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borjam

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Everything posted by borjam

  1. I have a working link. It's short, 20 m, but it supports 1 Gbps in full duplex. No packet drops, as I said. The equipment I am using is capable of sustaining that to 100, even 200 m unless there is a heavy hail storm or rain. Yes, my link is short, I had to reduce power to avoid overloading the receiver. The thing is, the high atmospheric attenuation together with the small wavelength really reduces that interference. I could run another link across the same street and my link wouldn't notice. I think you could achieve around 100 m without much problem. Human bodies absorb a lot, of course, but beamforming antennas exploit reflections on multiple surfaces. I don't have power consumption data and in my case it's distorted by the core CPU they need to be able to move 1 Gbps of traffic. Anyway, the power supply is not larger than the older 2.4 and 5 GHz equipment I used. It could be challenging for a small belt clipped wireless transmitter, right. I don't have figures for the current consumption of the RF part. A good aspect of this band, however, is that given the huge bandwidth available you don't need an elaborate coding scheme, which reduces the processing power needed. My link is using QPSK, not even QAM. As for 2.4 GHz, the band is too polluted. When I first tried wireless systems on 2.4 GHz the band was empty. You could achieve 100 - 200 m from laptop to laptop without an access point even. Now I detect around 100 wireless networks in the small street where I live. 5 GHz is better (walls add more attenuation) but it can be a problem with weather radars. https://transition.fcc.gov/oet/spectrum/table/fcctable.pdf Page 61: 59.3 - 64 GHz. RF Devices (Part 15) and ISM equipment (Part 18). According to note 5.138 the 61 - 61.5 GHz band is designated for ISM devices. You can already use the equipment I am trying. It was approved in the USA some months ago. https://fccid.io/TV7WAPG60AD Caveat, I am Spanish, I'm not that familiar with the US regulations but I guess "Part 15" covers wireless microphones.
  2. Hi Just wondering. I have been trying (with great success) a 60 GHz data link. It's equivalent to digging a trench and laying a fibre across the street and it provides 1 Gbps full duplex, no packet drops even. Apart from its small wavelength (5 mm, which means it can have trouble even crossing a window) it has a really big advantage: Oxygen absorption. That limits the maximum usable distance (Oxygen absorption adds an extra attenuation of 15 dB/Km) but proides an enormous advantage: An almost guaranteed interference free band. For now it's being considered as the candidate to be the next WiFi (which would need an access point inside each room but, again, would suffer no interferences from the neighbors) and being used for high speed data links. Just curious, seems like an ideal system. Moreover with the small wavelength it's well suited to advanced antenna techniques such as beamforming. The system I am trying now is even cheap. A pair of units capable of linking 1 Gbps at 100 - 200 m is just $200.
  3. I really doubt that ultrasound can affect the RF performance. Ultrasounds can create nasty nonlinear effects on a microphone however, that's an entirely different matter of course. Several years ago a friend was developing an audio reproduction system based on strong ultrasounds modulated in amplitude. When the ultrasound beam hit something (a wall or maybe your back) the ultrasound signal was demodulated. The effect was amazing, if it hit you in the back you heard someone speaking to you right behind yourself. He told me that some museums were considering similar systems so that you can have, for example, voice explanations for different elements of the exhibit. A room could have several of those audio recordings played at once with little interference between them and you would hear it when moving to a certain spot. If it's a microphone weakness there's no way to correct it after the fact, because those non linear effects that, for example, demodulated the voice recordings, actually produce sound in frequencies in our hearing range. So, back to RF. Might it be related to some microwave based motion detectors? I always thought those were mostly 10 GHz, but a friend called for help once, trying to set up a WiFi network without success and, voila, when I turned on the spectrum analyzer I saw a dirty, continuous signal within the 2.8 GHz band. It rendered most channels unusable. Something similar can happen with some crappy A/V transmission systems which, to add insult to injury, use wasteful analog modulation schemes. An example attached, a crappy A/V transmitter (note carrier and two side bands) saw on a WiPry spectrum analyzer for iPhone.
  4. Well, I asked about it. Good morning,I am considering the purchase of a MixPre 3, maybe for nature recording. It seems to have the perfect set of features, but I find an omission really shocking: no phase reverse.Are there any plans to add it to the MixPre 3 as you have done with input delay? I can’t come up witha technical reason to omit that feature from the MixPre 3 requiring a minimum of a 6 instead. And I received an answer worthy of the Ministry of Sound Recording Devices . No answer to my question about enabling it on the MixPre, though. Hello Borja, Your observation is correct: The MixPre-3 does not include phase reverse. Kind Regards,
  5. I've sent an email asking about it. I'm considering getting one and the limitation sounds outright silly to me. I might be wrong of course, maybe it's not a market segmentation decision and they decided to have just two on screen menus in advanced mode, rule that they have broken adding the input delay. We'll see.
