EEVblog - 2014-04-26
Part 4 of microphone technology with Doug Ford, former head designer at Rode Microphones. In this video Doug discusses how to design a condenser microphone, in particular the Rode Classic II microphone. Many things discussed include: External polarisation voltage generation and the relationship with sound pressure. The trade-offs involved in bias voltage vs physical construction and sensitivity. Diaphragm deformation and its effects. CMOS oscillator design for high voltage generation. Zener diode noise in relation to the knee type, and how to reduce it. Heating and dehumidification advantages of valve based microphones. Valve based amplifier design, and blending solid state for improved performance. http://www.rodemic.com/microphones/classic2ltd All videos in this series are here: https://www.youtube.com/playlist?list=PLvOlSehNtuHv98KUcud260yJBRQngBKiw Forum: http://www.eevblog.com/forum/blog/eevblog-609-condenser-microphone-design-tutorial/ EEVblog Main Web Site: http://www.eevblog.com EEVblog Amazon Store: http://astore.amazon.com/eevblogstore-20 Donations: http://www.eevblog.com/donations/ Projects: http://www.eevblog.com/projects/ Electronics Info Wiki: http://www.eevblog.com/wiki/
I would really like to see more videos with Doug. He is a great engineer and entertaining teacher. :) Thumbs up for the whole microphone series.
I have, or rather had, little interest in microphones. But I'm finding these videos extremely informative, they are great. Thanks Dave and Doug.
I really love these videos dave. I'm a music producer myself, and i rarely get to go this deep in the nerdery. I just hook mics up and use them usually. Thanx Doug and Dave!
Priceless video… need more like this out there ! Thank you so much!!!
Loving this series! Watching this made me think you should do a video on impedance... That would be pretty interesting. Keep it up!
More microphone talk! As HAM radio operator I take microphones for granted, without thinking about the hours of designing that went into the microphone. It intrigues me!
Thanks for doing the microphone series! I'm far from being an audio buff, so this was almost entirely new information for me! :)
Fantastic stuff. Never thought about the energy preservation concept thus causing the voltage to change with pressure waves.
yesterday i ordered a rode nt1-a condesor mic, and its so nice to see how Doug develops the circuits to keep the noise as low as possible. So i know there is somewhere a soft knee zehner diode inside to keep the noise low. fascinating. thanks a lot, Dave and Doug!
I love this series! Doug is the man! :D
This was so informative. Thanks for making these videos!
An excellent lecture by Doug on condenser microphones.Keep up with good by lectures Doug, love see more of you.
love the progression of this series. I'd never really understood condenser mics before this video. Thank you Doug and Dave! (JFET with a pilot light) ROFL!
I have a couple of old MK-219 microphones which I am in the process of restoring according to this article: http://www.recordingmag.com/resources/resourceDetail/316.html
Thank you for this video. It helped me to understand more thoroughly how these microphones work.
Could you make more videos with Doug on this topic? This is priceless, and the only series of videos on this topic out there.
I like it; some fun learning in a comfortable conversational style. Cheers, Mark
dave and doug pure aussie genius. watched this whole series many times over
What a lesson! Thank You master!
Thank you very much Dave for this tutorial.
How does the external polarisation voltage relate to the typically 48 volt phantom power? In the video much larger voltages are mentioned as typical. Is it really charge pumped (or by some other method) to a higher voltage in all condencer mics? And how about those tube/valve mics, they would need actual amperes, or at least mAs?
Triode gain stage with BJT emitter follower? I'm confused. The most common-as-clarts triodes are dual, so why not just use the second triode as a cathode follower? The filament supply might need to be elevated depending on the HT voltage, but that's unlikely with the voltages mentioned, and if it is needed, it's trivial to implement.
Please show more things like this!
Cannot believe this video has just 42k views 7 years after, there is so much priceless information in it...
Well explained ... Thank you both
Was fun watching the talk going from condenser mics to zener's knee;D
3:45 Why is the -3dB point 2pi lower than the RC constant frequency?
