EEVblog #616 - How Microphone Phantom Powering Works - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: May 15, 2014, 03:49:11 am
content: Doug Ford, former head designer at Rode Microphones explains 48V phantom powering of microphones and how it works.There is a ton of stuff here:Electrostatic and electromagnetic noise, differential amplifiers, common mode noise, transformer magnetisation current, JFET differential driver circuits, balanced impedances, phase splitters, miller capacitance and how it matters, and he explains how the Schoeps amplifier topology works.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 15, 2014, 04:21:44 am
content: As Mr. Ford alludes to in this video, modern, high-end transformer-makers discourage putting ANY DC current through their devices, even purportedly "balanced" current using a center-tap. They recommend using the same topology used in transformerless designs, the matched 6K8 resistors and even better with DC blocking capacitors to protect the transformer.

author: rdl
author_rank: Super Contributor
timestamp: May 15, 2014, 04:34:19 am
content: Seriously? Another microphone video? Yes, they're interesting but are you actually trying to lose audience? I had breathed a sigh of relief when the Prema multimeter and Cebit videos appeared, but I guess that was premature.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 15, 2014, 04:49:21 am
content: Perhaps Mr. Jones' audience is wider than just test-gear geeks. I'm sure I'm not the only recently-new member who was attracted by the microphone series.I hope Dave can arrange a similar series of interviews with another innovative Australian company, Blackmagic Design.

author: david77
author_rank: Frequent Contributor
timestamp: May 15, 2014, 05:19:06 am
content: As my main interest lies in audio electronics I find these videos with Mr Ford very interesting, looking forward to the next installment.How about getting in touch with Rod Elliott?

author: Monkeh
author_rank: Super Contributor
timestamp: May 15, 2014, 05:45:09 am
content: Quote from: rdl on May 15, 2014, 04:34:19 amAfraid of learning something on Youtube?

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 15, 2014, 06:07:12 am
content: Quote from: david77 on May 15, 2014, 05:19:06 amYes! I would like to see that also!

author: EEVblog
author_rank: Unknown
timestamp: May 15, 2014, 06:22:27 am
content: Quote from: david77 on May 15, 2014, 05:19:06 amI know Rod, so that's possible.

author: EEVblog
author_rank: Unknown
timestamp: May 15, 2014, 06:23:30 am
content: Quote from: Richard Crowley on May 15, 2014, 04:49:21 amI've asked around about that, and I hear they are super-duper secretive, so was told not to even ask!

author: EEVblog
author_rank: Unknown
timestamp: May 15, 2014, 06:25:22 am
content: Quote from: rdl on May 15, 2014, 04:34:19 amYou are welcome to unsubscribe at any time, or simply not watch them. As always, it is very clear from the title what the video is.Would you have complained if I didn't upload anything at all today?I got several hours of footage with Doug, so I'm breaking that up into useful chunks.

author: Monkeh
author_rank: Super Contributor
timestamp: May 15, 2014, 06:26:25 am
content: Quote from: EEVblog on May 15, 2014, 06:25:22 amAnd most of us are enjoying it immensely and learning things. Keep it up!

author: Lightages
author_rank: Unknown
timestamp: May 15, 2014, 06:47:47 am
content: Let me see..... I get to watch a short video of someone who knows what they are talking about so I can learn something for free and even ask questions and maybe get them answered. I have a choice if I want to watch. I am so pissed off......

author: nitro2k01
author_rank: Frequent Contributor
timestamp: May 15, 2014, 06:51:30 am
content: I for one find the microphone videos interesting. Keep'em coming, lads.

author: azi
author_rank: Contributor
timestamp: May 15, 2014, 07:19:35 am
content: Quote from: rdl on May 15, 2014, 04:34:19 amDave has said many times that he can't please everyone.Audio electronics is a special field that does not interest everyone, but the people who are interested are often fanatical.

author: EEVblog
author_rank: Unknown
timestamp: May 15, 2014, 07:49:40 am
content: Quote from: azi on May 15, 2014, 07:19:35 amThe number of views on the microphone videos has been about half the usual, and that's to be expected.I for one think this video has lots of circuit detail that can apply to more than just mics, so it's certainly bang on topic. Some other like the microphone patterns etc have been admittedly less so.

