Original DIY Tube Mic for Voiceover

[Tubetec]

Ive suggested an impedance balanced CF previously , but I havent had a chance to try it yet .

 

[rock soderstrom]

I've learned a bit about existing options in terms of what can fit into the suspended capsule design I'm looking to use, which I now know is referred to as a "ring mic" or "ring mounted mic."

Here are a few basic thoughts on your project.

If you want to go the tube route, I would go for a classic anode out topology, as that sounds more like a tube mic (IMHO). CF microphones are also good, but are used more for loud sound sources and "natural" recordings. Cathode followers are more neutral in sound.

The Royer LDC mod, the Neumann M49 (possibly in the cardioid only version) or the SELA T12 would be possible candidates, along with many other conceivable circuits. Have a read through this thread, lots of good information there: (your 5840 is a more or less a subminiature version of the 6AK5!)

https://groupdiy.com/threads/diy-tube-mic-project.87512/

On the subject of the "Ring Mic", the biggest challenge from my point of view is the somewhat long cable from the capsule to the electronics, due to the design. This has already been discussed in one of the threads you linked.

The challenge here is the extremely high impedance at this point. Even with "normal" microphone designs, this is a challenge that has to be mastered first.

You have to work very cleanly and carefully. Proper shielding for the entire electronics and capsule (keyword Faraday's cage) is a must!

Make sure that the cable from the capsule to the tube is not too long. It must of course be very well shielded but also very flexible, which is often contradictory.

Your setup will look something like this (1), right?
Perhaps you should think about optimizing it in this way (2). Just an idea, it depends on how big your ring will be.


PS: the really big advantage of an FET would be that you could attach it to the back of a one-sided capsule. That keeps the the cable from the capsule to the impedance converter unrivaled short.
PSS: When selecting the capsule, please also consider the preemphasis. All circuits discussed so far are flat.

Just my 2€cents...

 

[HikariFaith]

Suitable output transformers for CF circuits are relatively easy to obtain, as they have much lower step-down factors. OPTs for classic anode-out circuits have something between 7:1 to 15:1, whereas OPTs for CF circuits are more in the 4:1 to 1:1 range.

Inverted input transformers for microphone amplifiers based on transistor or opamp technology are very suitable. They are also not that expensive and are readily available second-hand.

I'm disappointed in myself. This whole time I hadn't tried looking at Mouser or Digikey for audio transformers. I didn't see anything usable on LCSC so had assumed I wouldn't find anything on those sites either, completely failing to remember that they often stock components LCSC doesn't. In your opinion, would this be a suitable transformer?
https://www.digikey.com/en/products/detail/triad-magnetics/TY-250P/7318267

Here are a few basic thoughts on your project.

If you want to go the tube route, I would go for a classic anode out topology, as that sounds more like a tube mic (IMHO). CF microphones are also good, but are used more for loud sound sources and "natural" recordings. Cathode followers are more neutral in sound.

The Royer LDC mod, the Neumann M49 (possibly in the cardioid only version) or the SELA T12 would be possible candidates, along with many other conceivable circuits. Have a read through this thread, lots of good information there: (your 5840 is a more or less a subminiature version of the 6AK5!)

https://groupdiy.com/threads/diy-tube-mic-project.87512/

On the subject of the "Ring Mic", the biggest challenge from my point of view is the somewhat long cable from the capsule to the electronics, due to the design. This has already been discussed in one of the threads you linked.

The challenge here is the extremely high impedance at this point. Even with "normal" microphone designs, this is a challenge that has to be mastered first.

You have to work very cleanly and carefully. Proper shielding for the entire electronics and capsule (keyword Faraday's cage) is a must!

Make sure that the cable from the capsule to the tube is not too long. It must of course be very well shielded but also very flexible, which is often contradictory.

Your setup will look something like this (1), right?
Perhaps you should think about optimizing it in this way (2). Just an idea, it depends on how big your ring will be.
View attachment 130778

PS: the really big advantage of an FET would be that you could attach it to the back of a one-sided capsule. That keeps the the cable from the capsule to the impedance converter unrivaled short.
PSS: When selecting the capsule, please also consider the preemphasis. All circuits discussed so far are flat.

