Greg J. Winter June 23, 2004
QUESTIONS & ANSWERS
Greg, thanks for the clarification. BTW, are there other alternatives to the MixPre that would work just as well?
Yes, There are a number of portable mixers on the market that will perform well, just about anything will work as long as the output can go to at least +4 dBu. Keep in mind that the more you turn up the gain to increase the sensitivity on your mics the mixer needs to have a low noise floor and large dynamic range. I went with one that I believe is one of the best in the market right now.... the Sound Devices MixPre. It allows for up to 2 mic's and active gain up to 60 dB, phantom power, cut-off filters, limiters, headphone amp & adds no practically no noise to the signal. The reason this mixer is expensive is the engineering required to produce plus and minus 15V power supplies for the analog circuits and plus 48V phantom power for the mics - all from 2, AA batteries. It's very well built but one of the most expensive ($665). Before you fall of your chair there are lots of options besides this one.
In the same league but less expensive is the MM-1 by sound devices if you plan to use just one mic. It is smaller too with similar specs as the MixPre and it costs around $350. Go to http://www.sounddevices.com for more info. Like the MixPre it does generate plus and minus 15V supplies and 48V phantom. I highly recommend this option if you are on a strict budget and only plan to use a single mic all the time. You will have to make a special cable (or have me make it) that splits the XLR output to both RCA input jacks of the modified camera.
Marenius makes a 3 input mono (could tie to both Stereo channels of mod'ed VX2K) ($395 at www.marenius.se) and 3 input stereo PSC DV ProMix 3 ($495 at www.dvaudio.com) reviewed by DV magazine May '04.
If you have AC power and don't need portability you can even use an inexpensive Behringer mixer available at a Guitar Center or music store and cost less than $100. With AC power it is easy to make plus and minus 15V for analog circuits. I would only use this mixer for hotter condenser mics due to noise floor of mixer.
Rolls MX54s ($150 at www.rolls.com) is a 3 input battery operated mixer with decent sound and limited features - see the review at DV magazine Nov. 2003 issure. This mixer uses 2, 9-V batteries to make plus and minus 9V power for the analog circuits. I would again use a hotter mic with this mixer such as the ME66.
Campressor ($399 at www.campressor.com) offers a rather large unit that offers 60 dB of gain, cutt-off filter, phantom, limiters and variable compressor. I am personally not a fan of using a compressor while recording events. There are no transformers between the mics and box. They also don't specify EIN or any noise figure.
Precision Audio Products Inc offers its mixer ($370 at www.preciseaudio.com) and features fine specifications but I do not have customers who have used it or any reviews.
I don't know much about this unit but ART's MicroMix ($65 at www.artproaudio.com) is worth looking at for again a single mic dirt cheap solution. You would have to supply 12V via battery pack for portable power.
Keep in mind you do get what you pay when shopping for a mixer. If you are going to the trouble having the camera modified to lower noise you don't want the mixer to add too much noise.... or use inexpenisve noisy mic either!
How does the modification affect sound recorded in VCR mode of operation?
Keep in mind that my modification is used when the camera power switch is on CAMERA mode only. It will record stereo signal from the left and right RCA cables from the MixPre in this mode. It will also record sound into the RCA cables when the power switch is moved to the VCR mode but the sound is not set at a fixed level - Sony forces us to use the AGC or automatic gain control mode.
You can still use your mics going into MixPre to record sound if you like. Or you can hook up line-level equipment as a sound source but keep in mind the gain is controlled automatically like the camera comes off the shelf. In this mode it does not matter if you keep the dummy plug inserted - I keep mine in all the time since I use the modification and MixPre all the time.
Also, trascoding of video using above input methods for sound and normal video inputs work fine too after the modificaiton. Put the camera in VCR mode and select DV-IN in the camera menu system. Now all video will be present digitally to the Firewire(IEEE1394) such that using Premiere you can capture the footage right to your hard-drive. You can also record this VCR footage direct to tape if you wanted to. Only thing you do not have to do is change the setting in your menu system to DV-IN.
OK, I still have the audio out via firewire, but if I'm playing back, or looking at firewire output using S-video out, will I still be able to monitor audio?
