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

[poctop]

Hi guys !

I'm starting a 49b build, but I still have to sort out a few things...

1/ what kind of wiring should I do to run the PSU on the European 240 V main ?

2/ just checking my combo will do : 49b + cinemag 2480 + 5840W + RK47 or RK7 (from parts) ? Anything looking wrong from there ?

Thanks !

Looks fine for the combo ,  what version are you building the round or sqaure version  ?

you main toroid transformer will be wired in series for 230 at the primary and then in parralle at the secondary for 120V out ,

will you be using the hammond 20V traffo dual primary for the heater ?

Best,
Dan,

 

[bioman666]

what version are you building the round or sqaure version  ?

Square, to fit a Thomann SCT-700 body.

will you be using the hammond 20V traffo dual primary for the heater ?

Well, it's in the PSU BOM, so i guess so... Are you worried about the space it requires ?

 

[poctop]

what version are you building the round or sqaure version  ?

Square, to fit a Thomann SCT-700 body.

will you be using the hammond 20V traffo dual primary for the heater ?

Well, it's in the PSU BOM, so i guess so... Are you worried about the space it requires ?

Well, it's in the PSU BOM, so i guess so... Are you worried about the space it requires ?


Have you replaced it with the dual primary 20V traffo as per the note on the first page of the build thread,
Let me know ,  you will need the dual primary version of this traffo for europe.

Dan,

 

[bioman666]

Ok so is this BOM correct ? http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=8508A2A30F

I changed to 0.3 A fuse to 0.1 A. Should i go for 0.15 A instead ?

 

[Winetree]

The P.S. BOM shows Rotary Switches SP3T SHRTNG 1.5" ACT
for the pattern select switch only allowing 3 choices.
Can another pot  be used for variable pattern select like the orginal M49? What value?

 

[poctop]

Ok so is this BOM correct ? http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=8508A2A30F

I changed to 0.3 A fuse to 0.1 A. Should i go for 0.15 A instead ?

Yes you have the corrected traffo for europe,  sometime the fuse is not slow blow enough for the draw considering having some tad higher rated Fuse is a good advice indeed.

best,
dAn,

 

[poctop]

Here is some  alternatives for the 5*11mm caps needed specifically for the M49bc square and round,  also in the U67 and 269c mic,


http://www.alliedelec.com/search/searchresults.aspx?dsNav=Ntkrimary|MKT1813310405|3|,Ny:True,Ro:0&dsDimensionSearch=D:MKT1813310405,Dxm:All,Dxp:3&SearchType=0


http://canada.newark.com/vishay-roederstein/mkt1813310405g/capacitor-film-0-01uf-400v-axial/dp/26M1636?Ntt=MKT1813310405

http://canada.newark.com/vishay-roederstein/mkt1813-310404/capacitor-poly-film-0-01uf-400v/dp/18M2494?Ntt=MKT1813310404

http://fr.farnell.com/vishay-roederstein/mkt1813310405g/condensateur-0-01uf-400v/dp/1166851?Ntt=MKT1813310405

 

[poctop]

The P.S. BOM shows Rotary Switches SP3T SHRTNG 1.5" ACT
for the pattern select switch only allowing 3 choices.
Can another pot  be used for variable pattern select like the orginal M49? What value?

https://cdn.groupbuilder.com/groupdiy/u/39511/58d0281993cfa.pdf

you absolutely can,  if you look at the schematic attached,  all you have to do  is :

use a 100K lin pot ,

and connect the wiper of the pot to the COM pad ,  one side of the pot to OM and the other side of the pot to F8 pad,  this way the pot will act as a voltage divider from 0V omni  to 120V figure 8 ,

I did that this way to avoid having to solder resistor on the 3 pole switch  I used a 3 pol switch cause i am not a very big user of the infinite pattern possiblity
of the mic ,  i am just using fig 8 , omni and cardiod ,  but this will not prevent you of doing this that way , that is why i like DIY , you can make it the way you like , but in this case it is very easy to modify,

Best,
Dan,

 

[Spencerleehorton]

HI Guys,

need a bit of help making sure this ac107 is wired in correctly.

pin1 = go through the board from the underside and attach to the fgrid, is this ok?
pin2 =  connect to K turret
pin3 = connect to HG turret
pin 4 cut
pin 5 + 7 = connect to A turret
pin 6 = connect to H+ turret
pin 8 cut off

please advise as I know im not understand this.

regards

Spence.

 

[poctop]

HI Guys,

need a bit of help making sure this ac107 is wired in correctly.

pin1 = go through the board from the underside and attach to the fgrid, is this ok?
pin2 =  connect to K turret
pin3 = connect to HG turret
pin 4 cut
pin 5 + 7 = connect to A turret
pin 6 = connect to H+ turret
pin 8 cut off

please advise as I know im not understand this.

regards

Spence.

That is exactely correct, 
Best
Dan,

 

[poctop]

Good news ,

For those that will be building the mic project that needs the 0.01uf  capacitor in the package 5*11mm  i have been able to change mouser minds to offer a 10% variation at a minimum qty of 1  ,

here is a link for it ,
http://ca.mouser.com/ProductDetail/Vishay-Roederstein/MKT1813310405/?qs=N5kmjX/bzE4Fjs7uA0EePA==

i aslo went over my BOM and added in the customer part number cell some nice subsitution for the parts that went back order , should be all good now ,

Best,
Dan,

 

[gary o]

What plate & Cathode voltages are you guys getting at what is optimal voltages  ...... thanks

All the best

 

[poctop]

What plate & Cathode voltages are you guys getting at what is optimal voltages  ...... thanks

All the best

I trimed to pot to get the proper bias wich is about 1.6V in self bias (c) or  it was easier to get the plate current in filament biased (b) where it is supposed to sit in this circuit so adjusting the plate voltage to about 50V with the B+ operated at 120V and a 100K plate resistor, would give the 0.7ma as per the original circuit.

Best,
Dan.,

 

[gary o]

Thanks Dan Im just messing with similar to C version circuit as experiment I have my own supply giving 118V ht 5.7V filiment & I get 52V plate & 1.3V cathode I guess Im in the ball park

Thanks

 

[poctop]

Thanks Dan Im just messing with similar to C version circuit as experiment I have my own supply giving 118V ht 5.7V filiment & I get 52V plate & 1.3V cathode I guess Im in the ball park

Thanks

the calculation of your plate current is the most important thing , are you using a 100K plate resistor ?

Dany,

 

[gary o]

Thanks Dany yes 100K plate resistor

 

[poctop]

Thanks Dany yes 100K plate resistor

you are indeed very close then ,
D

 

[gary o]

May add a pot on cathode then, to achieve 1.6V on cathode voltage

Thanks

 

[gary o]

Added trim pot trimmed to 1.6V mic sound great and very very quiet , love it

 

[0dbfs]

Gary, How does that adjustment affect your voltage drop across the 100k plate resistor (ie; operating current closer to 0.7ma?) as well as b+, and Vplate values?

Thx,
jonathan