author: G7PSK
author_rank: Super Contributor
timestamp: May 15, 2014, 08:09:05 am
content: I for one find the microphone and its construction and use very interesting. When the information is put over in such an entertaining manner by someone like Doug Ford it make learning so much easier.Microphones and audio is used in some form the majority of electronics that most people come into contact with so to my mind its a very important subject.Doug and Dave get a bigfrom me for this series.

author: jancumps
author_rank: Unknown
timestamp: May 15, 2014, 08:29:11 am
content: I learned a few things today.And it ends with a cliffhanger.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: May 15, 2014, 10:02:17 am
content: It's been a good series of videos on mics and, as you've noted, some circuit topologies and techniques that can be used outside the audio industry.Big thanks to Doug for spending the time to do this.

author: delmadord
author_rank: Regular Contributor
timestamp: May 15, 2014, 10:57:56 am
content: I must say I really like the microphone series too, even thou I do not make anything with them. There are a lot of other physics/electrical/electronics stuff explained by Doug that are really helpful/interesting to me. I think that it would be a shame to stop making videos like this.

author: Tuoppi
author_rank: Contributor
timestamp: May 15, 2014, 11:12:26 am
content: Quote from: EEVblog on May 15, 2014, 07:49:40 amThis. For me as a beginner, there are a lot of things to learn about general electronics from these discussions. And the most important of all, is observing the train of thought of people who actually know about the topic and have worked on that for a living for a long time.And then, well, this is free. Even if the video would be 30 minutes of Dave and Doug dancing a waltz together it would still be a good run for your money (and still better than 50% of the content you can see on Youtube.... ok, 30%). Watching this, or any other video, is not compulsory.

author: madires
author_rank: Super Contributor
timestamp: May 15, 2014, 11:49:36 am
content: I like the microphone 101 mini series, it's interesting and it gives a good insight into the technology which wouldn't fit into a single video of 20 minutes. It's a nice idea to have a mini series about a specific topic from time to time, especially if Dave can get another EE in front of the camera.

author: 13hm13
author_rank: Frequent Contributor
timestamp: May 15, 2014, 11:54:54 am
content: Most of Dave's videos "auto-captivate" ... I get drawn in and interested ... not feeling any urge to click away ... that said ...and despite having a great interest in audio (that's what got me hooked to EE decades ago) ... well, these microphone vids just don't have the usual EEV sparkle.But, hey ... that's just one person's 0.02 worth

author: Rigby
author_rank: Super Contributor
timestamp: May 15, 2014, 01:44:33 pm
content: Quote from: 13hm13 on May 15, 2014, 11:54:54 amYeah, same. Doug Ford is definitely a neat dude, and ridiculously intelligent but I'm Dougged out for a while. I'll come back and watch these microphone vids later.

author: rdl
author_rank: Super Contributor
timestamp: May 15, 2014, 02:31:11 pm
content: I just thought that 42% of EEVblog videos about microphones was a bit too much. If 6 of the last 14 videos had been about that little electric vehicle I bet you guys would be up in arms.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 15, 2014, 02:57:09 pm
content: Quote from: rdl on May 15, 2014, 02:31:11 pmThat's pretty selective statistical analysis. I could say the same thing about test equipment. I would bet that most of us are less enamored by analysis of test gear and consider it just a utilitarian tool like a screwdriver. And what's the obsession with soldering irons? As a newcomer here, I perceive that this community really has its fetishes. I strongly suspect that after Dave is finished doling out the episodes from Mr. Ford, we will likely never hear of microphones again. But I will still regularly slog through DMMs and soldering irons until the end of time. At least the mailbag brings some variety.

author: JackOfVA
author_rank: Unknown
timestamp: May 15, 2014, 03:47:46 pm
content: Although audio isn't my main or even secondary interest, I've found the Doug Ford videos extremely interesting.

