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

Super, Dennis!



Henk

...here's a quick sample of the Bouchard/Fox M49 (documented above) on a very dynamic female vocalist I'm working with...she was working about 6-8" from mic with Pearlman metal "Beatle" style pop-filter...

Chain: M49b > Great River ME-1NV > DAW

...thoughts are welcomed...

https://soundcloud.com/kidvybes/bouchard-fox-m49b-on-dynamic

Thanks for the sample.

This singer has a loud and very edgy voice to my ears. I can imagine she cuts like a hot knife through butter.
Differently put, there's much energy squeezed into a relatively narrow band. You hear that kind of thing a lot lately.
Obviously, this won't show what the mic can do in the lower regions.
But it does hold up well to this lady's singing which is not as obvious as it may seem.

You say she's a dynamic vocalist. By definition that would mean not just loud.
I'd love to hear her do some quieter stuff, too. 
On this mic, of course! 

micaddict said:

You say she's a dynamic vocalist. By definition that would mean not just loud.
I'd love to hear her do some quieter stuff, too. 
On this mic, of course! 

Click to expand...

...yes, I plan on continuing to use this mic for future tracking sessions on this vocalist...more importantly, she loves what she's hearing in her headphones when tracking with this mic, and I find that the vocalist's comfort with a particular mic is often critical in getting the most from a session...we will definately be doing some softer tracks...just as a point of reference, here are some other tracks from the same vocalist:

http://www.reverbnation.com/michellesongbirdgordon

Hey fellow forum-members,

I'm in need of some help from people that have built or have experience with the the M49-B-Version:

So how do I start without being boring  ;D

First some info about my build and how I got around some bugs:

1) Heater Voltage business: I didn't have a 1G-Ohm-Pot at hand so I installed a DC/DC step-down (buck) converter to get the 5,7V Heater Voltage, which seems to works fine

2) Plate current business: With b+ at 120V when R10 was still a fixed 100k I had only 37V on the plate (so 120V-38V/100k =0,83mA and I thought pretty close) But everybody in the thread said it had to be around 50V.  so I installed a variable Resistor to get the 50V, but it doesn't do me any good, because when I have 50V on the Plate i have only 30k on R10 which would result in 120V-50V/30k = 2,3mA which seems a little too high. So how did you guys balance this out?

3) Capsule: I bought a k47 replica of micandmod but it doesn't spit out any signal... If I measure the three terminals where the capsule is supposed to be connected against ground I have 5V on the Front Diaphragm, 5V on the Back-Plate and (depending on the polarization) 0V/2.5V/4.5V on the Back Diaphragm. Dany said the values look fine, but how can a condenser work without any electric potential between diaphragm and back-plate... i don't get this... and how do I find out what voltages actually end up on the membranes? I know everyone talks about the 120V/60V/0V- Polarization Voltage not taking into account the giant resistors in between the supply and the capsule.... so what voltages need to be on the membranes and looking at the m49b schematic: from where does the capsule get its ground?

thanks in advance for your time and input... I really want to use this mic and it seems i'm pretty close....
hope someone can help me... you can also send a pm at: info@fhon


thanks again,
Frederik

you cant measure DC polarisation direct on the capsule or backplate because of the High Meg Resistance will fool most meter, you have to measure it before those resistor and since there is virtually no current you should be able to read the full voltage there and regarding the data you sent everything is corect the backplate a 57V is fine B+ heater and such , Check your tube also ,
did you wire it in triode mode ? 

if you have constructed the Square version of the M49 Actually verify that the grid ( casule front) point near the bypass cap is not shorting
you need special attention to this place,  might also a picture of your build help as well, did you check out your transformer too

if all the voltage looks right you really must be just a tiny detail away from the success,

if you remove the capsule can you inject a sine tone and verify the amp portion of the mic check out,

beware also of the cardiod only switch that needs to be set for the pattern to work might have you connected the wrong side of the capsule with the cardiod only switch not jumpered ?.....

