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- Опубликовано: 27 сен 2024
- Part 7 of Microphone Technology with Doug Ford, former head designer at Rode Microphones.
This video Doug takes you through the design of the Rode NT3 and NT1000 microphone designs.
There is a ton of stuff in here:
Closed loop unity gain JFET and bipolar follow circuits.
Bootstrapping out miller capacitance.
JFET biasing.
How to eliminate expensive high value resistors.
How to add a bridged-T network to add marketing "pizazz" to a microphone.
How to stop oscillation in closed loop systems.
How to test and design closed loop systems for stability.
Dominate pole compensation.
Traps for young players in power amplifier stability.
How circuits with capacitive loads oscillate.
Emitter degeneration.
Parasitic inductances and their effects.
How to design a low noise and ultra high dynamic range valve based microphone preamplifier.
Microphone power supplies.
And how to design an amplified zener current source.
All other videos in this series are HERE: • Microphone Technology ...
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What a privilege to be able to watch an expert explain the reasoning behind their thinking. Excellent content!! Thanks Dave :)
I hope that all of us that are following Doug Ford's wonderful explanations, understand that this is a one-in-a-million chance to learn from Doug's career. Try going to Rhodes or other manufacturer and attempt to get them to teach you these trade secrets. You couldn't pay enough to learn any of this. With what I have learned, I could go into the microphone manufacturing business (if I wasn't retired). I once had the president of a company, say, "Anyone can see what we did, but the hard part, is learning WHY we did it." Thanks for taking the time to create, edit, and upload this material to RUclips.
Exellent series Doug and Dave. Thankyou, most entertaining and educational. Rhode might be a bit pissed though seeing all their trade secrets explained ):
Doug is a real character
Stuff Rhode, this is fantastically educational ;)
😂😊
@Danny Knapp Because he doesn't work there anymore
As an EE you should really appreciate the work that has gone into this. had to watch it several times to get some pretty darn good jewels out there.
1st year EEE student and I can barely understand a thing...
@@MangomaniacThe thing about the electronics hobby is you learn about it through watching and reading stuff of this nature repeatedly.
I have been an experimenter for 30 years and have had no formal education in electronics apart for some mentoring and I had no problems with it. So that's my suggestion, get really interested in it and watch and read things repetitively and you'll learn a lot.
Do you like to experiment with circuits much?
@Dazzwidd I haven't really experimented with any circuits, though I am interested in electronics and how they function. I've just never had the ability to get certain parts and design things myself in my free time.
@@Mangomaniac Well you only learn from practical experience and that comes from playing around. Start in an area you're most interested... audio, radio whatever.
I build circuits using blank pcb and employing what's known as "Rats nest" construction.
You can even roll out a coffee tin and use that glued to a piece of wood if you want to keep it really cheap
I have an original Rode NT1 (battleship grey version, not the 'A' model), best mic I've ever owned! Great to see the designer behind it and the genius in design. I'd love to see more pro-audio related videos on EEVBlog!
I'm pretty sure the old Rode NT1 is a Jim Williams design and not a Doug Ford's, it also wasn't made by Rode in australia, it was made by 797 audio in china, I believe back when rode started, they didn't make their own mics.
Actually the very first NT1 ( grey) has a transformer. The NT2 is J.Williams, which then became his NT1 ‘cream’ schoeps type.
That was so cool!! When he spoke of a -120V FET, the first thing I thought of was a tube; I fell off of my chair when he actually said it.
20:59 "Distinct preference" Doug Ford is an absolute genius and EE rock star. I've probably watched this series 134,789 times.
This is a fantastic series that I had not yet seen. Doug is a good teacher, and his designs are very interesting. Also interesting to hear about production issues/cost savings, etc. Thanks.
I really love this series. I'm familiar with Rode microphones, and it's really cool to hear Doug talk about the designs. Thanks again Doug and Dave. Really awesome.
Dynamic duo. Bring Doug back. This was informative and fun.
This series is a classic in the making - simple as that. Make sure you back up these vids for posterity
I watched this video before and after taking my first VLSI design class. After learning to design Opamps from Fets everything in this video makes sense. This might be one of the best displays of a good/real design process on RUclips, everything is organic and logical
I think I've watched almost all the videos, but I skipped this series about microphones. But as usual, now I'm very interested in microphone techniques, and this is a gold mine! Thanks, Dave, yet again. The RUclips channel that keeps giving.
Damn this video just opened my eyes. I have a pair of NT3s, and i always hated that bump, and eq-ed it out. First thing in the morning i am getting my soldering station and getting that part of the circuit out. Thank you so much!
polyputhekettleon caps - i hear those are popular amongst the audiophools.
