Jump to content


  • Posts

  • Joined

  • Last visited

  • Days Won


Everything posted by borjam

  1. In a system like the BP-TRX, the receiver is actually a transceiver because it's sending feedback information to the transmitter. It must be a problem in the analog domain. These units transmit digital audio, which means that RF interference would cause drops. Maybe RF interference to the microphone, as you say, is causing this. I would try to coil the microphone cable around a small ferrite bead, a couple of turns or so. If that works it would mean you found where the problem is. It doesn't need to be 2.4 GHz. The interfering signal affecting the microphone could be in a different band. Speaking of the 2.4 GHz band, and this is a long shot, look for alarm movement sensors. Some older ones transmit a strong signal on the 2.4 band, although more modern units work at 10 GHz.
  2. The main problem with Dante clock sync is, I am pretty sure, the appalling state of the computer industry and, hence, most of the networking products. You can't imagine how much disregard there is for standards, let alone bugs implementing complicated specifications for seldom used protocols. That protocol is based on multicast, which performance can vary widely. Internet time synchronization (the NTP protocol) uses statistics to achieve sub millisecond accuracy. In proper implementations it does it without "jumps", by carefully adjusting the clock frequency so that time is a monotonic funtion (I mean, each and every second exists, it won't adjust a clock sledgehammer style changing the second number). Still, hardware accuracy matters. If you don't have a good TCXO NTP will not make miracles although sometimes it really looks like magic. These techniques can be also used with a GPS clock reference which benefits from the accuracy of the GPS satellite clock. Maybe labelling each and every sample is overkill and it's better to focus on avoiding clock drift in the first place anyway. If you have an accurate label for the first sample in a video frame and clock drift it really small, well, we can say you nailed it. For a nice application of wide area clock synchronization for non audio purposes you can have a look at a nice website called Blitzortung. And this is dealing with radio waves travelling at the speed of light rather than sound. In a very succint way, sensors receive and timestamp the radio signals originated by thunderstorms and send the timestamped information to a central server where the positions of the discharges are computed. Especially the real time map is spectacular. https://map.blitzortung.org/#1/17.6/8 And, by the way, this website can be incredibly useful for outdoors shots, etc.
  3. Then I doubt my explanation is the good one. Maybe the signal received by the Micplexer was too strong and it was overloading? That would be the simple explanation. "My" theory would apply in a case in which the first element was amplifying a strong signal that would be rejected by the second filter. The impedance mismatch between the input of the second filter and the output of the first amplifier might cause overload on the amplifier, which would cause distortion. But, was there a strong signal within that 5 or 10 MHz difference between the two filters? Not intended as a interrogation or course!
  4. I see. Anyway unless the active antenna is passing a strong interfering signal to the Mixplexer filter there should be no problem. Is that the case? Is the Mixplexer filter narrower than the filter at the active antenna?
  5. Where did you place the attenuator? Between the amplifier output and the filter input? An attenuator should definitely help to prevent distortion at the amplifier output because it will help correct the impedance presented to it.
  6. Also, bear in mind that most RF filters are reflective, just “bouncing back” the energy present at the frequencies they reject. Their impedance on those frequencies is different than the design impedance, say, typically 50 or 75 ohms. If you set up a filter connected to the output of an active RF component such as an amplifier you can cause distortion in case the amplifier is feeding a strong, unwanted signal to the filter. So, filters should be installed between an antenna and the amplifier input. Mini-circuits is now selling a special kind of absorptive filters that dissipate that energy turning it into heat instead of reflecting it but I guess they are only useful in very specific situations.
  7. When we think about the spectrum of a signal we tend to consider the almost steady “sustain” part. I’m talking about the “classic” envelope phases: Attach, decay, sustain, release, which describes lots of sound pretty well. But the attack phase of a sound can have a lot of relatively high frequency components. They will only be present very briefly but without them the attack will be dramatically different. A prominent expert on violin construction told me many years ago (when I was very interested on synthesis) that attack is the most important part of a musical sound and what really imprints a “character”. Also, I guess an audiologist is only concerned about intelligibility. Capture some sounds like a kick drum (for example) and have a close look at a sonogram. The attack will show a brief surge of high frequencies. Or try to record a double bass using a microphone with a very poor high frequency response and the sound will be completely lifeless.
