Replacing built-in mics

[vidled]

Great!

My main question is of course how bad the noise floor is with the DVX gain at minimum and a good preamp doing the work... and of course what's going on with the two mics per channel. I'm trying to imagine what kind of matrix would do anything useful with that placement...

Anyway, we'll be waiting! Thanks!

DVX...wassat? Hehe!
The 4 mics:
I know, it certainly is not what I was expecting to find.

 

[vidled]

My main question is of course how bad the noise floor is with the DVX gain at minimum and a good preamp doing the work...

Darn you, ullanta!
After reading that I had to test it, and the difference is HUGE!
Tested a HVX gain first with a 2 o'clock setting, then taking it back to 10 o'clcok and adjusting the tube pre-amp acordingly.

At the HVX 10 o'clock setting there was CONSIDERABLY less noise!

 

[Spartacus]

Hey Vidled,
this seems promising, keep up the good work, pal!

 

[vidled]

Here's a sound clip using one Oktava mic in one of the 4 built-in mic circuits mixed to both channels in post; showing the difference between a high-gain on the HVX (approx. 3 o'clock) and low setting on the tube pre-amp, vs. a low setting on the HVX (approx. 10 o'clock) and a higher gain on the output of the tube pre-amp.

Clip - 350kb MP3


Note: the int. mic circuit would be recording at 12 o'clock (center) when also using external, XLR connected mics and recording using the four channels. This means there simply WILL be more noise on the int. circuit than on the ext. XLRs; the XLRs are simply much cleaner.

 

[ullanta]

Hey, just for clarification:

Are the mics the same, with some later processing EQing them differently, or are the mics tailored to different frequencies?

And, is there any chance the mics have different pickup patterns?

Just in case you're bored...

 

[vidled]

Are the mics the same, with some later processing EQing them differently, or are the mics tailored to different frequencies?

And, is there any chance the mics have different pickup patterns?

Just in case you're bored...

Bored? Nah, not with YOU around! :beer:

Yes, all four mics appear to be the exact same. And as far as I can tell their pick-up pattern is identical also (although that's not really "tested").

It seems that the two mics (per channel) are simply going through different EQ; i.e. that one is going through a low-pass filter, and the other through a high-pass filter, and then both are mixed together ~50/50.

Again, this is only after rudementary testing.

The end effect is that the int. mic circuits with external mics and a pre-amp can be made sounding A LOT better than what is currently achieved with the int. mics.

 

[vidled]

Okay, just tested one of the 4 internal mic circuits with a DYNAMIC MIC (Samson R11). Used that one as it's inexpensive. Workes well when going through a pre-amp.

Next test is using FOUR R11, each going through a separate pre-amp, and into the internal mic circuits. I will then upload a sound bite of that. I am hoping that will sound usable, even though it'll be R11s. Anything to take the mic away from the cam should help.
So far it still looks like the whole internal mic circuit is quite noisy, compared to the external mic one, but removing the internal mics and be able to put them elsewhere and record ambient, or other stuff is going to be worth it.

A pic:

 

[soren k jensen]

Any idea on the processing?

Any idea on the processing?

Does anyone have a clue as to what kind of processing might be done in the preamp? My techie will do a hack to enable two wireless receivers to feed into the hvx, instead of the built-in ones, and he's worried that four mics indicates some processing going on, that is going to be detrimental to a clean signal. I saw the idea of a split of frequencies, but has anyone got solid info on that?
thanks, soren

 

[vidled]

Does anyone have a clue as to what kind of processing might be done in the preamp? My techie will do a hack to enable two wireless receivers to feed into the hvx, instead of the built-in ones, and he's worried that four mics indicates some processing going on, that is going to be detrimental to a clean signal. I saw the idea of a split of frequencies, but has anyone got solid info on that?
thanks, soren

These preamps for the internal mics definitely aren't top-of-the-line. And why should they be? It's "only" for relatively poor quality internal mics anyway. So, not sure if this hack will ever be suitable for anything critical, such as dialog.
I suspect that 4 mics will yield better results though, as yes, there's some processing going on from what I can tell.
We'll be using it, hopefully, with 4 external hyper cardioid or cardioid mics for use as incidental and background audio. Final testing should be done soon...

And more specifically to your question regarding "solid info": I doubt if Panasonic would be ever willing to reveal what they did with this internal audio path. It's not meant to be tampered with, so it is what it is. They might give tech specs of the mics, but I don't expect they'd offer anything more than that. And it's not really in their interest to reveal this info anyway.

If you're willing to dig this deep into the HVX, you will probably have to do your own homework!

Let us know how you get on though. I'd be very interested.