Especially when they hit a snag in the design process :)
I dont know why in the hell im just now seeing this but it is awesome. Some of it is flying over my head at lght speed but im determined to be able to do this before im dead. I would love to see more of this type of content. Just designing different things.
This video is incredibly educational and well explained in such a way that I enjoyed watching. Thank you for creating this. I designed my own preamp / mic processor and ribbon microphone from scratch and it's nice to see youtube has some videos out there like this to help people learn right from the source.
Ok, so now I added some R0DE mics to my amazon cart :-) Thank you for doing this, and please more content like this. I really appreciate the deeper dives into practical analog
This has been a fantastic series, Dave. Hope to see more from Doug in the future. Maybe you could get some other designers from other companies to discuss the products they've worked on too?
Yupp, disconnected T bridge network, this is one hell of a mic now (even tho it was that allready, but less sibilant now). I'll have to do a tutorial on that.
Cool
Fantastic video series! I wish I had someone like Doug as a mentor.
another great Doug Ford video... could listen to him talk topology all day.
I love this video. Not only does it have a highly informing value, but is also very entertaining.... especially when the two of you have a great genuine laugh about them silly mic customers demanding more excitement in the upper range. I would say that many artists have way too much excitement in their own upper region (brain) anyways.
Thank you for this great video D^2.
Definitely not 101.
Yeah, closer to 331.
Room 101
Can someone please give Dave some good whiteboard pens in the next mailbag!? :D
Wont help I dont think he uses pen caps 😆
I've zapped my lips a when using my first DIY valve amplifier + PA not sharing the same ground.
Apart from the groin and heart, I think that's the worst spot to get zapped. It was the fastest lesson ever learnt.
Most interesting thing I've seen all week. Thanks Dave and Doug!
Nice Doug!
Feels like a lost art these days though.
I appreciate your time though. Thanks.
Great tutorial. I haven't designed (active) analog circuits since college.
'tis always good to hear why something was designed a certain way, not just how it was designed.
Please, more of these vids with Doug!
huge audio enthusiast here so this content with Doug I'm vibing with!
I enjoyed learning about the construction of the NT1000 as I've experimented with it before, very easy to make recordings at low volume with this mic, and hardly any gain needed. Now I know why!
It's very interesting (comical) watching a couple EEs at work. Very good!
I went to Sydney uni electrical engineering, we did some basic opamp stuff, I wish we were taught more practical designs and testing. We did more maths with pen and paper and maybe some simulations. Thanks Dave!
Yeah, i feel like today you can explain things differently. like explaining how transistors work together to make "topologies" rather than too much math that you forget what you are trying to even do.
I have an electrical engineering degree and just learned more in this video than all of college
Solved my problems about initiating a design from scratch! Thanks for that 😀
15:58
"Connected to a sig genny" is the most Australian EE colloquialism I have ever heard, fantastic.
"Bootstrap the buggaz"
That was awesome, I need to rewatch and take notes!
wow .... such a great time to have all that knowledge in reach by some clicks
I want to build my own preamp now :D
oh and thank you so much EEVblog
I'm two years into my elec engineering BS and when does it all click like this?
I was thinking the same thing when I was in EE school some years ago. It comes with practice.
Read some electronics books that aren't your textbooks. The Art of Electronics (Horowitz and Hill) is a must. It's expensive, but worth it. Anything by Bob Pease, Jim Williams, and Doug Self.
Cheap but harder to find: The old databooks (both tube and transistor) from RCA and GE. The old US Navy electronics course materials. The ham radio stuff from ARRL. Try libraries, used bookstores, and EBay for the old stuff.
Find schematics of things that interest you, and study them. Model them in SPICE and play with each segment of the circuit until you understand what each voltage and current is doing. Try making them better. Try making them worse in interesting ways. Cut and paste bits from different circuits and learn to make them work together. Then try to build them with real parts. Use them, test them, modify them, break and fix them. Rinse and repeat. You'll get there!
@@brettclark8020 The Art of Electronics is a very good book!
Do white board markers ever work properly? This video brought back memories of lectures in the 90's when lines were drawn, then drawn over again because they were faint, then drawn over a third time before the lecturer said "@#%& it" and threw the marker in the bin. Every lecturer saw two or three white board markers hit the bin :-)
+EEVblog Could you make a video, explaining this video for ... amateurs?
Thank you both ,I love mic design series
why not use an opamp instead of designing a unity gain power amplifier with jeft single ended input?
More expensive and higher noise (or rather, you have to trade those off against each other)
Absolutely gorgeous 💕💕💕...