Keep us posted when you find it because i beleive the oh My God is imminent

Hope this helps
Best,
dAN

I should be getting a Little Run of the square versions D-M49 b-c
very soon,
Best,
Dan,

fredbasement said:

Hey fellow forum-members,

I'm in need of some help from people that have built or have experience with the the M49-B-Version:

So how do I start without being boring  ;D

First some info about my build and how I got around some bugs:

1) Heater Voltage business: I didn't have a 1G-Ohm-Pot at hand so I installed a DC/DC step-down (buck) converter to get the 5,7V Heater Voltage, which seems to works fine

2) Plate current business: With b+ at 120V when R10 was still a fixed 100k I had only 37V on the plate (so 120V-38V/100k =0,83mA and I thought pretty close) But everybody in the thread said it had to be around 50V.  so I installed a variable Resistor to get the 50V, but it doesn't do me any good, because when I have 50V on the Plate i have only 30k on R10 which would result in 120V-50V/30k = 2,3mA which seems a little too high. So how did you guys balance this out?

3) Capsule: I bought a k47 replica of micandmod but it doesn't spit out any signal... If I measure the three terminals where the capsule is supposed to be connected against ground I have 5V on the Front Diaphragm, 5V on the Back-Plate and (depending on the polarization) 0V/2.5V/4.5V on the Back Diaphragm. Dany said the values look fine, but how can a condenser work without any electric potential between diaphragm and back-plate... i don't get this... and how do I find out what voltages actually end up on the membranes? I know everyone talks about the 120V/60V/0V- Polarization Voltage not taking into account the giant resistors in between the supply and the capsule.... so what voltages need to be on the membranes and looking at the m49b schematic: from where does the capsule get its ground?

thanks in advance for your time and input... I really want to use this mic and it seems i'm pretty close....
hope someone can help me... you can also send a pm at: info@fhon


thanks again,
Frederik

Click to expand...

Where is you post , ?
I remember seeing somthing and its gone ,
is the OMG moment yet, 
Best,

fredbasement said:

hey dan, you're right - it disapeared. I made such a foolish mistake, that i was too embarressed to keep the post up there for everyone to see. ;D  I'll post again, when I figured out where I'm at... greetz, Frederik 

Click to expand...

There is no Problem with mistakes , this is actually helpfull for others Group Member as well,

if you dont do mistakes you dont learn  ,

Well keep us posted then ,
Best,
Dan,

fredbasement said:

hey dan, you're right - it disapeared. I made such a foolish mistake, that i was too embarressed to keep the post up there for everyone to see. ;D  I'll post again, when I figured out where I'm at... greetz, Frederik 

Click to expand...

Keep Us in the Loop of your findings,
Best,
daN,

I should have some of the square version back in stock as of tommorow ,
Best, 
Dan,

I have a little run available for the square M49 Style,
Best,
DAn,

...I had the opportunity to use the M49b (with Fox Audio tweaks) on a male reggae vocalist this weekend...sounded real nice on his voice (he commented he loved how he sounded in the headphones)...

...here's a snippet of a ruffmix I did this morning...I can also post clips of raw vocals if requested...these are obviously treated in the mix...both lead and BGVs were tracked on Dany's M49:

https://soundcloud.com/kidvybes/stamina-allstars-ft-adam-1

OMG Dany!  ;D

it was quite a journey but I have a working Mic now!

but it's not the M49(b). after fixing my initial misktake of wiring the fgrid to the cathode/gnd floating pin instead of the s2a pin my voltages were all over the place and didn't look nearly as nice as before. I have literally spent hours of trial and error getting it right but the filament bias is a real pain to put it nicely.  maybe I should have been a little worried when you wrote something about "required creative bending". I guess my creativeness wasn't up to the task... anyway after being all frustrated I went back here to find the foxresearch m49(b) update and I thought hey that's great I'll do the modification. well after this the pcb just shorted out and I didn't even have a solid B+ anymore. so with the b-version all screwed up I went to a local electronics shop, got some new parts for stuffing the M49(c) and literally before the last resistor my soldering station died.... but even with that short delay (I go an awesome new soldering station) the c-Version was done that evening:

