EEVblog

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 ...
Forum HERE: www.eevblog.com/forum/blog/eev...
EEVblog Main Web Site:
www.eevblog.com
EEVblog Amazon Store:
astore.amazon.com/eevblogstore-20
Donations:
www.eevblog.com/donations/
Projects:
www.eevblog.com/projects/
Electronics Info Wiki:
www.eevblog.com/wiki/

[@BarriosGroupie]

This series is awesome because Doug knows what he's talking about.

[@matijatatomirovic3351]

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!

[@dearjulio]

What a privilege to be able to watch an expert explain the reasoning behind their thinking. Excellent content!! Thanks Dave :)

[@johnwheeler9994]

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 KZbin.

[@RobB_VK6ES]

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

[@Dazzwidd]

Stuff Rhode, this is fantastically educational ;)

[@dmeemd7787]

😂😊

[@eyescreamcake]

@Danny Knapp Because he doesn't work there anymore

[@PatrickPoet]

I looked at an NT3 frequency response curve just now and sure enough, there's a bit of a whoohoo! at 6kHz

[@jukees3658]

thank you for this high quality, free and enjoyable education.

[@kwazar6725]

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.

[@Mangomaniac]

1st year EEE student and I can barely understand a thing...

[@rish1459]

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.

[@JamieTyson]

I've watched EEV Blog for years but this is by far the most informative video I've seen! Thank you! Lots of great stuff in this one! Thanks Doug and Dave!

[@JWalterHawkes]

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.

[@PelDaddy]

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.

[@0tt0z]

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.

[@kenzingzong6704]

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.

[@JackZimmermann]

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 KZbin channel that keeps giving.

[@bitrot42]

Would love to see more videos with Doug. He's a class act, and analog design is a great subject. How about designating a day of the week as "Doug Ford Day"? :)

[@Dazzwidd]

He's pretty good hey? :)

[@pnjunction5689]

Fantastic video series! I wish I had someone like Doug as a mentor.

[@cameronwetzel7156]

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 KZbin, everything is organic and logical

[@matijatatomirovic3351]

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.

[@hemantakumarbujarbauah7104]

Cool

[@tomjones9137]

I love Doug's manner of speech...very interesting...I could listen to him for hours

[@userrnamenotavailabl]

How did I miss this? Amazing info download from Doug, thanks for bringing this out for us to learn from. Fantastic.

[@fpgaguy]

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

[@dinkc64]

Most interesting thing I've seen all week. Thanks Dave and Doug!

[@RayR]

Dynamic duo. Bring Doug back. This was informative and fun.

[@LektroiD]

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!

[@NoRobotAudio]

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.

[@gregcotter6992]

Actually the very first NT1 ( grey) has a transformer. The NT2 is J.Williams, which then became his NT1 ‘cream’ schoeps type.

[@gordslater]

This series is a classic in the making - simple as that. Make sure you back up these vids for posterity

[@tmmtmm]

polyputhekettleon caps - i hear those are popular amongst the audiophools.

[@Dazzwidd]

Especially when they hit a snag in the design process :)

[@Darzzr]

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?

[@elmo2you]

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.

[@deviantmultimedia9497]

20:59 "Distinct preference" Doug Ford is an absolute genius and EE rock star. I've probably watched this series 134,789 times.

[@uzairmughal4976]

Solved my problems about initiating a design from scratch! Thanks for that 😀

[@jrallen870]

another great Doug Ford video... could listen to him talk topology all day.

[@stonail665]

Thank you both ,I love mic design series

[@mw9558]

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.

[@ChaplainDaveSparks]

Great tutorial. I haven't designed (active) analog circuits since college.

[@snarkyboojum]

Can someone please give Dave some good whiteboard pens in the next mailbag!? :D

[@GoldenNuggetRec]

Wont help I dont think he uses pen caps 😆

[@chalecoflash]

+EEVblog Doug is just awesome, I hope we can get more videos from him soon.

[@Tjousk]

'tis always good to hear why something was designed a certain way, not just how it was designed.

[@OtakuSanel]

you should have him come back for more lessons! turn this into a permanent thing?

[@TheKingKorg]

@Olav Viking Mate, microphones are not used just in music industry.

[@TheKingKorg]

Yes, please!

[@johnyang799]

@Frank Olsen Are you fucking stupid?

[@duroxkilo]

@@johnyang799 :}} didn;t expect to read that

[@maciejgrzesik7191]

I'd love to see more videos with Doug as well !

[@petersage5157]

Years and several hour-long web searches later, and I think I have found Doug's jFET. Only match I could find is the Solitron FND15. Not a very common part; and I couldn't find that particular topology built from discrete components anywhere. CIA, you say? A conspiracy theorist might suspect that defense contractors have tried to redact all knowledge of this chip. By the way, we haven't heard anything from Doug in quite a while...

[@chrisreeves4110]

Nice work. I did a bit of searching and found a similar chip. IFD89 by Intergrated Diodes Funnily enough.

