Royer tube circuit in Neumann TLM49

[rascalseven]

Ever since Neumann introduced the TLM49 I thought it'd be a great candidate for a good tube mod. It has the right capsule and headgrill/acoustics, so why not put the Royer MXL2001 mod in it and see what happens?

I bought a TLM49 last month and actually think it's a very good mic stock, but really wanted to make it a tuber, so I did.

The stock electronics are on a little octagonal pcb that is sandwiched (with a rubber gasket) between the headgrill and main body of the mic. The capsule mount is directly in the center of this pcb. I fashioned a new pcb, same shape and dimensions as the stock one, but laid out to accept the Royer tube circuit. The only thing I did differently from David's design is to use Cinemag's CM2480 output transformer that is optimized for this circuit instead of pressing the DI transformer into service here. There is plenty of room for the circuit and transformer inside the cavernous body, so no problems there (I used industrial velcro with a tiewrap around the trafo to hold it in place). Otherwise, it is the same circuit as published in Tape Op a few years back.

http://i26.photobucket.com/albums/c107/rascalseven/TLM49.jpg\
http://i26.photobucket.com/albums/c107/rascalseven/TLM49grilloff.jpg
http://i26.photobucket.com/albums/c107/rascalseven/TLM49insidebody.jpg
http://i26.photobucket.com/albums/c107/rascalseven/TLM49stockelectronics.jpg
http://i26.photobucket.com/albums/c107/rascalseven/stockandmodpcbs.jpg
http://i26.photobucket.com/albums/c107/rascalseven/TLM49newtubecircuit.jpg
http://i26.photobucket.com/albums/c107/rascalseven/moddedTLM49headless.jpg
http://i26.photobucket.com/albums/c107/rascalseven/moddedTLM49withpsu.jpg

It sounds phenomenal. Just did female vocals with it tonight and it was amazing. Extremely intimate, clear, detailed, rich, and full, and just sat right on top of the mix with only a tiny touch of compression from my Drawmer 1969. The clients and I just sat there stunned at the amount of tone and detail it had. Every word, even the really quiet ones, were totally intelligible, even in a rough mix with other elements too loud. A truly gorgeous result. I highly recommend this mod.

And perhaps the coolest thing is that I can swap back to the stock electronics in about 5, maybe 10 minutes at the most, so I haven't destroyed the mic doing the mod.

Oh yeah, and the preamp I used was Jakob's G9 (with Cinemag 75101 input, wired 1:5, and Edcor XS1100 output).

One thing I will caution for folks doing a build like this that has the capsule mounted ON the pcb.... cover the capsule with something (I put a small ziplock bag, the kind made for holding prescription meds, around it an zipped it up as far as it would go). when soldering, flux tends to 'pop' off the hot iron in tiny droplets. I'm glad I covered the capsule, because some of these landed on the ziplock bag and didn't touch the capsule. They most definitely would have had I not covered it.

I'm going to do A/B's with it against another stock unit this next week or the week after (as soon as I get caught up... still gotta get knob shipping done for everyone on the Sifam group buy!)

Enjoy,

JC

 

[peterc]

That looks quite amazing. I love it when people have emotional reactions to sound......

Peter

 

[Martin B. Kantola]

Very nice work! Especially since you can get these microphones used for $1000 USD or 750 euro :grin:

What did you replace the output (3-pin) XLR connector with? If you do an A/B comparison, please compare the noise levels too (record something very soft). The original circuit gives 12dB(A).

Martin

 

[pucho812]

that is impressive work there. Did you find the sound of the tube to be more pleasing to your ears? If you ask me, I would keep the tube circuit in there.

Fudge, you just re-sparked my interest in that royer modded tube 414 I had in my hands for a second. I'm going to see if I can borrow it again and make a schematic. :thumb:

 

[MATTI]

I hope someone from Nuemann sees this!
Suberb!

Matti

 

[rodabod]

Great work. Max (Ioaudio) did something similar I believe and I thought it was a great idea. I'd like to hear an A/B.

 

[rascalseven]

Thanks for the kinds words, guys. Yes, I much prefer the sound of it now to the sound it had before. I've never been a big fan of the Neumann TLM stuff, though this mic stock seemed to have more personality than other TLM's I've used (193, 103), and it did seem to have a saturation character to it, which was Neumann's intent, but it sounded more smeared than harmonic to my ear, somehow. Not intending to slam Neumann, I just think a simple tube circuit is a better.

Its sound is now more focused with great clarity. The capsule has 'that' midrange vocal quality... voices (at least the one I recorded last night) are so intimate, like someone whispering in your ear. (This is a singer I've worked with on three other records over the last few years, so I'm VERY familiar with and love her voice. I can honestly say that last night was the first time I ever captured the sound for her that I've had in my head all along). Excellent midrange detail and air without fatiguing hype. The low's are solid, but controlled. Definitely a stellar vocal mic.

I haven't measured the noise floor, but I can tell you with absolute certainty that it is dead quite. No hissing, hums, buzzes or other anomalies.

As for the connector, I replaced the 3-pin XLR with the insert from a 5-pin panel mount XLR that I got from my local surplus store. Interestingly enough I tried to use an insert from a Switchcraft XLR, but the odd, reverse-threaded screw didn't fit the mic. A generic 5-pin XLR was perfect. The quality of the plastic in generic connectors is sometimes questionable, so when soldering be sure to use have the mating connector attached to help hold the pins straight in place in case the plastic softens under the heat.

