Original DIY Tube Mic for Voiceover

[HikariFaith]

Hi all,

I'm looking to put together a good design for a custom tube mic that I'd like to use for voice acting and general voiceover work and need some help working out the details. I'm not certain if I'll be building the design right away, but I would at least like to work on the research and early design process for a mic that can give me a good rich sound for a price that's ideally below $200 (which is why I'm going the DIY route). I'm currently eyeing the JLI-103 capsule after reading some good reviews of both it and the TLM-103's K-103 capsule that it's mimicking. What I specifically need help with are (1) figuring out how to pick the right tube(s) to pair with the capsule and (2) figuring out how to design the actual circuitry and pick the appropriate components for the microphone's circuit board.

As a stretch goal for my project, I'm hoping to get a bit creative with the presentation of my mic and design a body similar to the suspended capsule in this mic. Of course, there probably aren't a ton of great tube options that could fit that sort of form factor, so I'm willing to give up on that if it turns out to be too impractical.

P.S. - In terms of goal price of the tube, I'd like to keep it to something under $50/tube, if that's possible. I want something good that doesn't break the bank, if it exists.

 

[rock soderstrom]

Hi HF, I'll try to give you a few general tips.

First of all, tube microphones work with dangerous voltages in the power supply and in the microphone! If you have no experience with this, build a FET microphone.

The easiest way to build your own tube microphone is to adapt an existing tube microphone. This way you have everything you need (power supply, body, capsule etc...) and only change what you want. Ideal candidates would be the t.bone SCT700, 800 or 2000, for example, which are available second-hand for between 70-150€. There is plenty of information here in the forum on how to modify them, some of them already have ready-made upgrade boards...

Since you have special design wishes regarding the microphone body, I recommend the following video. It goes in your desired direction.



This type of microphone could also be set up with a tube impedance converter. You don't need a super expensive tube for this, there are still very good tubes for this job for very little money.

The 5456/6AK5W/E95F family comes to mind or the subminiature equivalent 5840 or similar Russian tubes would fit well. Unit price in NOS quality under 10€ each.

Circuits that are suitable for this are a dime a dozen. Have a good read here in the forum. A tip would be the Royer LDC mod with a 5840 tube or something from Neumann such as an M49 style mic with the 6S6B-V, EC71, 5718 or again 5840.

Good luck.

 

[kingkorg]

Hi all,

I'm looking to put together a good design for a custom tube mic that I'd like to use for voice acting and general voiceover work and need some help working out the details.

I'm just not sure if tube noise could be a bottleneck for this kind of work. As i understand people in this line of work go for quiet mics. There are some quiet tubes, but they will still be above of what solid state has to offer. Anyways you should take noise into the consideration.

 

[rock soderstrom]

I'm just not sure if tube noise could be a bottleneck for this kind of work. As i understand people in this line of work go for quiet mics. There are some quiet tubes, but they will still be above of what solid state has to offer. Anyways you should take noise into the consideration.

That's a valid point, so it can be an advantage to work with affordable tubes. You can then buy several and select for the quietest one.

However, the differences between the types mentioned above were rather small in my experience. Choose NOS quality tubes, avoid used ones, it's too much of a gamble

 

[LevinGuitar]

I have no experience with JLI103 capsule, but when I have experimented with the original K103 and chinese tube mics, it wasn't a good match mostly because of a round headbasket. So if you want to use a k103 style capsule, go for a u87 style headbasket microphone. If you'll use a cheap chinese tube mics as donor body, try with a k47 capsule instead.

 

[HikariFaith]

Hi HF, I'll try to give you a few general tips.

First of all, tube microphones work with dangerous voltages in the power supply and in the microphone! If you have no experience with this, build a FET microphone.

The easiest way to build your own tube microphone is to adapt an existing tube microphone. This way you have everything you need (power supply, body, capsule etc...) and only change what you want. Ideal candidates would be the t.bone SCT700, 800 or 2000, for example, which are available second-hand for between 70-150€. There is plenty of information here in the forum on how to modify them, some of them already have ready-made upgrade boards...

Since you have special design wishes regarding the microphone body, I recommend the following video. It goes in your desired direction.



This type of microphone could also be set up with a tube impedance converter. You don't need a super expensive tube for this, there are still very good tubes for this job for very little money.

