[poctop]

Hi I been watching these build threads trying to learn about great mic circuits as experiments I have knocked up some M49ish circuits using 5940 tubes & Olivers TLM149 conversion schematic... was also thinking buying a TLM149 for body & real capsule

Poctop you say this is your flavour of this mic so are you using the schematic posted at beginning I have only just noticed the neuman schemtic seems to have some sort of feedback built in, I havent made that part of the circuit for my experiments  YET


Anygood for a cheap body

I guess it is my flavor of the mouting and layout , but those are  the 49b or 49c as the per the orignal schematic ,  feedback included ,
BEst,
DAn,

[gary o]

I see what you mean Dan great stuff thanks, Im going to try adding a little feedback to my experiment

All the bast cheers

[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=Ntk:Primary|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://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993d09.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,

[poctop]

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,

[poctop]

All M49 models after 1957 had a “cardioid only” switch built in, to achieve a 4dB s/n improvement [as compared to setting the pattern] remotely, from the power supply.

Note:  To Operate S2 Cardiod only Switch

[poctop]

Hope checking those picture will help finding your issue , this is what i have here , works like a charm 

What is the ratio of your transformer ?  .....  Where do you actually Measure the Kathode voltage against what reference ?

B+ was readjusted to 120V afterwards hence the 50V  on the plate wich is about 4-5V higher than the cal point at (116V-120) = 50-4= 46Vplate.

[Spencerleehorton]

Hi guys,

With the PSU set to 116v i get the following:

K = 0.9v
A = 38.3v
H+ = 5.9v

any ideas?

regards

Spence.

[Spencerleehorton]

Hi,

Is there a way of going back through the voltages in my build until i find where its going wrong?

also this is my tube, could this be a problem?

http://www.ebay.co.uk/itm/380399247271?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

really want to sort this as im also building a M49 body and want this mic to work flawlessly in this.

regards

Spence.

[Spencerleehorton]

Hi All,

found my problem, leaky C9 cap, top tip always check the caps!!!
headache over now!!! onto building some!!!!

regards

Spence.

[poctop]

Way To go Spence,   

Best,
Dan,

[poctop]

thanks to micaddict this is an intersting about how the M49 is one of the most overlooked Mic in the neumann History and Many nice info and comments about those and the M149 wich is the modern Version.  it does also contain a Shameless Plug of mine.

http://www.gearslutz.com/board/high-end/840056-neumann-m49-vs-m149.html

Best, 

Dan,

[tonycamp]

Hi Dan, thanx for the 47fet stuff, getting going on it soon.
I'm also fired up for this M49 project, i want to get Erics new body thats coming out, but i just found out the AC701K is $500 large!!! Is there a substitution tube? I could handle the $500, but i hear through Christian Whitmore that they're not easy to test, a lot of fake, and a crapshoot at best. What do you recommend?

excuse me if this is covered somewhere, i looked and found nothing

thanx
Tony

[micaddict]

Is there a substitution tube?

Yes and no. There's no close copy. But the 5840/EF732 is a very nice substitute, in any case for the -b configuration (fixed bias). Many use it and the M49 clone in this here thread has it, too.

[bruno2000]

The first U64s used the AC701 tubes, but the latter ones used a 7586 Nuvistor.  Has anybody played with the 7586 for this build?
Best,
Bruno2000

[tonycamp]

thanx addict, good stuff

[tskguy]

Hi all,

Quick build update..
Everything is finished on the mic except for the capsule! Power supply needsto be finished and tested, i hope to have it finished by Saturday.
The spacers I ended up using are half inch on the very bottom 1 inch between the TX PCB and the circuit PCB and another half inch spacer at the top to hold the capsule board. From what I can judge this seems to be setting the capsule heighth about right.

[wave]

Lookin good Eric! Now finish making your HK-47 and stick it in there so I can come over and steal your mic! BTW, did you see that I put both stepper bits in that box today?

-Dave

[tskguy]

Ha, you can steal my mic anytime bro!

And yes I saw the bits thanks again,

Eric

[tskguy]

Hey boys the mic is completed,


http://www.groupdiy.com/index.php?topic=52563.60

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