B+ = 120V
Polarization = 118V / 58V / 0V
H+ = 5,8V
Plate = 48V
Cathode = 1,4V
with R7 @ 2262k (0,707mA)

(dany: how could I get up to 0,73mA?)

it works without hum or noise or anything and sounds rich and tasty. I will be able to really say something about the sound when I get to the studio in a couple of days, because I cannot really hear much at the bench. but I'll keep you updated about the sound.

but to end the little tale about non-professional soldering-enthusiasts wanting to build the M49(b): "JUST DON'T!". the M49(c) gives you much less headaches and you'll have a functioning mic much sooner. It is the safer route!

alright you guys. thanks so much for reading.

PS: Dany, any of those 47-FET pcbs lying around???

have a great day...

oh and here are some building notes i destilled, so to anybody that does not want to read the whole thread.

hope it helps.

Frederik

-------------
-------------

build notes:

-------------
-------------

Connection For AMI T49 to PcB
TRFO to Mic PCB
A- 4
B-3
C-1
D-2

--------------------

5840 tube:

For Converting the 5840 Tube to a Triode:
Tie pin 7-5 Togheter.
Do not use Pin 4 or Pin 8.

B+ = 115V
Plate = 53V
Drop across 100k (plate resistor)
= 115-53 = 62V Voltage drop across 100k
that means the tube running at .62ma
We want about 45V on the plate to get to
the specified 0.7ma then

--------------------

R7 = 2.2K (m49c)
R7 = 22K? (m49b)

--------------------

m49C:

self bias / heater isolated from cathode

R7 (cathode resistor) = 2.2K elevating cathode from gnd

bypass cap to prevent negative feedback (NFB) 

10uf (20uF / 25uF) cathode bypass cap is recommended with the 5840 tube.

(series standard diode for heater supply (just before the connector to drop the 6.3V heater down to about 5.6V for underheating)

proper bias = 1.6V (cathode voltage)

plate resistance: 103.5K / cathode resistance: 2.279K

--------------------


m49B:

fixed bias / cathode voltage ref'd to h+

H+ needs filtering to prevent ac in grid voltagen (Vgk)

With 1M ohm pot in power supply
set it to (4.4V-6 ) = 1.6V bias with 52V plate as results

adjusting plate voltage to 50V with B+ at 120V
plus 100K plate resistor leads to 0.7ma plate current in filament biased (b)


--------------------

Power supply:

passive choke filtering.
full recitfied B+ and heater.
120V-6V after warmup.

polarization voltage in cardiod should be exactely half the B+ voltage
minus a hair for current limiting resistor inside the psu. (ca. 58V)

B+ to 120V then adjust plate voltage to 50V to get 0.7ma plate current
calibrate plate current not the bias. 58-59V on the R6-R7 node.

M49 Power Supply transformer hook-up to main P.S.B.
Yellow & Red / Black & Orange To P.S.B.

X-1-2 and X-1-1 = where the Choke Goes

X-5-1 and X-5-2 = where the heater trimpot goes

--------------------

5840 correct wiring:

pin 1 = through the board to fgrid
pin 2 =  connect to K turret
pin 3 = connect to HG turret
pin 4 =cut
pin 5 + 7 = connect to A turret
pin 6 = connect to H+ turret
pin 8 = cut off

--------------------

fredbasement said:

OMG Dany!  ;D

it was quite a journey but I have a working Mic now!

