Neumann M49 Clone : D-M49c and D-M49b Tube Microphone Build Thread. (+Sample)

[poctop]

Dan - question for you from the other topic - i'm courious

How is connected input in your circuit?
Did you make switchable option for cardioid only - according to original schematic C1 via S2?

Input straight from tube grid and floating Fgrid capsule connection point ,

connect floating switch to those 2 points,  same points available on this round version as well,

Note:  To Operate S2 Cardiod only Switch

 

[Delta Sigma]

For North America, is the only point of the torridial transformer to isolate ground? 120V in, 120V out.

 

[mjproc]

Hi

  Been on and off with my build of a m49b, still not working properly, hope someone can help me bringing the mike to full glory ;-)

I use 5840, and the power supply for this project.

PSU: I could not get above approx 3,5 v for the heater (under load), so I had to short both R6 and R11 to get 6,3V.... strange, but it will work ok?  120V output and polarization  are ok.

M49:
I have problem getting to 1,6v bias, I´ve tried to replace R10 several times with other values, still no where nere 1,6V

My voltages:
B+:  120v
A:  47,08v
H+:  6,3v
R8-R9 junction:  57,38v
R2 (against centre of capsule); 5,5 (should be 56v according to Neumann scheme)
Polarisation voltage (pin 6 from pus): 119,6/half/0
Voltage after R11 : 10,92/half/0
R1: 5v
R7-R6-R5 junction: 57,5v
Bias: -0,87v

R10 is 100k and plate voltage adjusted for 0,73mA using R7 pot

Trying to measure Polarization voltage, gives me nowhere near 0/60/120v measured from gnd - capsule

Output is lower than d-U87, and noise is approx the same. 

The mike gives a desent signal, but I´m worried bout the low bias voltage and the low polarization voltage.....

I´ve tried to find a voltage reference sheet on the net, this would be very helpful if someone has taken the time to plot this on a working mike....

Brgds
Ole Peder

 

[Delta Sigma]

Output will be lower (?roughly 5dB?) than U87. U87 switches polar patterns where the M49 has both capsules paralleled, patterns changed by power supply voltage.

Are you sure you building M49b? Are you using a bypass cap on your cathode? If so that would be M49c and you would set your bias by R10, 5840 and R7 voltage divider.

See schematics in first post.

M49b bias voltage comes from the heater supply and the R6 R7 voltage divider.

M49c bias is cathode referenced to ground (grid @ ground potential). M49b bias is referenced from cathode to grid or the junction of R6 and R7.

 

[mjproc]

Output will be lower (?roughly 5dB?) than U87. U87 switches polar patterns where the M49 has both capsules paralleled, patterns changed by power supply voltage.

Are you sure you building M49b? Are you using a bypass cap on your cathode? If so that would be M49c and you would set your bias by R10, 5840 and R7 voltage divider.

See schematics in first post.

M49b bias voltage comes from the heater supply and the R6 R7 voltage divider.

M49c bias is cathode referenced to ground (grid @ ground potential). M49b bias is referenced from cathode to grid or the junction of R6 and R7.

I am sure it´s the M49b, but from the schematics I measured bias from grid to heater.  Should I measure grid - (R6-R7 juction)?

 

[Phrazemaster]

It's been awhile since I built my M49b but as I recall you cannot measure the grid bias directly.  Something about the high Meg resistors messing up the measurement. You have to set the correct voltage across anode resistor R10(?) if memory serves. You've only got 2 pots to play with and don't over turn them or they will break. I ended up rebuilding mine from scratch after a careful first build that even Poctop couldn't help me fix. Rebuild works fine.

 

[ln76d]

In case like this, good picture of the circuit is usual helpful.

Did you installed C4 - 8pF?

There would be hard to get 1,6V when heater voltage is 6.3V.
Difference is also in heater current where AC701k suck 100mA and 5840 150mA.
That's why it is much more easy to build "C" version using 5840.

Try adjust heaters to 6V (not 6.3V) and use R6  110k

Adjust B+ and back diaphragm polarisation voltage (pin 6) to 116V.

Measure  back diaphragm polarisation on Pin6, before R11
Measure backplate polarisation before R2.

Optional use internal switch S2 for "better" cardioid response.

Give us know is it working properly

P.S don't bend tube leads at the base, leave at least 2mm of straight wire.