author: dentaku
author_rank: Frequent Contributor
timestamp: May 15, 2014, 03:55:56 pm
content: I find all thins audio related interesting so Having Doug's practical information has been very educational.I may never use a microphone (synths don't need mics) but it's all audio so the same concepts apply.

author: ecat
author_rank: Frequent Contributor
timestamp: May 15, 2014, 05:49:19 pm
content: Quote from: Richard Crowley on May 15, 2014, 02:57:09 pmDave's most popular video is/was the soldering tutorial, it's a simple fact that anything mentioning soldering or soldering irons will attract an audience. Thanks to the internet, every year thousands of people discover a need for a soldering iron and go in search for advice and information and soon learn they also need a multimeter and the knowledge that V = IR. Soldering, test equipment, basic theory make for popular videos.I think this is great news for everyone with an interest in electronics: At the hobby level the market is increasing in size, people become more aware of the quality of the devices they buy, interest in electronics leads to the application of logical thought which hopefully will spill back out into the individual's other interests and activities... The list goes on.Microphones:Thousands of people out there have a web cam or mobile phone and are wondering why their Youtube videos suck. One big reason is audio quality which, of course, brings us to microphones. A quick search of Youtube for audio/microphone problems brings up a familiar list of ill-informed videos made by people with an ego, a big mouth, a video camera and often, funnily enough, a poor quality audio recording set-up. More quality information on microphones is needed.Rod Elliott:It was Rod's site that brought back my interest in electronics, at last I'd found a site that not only contained some interesting projects and articles but was written by someone who knew what they were talking about. That was long ago. Today I have Rod's phantom powered microphone amp in front of me ready for assembly in the hope that it will solve the problem with the low gain and noisy mic. input on my PC.

author: SeanB
author_rank: Super Contributor
timestamp: May 15, 2014, 06:31:41 pm
content: I learned a bit from the series, and quite enjoy Doug's style of teaching. Only thing is the hum from the aircon every so often, quite amusing ( but shows the good mic you have there) but a little intrusive at times on an otherwise very quiet audio track. The extra insulation you want to install should help a lot with that.

author: HKJ
author_rank: Super Contributor
timestamp: May 15, 2014, 08:20:08 pm
content: My interest in microphones is not that great, but I enjoy listening Doug talking about them, probably because I like learning stuff.Of course, a lot of the stuff is pretty obvious, at least when Doug talks about it.My biggest complain is that David only gives us small pieces at a time, I would have preferred an hour each time, not only 20 minutes.

author: Macbeth
author_rank: Super Contributor
timestamp: May 15, 2014, 08:27:34 pm
content: It's not just about microphones though is it? It's about differential lines like the XLR connectors and stuff vs. the fucking shit Monster cable gold plated silver oxygen free copper bollocks phono connectors. It's very interesting. I had a PA system recently and wondered what "Phantom Power" was all about, considering the cheap arse mic I had was just a battery powered jobby going through coax to a proper XLR connector. Indeed every device I had was just shitty coax going into some sham XLR rigged up by a roadie with a shit soldering iron.Years back when I helped crack the Ford ACP protocol for their car head units I found they used a balanced design with twisted pair. It was 10V peak to peak as i recall. A simple line-in or phono would not work whatsoever.I tell you, all those ground paths and stuff can seriously fuck up your audio experience, especially in such a noisy electrical environment of a modern car, if you don't follow some of this stuff. I find it very interesting.Audiophools can stick with their shiny phono cables.

author: ThisDoesNotCompute
author_rank: Contributor
timestamp: May 16, 2014, 12:37:07 am
content: Dave, thanks for doing this microphone series. I know it's not interesting to everyone, but as a self-taught hobbyist audio engineer I find the videos very educational.One question I have about this video in particular: Doug does a great job of explaining "traditional" phantom powering of condenser mics over balanced connections. What about bias powering, which is typically done over an unbalanced connection? (Example: a lot of video cameras offer 3.5mm mic inputs that have "plug-in power" for electret condensers.)

