. etc.. etc.. :-)

But I think this thread has become a theoretical one, instead of a practical one.
 
What I am wondering is if there is any point to spend big money on a recorder. For about $900 I can get EITHER the tascam hd-p2 or I can gte a sound devices mixpre and a zoom h4n and run the mixpre line outs right into the zoom as to bypass it's preamp. At least I think I can do this. I haven't played with the zoom.
 
Blackout said:
What I am wondering is if there is any point to spend big money on a recorder. For about $900 I can get EITHER the tascam hd-p2 or I can gte a sound devices mixpre and a zoom h4n and run the mixpre line outs right into the zoom as to bypass it's preamp. At least I think I can do this. I haven't played with the zoom.
Click to expand...

I checked out the specs on the HD-P2 and its competitor Edirol R4 Pro, it looks like the only bonus out of the two is that HD-P2 is solid state vs Edirol R4 Pro (though there is some 8GB compact flash limit) the latter has a built in HD. I don't like HD's personaly due to noise and physical/mechanical damage risk. (The higher priced recorders both Sync with TC, meanwhile the Editrol can act as a master TC, and the P2 prob cannot, it looks like it only has TC/Genlock in not out. - though has its own TC)

Zoom H4 worked well for me, I checked out the H4-N but it looks as if all the inputs are MIC level only on that model. Writes to SD cards. Easy to dump, does not honor Broadcast Wave TC format (i may be wrong on that one), and the new version though easier to operate and more visible might have that MIC level input thing.
 
camera input

camera input

This has been a great discussion...I guess I have one clarification to make.

If I set my HMC-150 to "mic-level" inputs for the XLRs, then I am going to be using the camera's preamps, correct?

If I set my HMC-150 to "line-level" inputs for the XLR, then I will bypass the pre-amps?

Which one is correct or is either correct?

If I have an external sound-devices mixer, and then out of the mixer into the camera XLRs, I want to try to avoid the camera's pre-amps,which will raise the noise floor again, negating the value of the sound devices mixer.

Thanks!!
Randy
 
No benefit for single-system sound.

No benefit for single-system sound.

rtmst3k said:
This has been a great discussion...I guess I have one clarification to make.

If I set my HMC-150 to "mic-level" inputs for the XLRs, then I am going to be using the camera's preamps, correct?

If I set my HMC-150 to "line-level" inputs for the XLR, then I will bypass the pre-amps?

Which one is correct or is either correct?

If I have an external sound-devices mixer, and then out of the mixer into the camera XLRs, I want to try to avoid the camera's pre-amps,which will raise the noise floor again, negating the value of the sound devices mixer.

Thanks!!
Randy
Click to expand...

Yes, if you have the input set for "mic-level" you are using the camera's preamps.

No, if you have the input set for "line-level" you are not bypassing the camera's preamps.

I have not examined the schematic for the AG-HMC-150, so I am only 98% confident of the accuracy of my statement. But I have yet to see a video camcorder at any price that has real line-level inputs. They are all mic inputs with a switchable pad.

I still see no added value in using a premium external mic preamp if you are then routing the audio through the mic preamp of the camcorder. If someone has a cogent explanation of how it would be beneficial please post it here. Certainly there are second-order benefits such as control, metering, monitoring, etc. but there is no primary benefit to the signal path performance because the deficiencies of the camcorder mic preamp cancel whatever benefits one derives from using a premium external preamp.

Now if we are talking about using a premium mic preamp and feeding a double-system audio-optimized recorder, that is a completely different situation. In that case you ARE bypassing the camcorder mic preamps (and the rest of the camcorder audio section as well.)
 
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