Actually, you only loose output audio on the RCA jacks, but the headphone jack set at 50% level using the volume control on the side of the flip-out screen gives excellent quality audio at -10 dBu level. So it works playing back tape, or firewire output using s-video or composite video out. I chose to use the RCA jacks that are built into the camera so that I would not have to drill any holes in the case or have lead wires jumping off the main board. The RCA jacks have built-in EMI and RFI protection that would be difficult to add to such a tiny, complicated board. I could land some leads to the audio outputs, but I would not recommend it... if you hooked up anything bad to the output leads -you could damage your camera. The way I do it offers the best compromise and protection of the camera electronics. Use the phones jack to monitor your audio.
Will the switches on top of the handle of a PD150 - CH1/CH2, Phantom On/off, line/att/mic will still work correctly in AGC mode? or will they be bypassed as well?
When in AGC or AUTO mode in the camera's TAPE menu, YES the above works just as before. When you switch it MANUAL mode, all signal will come from mixer, so your mics/line level signals will plug into your external mixer (such as the Mixpre). Therefore in this mode, the mics will get Phantom from external mixer so none of the stuff in the handle of the PD150 will be used in MANUAL mode only - with the exception of the Line level switch will need to be set to line-level. (I know it does not make sense, but this switch sends a logic level to the microprocessor to tell it to turn off the noise cancelling software that it uses for mic inputs).
When using the modified PD150 in manual mode, will the Channel1 switch on the handle still work -ie will I be able to record sound on both channels from the single mic input?
No - be sure to understand what the mod does. The mod bypasses all of Sony's inexpensive electronics in the handle and noisy electronic level controls on the mainboard. You will use an external high quality mic preamp to convert mic's low level to high level that gets inputted almost directly into the A/D converter. That is why we see 20 dB improvement in S/N ratio! Jay Rose did some tests that look great. See thread for more info: Jays Tests. So in short - you add a mixer or MM-1 etc. to your rig, lose the stuff in the handle to get DAT quality sound with your DV camera image. By using the menu to set to AGC or AUTO, you can still use everything up in the handle - but you get all the noise back.
My camera came back to me with this dummy plug going into the 1/8" mic jack in the handle of my Vx2000... why do I need this?
Due to poor quality of built-in microphone, Sony attempts to correct noise by signal processing done inside camera. When swich next to jack is set to line and an external mic is plugged into camera, the signal processing is removed. Your modified camera will work without the dummy plug in place, but you will hear a flanging sound with voice that may be barely audiable but it is there. Once you notice it and tune your ears to it, you will wonder why you have not heard it years ago when using the built in microphone! So the only time you need to remove this plug is when you want to use the built in microphone.
How did you mount your MixPre to the bottom of your VX2000?
The only downside to the MixPre is that Sound Devices assumes that we all carry around a sound bag and the only mounting holes are slots in the front tabs that are really for a strap. I like the sound from my mod so much I never go without it so I wanted to marry it to my camera.... it's not an easy process:
First I disassembled my brand new MixPre using Sound Devices instructions (see this link) and then drilled 1/4" hole through entire C-shell case at the location of the VX2000 mounting hole. My MixPre is aligned so that the output panel is flush with the rear of the bottom plate of the camera, and the front faces the LCD panel side of camera. I drilled this hole thru entire case so that you can insert an allen wrench up throught bottom to fix a 1/4-20 button-head socket cap screw that is 1/4 inch long to hold MixPre securely to the camera. Then I drilled and tapped a hole next to the 1/4 hole on the top of C-shell to mount a 6-32 socket cap screw that sticks out the top and fits into the hole next to the 1/4-20 tapped hole in bottom of camera. This prevents turning. I also applied foam tape to give added protection against turning.
Since the bottom of C-shell of MixPre is only 1/8 thick metal I decided to cut a 1/8 thick aluminum plate the same size of the bottom of C-shell. This added thickness for a new 1/4-20 thread for tripod mounting. I drilled and tapped 6 holes in the C-shell case to mount the additional plate and drilled 1/8" clear holes that match the tapped holes. Finally I drilled a #7 bit hole into the 2-piece bottom for a 1/4-20 tap. I determined the location using a round bar under the camera assembly with my wide angle lens and battery installed. I moved round bar in small amounts so that camera is balanced and used this point to establish location of tapped hole. Then I mounted my tripod base to this tapped hole and keep it mounted all the time.
Only thing left to do is to carefully reassemble MixPre. I hope in the near future to offer a machined U-shape plate that holds MixPre without drilling any holes into it. Here is preliminary info on this design found here.
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