  8. Nice, but. First, I don’t see the antenna is made of Oxygen free Copper. So, inferior materials. Second you are overlooking the devastating effect of femto vibrations on FM modulation. A proper granite support with less than femto metric oscillations would be in order. I said audiophile grade antenna
  9. I should start a business of audiophile grade antennas for wireless microphones
  10. Well, aligning using timecode achieves a precision of 1/24th or 1/25th of a second (a frame). While it is sufficient in order to align audio files from a macroscopic point if view (ie, aligning audio to video or, for instance, different instruments so that you won't perceive a discrepancy while listening to it), at the microscopic level consider the number of samples in a frame. Which would translate into phasing issues if two different microphones connected to different converters pick up a correlated signal (ie, the same instrument). Unless you keep a constant clock (which can be achieved using GPS, a word clock signal or Dante's synchronization over the network) clocks will surely drift. Even outstanding temperature controlled clocks can have a drift of 0.5 ppm (parts per million). As long as there is no correlation at all between them there is no need for phase accuracy, right. So, if two microphones pick up an entirely different signal, not sharing anything at all, you don´t need phase coherency. It's trickier than it seems. And it doesn´t help that the audio market is flooded by snake oil sellers
  11. I don’t think it requires power, as it is passive. The data sheet states that one port can pass DC if required which indeed is a handy feature.
  12. USB-C is a complex beast. Normal USB-C is 5.0 volts. Period. Power delivery is a special specification implemented only on some devices (like Macs, some USB-C monitors, phones...) but it is not mandatory. Devices implement some kind of negotiation to enable PD. Other than that, USB-C is 5.0 V. I wouldn't dare to do an expensive experiment and I would ask Sound Devices. But it is safe to assume that MixPres don's support PD and in that case the expected voltage on the USB-C port is 5 V. I am not sure if some form of over voltage protection or regulation is mandatory on USB-C ports but I wouldn't assume it beforehand. This is a question you should ask Sound Devices. Your best bet is to use the battery terminals, connecting a regulator to them. There is even a Hirose adapter designed to fit like the battery caddy and it includes a voltage regulator. I wouldn't worry much about power noise. I am pretty sure Sound Devices filters the USB-C power input thoroughly.
  13. TL;DR: Don't without a voltage regulator. USB-C is a USB port, I imagine they haven't added a voltage regulator because USB is just 5 V. USB-C can go higher but some negotiation between is involved. As a desperate measure play with the battery terminals, which can get 7.5V (NP-F battery packs). Again, regulate.
  14. I know it's an old topic, but some time ago I found a supplier in France that seems to have nice and cheap antennas. They have a cheap Yagi and several log periodics among lots of stuff for wireless experimenters. https://www.passion-radio.com/wifi/50
  15. Old topic but I also have my own answer As I have understood it LUTs are generally used for non linear color encoding schemes used in contemporary digital imaging sensors. An old example of an "audio LUT" could be the µ-Law or m-Law curve used for telephone voice encoding. Nowadays anyway I guess all the equipment we have uses linear coding. In the analog domain the rough equivalent could be a noise reduction companding system such as the Dolby family but with multi band dynamics processing it's no longer something you can specify with a straoghtforward calculation or, as its name says, a look up tablle. So, not really valid.
  16. Pity. Is your controller up to date? Anyway these switches can be managed in the old fashioned way, although it can be quite annoying for someone without experience on Cisco network equipment.
  17. John Eargle's book was updated in 2011. https://www.routledge.com/Eargles-The-Microphone-Book-From-Mono-to-Stereo-to-Surround---A-Guide/Rayburn/p/book/9780240820750
  18. Yes, I agree. If your network is dedicated to Dante you don't need to mess with priorities. Multicast flooding might be a problem if you have a lot of traffic and some 100 MBps devices that can't cope with all the multicast. Yes, I checked that one because it's the only UniFi switch I have around. Mostly I wanted to check whether it had the infamous EEE (Energy Efficient Ethernet) which it does not.
  19. Finally I had a chance to check it. I have updated an UniFi switch to version According to somewhat sparse information on Ubiquiti's forum and checking out the configuration from the command line it doesn't support EEE. So that's a good thing. The potentially troublesome feature would be IGMP snooping as well. You really want it because it prevents multicast traffic from flooding all the switch ports, but Ubiquiti has been known to be sloppy with its implementation. By default it is disabled: (UBNT) #show igmpsnooping Admin Mode..................................... Disable Multicast Control Frame Count.................. 0 IGMP header validation......................... Disabled Interfaces Enabled for IGMP Snooping........... None VLANs enabled for IGMP snooping................ None Anyway these switches can be a bit messy to set up without a controller. First you need to ssh to it using the "ubnt" user name and password, after finding out which IP address it got from your DHCP server. After doing that you need to do a "telnet" from the switch command line in order to enter the Cisco style configuration mode. US-48-G1-US.6.0.3# telnet Entering character mode Escape character is '^]'. Warning! The changes may break controller settings and only be effective until reboot. (UBNT) >enable (UBNT) #show startup-config network protocol none vlan database exit configure line console exit line telnet exit Maybe the best you can do is to use it in default mode and be happy if it works. I will try and setup a Dante network later using the IGMP configuration and I will post it anyway in case anyone is interested.