No other can teach us like that
Wow Nick, I needed this video, I have a ubit Xv6:2, the mic is the part I'm not happy with, the audio pre amp and compression, is the other part that, and here it is all together. Marvellous thankyou Nick , Paul M0BSW
learned alot from this series. Thanks. I like to tinker with wide band audio in CB communications. Now I have some better ideas for mic preamps and mic choices.
Love this. What a bromance.
Very useful! Convinced me that I don't want to do analog!
yes but as Dave's poster says. Any idiot can count to 1 :)
Rob B I just know that designing digital systems exclusively is on their own often a very challenging work. And from my today's point of view, I simply like it more.
There is a simple trick to reduce the noise figure. Simply add a voltage divider on the output. Your 12db noise figure will drop to almost nothing.
great video, I didn't think you would ever use a power amplifier in a preamp, very interesting topology.
We want to see more of Doug Ford.
My god! I would love it if an engineer would write "more excitement in this region" on the data sheet. I dont care what kind of device it is, but thats something that needs to be in a datasheet :)
14:33 Amateur question, why don't they add the different transfer wobbles with EQ?
*presses play again*
Oh, I see. So it's really just the "buy more stuff and show it off" drive.
What a beautiful mind. I using rode microphones in my studio btw. Thanks for very interesting topic and some topology suggestions, very exciting. Especially at the hi end of frequency response :)
damn you and thank you very much for dominant pole compensation, i have a failed guitar amp that i could not troubleshoot; analogue audio amps were glossed over in college
I'm a mining engineer, I'd love to see a very low frequency mic schematic or a tweak to one of those mentioned that allows for very low frequency pickup.
I still don't understand how to use BJTs because of their nonlinear behaviour. It's confusing. I am going to play with some JFETS or MOSFETS, because of their more linear response. (Mind you, my background is from mathematics, so I want things that are more ideal/linear.)
A BJT has an intrinsic exponential relationship between base-emitter voltage and collector current. An FET has an intrinsic square law relationship between gate-source voltage and drain current. Neither of them is linear, and transistor circuit design consists of ways of using them in such a way that the effect of variance in transistor characteristics becomes negligible. Good luck with the MOSFETs and let us know if you manage to bias one to your calculated design without using a trimming potentiometer.
Great stuff, guys - really fascinating stuff.
Dave, I know this is a bit offtopic, but check out this alternative uses for a scope people are coming up with these days, Beams of Light by TRSI
"Did you stick one until it works ..."
Dave, please don't give away the most important trick in electronics design!
Thanks for these vids on Microphone Technology Amazingly Interesting :)
That's an old but nice one with a real deal mike design pro! Very interesting and enlightening. Makes me wish I could work with Doug and learn tons of cool stuff he knows.
35V RMS? Then you just put a step-down transformer on the output, but then I'd just o for an all-tube construction putting the transformer in the plate circuit.
I bet a low-noise +48V to filament and plate converter is perfectly viable especially if you go for a hybrid design where the tube (subminiature, preferably) is there for specific distortion rather than being an amplifying workhorse.
Very nice and informative video.
Legend - amazing knowledge, thank you :)
Your best video yet. But i cant stress enough: your trade is a SCIENCE. Recording music is an ART. If your favorite songs were recorded with flat freq response mics and everything dead flat - quite simple they wouldn't be your favorite songs any longer.
It's OK... we laugh at product engineers and electronic technicians also at some choices made.
That guy in your video (ex-Rode) is an absolute genius. I use both the NT1K & NT3 every week! Great mics are some of the others made by Rode. Lately seems they are to focused on consumer level goods however - worryingly.
The one thing I don't like about Dave is that he tries to finish everyone's sentences to show that he's aware of the topics too. This may be due to an insecurity about where his knowledge level is. Other than that, great stuff.
What a super series - absolutely fascinating! A big thank-you from me, Dave. I'm curious about one thing. Doug used a JFET in the early part of the video, which I might understand to be because of their high input impedance and low noise (compared to say, a BJT). Would a MOSFET also be ok in that position or is a JFET preferred? Thanks for any light you can shine on this point.
MOSFETs are pretty much all enhancement mode devices, which means the gate sits at a voltage somewhere between the source and the drain and it's a pig to set a reproducible dc bias point.
JFETs, on the other hand are depletion mode devices, and their gates sit at a voltage below the source, making it easier to set a dc bias point, especially if you have a source resistor to stabilise it.
I find a very low resistor on the emitter of the top pnp going to 15V can sometimes increase stability quite a lot..