  6. I understand that, of course, but we are talking about changing the sign of audio samples. And, curiously, input delay was only supported on the -6 an -10 until it was backported to the -3 in firmware version 1.20. Sorry about the botched reply, I attached the previous menu comparison (from the -3 and -6 user manuals) to a longer post and the text disappeared. I understand that, of course, and I have paid for software licenses without hesitation. For example, a +DSP license for a Metric Halo interface. If someone from SD reads this, of course no offense intended at all, come on! Really??
  7. I say offensive because it has been excluded from the MixPre 3 purely for marketing reasons, not because the operation has some unbearable processing cost. Curiously, channel delay, which is a bit more expensive in signal processing resources, has been added to the MixPre 3 which previously didn't have it. Not trying to start a flame war here of course, but the "let's remove this feature so that some users will go for the 6 instead" is not something I "like". Now I wonder, how come they added channel delay while it wasn´t listed in the original specifications? It's not even mentioned in the user manual. Of course I understand that they have put a lot of effort to release a product in that price class. But removing a "change sign" operation is outright silly in my opinion.
  8. Still with the Zoom/SD conundrum, I must admit that at least one of the limitations of the MixPre 3 is outright offensive. Why doesn't it offer polarity inversion/phase reverse (pick your favourite term) like the MixPre 6 and 10 do? It's certainly not rocket science. I noticed that they added channel delay to the 3 with a firmware update, which was only available for the 6 and 10. For the very budget conscious user having polarity inversion in the MixPre 3 would be very useful if you want to try a poor man's MS setup (two cardioids but one of them with reversed polarity) for the S. (I know many users here will laugh at it but the MixPre series seems to be about conquering new markets).
  9. I wonder about the invisible, under the hood fine details. Like, has anyone made an evil test like simulating a dying battery using a laboratory power supply? I bet Sound Devices are world class experts on data surviving such an event.
  10. This can be very bad for Sound Devices. If the prices of the MixPres go up it's open season for Zoom.
  11. I'll contribute the old war story about lack of respect for sound here . It doesn't happen only in professional movie sets. I was 16 (it was 1986) and I was part of an amateur theatre company (I did light and sound). We made an "Electra" with many modern elements, the only resemblance to the the classic Sophocles play was some dialogue and of course the whole story. Setting up everything for the performance I thought I noticed some broadcast radio interference on the sound equipment (which was a glorified HiFi system, how I had to prepare the recordings and sound effects would merit long post by themselves). It had never happened to me but I was well aware that "there be shit". There was "talent" chatter all around of course, and I yelled "slience, we have a serious problem, I need to check it out!" Guess what the answer was? Yes, "oh come on, stop playing with the toys, are you going to make us deaf playing loud or what?" and of course they didn't shut up. Turns out it was a false alarm, but, well, it was scary as hell! Sound was a very important part of the performance. I used some elaborate sound clips with which I managed to really scare the audience. I left the group a couple of months later. Not just because of that, but certainly the actors were a bunch of assholes. The director was very good, though (he also left that group a year later) and I still stay in touch with him, helping when I can. Know what? A year after I left he told me, in laughter, "remember that incident when you mentioned parasites on the sound equipment and everyone thought you were nuts"? "Of course, I almost killed someone!". "Well" - he told me - "turns out the idiots saw that happening, we were watching a play and, suddenly, a football broadcast broke out, C.... really turned pale". C... was the guy who had said "hey, going to deafen us?" and he obviously remembered. The director told me he said "Remember that incident with Borja? Well, seems to be exactly that". Sound is subtle, subconscoius even, and the more invisible it is, the more effective. Sadly the more invisible the less respected I guess. Is there a sound equivalent of the typical shot of a sunset that makes people say "hey, this movie has an amazing cinematography!"?
  12. After several years waiting (I always said this wasn't a Moon shot, but a Mars shot) seems the early access program will begin soon. http://www.mhsecure.com/3dEarlyAccess/3dIntroMHRN.html This is intersting, you will be able to update all their existing models, at a cost of course. In the past I updated my first series ULN-2 to the 2d Expanded version swapping a card inside and replacing the back panel.