[@RuneBroberg]

He mentioned Siliconix, and their Si1000 are a good match. There's an app note in their 1986 databook on using it for electrets etc. The databook is available on bitsavers.

[@declanallan885]

huge audio enthusiast here so this content with Doug I'm vibing with!

[@TheKingKorg]

Please, more of these vids with Doug!

[@kgsalvage6306]

It's very interesting (comical) watching a couple EEs at work. Very good!

[@Necrocidal]

That was awesome, I need to rewatch and take notes!

[@robinparnaby3335]

Nice Doug! Feels like a lost art these days though. I appreciate your time though. Thanks.

[@HitchHiker4Freedom]

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.

[@JuddNiemann]

Great stuff, guys - really fascinating stuff.

[@cj.tranzistor]

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 :)

[@Landrew0]

Definitely not 101.

[@MarkMcDaniel]

Yeah, closer to 331.

[@Frohicky1]

Room 101

[@roshandev8604]

Absolutely gorgeous 💕💕💕... No other can teach us like that

[@VirtuelleWeltenMitKhan]

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

[@erg0centric]

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

[@ambientograph1]

The pure enthusiasm and inside jokes are really nice to watch! Now if I could only understand what they're laughing about... Maybe one day.

[@mrfeenix1]

Thanks for these vids on Microphone Technology Amazingly Interesting :)

[@anderslennqvist6168]

Very interesting, great content. Thank You!

[@sugameltpastriescoffee7186]

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!

[@darer13]

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.

[@Tannz0rz]

15:58 "Connected to a sig genny" is the most Australian EE colloquialism I have ever heard, fantastic.

[@NVM_SMH]

"Bootstrap the buggaz"

[@jozzef1990]

great video, I didn't think you would ever use a power amplifier in a preamp, very interesting topology.

[@MrPolymath0]

wow this is real interesting, my favorite thing to learn about is microphones. its the most interesting component in the world

[@thekaiser4333]

+EEVblog Could you make a video, explaining this video for ... amateurs?

[@justin3594]

Love this. What a bromance.

[@kevinbeckenham3872]

Thank for a very good lecture on condenser mic pre-amp's , especially on the valve pre-amplifier; is there limit on the Ht supply voltage on the condenser element when useing valve pre - amp

[@halisidrysdale]

Legend - amazing knowledge, thank you :)

[@wesleyxu8849]

This video helps a lot, thanks!

[@alexcrouse]

I have an electrical engineering degree and just learned more in this video than all of college

[@silverioclaudio604]

I just love watching this

[@jtn191]

Yes!! Great stuff. Thanks!

[@shubhambahl]

Look at him and his love for circuits

[@tomormiston6592]

very interesting... Ive soooo much to learn!

[@phychemnerd]

Analog design is a lot of fun!

[@grantfullen9559]

Very nice and informative video.

[@antinumerology]

This is so awesome.

[@user-rp4cw9jn3k]

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

[@ForViewingOnly]

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 :-)

[@springrollwang4441]

Top notch video.

[@rimmersbryggeri]

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.

[@artifactingreality]

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!

[@theonlyari]

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 :)

[@niklaswallin9478]

I find a very low resistor on the emitter of the top pnp going to 15V can sometimes increase stability quite a lot..

[@MrBanzoid]

Very informative! Hilarious as well.

[@annsj9283]

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??

[@sergeyivanov3453]

Great video! Good old Dave :)

[@jefflambricks]

why not use an opamp instead of designing a unity gain power amplifier with jeft single ended input?

[@eyescreamcake]

More expensive and higher noise (or rather, you have to trade those off against each other)

[@kris.ell.b.7768]

So Good!!

[@PsychoticusRex]

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.

[@egeotomasyon]

We want to see more of Doug Ford.

[@garyhunkin]

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.

[@topquark22]

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.)

[@RexxSchneider]

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.

[@buffplums]

Very useful thank you 🙏

[@k7iq]

Don't vacuum tooobs have a bit more noise than semis ?

[@SetMyLife]

Very useful! Convinced me that I don't want to do analog!

[@RobB_VK6ES]

yes but as Dave's poster says. Any idiot can count to 1 :)

[@SetMyLife]

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.

[@me000]

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.

[@KeritechElectronics]

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.

[@matmay]

please more of that!

[@dinkc64]

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

[@TomAtkinson]

I have a lovely pair of factory matched Rode NTK mics.

[@uwepolifka4583]

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?

[@RexxSchneider]

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.

[@japrogramer]

Can we get a pcb Gerber file for a large diaphragm 34mm capsule and phantom power. It seems many people are building them but I can not find any open source designs.

[@helli3088]

Coluld anyone explain or make a more detailed circuit diagram of the one at 30:00. I am a novice on this but is it possible to make a simple but good preamp for an electret with that one. Anyone who can give example on components and a more complete circuit. Best regards.

[@darrylgodfrey9604]

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.

[@RexxSchneider]

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.