Just my 2€cents...

I figured it would be a difficult task to make a ring mic. My design inspiration is primarily the Myrtle mic from Ear Trumpet Labs. My idea for solving the whole wire length problem was actually putting the tube either on the back of the capsule (where a FET would've gone) or directly under it if putting it on the back interfered with the sound. So rather than at the edge of the ring, I was hoping for the tube to be incorporated into the capsule's enclosure at the center of the ring.

 

[rock soderstrom]

I figured it would be a difficult task to make a ring mic. My design inspiration is primarily the Myrtle mic from Ear Trumpet Labs. My idea for solving the whole wire length problem was actually putting the tube either on the back of the capsule (where a FET would've gone) or directly under it if putting it on the back interfered with the sound. So rather than at the edge of the ring, I was hoping for the tube to be incorporated into the capsule's enclosure at the center of the ring.

I know this microphone, I like it, it looks great. Positioning the tube really close to the capsule will cause acoustic problems, I think.

In your opinion, would this be a suitable transformer?

You are talking about a OPT for a cathode follower? I do not know this transformer but I think there are better. You are from the US? Check Cinemag, Lundahl, Jensen and similar or used OPT on ebay or craigslist.

 

[s wave]

I would like to add my 2 cents (from more of a producers POV) If you want a 'general' tube mic; and since it is cheap... I say go for it and this forum/people should get you there.

BUT if you are specifically looking for that magic mic for YOUR specific voice for various voice over - I think things change a bit. IMO most voices are very specific and unique and in-turn many mic models are voice specific. Meaning some kind of fit a voice and some kind of don't. I would try every mic you can get a hold of and get a test recording... I would also say test numerous different rooms and acoustics. When you find a mic that kind of flatters your voice; find out why. Same for if a mic makes your voice sound terrible, find out why. You can throw your voice samples up on a good free spectral graphic analyzer and zero in on exactly what you are looking for. When you get clarity here... it is kind of a light bulb moment. Suddenly you see mud ranges and upper brittleness or frequency bands where your voice really shines. Armed with this info dial in that DIY tube build. When I started out years ago trying to find 'my' mics; I thought it would be an SM57/58 and either the U47 U67 U87 from all the reading I had done. Reading only takes you so far. I ended up the mics that fit me are actually the AKG d8000m dynamic mic (an onsale GC mic I got for $19.95) that actually emphasizes and flatters most of of the frequency bands that I like in my voice. Another mic is an old electret AT813 (picked it up for $12) that zings my upper voice range like the Bee Gees or Petty type stuff. Another mic that surprised me was a very hot omni dynamic mic; the EV50 ND/B (I got this like new for $60) and being a detailed hot omni - it give me a wonderful voice capture that is in the wheel house and oh-so wide dynamically, of course for songs I often WANT to cut the frequency depth and width and will choose another mic - BUT for voice over perfect! I can do all kinds of things with this. Finally my wish list mic is NOT the U47'67/87 - in fact it is the Telefunken ELAM 251. So in a nutshell: what I THOUGHT would be great wasn't - I was wrong on all choices. Go figure. I was well informed - I thought. BUT when I had a light bulb moment... I was on my way. I have run across many artists and voice over people who can NEVER seem to dial in that perfect type mic and acoustics/set up. Right now I am doing the same but with ribbons. In fact I said screw it; I will make it... (including the preamp) jsut to get more informed and have a better chance of actually manifesting 'my' magic ribbon mic. Best of luck to you

 

[k brown]

I was surprised to find out a couple of years ago that some of the top voices in the VO biz recorded their work at home using short shotguns!

 

[cyrano]

The MKH416 is a piece of standard equipment in the movie business. A bit less today, perhaps, but nearly all recordists will have at least one...

I sold my MKH816 to the VO actor who handles all NatGeo documentaries in Dutch. But that's a long shotgun. Doesn't fit in smaller booths.

 

[HikariFaith]

I was surprised to find out a couple of years ago that some of the top voices in the VO biz recorded their work at home using short shotguns!