The 5456/6AK5W/E95F family comes to mind or the subminiature equivalent 5840 or similar Russian tubes would fit well. Unit price in NOS quality under 10€ each.

Circuits that are suitable for this are a dime a dozen. Have a good read here in the forum. A tip would be the Royer LDC mod with a 5840 tube or something from Neumann such as an M49 style mic with the 6S6B-V, EC71, 5718 or again 5840.

Good luck.

Thank you for the suggestions!

I actually have pre-existing experience with high voltages from working with nixie tubes and from my current job. While I don't know if it will help on this project, I also have experience working with PID loops for transformers.

Ideally, I'd be making a new mic rather than adapting an existing one. Are there any good standalone boards out there for DIY tube mics? I'm also not certain about compatibility with different tubes and capsules. Are there any special considerations I should take? I'm currently thinking of going with the 5840 tube or some other subminiature tube. The same goes for the body and what I should pay attention to when making/designing one.

 

[Wordsushi]

Years ago, I built @RuudNL's "u67-ish Project" for VO, making sure to source a super quiet tube from Bowie at ProAudioTubes (which wasn't cheap) and overall, I was satisfied with the self-noise level, but it's daily use was curbed after reading a true horror story post from another VO artist about having a tube in his Manley Ref Cardioid die on him during the middle of a client-directed session, and not having a spare. And it occurred to me that even if you had a spare, you'd still have to burn it in and there's a good chance the mic may sound a bit different. So, I decided to switch to FET mics only for my work if only for the dependability and consistency and that ended up being my brief flirtation with a tube mic for daily VO use.

All that being said, Ruud's little 67-ish circuit is fantastic, not too involved and can run off a standard Chinese tube mic power supply and I'd recommend it to anyone.

https://groupdiy.com/threads/u67-ish-microphone.75162/#post-957415

 

[HikariFaith]

UPDATE:
I've made some progress on deciding my approach to this project. I'm currently pretty settled on two of the key parts I want to use, those being the capsule (JLI-103) and the tube (5840W). A brief email exchange with Christian Whitmore of ProAudioTubes turned up some really good tube suggestions, among which were the 5840, which he'd described as "a great tube that is neutral and transparent." This is a tube I've encountered several times already in my research as a well known and good quality subminiature tube. With the price of these tubes also being sub-10 USD, these tubes seem like the best choice for the time being.

On the subject of circuitry, 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." Because I want the capsule to be mostly separated from the remaining circuitry, that limits my circuitry options. My current choices appear to all be based on a cathode follower. I've seen some talk around the forums about a few different CF variations that I'm interested in looking into. For one, there's a short thread on the subject here. Other stuff I've seen mentioned are the Bruel & Kjaer CF circuit and zebra50's circuit, neither of which I can verifiably find the schematics for (if anyone has links to those I'd greatly appreciate it).

There's been a lot of mention of Royer mods, but I'm not actually certain of the details of the Royer mod. Is that a mod of existing circuitry? Or swapping existing circuitry for an entirely new board?

My plan for the mic body seems to be heading in an interesting direction now that I'm becoming more confident in the feasibility of a ring mic with good performance. Currently, I'm thinking of a suspended enclosure containing the capsule in the front (I'm not sure how I'd go about mounting the capsule within its enclosure), the minimum circuitry necessary to safely send signal through shielded wire to the main body behind it, and the 5840W mounted on the back of the enclosure, with my thought being that I have the tube visible for aesthetic purposes (details TBD). The finishing touch on the suspended enclosure would be mesh shielding over top of the capsule for both aesthetics and, of course, shielding. The main body would be attached to the bottom of the ring and contain the remaining circuitry for the mic, with a male XLR port at the very bottom.

If anyone has thoughts, comments, suggestions on how to think about designing the custom body, or anything else I've mentioned thus far, I'm very open to feedback, as audio electronics are fairly outside of my element. Main sticking points I'm currently on are deciding on a circuit and (really a subset of that problem) deciding on a transformer. I've seen a lot of info on transformers out there and I'm hoping I might be able to find a good transformer that doesn't run as expensive as what I've commonly seen used, as a lot of them appear to be almost as expensive as my capsule ($50).

 

[k brown]

One of the beauties of the Royer tube mic project is that the mic itself has no circuit in it - just the capsule and the tube. The power supply has the cathode resistor, DC block cap and output transformer.

