The View Up Here

Random scribblings about kites, photography, machining, and anything else

  • Flickr Gallery

34mm LDC Alice

Posted by Tom Benedict on 22/04/2018

I built a new vocal microphone!

Up until now all the vocal mics I’ve built have been based on the Schoeps CMC 5 circuitry and a Transound electret capsule. The first was back in September, 2016, when I made my first Alice, based on Jules Ryckebusch’s Instructable. Almost a year later I built three more along similar lines using BM-700 donor bodies and the Transound TSB-25AX capsule. That first one I built is still my main vocal mic, but I’ve been using all four in one form or another ever since.

This time I wanted to try something different. I’ve wanted to build a 34mm non-electret condenser ever since I started dabbling in voice acting. A combination of events finally let that happen.

The first was finding some relatively inexpensive 34mm capsules on Ali Express back in December, 2017. I wound up getting one with the plan of developing a charge pump board to go with the Alice boards I’d used on the last set of mics. Before I could do that, though, a long-term project at work took my full attention and I had to set the capsule aside.

Around the same time the work project began ramping up, Homero Leal posted a new version of his Pimped Alice board to the Yahoo! micbuilder forum. This one included circuitry to bias a non-electret condenser capsule. (Yahoo!!) I ordered ten. But until the project at work ramped down enough for me to have a real life again, the capsule and boards sat in a box, waiting for me to get back to them.

Just when I started to worry I’d never build this thing, the project reached a good pause point and the rest of the pieces came together. I ordered a donor body, designed a capsule mount, and finally finally got busy. (Considering this is coming only six months after my TSB-25AX Alice trio instead of the year it took me between the previous two sets, I’m doing better this time! I really can’t complain.)

34mm LDC Alice Open>

Everything fit nicely inside the donor body, including the capsule and mount. I was concerned that the thicker capsules wouldn’t fit inside the head basket without requiring modifications, but it juuust barely fit. (The big exposed diaphragm on this capsule gives me the heebiejeebies every time I take the head basket off, though!)

Capsule Mount

Unlike the other capsule mounts I’ve designed, this one uses four M1.6x6mm screws to hold the capsule in place. (Normal for an LDC capsule.) It uses the same shock mount system as the previous mounts, though, and still has the tunnel down the center for routing the capsule’s wires to the PCB. (Version 2 of this mount will have holes on both sides of the post so it can work with dual-diaphragm capsules.)

34mm LCD Alice

Once the microphone is all closed up, it’s ready to go!

I’ve only just begun testing it against the other Alice mics I’ve built, but so far I’m pleased as can be. The 34mm capsule has a little more low-end punch (which is great on my voice!) and a subtly different high end. I haven’t decided which microphone I prefer for higher frequencies, but for my voice the LDC Alice is a clear winner.

Three Generations of Alice

And here’s the multi-generational line-up of the Alice mics I’ve built, starting with my very first one on the left, retrofitted with a shock-isolated capsule mount. The TSB-25AX Alice is in the middle, featuring the first shock-isolated capsule mount I designed. And the 34mm LCD Alice is on the right, featuring Homero’s board and the new capsule mount.

For anyone else itching to build one of these, here are the links to the version 1.0 capsule mounts, both for those who don’t have their own 3D printers:

34mm LDC Capsule Mount on Shapeways

And for those who do:

34mm LDC Capsule Mount on Thingiverse

(Mounts for the internal switch for switching the HF EQ in and out can be found on the same sites.)

Happy mic building!


18 Responses to “34mm LDC Alice”

  1. Congrats Tom! They look really great!!

    Cheers my friend!

    • Tom Benedict said

      Thanks! And thank you for the v.39b boards!

      Last week I loaned all three generations of Alice mics to a friend who runs a studio in a nearby town. He’s going to try them with a singer who records with him pretty regularly. After that I’m sending them to another friend who does commercial voice-over. I’ll let you know what they think!

      • Thank you, Tom!

        On your pics I can see that you used films instead of ceramics for some of the caps. Was this for a particular reason? Just wondering…



      • Tom Benedict said

        It was a mistake on my part. Once I figured out it’s a lot cheaper to order components in bulk, I started keeping an open Excel page to tack on whatever I think I’m short of. When I went to build the v.39b boards I THOUGHT I was out of the ceramic filter caps, so I jotted down the size I needed. When I went to order, everything else was a film resistor, so I ordered those as film resistors, too. (Then, of course I found my bag of ceramics after I’d already built out the boards!) Do you think using film capacitors there would be a problem? Or do you think I should go back and re-populate them with ceramics?

      • I don’t think that will be a problem, assuming equivalent value caps were used. Most of the time I prefer 100V C0G ceramics, but I confess it’s a little bit excessive. May be a trace of my audiophool subconscious. 😉

      • Tom Benedict said

        All the values are true to the schematic, and they all use a C0G dielectric.

        Excessive is okay in my book. Too much is always better than not enough. 🙂

  2. By the way… I just published two EBay pages for the Pimped Alice V.40 boards. Two versions, regular & gold plated PCBs. Let’s see how it goes. 🙂



  3. Leander said

    I cannot find any info on the smal capacitors you have directly soldered on the xlr connector. What is the purpose of those and can you give any info ?

    • Tom Benedict said

      They’re decoupling capacitors. They help to filter out RF. There was a really good thread about them on the Yahoo! micbuilders forum several years ago. I think Jules Ryckebush may have also mentioned this in his LDC Alice Instructables article.

      • Simon P. said

        Are those caps 22 nF ones? To quote Jule’s article:

      • Tom Benedict said

        Yep! Those are the ones.

      • Simon P. said

        I’m about to build my first Alice mic on Homero’s latest PCB (with the LDC capsule you recommended, the HFEQ and LFEQ options, and all bells and whistles)

        Some questions if you don’t mind:

        1. My local stores offer some good film capacitors from Kemet, Vishay, Murata, Panasonic that would seemingly fit if I used double side mounting (so that whatever ‘instersects’ due to width, sits on opposite sides of the PCB) If I switch everything ceramic for film, will it give me some kind of advantage? I keep reading / hearing that ceramics are unwelcome in audio. I might want to use ceramics for the decoupling caps and the 8200 pF HF cutter cap.

        2. Homero’s instructions say some R’s and C’s need different values if I go for LDC, but his schematic looks like it uses those ‘LDC’ values So if I buy exactly the same LDC capsule as you linked in your article, and use the exact component values from Homero’s schematic, is it going to be fine? I’m gonna use exactly 2N5087, PF5102 and the capsule you’ve linked (13.5 mm thick variant)

        3. EMP noise suppression caps. I know those are in a way different from the regular caps. Is it a bad idea to use them in place of regular caps for decoupling, or somewhere on the PCB? From what I’ve gathered, I’m not winning much but rather inviting trouble.

        Thank you!

  4. Timothy said

    I noticed that you ordered a different capsule that doesn’t require HFEQ on the Alice PCB. How does that one sound compared to the one your originally put in?

    • Tom Benedict said

      I hate to admit it, but I haven’t really done any thorough analysis. Just from listening, though, I like it better. It’s less brittle, if that makes sense.

  5. […] 3D Printed 34mm LDC capsule mount(Big thanks to Tom Benedict!) […]

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: