M49c Build p2p in Flea body.

[SparkleBear]

Hey all,

Im finally getting around to building my personal M49c after many months of waiting... All the parts are finally in one place and ready to assemble. I have an old ac701 that was pulled out of an old build, should still work fine. Have a 6s6b-v that ill use for testing and calibration before throwing in the real deal...

Parts:

M49 body from Flea
Neumann K49 Capsule
Haufe BV11 Transformer
Mouser BOM
GAC 7 Cable
German Tuchel Connector



Photos of the flea body mechanicals.







As I've never held a real m49, I will have to go from pictures and the schematic. The only reasonable closeups I could find were from Klaus's m49v tear down (Photos below from Klaus's site: Neumann M49V: Complete Tear Down and Analysis) So, thats what Ive been studying.

. . .

Parsing from mostly the overhead photo I landed with this layout so far... Realizing I can run wires in a routed channel in the black poly material underneath the turret board. The layout of the flea vs the original seems pretty darn close.. Mounting holes and pass throughs seem a bit different. But I think I can sort it out for the most part. I may drill a small hole in the board to pass the 5M resistor wire through just like the neumann does.

Since my transformer is internally strapped I don't really have traditional need/use of the small vertical turret board. So I might use that as a convenient breakout point for the incoming wires so i can meter them easily in testing.









Main questions moving forward:

So, I've mapped out most of what I have got to do next. I had a question about components I can leave out if I am NOT doing a calibration input. I was imagining leaving out R12. But do I need c3 or R4, or C8? I could imagine needing those but I don't know as much as y'all experienced wizards out there. Unrelated to the calibration circuit, I've been advised to leave out C4 as well. And I've raised R1/R5 to 250M.



What kind of switch is appropriate for S2? I want to make sure its the right one in that HIGH Z position.
Neumann used:







Thanks so much for the help and advice!

 

[rock soderstrom]

Interesting project! I'm curious about the difference when you switch from 6s6b to AC701.

Looks good so far, bookmarked

 

[SparkleBear]

Ok. Progress...

Worked on routing the wires underneath the deck.

Measuring and routing:


Closed up the decks:



Soldered down leads on top deck:


Decoupling Cap, Voltage divider, plate resistor and the anode to ground capacitor.



Bottom Bell area wiring:





Unfortunately at this point, I accidentally broke off the m1.6 screw in the tapped hole!!! NOOO!



Off to the hardware store to see if I can get an appropriate drill and tap to make a new machined hole. *facepalm*

Upper deck looks good, double checked wiring... I can attach the tube very soon. Still have questions about the calibration circuit components though.

 

[EarthTone]

This looks awesome! Following. Nice work. Hey where did you get that body- Is Flea currently selling them?

 

[bremusound]

The switch Neumann used is called a ‚DIL switch‘

I‘m using these NOS switches for this purpose, they work great:

https://www.ebay.de/itm/12499788332...6r-DE6hT4a&var=&widget_ver=artemis&media=COPY

What kind of switch is appropriate for S2? I want to make sure its the right one in that HIGH Z position.
Neumann used:

View attachment 109999

 

[Murdock]

Ok. Progress...

Worked on routing the wires underneath the deck.

Measuring and routing:
View attachment 110008View attachment 110009 View attachment 110010

Closed up the decks:
View attachment 110011View attachment 110012View attachment 110013


Soldered down leads on top deck:
View attachment 110014View attachment 110015

Decoupling Cap, Voltage divider, plate resistor and the anode to ground capacitor.
View attachment 110016


Bottom Bell area wiring:

View attachment 110018View attachment 110019

View attachment 110017

Unfortunately at this point, I accidentally broke off the m1.6 screw in the tapped hole!!! NOOO!

View attachment 110020View attachment 110021

Off to the hardware store to see if I can get an appropriate drill and tap to make a new machined hole. *facepalm*

Upper deck looks good, double checked wiring... I can attach the tube very soon. Still have questions about the calibration circuit components though.

Are you sure the wires from the connector should go through the transformer plate? Does your transformer still fit on there?
Normally the wires go through a hole in the rubber disk.

And good luck with the broken screw! Hope you get it out.

 

[SparkleBear]

So, I ended up drilling out the broken screw shaft. I went looking for more taps but couldnt find any small enough for this application with out having to buy it on the web. Fortunately, the hole was still snug enough to finagle an m2 screw into the hole and call it a day with that. Not ideal and would not be ok for a client, but for me? Its fine!

Are you sure the wires from the connector should go through the transformer plate? Does your transformer still fit on there?
Normally the wires go through a hole in the rubber disk.

Yeah, everything fits... I have never really opened up a real m49 so i had no idea how it actually goes. LOL, well everything fits and its working so *shrug*. hehe

This looks awesome! Following. Nice work. Hey where did you get that body- Is Flea currently selling them?

Yeah, if you email flea they will sell mechanical kits of most of their mics. Super high quality. A bit pricy but for a life long piece like this its worth it. Its leagues above what chunger/ami has in terms of build quality. For sound quality? Imagine resonance wise its very similar. However the internal rubber base as well as the rubberized foam circle that holds the plexi deck centered would probably damp out vibrations from the environment so thats probably useful in some applications.



Anyway, Pretty much finished the Microphone last night. Added all components as per the schematic (except c4). The tolerances on the flea parts are so tight! I couldn't fit SQ's flat 47 in there. It was fractions of a mm too big for their mount. The neumann fit in there perfectly snug... The female tuchel also had an extremely tight fit into the bottom socket too... it will wear down over time and get easier but I was surprised how tight the fit was.

First thing was to finish the s1 deck and wire up the top deck to the cable connector.


Next solder in the tube , Planning for the AC701 so needed to make the grid lead travel to the other side of the mic. Put some PTFE insulation tube to protect it. Little rubber foam to hold tube is from flea and is very nice.



Also, added in the 10n cap 2M and 200R resistor to the fold.




Mounted Capsule in holder and wired leads to acrylic deck. Connected and installed deck to rest of mic circuit.





Really turned out beautifully... fired right up first try. Made a few test recordings but not a great room and the fridge is on ;P



Test Recordings:
Just guitar-
https://www.dropbox.com/s/3yapm5p0h2xf9wv/M49c guitar.mp3?dl=0
Guitar and voice captured on one mic:
https://www.dropbox.com/s/k0dcbw4wd796as2/M49c guitar+voice.mp3?dl=0
Still want to make more test recordings. But this was in the morning after a 12 hour burn in of the tube. Sounds promising. Still need to get that switch and add the 1000pF cap to make the multi patterns active. For now this is fine

Next I'm working on a psu build specifically for this mic. Right now Im just using my trusty Oliver Archut supply... Cable will be GAC7 @30'... My psu will be my own PCB with both regulated rails. Ill use Analog vibes' ultimate psu chassis, edcor transformer, tuchel and neutrik connectors, and a vintage indicator light

Its gonna be awesome!!

 

[EarthTone]

Really fine work and inspiring. Thanks so much for posting! Also, I'll email Flea about their body kits. That's great to know. You can't get M49 bodies right now... Except the ShuyaYin ones and they are too narrow on the chassis for most pcb's. And smaller than what most people build p2p builds in too.

Does that LED lamp built into the mic body light up?

 

[SparkleBear]

Really fine work and inspiring. Thanks so much for posting! Also, I'll email Flea about their body kits. That's great to know. You can't get M49 bodies right now... Except the ShuyaYin ones and they are too narrow on the chassis for most pcb's. And smaller than what most people build p2p builds in too.

I've been disappointed with the m49 choices out there right now too... I've been hoping the chunger body would come back one of these days.

Does that LED lamp built into the mic body light up?

Its not an LED lamp but just a jewel. There is certainly a way to do that im sure... I could probably put an LED in there powered from the heater circuit. I wouldn't want the light to shine through the head basket.

Any chance this would cause noise for the audio? Maybe better would be a 120v indicator light powered off of B+. I don't want anything potentially messing with the AC701 voltage once thats in there.

 

[EarthTone]

I've been disappointed with the m49 choices out there right now too... I've been hoping the chunger body would come back one of these days.



Its not an LED lamp but just a jewel. There is certainly a way to do that im sure... I could probably put an LED in there powered from the heater circuit. I wouldn't want the light to shine through the head basket.

