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

[kidvybes]

...separated at birth...

 

[kidvybes]

...solo...

 

[mgronroos]

Really nice!

I like that you are using the same colour on all Mics.
It looks really good and professional.

Something tells me that Santa is coming early this year, and that he may have a powder coating gun with him..  8)

//Michael

 

[kidvybes]

Really nice!

I like that you are using the same colour on all Mics.
It looks really good and professional.

Something tells me that Santa is coming early this year, and that he may have a powder coating gun with him..  8)

//Michael

Thanks Michael!...actually, each time i bring mics to the powder-coater, I'm limited to what color they are spraying that particular day (or just come back another day) since they allow me to just add my mics to the existing work order to avoid paying any setup fees...

...the MataChung C12 was coated in a "cream" tone, and this Poctop duo are more like the "seamist" that Bock uses on his 251 (a kinda "greige", grey-beige)...these shades definately have an old-school vibe, and give the mics a more "boutique" look...and at these prices (about $20 a mic) I couldn't resist...

 

[Nyquist]

I have nailed this mic. Have spent quiet a bit of time trying a few different ideas provided by an old tech mate of mine.

So after going through a few more tubes I have one! A Jan 5840 USA NOS tube. Burnt in for 2 days and it come up nice a quiet.
I have also removed R3. This is a common mod on original M49's. It opens the low end up all the way down to 20hz.
Also another common mod to these mics is to swap out C4 (8pf) with a 2pf 300v mica cap. This gives lower noise and higher gain (about 3db)
Last but not least I swapped C5 with a 1uf oil in paper cap. This made a huge difference and really gives the mic that smooth and creamy sound like the original.

My studio is currently on a location recording job so I'll have to wait until I've finished that project until I post a new sample.

 

[poctop]

I have nailed this mic. Have spent quiet a bit of time trying a few different ideas provided by an old tech mate of mine.

So after going through a few more tubes I have one! A Jan 5840 USA NOS tube. Burnt in for 2 days and it come up nice a quiet.
I have also removed R3. This is a common mod on original M49's. It opens the low end up all the way down to 20hz.
Also another common mod to these mics is to swap out C4 (8pf) with a 2pf 300v mica cap. This gives lower noise and higher gain (about 3db)
Last but not least I swapped C5 with a 1uf oil in paper cap. This made a huge difference and really gives the mic that smooth and creamy sound like the original.

My studio is currently on a location recording job so I'll have to wait until I've finished that project until I post a new sample.

Thanks For your post , this makes all sense, R3 will indeed affect the feedback to transformer Primary.
C4 is actually tweakable in the M49 , from 2-8 pf depending on what you want to balance out , it is a Flex point in the response curve ,
C5 is the Flavour-Spice Cap ,  PIO is always a good choice

I do Like the 5840 JAN this is what i used as well in my builds, LOve em ,

Thanks again for taking the time to expose your observation and feedback looking forward to listen to your sample.
Wich capsule are you using.

Best,
DAn,

 

[Nyquist]

Cathedral Pipes(Dale) M7 Capsule 

 

[Nyquist]

Hi Guys. Final sample uploaded. Check it out https://www.dropbox.com/s/3ssfesucttd3doy/M49B%20Final%20sample.wav?dl=0

Cheers!

 

[mgronroos]

Sounds great!

I think I may also make the R3-mod and use a green Russian PIO for C5.
Really looking forward to finish this one!

Best,
Michael

 

[bioman666]

Hi Guys !

I got back to my M49b build, and finished to check the PSU. Before I plug it into the mic, I'd like to clear something out : I can't figure how to measure plate current once your PSU is all soldered up. To me, current can only be measured by putting the multimeter across (instead of) the path it is supposed to follow... that seems pretty impossible when everything is soldered. I know it must be a very noob question though !

The only things i could measure (after playing with both pots) were :

• polarisation = 57.4 V
• B+ = 120.2 V
• voltage across the 5W trim pot = 1.63 V

Is it possible to tell anything from these voltage alone ?

 

[0dbfs]

Measure on each side of the plate resistor to calculate voltage drop across the resistor. Then use ohms law to calculate current.

Cheers!
jb

 

[bioman666]

That makes sense, yet I'm not sure wich one is the plate resistor. Everyone give very variable values for it...

 

[0dbfs]

In the 49b schematic it's R10, 100k.

For the most accurate reading you should also measure the value of R10 and use that to compute current because it's not likely to be exactly 100k. Probably close enough for rock and roll tho.

Different tubes will draw slightly different current and you can modify/control the amount to an extent by adjusting the resistor ladder connected to the cathode, and the heater voltage. All those points affect eachother to a certain extent including the grid bias which is also derived from the heater voltage.

How does the mic sound?

Cheers!
jb

 

[bioman666]

Nice, thanks for the full answer !

I'll post some vocals as soon as it works -- Don't expect much though, i'll sing myself 8)

 

[bioman666]

I'm definitely getting closer ! Here's what I have so far :

bias = 0.747 V
plate = 75.2 V
pola = 56 V
B+ = 120 V

Ain't that a weird bias voltage ? In case I measure it wrong, here's where I put the voltmeter probes :

 

[bioman666]

It's aliiiiiiiive ! It's freakin alive ! after a 2 years lazy wait, I finally nailed it !

I don't know if my voltage tuning is optimum -- I hardly can tell as I'm recording in my bedroom, and its acoustic sucks.

## disclaimer ## I'm no audio engineer, no guitarist, no singer. Just regular hobbyist, so don't expect perfect pitch, nor inspired mix ## disclaimer ##

I have recorded over the last hour a song (guitar + vocals, both m49b, + drum loop to keep the beat). Path is m49b in SCT-700 body --> Soundskulptor MP73 --> M-audio Fast track ultra 8R. Guitar is a 150 € folk from Thomann :

• the ogg "mix"  : http://goo.gl/ACYlFu
• the wave dry vocals : http://goo.gl/69IGmn
• the wave dry guitar : http://goo.gl/zioX0B

My opinion so far :

• Definitely smooth highs. I used to tame these with my t.bone SC1100, i got to try out some EQ to accomodate this m49b.
• I really like the way it handles my "loud" singing. That was always the weak point of any of my recordings with the SC1100 or KMS105, it looks like life just got easier
• I can hear some noise -- i did not used to. Not quite bothering, though

It may not be the end of the tweaking, but I still would like to thank you guys for your help and making it possible !

Cheers ! 

 

[poctop]

I'm definitely getting closer ! Here's what I have so far :

bias = 0.747 V
plate = 75.2 V
pola = 56 V
B+ = 120 V

Ain't that a weird bias voltage ? In case I measure it wrong, here's where I put the voltmeter probes :

Thanks For your post , 8)
Did you try to adjust the bias pot ? ,  you should be able to aim at a lower Plate voltage measure on A ,
you should be able to get it down in the 50V range , try that and let me know if it improves your recording, sometime measuring bias can be tricky when a high Megohm resistor is invlolved it will fool your meter,  (R5)
Best,
Dan,

 

[bioman666]

Well, doesn't a 50 V plate voltage across a 100 k R10 would lead to a weak plate current (~50 mA) ?

A what kind of improvement should I expect ? Do you hear something odd -- apart from the playing -- in the files I've posted ?

 

[0dbfs]

No necessarily. You need to measure the voltage drop. ie; the difference between V on each side of the 100k resistor. So if B+ is 120V on the B+ side of the plate resistor and you measure 50V at the plate then you get 70V of drop. I=E/R or 70mA=70/100k.

Cheers,
jb

 

[bioman666]

OK my bad, I thought "plate voltage" stood for "R10 voltage".