I made two SDCs with Oktava MK012s, and all the mic is, is the capsule and the body shell with the tube in it; not even an output connector - I used a captive cable.

One caveat for your puposes is that the Royer, being a cathode follower, has no 'tube color' unless you use an output transformer that would provide it.

 

[rock soderstrom]

There's been a lot of mention of Royer mods, but I'm not actually certain of the details of the Royer mod. Is that a mod of existing circuitry? Or swapping existing circuitry for an entirely new board?

David Royer has published two mods. These are total conversions of existing microphones. This means that at least the circuitry is completely replaced, often also the output transformer and sometimes even the capsule.

There is the mod for (originally MXL2001) large diaphragm microphones, which is a classic grounded cathode amp. I call it the Royer LDC mod.




Then there is the Royer mod for (originally MXL603) small diaphragm microphones, which is a cathode follower. A good name for it would be Royer SDC mod, then you can better distinguish between the two circuits.


The power supply is pretty similar for both mods and is based on a voltage trippler, see links.

Edit: both mods use 5840 tubes and of course you can also build a completely new microphone with it. Both mods can be realized with different capsule types. LDC, SDC, with or without external polarization voltage, you name it.

 

[rock soderstrom]

Other stuff I've seen mentioned are the Bruel & Kjaer CF circuit and zebra50's circuit, neither of which I can verifiably find the schematics for (if anyone has links to those I'd greatly appreciate it).

@zebra uses the Royer SDC mod. Here is a list with mics they are based on a cathode follower design.

 

[HikariFaith]

David Royer has published two mods. These are total conversions of existing microphones. This means that at least the circuitry is completely replaced, often also the output transformer and sometimes even the capsule.

There is the mod for (originally MXL2001) large diaphragm microphones, which is a classic grounded cathode amp. I call it the Royer LDC mod.

View attachment 130719


Then there is the Royer mod for (originally MXL603) small diaphragm microphones, which is a cathode follower. A good name for it would be Royer SDC mod, then you can better distinguish between the two circuits.

View attachment 130721
The power supply is pretty similar for both mods and is based on a voltage trippler, see links.

Edit: both mods use 5840 tubes and of course you can also build a completely new microphone with it. Both mods can be realized with different capsule types. LDC, SDC, with or without external polarization voltage, you name it.

Okay, wow. That helps a lot! Thank you!

When it comes to the power supply, are there any special considerations I should take? I know of other ways to triple voltage that can use smaller and more efficient components (at a lower cost, too) but don’t know if there’s anything about the tripler that affects the sound of the mic. I guess the transformer from what I hear? Is the tripler setup particularly low noise compared to other circuits?

 

[Khron]

but don’t know if there’s anything about the tripler that affects the sound of the mic

Spoiler alert - microphones don't know or care where the DC supply they're getting (AC, batteries, whatever), comes from. As long as the remaining AC ripple / noise is as low as you can practically get it, and the source impedance of it is low enough (you'll want a sizeable capacitor to ground as the last element), you won't "hear" the supply. And that much less, the power transformer (!!!) - keep in mind there's a couple diodes and a bunch of resistors & capacitors between that and the tube.

I hope we're not gonna start to argue that there's more than one "kind" of DC, and that one's more audible than the other...

 

[Accelerator]

Nuh…

In this kind of very “sort” economical range (around) 200-300 U.S.D. that you have in your hand and for general voiceover work you can buy:

Lewitt LCT 440 PURE Condenser Microphone $289.00

https://www.sweetwater.com/store/detail/LCT440PURE--lewitt-lct-440-pure-condenser-microphone

or even better

Sennheiser MK 4 Large-diaphragm Condenser Microphone $349.00

https://www.sweetwater.com/store/detail/MK4--sennheiser-mk-4-large-diaphragm-condenser-microphone

And you can thanks me letter…

Tube – Valve Microphone Systems are nice if you are a vocalist – songwriter, an instrumentalist musician or even a sound engineer – music producer with very specific demands for the timbre - “character” of your sound, they are not for a “runaway” general voice-over wonderer as the matching between the capsule to the amplifier and then to output transformer and the powering by the power supply should be indexical to make a specific timbre for your sound and gives you a specific “character”…