Any chance this would cause noise for the audio? Maybe better would be a 120v indicator light powered off of B+. I don't want anything potentially messing with the AC701 voltage once thats in there.

Cool thanks for the reply! I'd be interested to know how to do it as well. It would be cool if you could get a low light emitting diode in there. Not too bright so as not to be distracting to the performer. Keep us updated if you discover a way to do it easily without changing the audio sound of course!

 

[Delta Sigma]

What kind of switch is appropriate for S2? I want to make sure its the right one in that HIGH Z position.
Neumann used:

I used a reed relay. Cardioid only can then be enabled by a switch on the power supply.

 

[Murdock]

I used a reed relay. Cardioid only can then be enabled by a switch on the power supply.

Yep, me too. Pretty neat solution. I even used a pot with a built in switch. So I can turn my pattern pot all the way to omni and then a click further it is cardiod only. Works great! And is really great feature. "Pure" cardioid sounds noticably different than the multi pattern cardioid. And to have that option without the need to open the mic each time is awesome.
The reed relay can fit on a plexiglas board similiar to where the solder tag switch were in the original M49.

 

[SparkleBear]

Thanks for the replies friends. Appreciate the support and dialogue.

I used a reed relay. Cardioid only can then be enabled by a switch on the power supply.

I had that set up in my last m49, but it made the heater voltage swing by .3v and I didn't like that for my ac701. In cardioid it would be 3.95, but then jump up to 4.25 when the relay was disengaged. Its easy enough for me to open the mic and flip a switch for a session. That was the trade off for me.

I used a two deck rotary so that when I was in card mode it sent a 0v down the 3rd pin to engage the relay and cut off the back capsule.

The reed relay can fit on a plexiglas board similiar to where the solder tag switch were in the original M49.

Thats a chonky boy there. Is this a better choice part than one of those panasonic relays (like the ones we used in walter white 251)?

I could be convinced to switch over to reed/relay... I definitely see the ease factor, I just dont want to endanger my ac701.

@Murdock Thats a gorgeous build mate... is that a m49B Circuit? I notice a few differences. Is that a flea body too? But with the bayonette connectors?

 

[Murdock]

Thanks for the replies friends. Appreciate the support and dialogue.

I had that set up in my last m49, but it made the heater voltage swing by .3v and I didn't like that for my ac701. In cardioid it would be 3.95, but then jump up to 4.25 when the relay was disengaged. Its easy enough for me to open the mic and flip a switch for a session. That was the trade off for me.

I used a two deck rotary so that when I was in card mode it sent a 0v down the 3rd pin to engage the relay and cut off the back capsule.

Thats a chonky boy there. Is this a better choice part than one of those panasonic relays (like the ones we used in walter white 251)?

I could be convinced to switch over to reed/relay... I definitely see the ease factor, I just dont want to endanger my ac701.

@Murdock Thats a gorgeous build mate... is that a m49B Circuit? I notice a few differences. Is that a flea body too? But with the bayonette connectors?

That is a Coto reed relay. It has a pretty high insulation resistance between the pins which is important when you deal with capsule/Hi-Z connections. I think it is around 10^12 (1 000 000 000 000) Ohms compared to the 100M Ohm from Panasonic.
Also it is hermetically sealed and has an electrostatic shield.
I haven't noticed any voltage drop in the heater. Probably because I took the relay voltage from the B+ and not H+. The Coto relay needs 24V so the relay needs "only" about 6mA. Also there is a resistor in the power supply which "replaces" the relay coil resistance if the relay is off so there is no voltage variation when switching. You can check D-EF47 PSU schematic for it.

Thanks!
The build in the picture is a M49b circuit. But I switched to -c circuit and will rebuild both of my M49 completely with some new features and better layout. The one in the picture was my first build. And something can always be made better...

The body shell is from Aputis. I was one of the lucky who did not have any problems with him. But I asked for unplated bodies and got them nickel plated at a local company. They did a great job and were pretty cheap.
The Bayonette connector I got for a few bucks from eBay.
All the internals I did myself except for the machining of some parts.