but it's not the M49(b). after fixing my initial misktake of wiring the fgrid to the cathode/gnd floating pin instead of the s2a pin my voltages were all over the place and didn't look nearly as nice as before. I have literally spent hours of trial and error getting it right but the filament bias is a real pain to put it nicely.  maybe I should have been a little worried when you wrote something about "required creative bending". I guess my creativeness wasn't up to the task... anyway after being all frustrated I went back here to find the foxresearch m49(b) update and I thought hey that's great I'll do the modification. well after this the pcb just shorted out and I didn't even have a solid B+ anymore. so with the b-version all screwed up I went to a local electronics shop, got some new parts for stuffing the M49(c) and literally before the last resistor my soldering station died.... but even with that short delay (I go an awesome new soldering station) the c-Version was done that evening:

B+ = 120V
Polarization = 118V / 58V / 0V
H+ = 5,8V
Plate = 48V
Cathode = 1,4V
with R7 @ 2262k (0,707mA)

(dany: how could I get up to 0,73mA?)

it works without hum or noise or anything and sounds rich and tasty. I will be able to really say something about the sound when I get to the studio in a couple of days, because I cannot really hear much at the bench. but I'll keep you updated about the sound.

but to end the little tale about non-professional soldering-enthusiasts wanting to build the M49(b): "JUST DON'T!". the M49(c) gives you much less headaches and you'll have a functioning mic much sooner. It is the safer route!

alright you guys. thanks so much for reading.

PS: Dany, any of those 47-FET pcbs lying around???

have a great day...

oh and here are some building notes i destilled, so to anybody that does not want to read the whole thread.

hope it helps.

Frederik

-------------
-------------

build notes:

-------------
-------------

Connection For AMI T49 to PcB
TRFO to Mic PCB
A- 4
B-3
C-1
D-2

--------------------

5840 tube:

For Converting the 5840 Tube to a Triode:
Tie pin 7-5 Togheter.
Do not use Pin 4 or Pin 8.

B+ = 115V
Plate = 53V
Drop across 100k (plate resistor)
= 115-53 = 62V Voltage drop across 100k
that means the tube running at .62ma
We want about 45V on the plate to get to
the specified 0.7ma then

--------------------

R7 = 2.2K (m49c)
R7 = 22K? (m49b)

--------------------

m49C:

self bias / heater isolated from cathode

R7 (cathode resistor) = 2.2K elevating cathode from gnd

bypass cap to prevent negative feedback (NFB) 

10uf (20uF / 25uF) cathode bypass cap is recommended with the 5840 tube.

(series standard diode for heater supply (just before the connector to drop the 6.3V heater down to about 5.6V for underheating)

proper bias = 1.6V (cathode voltage)

plate resistance: 103.5K / cathode resistance: 2.279K

--------------------


m49B:

fixed bias / cathode voltage ref'd to h+

H+ needs filtering to prevent ac in grid voltagen (Vgk)

With 1M ohm pot in power supply
set it to (4.4V-6 ) = 1.6V bias with 52V plate as results

adjusting plate voltage to 50V with B+ at 120V
plus 100K plate resistor leads to 0.7ma plate current in filament biased (b)


--------------------

Power supply:

passive choke filtering.
full recitfied B+ and heater.
120V-6V after warmup.

polarization voltage in cardiod should be exactely half the B+ voltage
minus a hair for current limiting resistor inside the psu. (ca. 58V)

B+ to 120V then adjust plate voltage to 50V to get 0.7ma plate current
calibrate plate current not the bias. 58-59V on the R6-R7 node.

M49 Power Supply transformer hook-up to main P.S.B.
Yellow & Red / Black & Orange To P.S.B.