Yeah, the voice actor I have a workshop with tonight recently told me that they use the Perception P220 as their general workhorse mic, and have done so for much of their career to great success. Another voice actor I've been doing workshops with said any mic can sound professional with the right room treatment and mic technique, which is why my current focus is sound treatment for my room. DIY tube mics are a later thing, because there's no point in a fancy mic if my room has bad acoustics (and sadly my bedroom is my only option for a recording space). I'm currently trying to plan out how to sound treat/proof my room without breaking the bank or requiring me to leave the walls devoid of any decorations. My spare time in between is being spent on research for my tube mic design for fun.

 

[Emmathom]

In a studio doing mostly voiceover with many different speakers (people who speak I mean..) AND for a decent-low budget (let's say 1000$ max.) I would buy several LDC second-hand mics like for example AKGP220, AT4033, MK4, SM7 (and more) to be able to switch according to each voice... (why not a cheap ribbon too ? like sE Voodoo I + micbooster)

 

[s wave]

Great Mics for the budget ~ are 3U for sure, from the Black to the Teal to MKI thru MKV. Choose from the classic modelling chart.

 

[MicMaven]

I would buy several LDC second-hand mics --- and (maybe) a cheap ribbon too . . .

While I may be hounded out of the principality for heresy or treason - I suppose I am the only one who favors dynamic type microphones for speaking assignments. I find dynamic microphones easier to set gain and close talk, rejecting or minimizes ambient noise from the speaking venue. While they lack the "cool" factor often atributed to condenser microphones, I much prefer dynamic microphones for many speaking assignments. Consequently, I prefer dynamic elements for computer speech recognition and amateur radio, among other applications.

Shoot, even the late Bob Heil (K9EID SK) agrees with this preference. Bob is the only non-musician in the Rock and Roll Hall of Fame (as a sound man - you know, he created the Quadraphenia sound system for The WHO and live systems for the Greatful Dead, among others) and owned HEIL SOUND selling rophones for recording and broadcast. Bob concurred with many of my decisions to use dynamic microphones.

So ... I confess my little peche mignon: I prefer dynamic mics for many speaking assignments. (He typed, as he donned his trusty Teflon(R) suit)

James

 

[s wave]

While I may be hounded out of the principality for heresy or treason - I suppose I am the only one who favors dynamic type microphones for speaking assignments. I find dynamic microphones easier to set gain and close talk, rejecting or minimizes ambient noise from the speaking venue. While they lack the "cool" factor often atributed to condenser microphones, I much prefer dynamic microphones for many speaking assignments. Consequently, I prefer dynamic elements for computer speech recognition and amateur radio, among other applications.

Shoot, even the late Bob Heil (K9EID SK) agrees with this preference. Bob is the only non-musician in the Rock and Roll Hall of Fame (as a sound man - you know, he created the Quadraphenia sound system for The WHO and live systems for the Greatful Dead, among others) and owned HEIL SOUND selling rophones for recording and broadcast. Bob concurred with many of my decisions to use dynamic microphones.

So ... I confess my little peche mignon: I prefer dynamic mics for many speaking assignments. (He typed, as he donned his trusty Teflon(R) suit)

James

I think dynamics are very good for untreated rooms ~ and over all a great choice. Heil did say, for a long time, that up to 3/4" dynamics (for 30 years) "the market has been stuck with mushy, mundane-sounding dynamic microphones". I think his attitude changed when he talked with Joe Walsh http://recordinghacks.com/2008/07/15/large-diaphragm-dynamics-bob-heil/ and made LARGE dynamic mics. I personally love the old reporters standard EV50 ND/B dynamic - a smaller diaphragm mic for much voice over and more.. With all the better magnets and materials it seems like every category has winners. There are el cheapos that work great too and some sound like condensers and vice versa. Generalities hold pretty true. BUT for a specific voice; I like a specific mic. tc

 

[Emmathom]

Beyer M88 !

The problem with dynamic mics and voiceover is their lack of sensitivity which makes them sensitive to the mouth to capsule distance. You move foward for 5 cm and the level (and even the sound) changes. The speaker has to maintain exactly the same distance throughout his performance and that's not easy...

 

[Khron]

Beyer M88 !

