Patrick Farrell

5 hours ago, Domingo said:

 

My preamp is quite simple and single ended (unbalanced), so I'd be shorting pins 1 and 3 of the XLR. I'm not so afraid of interference because I keep the cable short, but would a DC-DC converter such as you suggest @Patrick Farrell be quiet enough to feed a very low noise mic? Being an unbalanced system (unfortunately), I wouldn't count on common-mode rejection of the two phases, so the power supply's filters would have to do all the job. That's why I was leaning to a directly powered 12V mike.

I haven't done any measurements but I don't hear any added noise compared to other power supplies, including the Denecke which doesn't use a DC-DC converter. As long as you adequately smooth the output ripple I don't see why it would add any noise. I do know some capacitors are noisier than others so component choice could be important. I think I ended up going with the Nichicon audio line.

9 hours ago, Domingo said:

@Patrick Farrell
Could you please share your suggestion on DC-DC converter (and if possible some implementation schematic)? I did some shy research attempts already, since that would allow me to use a wide range of new mikes in the future. Even though I'm anyways curious about how the 'T' will sound without any conversions directly from batteries.

For quick and easy implementation, I've used prefab boards like this based on the XL6009. They have a built in trimmer to dial in the output voltage you desire, simply connect a multimeter and set to 48V. Then feed that into a typical phantom powering scheme like this:

(I modified that from a shure tech article.) R1 and R2 should be 6.8kΩ. The C5/R6 and C4/R7 combos not only block DC current reaching the output, they also form a high pass filter so choose values based on what you'd like. I think I ended up using something like 100µF and 1kΩ.

For better efficiency and lower input voltage (allowing using AA batteries) I really liked the LT1307B. The datasheet has everything you need to know but this is the schematic I ended up basing my design on:

My notes indicate I used 1MΩ for R1 and 25.5kΩ for R2 to get the typical 1.22V feedback voltage. You can use the LTSpice software to plug in whatever components you choose. I also added two capacitors (I think 1µF and 100µF) in parallel with the output to further smooth the ripple. Different values smooth different frequency ripple. Then of course that will feed into the phantom power scheme above.

Since you already have the phantom powered version and are happy with it's SNR, I'd recommend adding a phantom power section to your homebrew preamp. It's really quite simple, I built one in an altoids tin. I've tested several dc boost converters that can take your existing battery voltage and get it up to 48 if you'd like recommendations.

While I don't own a 788t I think they're great machines worth preserving functionality into the future. Another idea which would make it device agnostic is hosting a web app on something like a raspberry pi zero W. The RPi could do all the serial communication and create an ad hoc network with it's on board wifi while hosting a web server. Then any device the user chooses can connect to the network and pull up a browser to control the 788t.

I've done this very thing with Peter Schneider before. We used DPA gooseneck tabletop mics (I think the 4098) hardwired into a RIO stagebox with dante back to a Yamaha QL5 console. That board gives you 16 Dugan automix channels so just pick 4 minor characters and assign them to a fader you bring into the mix as you follow along the script. I think we recorded everything on a scorpio or a pix970 but anything with enough tracks is fine. Lastly since the actors were so spread out around the tables and there was also a gallery of producers, we set up several reinforcement speakers with a mix-minus for whatever group was in front of each speaker. The Glensound Divine monitors made quick work of that with their dante and POE.

10 hours ago, Mungo said:

It still seems impossible to build a digital IEM system with stereo transmission with zero delay, long running time and within the specification (50mW max, 200kHz bandwith max).

 

I guess the MiPro 909 is the only digital stereo IEM system in the UHF band, released nearly a decade ago, but with a latency of 5.8ms which may be too much for musicians and presenters.

There are also IEMs in the 2,4 and 5,8 GHz band (mostly not aimed at professionals).

Zero delay is indeed impossible but the Lectro Duet system is a digital stereo IEM with 1.6ms latency which is good enough for most situations, although my experience with the system hasn't been stellar for other reasons.

As a utility I use this chair. https://www.amazon.com/gp/product/B00339C3PK/

Folds really flat and is easy to tuck away on the follow cart while being easier on the family jewels. But it sits pretty low which depends on how small your cart is.

I mostly see people using the aluminum, "low" version of director's chairs but another option I've seen is something like this. https://www.amazon.com/dp/B0C2KKT2YB/?th=1

20 hours ago, Patrick Tresch said:

But your video assist recieve a wireless signal or is it hard wired to the camera? 

If there is DIT then the video assist is hardwired to them. If no DIT then video assist will have the teradek receivers.

5 hours ago, Philip Perkins said:

Once the local videoists went to QTake all video became wireless.  Teradek on cams, wireless to monitors.  We don't hook them up for sound anymore, they take the wireless hop audio from the camera Teradeks.

 

Not true. On every union show I work, the sound cart is hardwired to video assist to receive SDI and send audio. Very rare for sound to have wireless video in NYC. The latency tends to be too much on Qtake to mix accurately.