 

[vidled]

A quick update: this now works perfectly!

We have successfully removed the [4] internal mics, and can now feed our HVX200 with 6 EXTERNAL mics. 4 going to the replaced internal mics, and 2 using the normal external XLR inputs.
A test using only the internal circuitry with a short shotgun stereo mic and two cardioid condenser mics worked amazingly well. It's much cleaner sounding than I originally thought it would be.

Here's a quick'n'dirty test using ONLY the INTERNAL MIC circuitry with an AT835ST stereo mic, and two Studio Projects C4 mics. The set-up also involves a [cheap] 4 channel pre-amp.
(9.2MB): http://pig.us/cars_test.mov
(I can't compare this to the factory internal mics anymore, but I bet it wouldn't sound as clean).

 

[doccutter]

How does it sound with just 2 additional mics? I'm thinking about say 3 lavs and a shotgun, 2 thru xlr, 2 thru your contraption? Does the internal audio circuitry make for a funky mess?

 

[soren k jensen]

4>2 or 2>2?

4>2 or 2>2?

Hi Vidled,

We haven't been able to free the HVX for audio hack testing yet, as we are filming intensely. What is the benefit of feeding 4 mics instead of two, to the internal feed?

SAme question as Doccutter, really. And we want to do the same: 3 wireless lavs and one 416 on cam.
I have guessed that there is some different processing between the two mics that make up one channel. Frequency split, maybe? -Have you noticed any difference between the sound of the two sources going to one channel?

thanks again for the good work, soren

 

[vidled]

Soren, Doccutter,
yes, using only two mics into the internal circuitry doesn't sound as good as using four mics. No doubt about that.
As I mentioned before, there's some different EQ setting between two sets of the built-in mics, which then get blended together.
We actually like using the 4 mics, and it sounds pretty darn decent, so I'm not sure how much time I want to invest into finding out what the exact differences are; but I may be able to do a test recording of using two identical mics on the one EQ circuit and another recording on the other EQ setting, for comparison.

Oh, and just so everyone is clear, I'll mention this again:
We ended up buying a GREYMARKET HVX knowing that we'd probably end up modifying it so much, that we'd void any warranty anyway. Opening, and removing the built in mics, IS NOT FOR THE FAINT HEARTED, and will void your warranty! Many things could go wrong, including damage to your HVX.

 

[Spartacus]

So the big question is:
will Vidled offer an adapter kit and modding tutorial? ;o)

(PS and OT: wasn´t there talk about a new Vidled model soon...?)

 

[vidled]

So the big question is:
will Vidled offer an adapter kit and modding tutorial? ;o)

(PS and OT: wasn´t there talk about a new Vidled model soon...?)

Hahaha....to both!
I don't think there will be a modding tutorial (from me), it's just way too finicky. Just to get to the internal mics, you have to take off the handle completely; and them wires for the internal mics are awfully short and have to be made longer, etc.

Re: new VIDLED:
we haven't even looked at manufacturing/cost/timeframe yet. The prototype works well, but there's no schedule for its release right now....maybe mid-next year? Not sure.

 

[Spartacus]

Well,
just keep up the good work than ;-) !

 

[ullanta]

yes, using only two mics into the internal circuitry doesn't sound as good as using four mics. No doubt about that.

Greetings!

Just to be clear - are you talking about:

a) two mics, each "split" into two of the four internal mic connections; or

b) two mics, each feeding ONE of the internal mic connections (if so, what have you done with the other two internal mic connections)?

Could the sound-quality difference be as simple as a signal-strength issue of 1 vs. 2 mics?

Thanks!
-Barry

 

[vidled]

Greetings!

Just to be clear - are you talking about:

a) two mics, each "split" into two of the four internal mic connections; or

b) two mics, each feeding ONE of the internal mic connections (if so, what have you done with the other two internal mic connections)?

Could the sound-quality difference be as simple as a signal-strength issue of 1 vs. 2 mics?

Thanks!
-Barry

I have 4 connections, each one replacing one of the four internal mics. So my statement where I said using only two mics going to the four internal channels was based upon a rudementary test by simply plugging only two mics in, not four. So it would be b) in your options above. The other two mic connections were left un-fed.
The difference isn't only signal-strength though, there is definite EQ difference. The real test could only really be made though, if four identical mics were used, and I don't have 4 good mics.

 

[ullanta]

Any chance you'd be able to try "a"?

That should be equivalent to using two perfdectly-matched mics on each input...

 

[ullanta]

Also, just out of curiosity about the 4-mic mystery:

Are you certain of how the mics are combined? That is, are you certain which mics feed which channels?