I wonder if it is possible to use piezo crystals as a microphone (like an inversed piezo tweeter)...
Btw, I like how you use the DIN symbols instead of those goofy zigzag resistors.
JFET with pilot light....I'm using that from now on. Great stuff
I like the way Doug calls valves "JFET's with pilot lights"
Me too! Had a good long giggle at that.
Also it seems I can comment on YT again. That was way more irritating to fix than it needed to be :-/
Great video, I may try making another microphone.
Doug Ford is true guru of microphones. Hat down.
One thing bothers me... 10:39
10 microns with polarized voltage of about 50 - 200V? Is there air inside mic, or something else? Typical arc scenario that happens in free air should be about 1 mm per 1000V. With 10 micron gap it can start arcing at about 10V. Am I missing something, or didn't understand this properly?
That got me thinking too.
The mean free path of a molecule in a gas is the average distance between its collision with other molecules. This is inversely proportional to the pressure of the gas. In air the mean free path of molecules is about 96 nm. Since electrons are much faster, their average distance between colliding with molecules is about 5.6 times longer or about 0.5 µm. This is a substantial fraction of the 7.5 µm spacing between the electrodes for minimum arc voltage.
The electron mean free path can become long compared to the gap between the electrodes. In this case, the electrons might gain lots of energy, but have fewer ionizing collisions. A greater voltage is therefore required to assure ionization of enough gas molecules to start an avalanche.
High pressure and air medium are bad conditions for discharges. A REAL BUMMER IF YOU ARE PLASMA PHYSICIST AND YOU WANT the discharge and you are not avoiding it
There is no current there because of 5G resistor ;)
Thanks,now I have a basic idea how this magic works
Voltage is proportional to plate spacing on an isolated capacitor, so decreasing the capacitor increases the voltage, not decreases it. The charge is trapped on the plates so the electric field strength stays constant, therefore voltage proportional to separation.
The energy is not constant, the air does work on the plates...
KT315 is a noisy transistor to use for microphone amplifier.
As a self appointed audio engineer this is interesting
Can they explain why so few budget friendly price point mics (sub $100) will list frequency responses of like 100Hz to 16,000Hz? What is with the lack of mics with good bass response. Are the microphone companies scared of bass?
The condenser diaphragm in these mics are 24K gold sputtered. They are very expensive to manufacture. They run batches of diaphragms through the vacuum sputter process which is not perfect. The pic of the crop which are few for each batch, goes only into the high quality mics. The rest are sold off at a lower price to the lower end builders. This sputtering process is highly critical to the final sound of the mic. Hence the reason for the cost vs frequency response.
Alctron mc410 has full frequency response 30-22.000 hz for example and costs 45$.
That could happen when they made them cardiod. That canceling of noise in the side and back cancels the bass too. But for voice is something good because the voice is not that low, so you end with an auto High pass filter. You can always EQ.
Audio Engeneer student here! Awesome info
that “20Hz” are not Hz. They are radiants/seconds that divided by 2*pi becomes Hz.
good video. i like talking with a whiteboard and share experience. great :D "we want more we want more"
What was that first tube mic that he designed for Rode?
What's the function of the bipolar in the last circuit?
I wish I'd understand more of this... :)
How to step up for + and - 60 from 48 v phantom power for the capsule? Can i get any help?
Awesome!
Dave looking at the camera is as funny as" toasty "popping up in mortal Kombat lololol
I fucking love the English accent of Australia peeps. I wish, I could manage to get even 1% of that… 😂😂😂
fan-damn-tastic... another great one.
Please video part nr so that viewer can select from list at following nr.
Great video! :-)
you know that episode of The Simpsons where Ned Flanders meets his near-duplicate? this is like that.
I hate Gravity - 2017-01-31
whenever dave looks into the camera i feel like he is checking on us whether we are asleep or awake.. haha
The Engineer - 2019-05-06
At 18:00 it's like when frodo put on the ring by accident " I see youuuuuu " hahahaha Dave's hilarious