If you have some of the sony np-f style batteries for your 633 you could also use them with this adapter https://www.gothamsound.com/product/dv-sqnr-power-adaptor

Dante uses PTP for sync which is more accurate than the traditional 48kHz word clock.

I'm level 3 certified and have found any time I have an issue with dante it's because of a networking error which in practice means either it all works or it doesn't. Once you understand how to build a proper network, it is absolutely rock solid and dependable.

Use the input attenuation on the UTX-B40 to adjust the mic's sensitivity to be relatively similar for each channel. 

47 minutes ago, chrismedr said:

the better way would be to just test the system and see if we can adjust the signal level without loosing quality.

This. Rather than a thought experiment, how about a listening experiment? Borrow a couple systems that are as you describe and see how they sound. I personally find they sound better than some systems which utilize adjustable preamps in the transmitter.

A couple of thoughts:

From my recollection, removing the XLR section shouldn't be necessary to get to the board. I guess that could be revision specific though.

Replacing a 10 ohm resistor with a tighter tolerance 10 ohm resistor will not have an audible difference in any schematic.

2 hours ago, B_Van_Deusen said:

I came across this before, its technically labeled as "splitter" rather than "injector." It could theoretically work both ways but i'm unsure thats the case, can you speak to it being able to do the reverse of the intended function properly?

That particular one has a network filter IC in it which could possibly get fried if you inject voltage into it. There are fully passive versions that work both ways but that still wouldn't help in your case because the device on the other end is expecting spec PoE power but would only receive the voltage of your battery. The injector you posted up above would work because it has a DC-DC converter built in to provide the proper voltage but you're limited to connecting just one device. If you want the flexibility of a switch in your bag, Gotham has this one that can be powered from your BDS. Sadly it's not gigabit but should be plenty fast for a few channels like the AVIO devices and similar.

Boom poles are generally a personal preference. For me, I was able to work with several mixers and try out a variety of poles in the field before deciding to buy an Ambient for myself. If you're getting boom op gigs, the mixers likely have a selection of poles for you to use until you find your preference you want to invest in. Heck, I even know boom ops that have gone a whole career without buying a pole and only use mixer's poles.

Very interesting topic. I think Realtek used to publish a driver for macOS, though not sure it's compatible with the latest versions. Have you investigated using a non-default driver? Also interested how the D-Link adapter performs. It was a sad day when Apple stopped including an ethernet port on their laptops.

15 hours ago, Philip Perkins said:

Not only no TC but most all of them have internal clocks much inferior to what we're used to, so they need to get WC from an external source, preferably one that is also making the TC for the whole system (and camera boxes).  Most low budg digital mixers (incl. this one) do not have external WC inputs, which makes them kind of useless for movie sound no matter how great the rest of it is. 

In our business, you'd most likely be feeding your recorder over dante. Set your recorder as the master clock on the dante network and clock the board from that. Works great for this type of scenario.

It is DC powered (although 24V) which is a step in the right direction. If it had some dedicated knobs for gain it just might find its home on a cart. Although these days I think most people want more than 8 faders.

Does the device you have measure the conducted power at the output or the radiated power? If radiated, this site https://www.antenna-theory.com/definitions/eirp.php has a formula to work from as well as lots of other useful information. But be careful because distance greatly affects the measurement and won't accurately reflect the conducted power (i.e. 50mW, etc). The FCC has a document that provides even more guidance. https://apps.fcc.gov/eas/comments/GetPublishedDocument.html?id=204&tn=255011

I think he's asking what the thread size is for the interface of the shell and boot. Google didn't yield any results for me. Large hardware stores usually have thread gauges so you could take a connector in and measure it. Or you could always call Neutrik.

2 hours ago, Allen Cavedo said:

Good info except for one thing, I use standard stereo wired headphones from JVC and Sony all the time with my Comtek receivers and they work just fine. Sometimes clients use their own HP or a Apple EarPods and they all work providing mono sound in both ears. 

It works, only the left and right ears are reversed polarity. If I listen on a comtek it drives me nuts but most producer types don't notice.

1 hour ago, Allen Cavedo said:

Any idea why the Comtek RX has phase reversed outputs?

It creates a pseudo-balanced output so that you can use an off the shelf cable wired pin to pin and feed a balanced input.

On 4/23/2023 at 2:33 PM, TimMey said:

Because it can handle 12V and it's better runtime, so why not.

But I realized, that the hiss is a little bit less on 48V, so 48V it is (though I don't understand why that's a difference).

I also changed Tx-Power down to 25mW and put on the expander to get some results I can live with...

But there must be a better solution.

I've had good success with the sound devices a-filter. Haven't used it with zaxcom but works great with other digital transmitters.

52 minutes ago, Jeff Wexler said:

Agreed. I would never want to put that amount of gack on the mic end of the fish pole. My boom operator would never do that.

It's a far cry better than the Denecke power supply and UM400 days. Still beats having a cable run around or through your pole.