X-1-2 and X-1-1 = where the Choke Goes

X-5-1 and X-5-2 = where the heater trimpot goes

--------------------

5840 correct wiring:

pin 1 = through the board to fgrid
pin 2 =  connect to K turret
pin 3 = connect to HG turret
pin 4 =cut
pin 5 + 7 = connect to A turret
pin 6 = connect to H+ turret
pin 8 = cut off

--------------------

Click to expand...

thanks Fred for the OMG moment reat work , you should have been using the 0.01uf/400V I had in my BOM , i just cant figure out how you did it with those fat bastard Capacitor you have there but you made it  ,  congrats  Thanks for the nice documentation note also , the plate current you have is very well close enough to be on the benchmark, since you have a different tube the bias can also be a bit different so it is not a mandatory to end up a perfectly 0.73ma as this is related to the ending plate voltage and the cathode bias this is more like a guideline since your are using a another tube. you can actually bias it to your taste, you should not only look at the schematic perfect value since another tube will give slighltly different results this shall and will not be exactely the same depending on the tube used in those condition. but more if it make sense and it sounds right also, dont forget that the cathode bias and plate final voltage are related as well

I have built both b and c in the square format and i could not really see that much of a difference in the build difficulty could you explain further on this that would greatly be appreciated.

PS: if you need the U47Fet all the pcb are in stock on the webstore at the moment.

Again Thanks for your post,
Best,
DAN,

thank you for your help dan. I know the 0,01uF in your bom would have been much easier to fit, but after my shorting out things I wasn't sure if they were still good and I have no meter to test capacitors (next thing I'm gonna get) so I bought those big boys because the electronic shop didn't have those 400V caps and I wasn't patient enough to wait for another order. about the building difficulty: It probably was just my inexperience but I couldn't get the balance between plate voltage and plate resistance. i tried a trimpot on the plate resistor becayse the voltage drop was never right. either I had 50v plate but 22ohm on the plate resistor or I hat 100k on the resistor but 32ish volts on the plate I tried to crank the b+ but there wasn't enough juice. and as I read the plate current was the most important thing in filament bias I had no idea how to get the values right. anyway im glad it works now and I'm super psyched to try it out. you can send me the paypal money request for the 47fet because my omg-moment triggered an instant "I want more"-feeling. love your work, keep it up and I'll post some samples when I recorded something. have a great day dan. fred.

Finished my build tonight. Came up great. This is a quick soundclip. I have not set the bias on the scope yet. I'm certain I can milk a bit more creamy goodness from this mic yet. 

https://www.dropbox.com/s/cq4nek1f452r0lj/Dale%20M7%20M49B.wav

Hey guys. Have had a bit more time to muck around with this build. I have added a 100K lin pot for a fully variable pattern (removed the 3 position switch). I have also been mucking around with the bias both by ear, scope and using my multimeter. Simply dialling in 120V,50V exactly and exactly 1.6v bias gave the best results both sonically and headroom wise. I have ordered a bunch of different 5840 tubes to find the quietest and nicest sounding option. At the moment I'm running a Sylvania USA made 5840w. It's a bit noisy, but sounds okay.
I'd love to get a AC701K for it but they are stupid money.  Last but not least I removed C6. This opened the mic up added more air and seemed to balance the whole shooting match a bit better.

Clip

https://www.dropbox.com/s/aqvujev9x27qdt6/M49B%20bias%20and%20C6%20removed.wav 

Nyquist said:

Hey guys. Have had a bit more time to muck around with this build. I have added a 100K lin pot for a fully variable pattern (removed the 3 position switch). I have also been mucking around with the bias both by ear, scope and using my multimeter. Simply dialling in 120V,50V exactly and exactly 1.6v bias gave the best results both sonically and headroom wise. I have ordered a bunch of different 5840 tubes to find the quietest and nicest sounding option. At the moment I'm running a Sylvania USA made 5840w. It's a bit noisy, but sounds okay.
I'd love to get a AC701K for it but they are stupid money.  Last but not least I removed C6. This opened the mic up added more air and seemed to balance the whole shooting match a bit better.

Clip

https://cdn.groupbuilder.com/groupdiy/u/39511/58d028199430b.wav

Click to expand...

Thanks for taking the time to report on your findings,
,
Best,
DAn,