  20. Oh no problem then! As I said, I have spent like €500 on Ubiquiti wireless hardware and I am very happy. I recommend it to friends and I basicly forget that they exist except when I feel like tinkering. So, it's a good thing. I cautioned about Dante because the topic is "Small switch for a small Dante network". But I would only be careful about Dante specifically. Anyway give me an hour and I will check whether it is possible to disable Energy Efficient Ethernet using the mobile app, at least for a USW-48 (48 port).
  21. However, I would be careful with Ubiquiti for this application. Don't get me wrong, I use Ubiquiti wireless gear at home and I am happy. I also track beta/prerelease firmware versions. BUT (and it's a big BUT) they tend to disregard features that they don't perceive as important, and it usually means those features will be unstable. It took some time for them to fix a simple bad multicast implementation (they equalled IGMP to all multicast, which is wrong, breaking an IPv6 address assignment). What worries me in this case is energy efficient Ethernet (EEE), which is a know no-no for Dante. I am not sure you can disable it. Second problem with Ubiquiti, they used to have two different Ethernet switching families: UniFi and EdgeSwitch with the former designed for "enterprise" networks and relying heavily on a controller you need to install somewhere, although you can use a mobile app to manage them, and the latter being more "classical" with no proprietary centralized management and configurable via a command line (similar to Juniper Networks equipment) or a web interface. Sadly the EdgeSwitch line seems to be discontinued. I am not sure whether they have sacrificed it temporarily due to component shortages or it is a permanent decision. I have a 48 port UniFi switch I haven't used for some time, I will plug it this evening and report back what I see. That said, I wouldn't trust them much for this particular application. And, trust me, I don't have anything against Ubiquiti. The 48 port switch was a gift from them in order to test beta versions, so I have reasons to be even grateful. Talking to them in case of bugs is also easy thanks to the forum and the bang for the buck is incredible. BUT they tend to be a bit chaotic with software development and (I know I am repeating myself) little used features are sometimes overlooked.
  22. Some time ago they warned about component shortages and they even stopped selling low end models (MixPre 3 and 833) for now. There are also serious shipping issues. I guess that's it. The NY Times has had a pretty good coverage.
  23. Even if the network is dedicated to Dante (it can get tricky if you have other high demand or bursty applications running) I would never consider an unmanaged switch. The price of a reasonable managed switch from a reputable vendor is peanuts compared to the equipment usually discussed in this forum. And you can't imagine the amount of pain that crappy networking gear is capable of inflicting. And indeed multicast Dante can be taxing for poor switches. And it can become a nightmare in case you plug a wireless access point to your network. If only thanks to the capability to show interface statistics (errors, etc) managed switches are, in my opinion, mandatory. (Note that I am writing this with my ISP guy hat on)
  24. It arrived on Friday. I had ordered a 16 inch model with 512 GB of storage and the 24 GPU core M1 Max, 32 GB of memory. The thing is insanely fast. I was installing software, including XCode, and it was still at body temperature given that I had it on my lap while I sat on the couch. I didn't even bother to plug it to do that. Funny enough, my odl 2009 Macbook Pro was sitting idle on the table and I looked at them with a small thermal camera. While the 16 inch was busy working, the 2009 MBPro showed hot areas (top left corner of the keyboard and power connector) while, as I said, the new 16 inch didn't sweat at all. Bringing back MagSafe is a very welcome change. Unlike previous models, the power supply does not have an unremovable cable. It is actually a high power USB-C to MagSafe cable so in case of need you can plug it to a different USB-C supply. Although only with a high power one you will achieve the promised 50 % charge in 30 minutes. The keyboard has an excellent feel reminding me of the old Powerbook G4 I got back in 2003 which was really impressive. This can be a game changer even for real time audio processing as using shared memory between the CPU and the GPU eliminates most of the latency. We'll see though.
  25. So I operated my old Mac Pro. It was easy although I really hate those tiny u.FL RF connectors. It looks like you are going to destroy them but they are surprisingly sturdy for their size. Bluetooth has improved (as has WiFi being now 802.11ac compliant) but it still struggles trying to use the Airpods Pro in duplex mode (microphone and hearphones) so it may be a deeper issue in Mac OS X (the Mac Pro is running Mojave).
  • Create New...