When you run a dynamic mic with the phantom power on it can be hard to sing. Happened to me on a mixer that could only have phantom on or off for all inputs rather than individual inputs.
This video helps a lot, thanks!
In the circuit at Min 4:00 the FET would get a 90V spike impuls over the 50pF capsule in the moment when it is switched on. Will the FET survive this?
It's a JFET, so there's just a robust PN junction which will forward bias to absorb the spike. It's not like the fragile gate insulation layer in a MOSFET.
very interesting... Ive soooo much to learn!
Yes!! Great stuff. Thanks!
Great video! Good old Dave :)
EEVblog, and I'm SURE you wouldn't mind a few thoughtful people "borrowing" that low noise power supply configuration (around the 30 min. mark) for a modern preamp... would you? LOL
Top notch video.
If that's his pre-amp design, I want to see his power-amp design!
You probably need a firearms license for that.
These mics usually have balanced outputs. He is most likely not showing the output transformer ?
SPIN A YARN WITH DOUG ON THE AMP HOUR PLEASE.
@EEVblog: Even by watching the video again (don't know how many times) I can discover some new details again and again! I also liked the frequency with the little more "woohoo" very much. :-D
That kind of videos are very interesting and very well in teaching electronics basics and circuit design - wouldn't that be good to have some more of those type of videos? Maybe (if you are allowed to) some more out of your field of operations back from your days at other companies?
please more of that!
Very useful thank you 🙏
Depletion mode fet and PNP BJT?
The guy loves his p-doped components. This will raise the cost a lot
Motivates
I'm with Dave. As an engineering "purist", I'd suggest a flat response at the preamplifier and let them boost treble at the mixing board. That is ... unless that preemphasized response were part of an accepted industry standard. (Or at least make it switchable for customers who DON'T want it.)
I removed that boost in my NT3s thanks to this video, and it sounds way better! :)
Damm i have a lot to learn
Don't vacuum tooobs have a bit more noise than semis ?
So Good!!
Which JFET is he using? Genuine ones seem to be as rare as hens teeth these days.
LSK170 (2SK170) is considered the “duck’s guts” when it comes to mic preamps, and they aren’t that expensive. Whether you get a real one or a fake though, is anyone’s guess…
Any tips for beginners plz 🙏🙏🙏
mic has not seen in all vidio ?
Hi,
We appreciate the tutorials
Ermm can you please do about how to make a simple fm radio especially from this circuit I followed from after designing a microphone in this circuit!! Have done some research but I don’t under what section is modulator or mixer combining the carrier frequency to audio waves being transmitted “what’s the schematic or circuit for audio mix??
Cool, but why are they designing amplifiers with discrete transistors and not just using high quality op amps? Is it all marketing?
Probably cost vs noise vs supply voltage (= max output)
This I love
Grate!
Thanks
The best regards :)
Great video, but there is something puzzling me..
is there any particular reason for not using op amps in this kind o circuits? when should an op amp be used versus these transistor based amp stages?
Try finding opamps that run at the high voltages needed by the microphone capsule's he's talking about :)
@@jaycee1980 LTC6090 will run from a 140V rail. About £7 from DigiKey in one-off. It's a CMOS opamp so might be a little bit noisier that you want : 3.5μVp-p 0.1Hz to 10Hz, 11nV/√Hz at 1KHz, 14nV/√Hz at 10KHz typ. Sadly, designing with discrete components is becoming a dying art.
@@RexxSchneider it is indeed becoming a dying art.. the big bugger for these sorts of things is discrete JFETs seem to be practically obsolete now. I doubt they would like to commit to one opamp like the one you mentioned, and the noise might well break the deal for them
@@jaycee1980 Discrete JFETs never really became popular in my experience. Back in the 1960s and '70s, we had the 2N3819 and later on the cheaper MPF102, but there wasn't a lot to choose from. Part of the problem was matching and I remember having to specify an expensive dual matched JFET pair in a single can for a project where the client needed very high impedance and excellent thermal stability. You just couldn't do it with a discrete pair. Then along came the TL071 family and it became pointless using discrete JFETs for anything other than very niche applications. That was the nail in the coffin of discrete JFETs, along with the growing popularity of robust MOSFETs - the early ones were too static sensitive. Now we're starting to see the demise of small-signal MOSFETs because you might as well use a CMOS opamp most of the time.
Dave,
I'm not trying to be funny... But, what is a 10 puff capacitor. Does it mean that I only have to pass it 5 times... puff, puff, pass... seriously, is that a 10 pico-farad capacitor? Thanks.
Yes pF
Tons of treasure, but not for beginners.