  13. Hehe, I see SD can attract devoted followers like Metric Halo (<-- Happy Metric Halo user).
  14. I forgot. In order to find the right part number it's mandatory to identify the coaxial cable. Otherwise you could introduce some loss, which of course you don't want given that you are using low loss coax Gosh I can be sloppy at times, sorry. So Lectrosonics say that it's Belden 9913F7 which is RG8. I found these references from Amphenol (one of the best known brands). These ones are crimp plugs, not soldering. Maybe easier to fit. https://www.amphenolrf.com/search/?q=belden+9913+bnc Anyway, if ordering somewhere, specify the brand and type of cable (Belden 9913F7). Any knowledgeable electronic components vendor will be able to match it. And beware el-cheapo RF connectors from unknown sources... If only I could describe what I saw at the Gates of Tannhauser...
  15. Hmm what kind of coaxial is that? RG213+? That looks like a somewhat Frankenstein BNC connector. It's very unsual to attach thick coax cables to BNC connectors directly, but I found some: http://www.wimo.de/connectors-bnc_e.html The ones that would work for you would be (depending on the actual coax cable used by Lectronics) are the RG213+ or the Airborne/Ultraflex/Ecoflex. There is an easier approach, probably easier to terminate and with a minimal impact. Use N connectors (easier to find and certainly easier to install for those thick cables) and an N-BNC adapter. With good quality adapters the losses are really ridiculous. Speaking of low loss coax cables, there are thinner alternatives with excellent performance if you want an alternative. These thick coax cables use to be very stiff and heavy.
  16. Hmm must be that the world is upside down where you live (compared to my place ) The Zoom F8 has the same price as the MixPre Three here. In a well known German store both are 766€ (final price, tax included). I say Foxtrot-eight and MixPre Three In my case, if I decided to go that route (I'm going to hook an oscilloscope and see how Fostex configures the codec chip to see if I can "fix" the headphone output) it would be the MixPre 3 or maybe the 6. Regarding the M series, surprisingly they are cheaper although I don't see pricing at the usual suspects in Europe yet. But seems that the M series have lost M/S and some other interesting features. Guess the M series is an attempt to enter the music recording business, where Sound Devices is not one of the well known firms as far as I know. So, if going the MixPre route it wouldn't be an M. For music oriented features I have a Metric Halo interface. I could even bag it (it can be powered with a Martin Bauer battery) and it can be configured so that it doesn't need a computer, I can just hook it to a bit bucket) but it would be heavy and cumbersome. I have some doubts about the Zoom F series, especially how they have implemented the limiters. In the FR-2LE for example, the limiters could be described as "hybrid", a technique used on some software defined radio receivers. The limiter in the codec (CS42L51) checks the signal level in the digital domain but in order to attenuate the signal it uses a programmable amplifier in the analog domain just before conversion. I wonder wether Zoom have followed a similar route. Look ahead limiters (one of the new features of the F8n) can be awesome when your original program material is digital (which means it hasn't clipped before the limiter checks the levels). For example, in music mastering when your digital stream is floating point and you haven't gone back to 24 or 16 bit yet. However, if the delay buffer is in the digital domain and you are dealing with an analog signal the limiter won't help. You will decrease the level of an already clipped signal, so at least the beginning of a transient will be already recorded in all of its distortion glory Unless they have used an analog delay buffer. So, I guess it would be the MixPre 3 or the MixPre 6. I don't think I'll use more than three microphones, mostly one or, if playing with M/S, two. The HFI-650 are quite nice. I've used them for several years now in live music settings. The response is quite good, with the bass somewhat lowered (sound like a shelving filter) which can help reduce fatigue but, once you get used to it, can still help you judge what's going on. The very slightly emphasized mid-highs somewhat help me to make a better judgment with adjusting dynamics processing. That's especially critical for me in a small jazz club venue because my goal is the "invisible FOH", combining it with actual, live sound so that the audience thinks they are listening pure, acoustic sound. But remember I'm talking about live concerts, a very different world. By the way, the Ultrasones had some serious design flaws at first (poor quality plastics, sometimes even noisy in the headband) but when I ordered a new headband for my battered Ultrasones I was surprised by a headband for a much more recent model which was still 100% compatible and with very much improved materials.
  17. I've been looking at both (MixPre and Zoom F4). Right now I have a Fostex FR-2LE as well and despite having good pres the headphone output is atrocious and I don't trust the metering at all. If I considered an upgrade, and considering that I am not doing audio on camera for now (so synchronization and those camera oriented functions are not an issue for me), I guess the resale value of a Sound Devices recorder will always be higher, and I've read somewhere that the headphones amplifier in the MixPre is really in a different league from the F4. Right? Not that my headphones are difficult to drive (Ultrasone HFI-650) but at least the Fostex struggles really badly.
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