I'd bet someone over at Sennheiser/Neumann had already considered a tube for this circuit, but take a look at the stock electronics -- they can get those boards made and populated for pennies compared to the cost of a quality transformer and tube, even in quantity, never mind the cost of a separate power supply. This mic would sell for over $2000, street, if they made it a real tube circuit. For $100 in parts, plus the cost of the mic, I'd rather just do it myself.

I'll share some audio files of the A/B comparison when I do it.

Peace.

 

[okgb]

the job in general looks good , but
the pcb , you ought to make some of those available
, puts it in the realm of possibility for someone like me
good tips on the connector , thanks

 

[Gus]

Oliver posted a picture of a tube mod of the 149 at Klaus's some time ago.

I have been working on circuits to fit in my 103 and other microphones.

I do like the build.

Maybe one day I will post my changes to the Royer supply and circuit.

 

[ioaudio]

neat :thumb:
thats a cathode follower with the transformer in the psu i assume.
did you solder the high-Z part directly on the pcb? (without teflon/ceramic isolators)

*additionally you can try connecting the back membrane, i had very good results for omni with a m147 capsule.
http://www.twin-x.com/groupdiy/thumbnails.php?album=245

*as i just found out the tlm49´s rear membrane has no gold...

-max

 

[Martin B. Kantola]

[quote author="rascalseven"]I haven't measured the noise floor, but I can tell you with absolute certainty that it is dead quite. No hissing, hums, buzzes or other anomalies.[/quote]

Sounds promising! But please compare the noise with the original circuit if you can to get a reading or dB(A) number, all microphones have some noise, and I'm really interested in hearing how the noise compares to the Neumann TLM version.

Again, congratulations on a very neat project!

Martin

 

[Marik]

Very nice. There is always something cool when people don't afraid to get their hands into those expensive mics and still improve them... :thumb: :thumb: :thumb:

I always been wondering if the capsule backplate similar to K87. Does it have a HF boost?

Best, M

 

[rascalseven]

ioaudio, no, its the first Royer mod (for the MXL 2001 large diaphragm mic). The transformer is, indeed, inside the mic. Take a look at the picture that shows the vacant interior of the mic body. I didn't take a picture of the transformer inside there, but you can see that there's plenty of room for a larger transformer than the one I used, though I highly recommend the Cinemag 2480. I used industrial velcro to attach it inside. In addition to the adhesive on the velcro sticking to the transformer I also reinforced it with a tie-wrap to make sure it doesn't knock loose inside. I didn't want to do anything more permanent than that, at least not until I know for sure I'm going to keep the mic this way.

For those who haven't seen a TLM49 in person it is MUCH larger than the TLM103. I've never held an M49, but this thing measures 3" in diameter... it's big, so I'm guessing it is somewhat similar in size to the original M49 that this is obviously patterned after.

Martin, I'll try to get a comparison of noise for you when I do the A/B comparison.

Marik, the capsule is a single-sputtered version of the KK47, not the KK67/87. Both sides of the capsule have mylar film, but only the one side (front) is gold sputtered, so it's only capable of cardioid pattern.

I believe it is the same capsule they're using in the M147, and this design is, of course, the backplate design used in the U47, M49 and Fet47. I didn't have this type of mic in my locker, and I really wanted to get something capable of really nice midrange, U47/M49-ish type of sound (yes, those two mics are pretty different due, in large part, to the acoustic properties of each's headgrill, however, both have excellent midrange vibe, and this mic is no different). No, it doesn't have a pronounced HF rise like its kk87-equipped cousins.

You can see the backplate hole pattern/design in the backside of the capsule here: http://i26.photobucket.com/albums/c107/rascalseven/TLM49grilloff.jpg Definitely not the kk87-type used in so many other mics.

Peace.

 

[ioaudio]

[quote author="rascalseven"]the capsule is a single-sputtered version of the KK47, not the KK67/87. Both sides of the capsule have mylar film, but only the one side (front) is gold sputtered, so it's only capable of cardioid pattern.

I believe it is the same capsule they're using in the M147[/quote]

interesting. my m147 has both sides equiped with gold sputtered membranes, otherwise it would not have made any sense to connect the rear side

 

[pucho812]

correct the 147 Has both sides sputtered.

 

[rascalseven]

I stand corrected! :?

I thought the M147 was cardioid only? Why are both sides connected?

JC

 

[ioaudio]

they are not. i made the connection myself.

 

[rascalseven]

Ahh... so it was sputtered on both sides, but only one side was connected from the factory? I wonder if they're using the same capsules as in the multi-pattern M149? Perhaps in quantity they're less expensive. I wonder why the single sputtered capsule in the TLM49 then?

So did you put a switch in there to engage omni mode?

JC

 

[hotbaby]

hey thats a nice mod. Do you have a part list of all parts and cheme? i would be very pleasered if you would sent it to me. i want do this mod with my tlm 49 too.
best

 

[rascalseven]

Update:  I swapped the Cinemag output for Oliver's UM351 which is a milder ratio output, larger in size, and richer character.  The other was clear and clean, but I must admit I prefer more tone, and the AMI (http://tab-funkenwerk.com/id83.html) is very satisfying in this circuit.

I also found some nice Russian paper-in-oil caps and squeezed one in here in place of the film I had originally used on the output (these things are big!).  Hard to quantify what it does compared to the film cap (some will no-doubt think me an audiophool for mentioning this), but it seems to feel more relaxed, and perhaps mildly larger.

Or it could be the drugs  ???

Suffice it to say, I'm an even bigger fan of the tone of this mic now.

JC