Just for example:
If you in desperately need to use the JLI-103 capsule you need a de-emphasis U-67-ish system, not a flat U-47-ish system, but like it or not all these Tube – Valve Microphone Systems are and will be too much expensive, even as mechanical kits for your 200-300 U.S.D. economical range “pocket”…

The Ami - Tab – Funkenwerk U47a Premium Kit runs up from $1,100.00 – to $2,015.00…

U47a Premium Kit $1,100.00 – $2,015.00

https://www.tab-funkenwerk.org/product/u47pk-u47a-premium-kit/

In the same way the Slovakian Flea Pro Audio Flea12 mechanical kit will not “comes” to you for any less in any economical matter than this expansive range…

Flea12 Kit & Parts

https://www.flea-microphones.com/parts/flea12-kit-parts/

 

[k brown]

UPDATE:
I've made some progress on deciding my approach to this project. I'm currently pretty settled on two of the key parts I want to use, those being the capsule (JLI-103) and the tube (5840W). A brief email exchange with Christian Whitmore of ProAudioTubes turned up some really good tube suggestions, among which were the 5840, which he'd described as "a great tube that is neutral and transparent." This is a tube I've encountered several times already in my research as a well known and good quality subminiature tube. With the price of these tubes also being sub-10 USD, these tubes seem like the best choice for the time being.

On the subject of circuitry, 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." Because I want the capsule to be mostly separated from the remaining circuitry, that limits my circuitry options. My current choices appear to all be based on a cathode follower. I've seen some talk around the forums about a few different CF variations that I'm interested in looking into. For one, there's a short thread on the subject here. Other stuff I've seen mentioned are the Bruel & Kjaer CF circuit and zebra50's circuit, neither of which I can verifiably find the schematics for (if anyone has links to those I'd greatly appreciate it).

There's been a lot of mention of Royer mods, but I'm not actually certain of the details of the Royer mod. Is that a mod of existing circuitry? Or swapping existing circuitry for an entirely new board?

My plan for the mic body seems to be heading in an interesting direction now that I'm becoming more confident in the feasibility of a ring mic with good performance. Currently, I'm thinking of a suspended enclosure containing the capsule in the front (I'm not sure how I'd go about mounting the capsule within its enclosure), the minimum circuitry necessary to safely send signal through shielded wire to the main body behind it, and the 5840W mounted on the back of the enclosure, with my thought being that I have the tube visible for aesthetic purposes (details TBD). The finishing touch on the suspended enclosure would be mesh shielding over top of the capsule for both aesthetics and, of course, shielding. The main body would be attached to the bottom of the ring and contain the remaining circuitry for the mic, with a male XLR port at the very bottom.

If anyone has thoughts, comments, suggestions on how to think about designing the custom body, or anything else I've mentioned thus far, I'm very open to feedback, as audio electronics are fairly outside of my element. Main sticking points I'm currently on are deciding on a circuit and (really a subset of that problem) deciding on a transformer. I've seen a lot of info on transformers out there and I'm hoping I might be able to find a good transformer that doesn't run as expensive as what I've commonly seen used, as a lot of them appear to be almost as expensive as my capsule ($50).

If you're not aware, the 6205 is often more easily available/cheaper than 5840, and is the same tube but with an extra lead which in this usage is simply tied to one of the others.

https://messageboard.tapeop.com/viewtopic.php?t=59303

 

[rock soderstrom]

When it comes to the power supply, are there any special considerations I should take?

Yes, build it as safe and clean as possible. The topology used is secondary, it doesn't have to be regulated, but it is more practical.

Pay attention to good thermal management and grounding scheme.

Is the tripler setup particularly low noise compared to other circuits?

No, the only advantage is that you can use relatively easily purchasable transformers with only one winding.

On the subject of DIY and tube technology. I think it's clear to everyone that you don't save money with DIY and that tube technology is inefficient, so why are there always these discussions? I think it's about something else here...

I have successfully used a DIY tube microphone alongside a Neumann TLM103 for professional, well-paid voiceover jobs (often together) for years. Allegedly, neither of them are any good, but the stupid thing is, nobody ever complained. No voice actor, no producer and no audience.

What do I mean by that? If someone wants to build a DIY tube microphone for VO jobs themselves, it can be done without any noticeable qualitative limitations if it is done well and just as a reminder, this forum is called groupDIY.