author: EEVblog
author_rank: Unknown
timestamp: May 16, 2014, 01:49:14 am
content: Quote from: rdl on May 15, 2014, 02:31:11 pmThey have to be uploaded at some point. And uploading one huge multi-hour episode would be a disservice to everyone who wanted to watch.I'm already spreading the material out enough I think. Any closer together and I'd be accused of flodding the channel, the current level I get a few complaints, and if I wait wait month between videos to those few who care about content ratio, then I get complaints about not getting them out soon enough.It is what it is. I can't win, and those who don't like the videos or the frequency of them will never be happy anyway.

author: Rory
author_rank: Frequent Contributor
timestamp: May 16, 2014, 02:04:14 am
content: It's a pleasure watching you two go at it about microphones, Dave. I wish I had a good friend like Doug. You're a lucky guy to have all these interesting people to talk with.

author: David_AVD
author_rank: Super Contributor
timestamp: May 16, 2014, 02:11:08 am
content: I haven't watched all the mic videos, but don't see any problem with having a series of them. There was clearly a lot of content to get through.If someone doesn't want to watch, they don't have to. You can bet if you did a series on their (the complainers) pet subject, they wouldn't be upset.

author: SeanB
author_rank: Super Contributor
timestamp: May 16, 2014, 04:51:00 am
content: Quote from: ThisDoesNotCompute on May 16, 2014, 12:37:07 amthat has been done earlier when discussing electret microphones and the pitfalls of the PC phantom system with noise.

author: lewis
author_rank: Frequent Contributor
timestamp: May 16, 2014, 08:44:12 pm
content: Dave, don't listen to the nay-sayers, you're doing a great job. Doug is effing awesome, and, how'd-you-puddit, really knows his stuff. Meh!Also, DEFINITELY get Rod on the blog if he's up for it, it was his site that encouraged my interest in audio electronics many moons ago, and he really knows his stuff too. Ask him about light bulbs.In fact, some more guests more regularly would be great!

author: zapta
author_rank: Super Contributor
timestamp: May 16, 2014, 09:02:17 pm
content: That microphone guys is a natural showman. I enjoy watching him, maybe because he reminds me of Robert California. He also knows his stuff through and through and knows how to explain it.For me one or two microphone episodes would be enough. Hopefully he does not have a tween brother that specializes in headphones.

author: atw60444
author_rank: Contributor
timestamp: May 17, 2014, 12:39:17 am
content: Yeah, keep getting Doug back, I really enjoy his talks. I've got no particular need to know all about microphones. But I find the videos really interesting. The train PA / communication system teardown was another great example of Doug talking through something that he'd actually designed, the whys and wherefores of it all

author: Towger
author_rank: Super Contributor
timestamp: May 17, 2014, 08:02:38 am
content: I am sure it will get complaints.But how about getting Doug to do an episode or 3 on different types of microphones and their correct use in different situations. There is much more to recording sound than picking a generic Mic and placing it in front of its source.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: May 17, 2014, 08:22:45 am
content: Quote from: Towger on May 17, 2014, 08:02:38 amPlenty of good videos already by well respected recording engineers on mic usage and placement.

author: jaxbird
author_rank: Frequent Contributor
timestamp: May 17, 2014, 08:40:07 am
content: Thanks, great videoLooking forward to more Doug / Dave videos.And if you can, as suggested previously, do some sessions together with Rod Elliott, that would be really greatRod has for many years been a voice of reason.

author: Dave
author_rank: Super Contributor
timestamp: May 19, 2014, 06:06:29 pm
content: I have never given microphones too much thought, so it really is interesting to get insight like this from a pro. I look forward to seeing more of these.

author: ciccio
author_rank: Frequent Contributor
timestamp: May 19, 2014, 08:01:53 pm
content: I build audio gear for a living, and the microphone series was interesting: I knew about everything Mr.Forf explained, but he gave a good refresh to my knowlwdges.Decades ago I spent days searching some informations about the design of a phantom powered mic preamp. It was an urgent project, and not many infos were then available.The video could have saved a lot of my time....What about a video on low noise mic preamplifers?Best regards