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

[JW]

What power rating is needed for the 150M resistors? Is 1/4 watt fine?

 

[Murdock]

What power rating is needed for the 150M resistors? Is 1/4 watt fine?

Yes, as there is almost no current flowing, it should be fine.

 

[elskardio]

10uf cathode bypass cap is recommended with the 5840 instead of stock 20uf but experimentation and tuning is recommended.

Anyone tried different values here and care to comment?

10uF vs 22uF vs 47uF with the 5840 tube.

Thanks

 

[HerbertR]

Anyone tried different values here and care to comment?

10uF vs 22uF vs 47uF with the 5840 tube.

Thanks

It is a matter of taste. In my experience, 5840 tubes are not the least "microphonic" tubes on the market, and so depending on the 5840 tube used, I prefer a nice 22 µF or 33 µF tantalum capacitor to suppress the LF rumble a little bit more. It is a bit of finding the balance. Just try different values, you can't break anything and it only costs a few bucks. The experience and the feeling for it is worth its weight in gold. Believe me.

 

[justinheronmusic]

What are the transformer pads 1-4 on the PCB? I just purchased the beesneez BV11 to replace my cinemag and I'm looking for which numbers correlate to + & - and which leads are which.

 

[gbruler]

Hey guys, I'm not sure where to ask this, but I'll try here.
I'm trying to build the m49 by Poctop schematics and there are some things I’m not sure of.
I have a Flea body, Beezneez capsule, 5840 tube, and moby transformer B.v 11 10:1. I want to build the m49b version, as most people suggest it sounds better for vocals. I’m not sure what we should do to make the m49b schematics compatible with the 5840 tube (I’ve seen Oliver’s schematic but I figured it has the m49c bias?). Also, when I go to the BOM link there several things missing and I’m not sure what to do with that. If you guys can guide me a little bit with this it could be so awesome! Thanks!

 

[Delta Sigma]

You should be able to follow the schematic in post #1. There is info somewhere in this thread on what to do with the 5840 screens. Bias it by replacing R7 with a pot (2M?). Bias it to roughly 0.73mA plate current, then adjust +/- to where you want it.

It's important you use the optional power supply choke and have clean grounding.

For parts that are out of stock or obsolete, you will have to find substitutes. If it's your first time finding replacement parts on Mouser, it can be tricky to get used to, but their part filters are quite good.

 

[gbruler]

You should be able to follow the schematic in post #1. There is info somewhere in this thread on what to do with the 5840 screens. Bias it by replacing R7 with a pot (2M?). Bias it to roughly 0.73mA plate current, then adjust +/- to where you want it.

It's important you use the optional power supply choke and have clean grounding.

For parts that are out of stock or obsolete, you will have to find substitutes. If it's your first time finding replacement parts on Mouser, it can be tricky to get used to, but their part filters are quite good.

Thank you! So, on the schematic of the 49b I can see that they already changed R7 with a pot (it's different to the neumann schematic) so I'm not sure if it's already compatible with 5840 tube.
About the power supply, is that option in the schematic of the PSU?
Thank you so much

 

[Delta Sigma]

Dany's power supply can do the 5840. His M49PCB comes with the appropriate PSU PCB. Just make sure you add the optional choke.

Don't expect finding replacement parts (for out of stock & obsolete) on the BOM to be quick. If it's your first time using Mouser and finding equivalents, it can be a learning process.

 

[gbruler]

Dany's power supply can do the 5840. His M49PCB comes with the appropriate PSU PCB. Just make sure you add the optional choke.

Don't expect finding replacement parts (for out of stock & obsolete) on the BOM to be quick. If it's your first time using Mouser and finding equivalents, it can be a learning process.

Yes, thanks, it is my first time, and I'm afraid that I'm going to need some help with it. I will start and see what's exactly missing and maybe consult with a friend of a friend that might be able to help me, or maybe I'll ask you guys here
Thanks again!

 

[gbruler]

I’m not sure, but from what I gather from information I find on several threads, it seems that it’s impossible to do the m49b with the 5840? I can only find the 5840 implemented in the m49c circuit. Is it true?

 

[Migs 31]

@gbruler
I don't think that is correct.
From what I understand: you can use 5840-CV3929-CK6205, 5718, 5703
And many more to make a M49 B or C type of circuit.
What changes is the way/method to bias the tube/valve.

I'm working on those babies as we speak.
The C version seems easier to implement.
The B versions requires a bit more work and a very clean PSU/Heater.

Please note that I am not using anyones' kit.
I'm experimenting on my own (with a little help from my friend Thomas )
But correct me please anyone, if I am wrong.

M

 

[Delta Sigma]

I don't see why B vs C would matter in tube selection. They're just two ways of biasing the tube. In the B version, the 6V heater (4V in original, 6 for 5840) is tied to the cathode so there's always 6V from cathode to ground. R6 & R7 form a voltage divider so the junction with R5 is 1.6V below the cathode. C version, the 0.73mA cathode current brings through R7 brings the cathode to 1.6V. R7 is bypassed for audio so there isn't the 2.2k ohm feedback bringing the gain down.

Both ways, you'll have to replace one of the fixed resistors on the schematic with a pot and adjust the cathode voltage until you get the 0.73mA plate current. Adjust from there by ear if you want, as the tube curves will be different from the AC701k.