 

[SparkleBear]

That is a Coto reed relay. It has a pretty high insulation resistance between the pins which is important when you deal with capsule/Hi-Z connections. I think it is around 10^12 (1 000 000 000 000) Ohms compared to the 100M Ohm from Panasonic.
Also it is hermetically sealed and has an electrostatic shield.
I haven't noticed any voltage drop in the heater. Probably because I took the relay voltage from the B+ and not H+. The Coto relay needs 24V so the relay needs "only" about 6mA. Also there is a resistor in the power supply which "replaces" the relay coil resistance if the relay is off so there is no voltage variation when switching. You can check D-EF47 PSU schematic for it.

Thanks!
The build in the picture is a M49b circuit. But I switched to -c circuit and will rebuild both of my M49 completely with some new features and better layout. The one in the picture was my first build. And something can always be made better...

The body shell is from Aputis. I was one of the lucky who did not have any problems with him. But I asked for unplated bodies and got them nickel plated at a local company. They did a great job and were pretty cheap.
The Bayonette connector I got for a few bucks from eBay.
All the internals I did myself except for the machining of some parts.

Ahh, i see the slight difference in the rubber mount at the bottom of the mic... Flea has the rubber diaphragm and aputis is using rubber standoffs. That body does look very nice... too bad about all the drama with Aputis. I always wanted one of those bodies but never pulled the trigger. IIRC they were like $700, so thats definitely like half the price of the flea body. I guess there is a no BS upcharge for choosing Flea. ;P

Do you have a specific part number for the reed switch you used? I think this is a better idea and takes care of my design goal of not effecting the heater voltage. I will have to deadbug the dropper circuit in the psu but that should be too hard. Ill reference the def47 psu and go with that solution... Although, I do like the simplicity of the regular switch too.

Cheers!

 

[Delta Sigma]

When switching a relay, you should switch to/from a resistor equivalent to the relay's DC coil. ie, switch between a 110ohm resistor and a 110ohm DC coil of a relay. This way, your heater voltage does not drop. Same idea if you put a relay on your B+.

 

[SparkleBear]

@Murdock What capsule did you use in your build?

When switching a relay, you should switch to/from a resistor equivalent to the relay's DC coil. ie, switch between a 110ohm resistor and a 110ohm DC coil of a relay. This way, your heater voltage does not drop. Same idea if you put a relay on your B+.

Brilliant, gonna go revise my last design that uses a relay. Small body enclosure and tight pcb so cant use the reed... have to stick to the panasonic.

 

[Delta Sigma]

@Murdock What capsule did you use in your build?



Brilliant, gonna go revise my last design that uses a relay. Small body enclosure and tight pcb so cant use the reed... have to stick to the panasonic.

I used this one. Smaller than the Panasonics that Dany used.

https://www.digikey.ca/en/products/detail/littelfuse-inc/HE3621A0510/133258

 

[Murdock]

Ahh, i see the slight difference in the rubber mount at the bottom of the mic... Flea has the rubber diaphragm and aputis is using rubber standoffs. That body does look very nice... too bad about all the drama with Aputis. I always wanted one of those bodies but never pulled the trigger. IIRC they were like $700, so thats definitely like half the price of the flea body. I guess there is a no BS upcharge for choosing Flea. ;P

Do you have a specific part number for the reed switch you used? I think this is a better idea and takes care of my design goal of not effecting the heater voltage. I will have to deadbug the dropper circuit in the psu but that should be too hard. Ill reference the def47 psu and go with that solution... Although, I do like the simplicity of the regular switch too.

Cheers!

Aputis didn't use rubber mounts in his kit. I drilled new holes and cut threads to use rubber mounts with my transformer plate.
I don't know if Aputis ever sold some of his kit version.

The reed relay is coto 7101-24-1010.

@Murdock What capsule did you use in your build?



Brilliant, gonna go revise my last design that uses a relay. Small body enclosure and tight pcb so cant use the reed... have to stick to the panasonic.

At first I used Maiku K47 but switched to Ari's flat K47.

 

[Delta Sigma]

Something to consider if you're using a relay is your heater transformer. If your heater transformer is near its current rating, do not add extra load by power a relay with your heater supply.