The problem with dynamic mics and voiceover is their lack of sensitivity which makes them sensitive to the mouth to capsule distance. You move foward for 5 cm and the level (and even the sound) changes. The speaker has to maintain exactly the same distance throughout his performance and that's not easy...

Well, for voiceover, it's not impractical to use a pop-filter, so that can be used as a "reference"..?

 

[rock soderstrom]

The problem with dynamic mics and voiceover is their lack of sensitivity

But this is also an advantage, acoustically suboptimal rooms are not so strongly emphasized. It's true, the voice talent must be more disciplined to keep their distance from the microphone constant. Pop filter helps with this...

 

[Emmathom]

But this is also an advantage, acoustically suboptimal rooms are not so strongly emphasized. It's true, the voice talent must be more disciplined to keep their distance from the microphone constant. Pop filter helps with this...

Yes there's great acoustic advantage in a non treated room for sure

 

[jeremynothman]

In a studio doing mostly voiceover with many different speakers (people who speak I mean..) AND for a decent-low budget (let's say 1000$ max.) I would buy several LDC second-hand mics like for example AKGP220, AT4033, MK4, SM7 (and more) to be able to switch according to each voice... (why not a cheap ribbon too ? like sE Voodoo I + micbooster)

I can certainly agree with the practicality of this (especially if you have time to test out mics on the talent), but if you need to sell your studio based upon the gear, sometimes one Neumann mic is worth more than all of those combined. I would think that a TLM103 or a U87ai would be a better investment.

But anyway, this thread started with a DIY tube mic, and it could still have its value.
Is it just for voiceover, or also for ADR?

Also, there are TLM103 style bodies available for pretty cheap, so why not match that to the JLI-103? Also, I know someone has done a version of the M49c PCB to fit it!

 

[HikariFaith]

Is it just for voiceover, or also for ADR?

I actually don't know what ADR is. Intended use is voiceover/voice acting.

 

[HikariFaith]

I know this microphone, I like it, it looks great. Positioning the tube really close to the capsule will cause acoustic problems, I think.

I'm assuming that's mostly from heating as opposed to EM interference? I'm hoping to suspend the mic upside down from a boom arm when it's complete, so the tube would actually be above the condenser. I've also been thinking of a physical separation between the tube and the capsule, primarily for heat dissipation. if that doesn't work, then I'd just accept defeat and put the tube on the outside of the ring. I don't know what sources there are out there for info on how far a tube can be from its capsule before distortion becomes a factor.

You are talking about a OPT for a cathode follower? I do not know this transformer but I think there are better. You are from the US? Check Cinemag, Lundahl, Jensen and similar or used OPT on ebay or craigslist.

The output transformer, yeah. Looking at it again, it does appear to be from Triad, which I've heard good things about on here, so I'm confident it can at least serve its purpose even if it's not perfect. My power input transformer is also from Triad: https://www.digikey.com/en/products/detail/triad-magnetics/F4-24/4878613. I'm hoping it has enough output current to actually power everything, cause it was like half the price of the recommended transformer in the schematic.

After re-examining my plans and the components needed, I've actually decided to postpone any sort of PCB designs and will instead be using exclusively through-hole and chassis-mount components on perf board for prototyping purposes. That way, if things don't pan out as expected, I can simply remove the components and rearrange them on a fresh board. Biggest concerns with doing this are issues with impedance control and ensuring proper wiring/routing of the tube and capsule. Odds are, I'm gonna be using a bunch of screw terminals and butt splices to minimize soldering of the more important components. Thinking of doing tests without an enclosure at first, or something minimal and cheap, then going to the ring enclosure once I get the basic setup to work.

 

[jeremynothman]

I actually don't know what ADR is. Intended use is voiceover/voice acting.

ADR stands for Additional Dialogue Recording. It’s recording voice to screen for film/TV, trying to match with the originally recorded audio, which needs to be replaced (usually because it was too noisy on set).

I asked, because usually one would try to use the same mics as on set, wherever possible. A lot of Voiceover studios do that kind of thing too, and then having mics like an MKH-416 or MKH-50 are reasonably normal in addition to a U87