M49 Alternate schematic for cardioid only

[Khron]

Now i don't understand what's wrong with C2, please help me out i'm totally out on this one

You only posted (a part of) this schematic AFTER my first observation, so that 10nF C2 is not the issue

Edit: Ah, nevermind, you deleted that schematic, but Drosselmeier corrected it...

 

[Papa Tango Charly]

Ôk great

You only posted (a part of) this schematic AFTER my first observation, so that 10nF C2 is not the issue

Ok great, thank you best

 

[elskardio]

@Papa Tango Charly
Do you have a problem with your mic or not? By reading your posts it's pretty unclear!

 

[Khron]

@Papa Tango Charly
Do you have a problem with your mic or not? By reading your posts it's pretty unclear!

Schrödinger's M49...

 

[Papa Tango Charly]

@Papa Tango Charly
Avez-vous un problème avec votre micro ou pas ? En lisant vos messages, c'est assez flou !

Like I said, I think that the low end is kind of muddy. I would like to have a better result on the low end. As a singer, I like to hear a nice low mid. I was wondering how could I manage to improve the microphone. Best.

 

[elskardio]

Schrödinger's M49...

I'm not sure the flask of poison would kill the M49 though

 

[elskardio]

Like I said, I think it's the king of low end is kind of muddy. I would like to have a better result on the low end. As a singer, I like to hear a nice low mid. I was wondering how could I manage to improve the microphone. Best.

Which capsule are you using?

 

[Papa Tango Charly]

Which capsule are you using?

My capsule is a M7. I don't really get the role of C6 on my schematic or C1 on your microphone. ). it might be the proximity effect like you said. Thank you. I love your microphone!

 

[elskardio]

My capsule is a M7. I don't really get the role of C6 on my schematic or C1 on your microphone. )

It creates a low pass filter. Probably to deal with RFI.
Just remove it and test the mic without... but it won't fix your low mids problem.
Did you test your M49 with various polar pattern? The frequency response will change.

 

[Papa Tango Charly]

It creates a low pass filter. Probably to deal with RFI.
Just remove it and test the mic without... but it won't fix your low mids problem.
Did you test your M49 with various polar pattern? The frequency response will change.

Ok thank you i will try that. i let you know i soon as i come back in france. thank you

 

[Drosselmeier]

@Papa Tango Charly, is this some kind of filter?
like this

 

[Papa Tango Charly]

You only posted (a part of) this schematic AFTER my first observation, so that 10nF C2 is not the issue

Edit: Ah, nevermind, you deleted that schematic, but Drosselmeier corrected it...

Yes that's really cool!

 

[Papa Tango Charly]

Does it affect the sound if you put 100K after C2 an C6? thanks

 

[Papa Tango Charly]

That's the correction of my initial schematic M49 6S6B-V and M7

 

[Khron]

Does it affect the sound if you put 100K after C2 an C6? thanks



View attachment 128299

Well, with the 100k where you originally had it (and especially with C2 connected as it was), you would have had pretty much ZERO sound. I can't say for sure how that affects the sound, but the amplitude would be virtually none.

 

[Papa Tango Charly]

Well, with the 100k where you originally had it (and especially with C2 connected as it was), you would have had pretty much ZERO sound. I can't say for sure how that affects the sound, but the amplitude would be virtually none.

Yes i understand, in fact i was trying redraw the schematic of my friend and i have made lots of mistake. Drawing schematic helps my analyse... R9/C7 form a low-pass filter. (More feedback for low frequencies.) I might want to keep it if i want a better low end roll off?

https://groupdiy.com/threads/m49c-circuit-details-questions.80237/

Ruud comment

I must have measurements of the M49 circuit with and without the filter active.
But I suppose they are on my old computer.
You can simply disable the low-cut filter by lifting one end of the 5M.ohm resistor.

EDIT: found it! Blue is the fixed low-cut active.

 

[Papa Tango Charly]

Hello Guys i found these informations

I have the impression that C6 560pf plays a very important role in the midrange.
If the capsule is well balances maybe i don't need C6?

I found this information about C6 can you confirm?

o C6=100pF
▪ Cutoff frequency = fc = 1 / 2πRC
▪ fc = 40,000 Hz

o C6=220pF
▪ fc = 18,086 Hz

o SiC6=470pF
▪ fc = 8,466 Hz

o SiC6=560pF
▪ fc = 7,105 Hz

o SiC6=680pF
▪ fc = 5,851 Hz

o In conclusion, it will be necessary to test the appropriate value in practice on the prototype if we wish to correct the presence of the capsule.

▪ For treble attenuation: C6 = 470, 560 or 680pF

I found this information about R9 and C2 can you confirm?
• R9: feedback resistance between the transformer primary and the backplane to filter to suppress subsonic frequencies (1H to 20Hz).
o Subsonic frequencies (1 Hz – 20 Hz) are generally produced by earthquakes and by large organs found in churches. It is therefore more a matter of vibrations felt than heard.
o 4.7MΩthrough-metaloxide1/4W
• C2: Forms a low pass filter with resistor R9 to remove the audio signal from the transformer
o C2 = 10nF/200V (metalized polypropylene MKP)
▪ fc = 1 / 2πRC
▪ fc = 3.4 Hz
The audio signal (cutoff frequency <3.5Hz) is brought back to the input of the amplification stage
triode inverter.

 

[RuudNL]

I have the impression that C6 560pf plays a very important role in the midrange.
If the capsule is well balances maybe i don't need C6?

I don't know how you calculated the influence of C6 on the frequency response, but if you measure the influence of this capacitor in a real M49 circuit, you will find completely different values.
In fact a value of 500 pF has hardly any influence on the highest frequencies of the M49.

 

[elskardio]

I finished my second microphone today

 

[Papa Tango Charly]

I don't know how you calculated the influence of C6 on the frequency response, but if you measure the influence of this capacitor in a real M49 circuit, you will find completely different values.
In fact a value of 500 pF has hardly any influence on the highest frequencies of the M49.

Hello Ruud, i took off the 560pf on C6 and my M49 with the M7 sound more clear. I has changed something on the top end of the microphone. Thank you. Best regards.