 

[HikariFaith]

On the subject of DIY and tube technology. I think it's clear to everyone that you don't save money with DIY and that tube technology is inefficient, so why are there always these discussions? I think it's about something else here...

I have successfully used a DIY tube microphone alongside a Neumann TLM103 for professional, well-paid voiceover jobs (often together) for years. Allegedly, neither of them are any good, but the stupid thing is, nobody ever complained. No voice actor, no producer and no audience.

What do I mean by that? If someone wants to build a DIY tube microphone for VO jobs themselves, it can be done without any noticeable qualitative limitations if it is done well and just as a reminder, this forum is called groupDIY.

I'm in agreement on what you're saying here. My goal in going the DIY route is making something of good quality that I can be proud of. While a lot of people disagree, tube mics are still believed to be a great addition to a voice actor's arsenal of mics. I personally love the character of the TLM-103, but can't afford the price to even get it used (nor do I expect to anytime soon), which is why I'd like to DIY using an imitation capsule with good reviews and an affordable price point. The goal with going the route of a tube mic is adding a little bit of tube color to compliment the brightness of the capsule.

I know full well that the output will be noisier than a pre-made FET mic. That's why I'm trying to optimize for noise. At the same time, I don't want to eliminate the noise outright, because IMO that noise adds character. The general audience won't be able to tell that there's a bit of feedback to the mic. All they'll know is that they like the sound of it. What I'm going for here isn't cost efficiency, where I'm min-maxing the bang for my buck. I want cost effectiveness: getting what I want out of a mic for special circumstances like commercial work or educational content, which tends to like friendly natural voices, at a more affordable price point. If I don't reach the quality of a professionally made mic, so be it. It will still accomplish what I want it to.

I remember when I was working on my nixie tube test board. I went through quite a bit of frustration just trying to get the thing to work and went through multiple complete re-routes in the process, as well as two complete re-writes of my code. But when I finally got my nixies to light, I was ECSTATIC. I spent hours just staring at the orange glow of the digits appreciating how beautiful they were and basking in the knowledge that I'm the one who designed, assembled, and programmed the circuitry they were running on. While I'm sadly stuck on the design of my full-sized clock and calendar (despite my best efforts the microcontroller continues to thwart my every attempt to power and connect to it), I know full well that I'll find a way to get it working, and when I do I'll be proud of myself for another job well done. That's how I want to feel about my microphone.

EDIT: Not only that, working on electronics projects like these are how I taught myself the skills I needed to get my current job back in March. Finding something I'm passionate about building is motivation for me to learn how these circuits work and gain better appreciation for them when they do what I expect them to. If I understand how the mic I'm using works, I then have the knowledge later down the line to modify it into something better by swapping out parts for better ones, for example.

 

[HikariFaith]

Then there is the Royer mod for (originally MXL603) small diaphragm microphones, which is a cathode follower. A good name for it would be Royer SDC mod, then you can better distinguish between the two circuits.

View attachment 130721

Quoting the page for the 603S mod:

The 3-prong XLR plug for the output of the microphone is fed from either the cathode follower or from the output transformer secondary. Refer to the diagram in Figure 3 for the correct pin assignments. Remember that the pin numbering of a 3-pin XLR plug defies reason and double- check this. For an unbalanced feed, use Pin 2 as signal "hot" and leave Pin 3 empty.

Does this mean T2 isn't necessary? If it is necessary, I'm curious what specs of the transformer are most important, because these particular transformers run really expensive from what I can tell.

 

[rock soderstrom]

Does this mean T2 isn't necessary? If it is necessary, I'm curious what specs of the transformer are most important, because these particular transformers run really expensive from what I can tell.

In the original context, this means that the transformer is either in the microphone body (if there is enough space) or in the PSU. Both are possible and have already been practiced wit CF circuits.

In principle, a CF microphone can also be operated without an output transformer due to the lower output impedance if the cable runs are not too long.

This has already been done (also by members here), which can lead to very good results. Nevertheless, I would first plan to use an output transformer because it expands the possible uses of the microphone in the long term and you can also test what you prefer (with or without OPT).

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.

 

[Khron]

In principle, a CF microphone can also be operated without an output transformer due to the lower output impedance if the cable runs are not too long.

Impedance-balanced output, anyone?