 

[mjproc]

I will rebuild the mike using the 49c pcb.... As I have no idea how the different versions really sound, I think this is the way to proceed as of now... ;-)

Thnx

OleP

 

[micaddict]

Klaus Heyne, Oliver Archut and maybe others described the tone difference on the R/E/P forum.
Some googling will get you there.

To my ears and in my words:
M49b is somewhat meatier, thicker, ballsier etc. Great low mid character. Maybe slightly preferrable for lead vocal.
M49c is a bit airier and has a little less noise (not that the M49b is noisy). Less demanding on tube and PSU. Perhaps slightly preferable as an allrounder.

The late Dennis Stone (kidvybes) bought Dany's M49b prototype and had Brian Fox finetune it. Brian turned it into a cross between the -b and -c version.
You can read more about this on page 10 of this thread, particularly reply #181.

 

[ln76d]

I will rebuild the mike using the 49c pcb.... As I have no idea how the different versions really sound, I think this is the way to proceed as of now... ;-)

Thnx

OleP

If you build already B version, change it should be simple, use my recipe and check first.
This way should work much more close to the original.

 

[mjproc]

Moved the components to 49c pcb this afternoon.  Took 1 hour of soldering and all is ok.... Bias adjusted to 1,6V, B+ at 116 heater at 5,8V

All is ok technically....will test the audio later......

Feel good now ;-)

 

[cariocaman85]

Hello Dan,

I wanted to buy your capsule D7 and the square D49 PCB but paypal just told me that you’re out of stock.
When will it be possible to order?
By the way I tried to email you from your site, but the mail came back undelivered, and your Groupdiy box is reported to be full...

Thanks,

Best regards,


Rémi Bourcereau
Ingénieur du son
[email protected]

 

[MPM]

Hello Dan,

I wanted to buy your capsule D7 and the square D49 PCB but paypal just told me that you’re out of stock.
When will it be possible to order?
By the way I tried to email you from your site, but the mail came back undelivered, and your Groupdiy box is reported to be full...

Thanks,

Best regards,


Rémi Bourcereau
Ingénieur du son
[email protected]

Hello Dan,

I tried to contact you by mail and here in GroupDiy, but got the same reports as the poster above.

Cheers,
Mikko PM

 

[micaddict]

I believe Dan is busy moving to another place.

So the connecting problems could be a result of that.

 

[poctop]

Hello Dan,

I wanted to buy your capsule D7 and the square D49 PCB but paypal just told me that you’re out of stock.
When will it be possible to order?
By the way I tried to email you from your site, but the mail came back undelivered, and your Groupdiy box is reported to be full...

Thanks,


Best regards,


Rémi Bourcereau
Ingénieur du son
[email protected]

Hello Dan,

I tried to contact you by mail and here in GroupDiy, but got the same reports as the poster above.

Cheers,
Mikko PM

yes indeed i am moving to another location ,
i should be resuming business soon ,
Thanks for your patience,
Best,
Dan,

 

[poctop]

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Connection

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[G-Sun]

So, is square for standard bodies
and round for 49-style bodies?

 

[poctop]

So, is square for standard bodies
and round for 49-style bodies?

The Square one was initially made for the GT2B style mic
and the round one for Andriejus Style , AMI Style ,And Ben
standard M49 enclosure ,
Best,
Dan,

 

[G-Sun]

So, is square for standard bodies
and round for 49-style bodies?

The Square one was initially made for the GT2B style mic
and the round one for Andriejus Style , AMI Style ,And Ben
standard M49 enclosure ,
Best,
Dan,

Thank you!
Trying to get an overview of project, main parts, budget and quality-considerations.

The GT2B typical goes along with .. the TPS100 psu?
Any SYT-options that are easy fit?
Transformer and capsule seems expensive.

Beesneez M7 Capsule + body + psuBody = 800-900aud
Edit: That's not for psu enclosure. Mic body only
TAB Funkenwerk AMI T49 Transformer $85
You're selling D7. That's for this project, right?  235usd

Ok, Mouser boom is for all psu. I see
Mic parts are not so expensive.
Nor the 5840 tube.

Many vendors, ++shipping and vat-costs

Hm.. I'll have to see if I can afford this one.

 

[G-Sun]

Looking things over I'm coming to a cost of $990 / 8251nok
shipped to Norway.

Spot any big errors?

Typical Exchange fees adds quite a little.