G7 mic ... Big hum for now

I 'm near to be at the end of the construction of G7 mic but the result is a lot of Hum and a small signal..
i need to use a screen cable inside the psu for the signal?
or any suggest on the grounds connection is well accepted.
Regards, Corrado.

Is the electronic already inside the microphone body? Otherwise hum is normal. I had the same with my mic 'till the body was fully closed.

Even if the mic is in the body you can still get quite a hum if the screen around the capsule is not good enough. A low signal could be caused by many things. Trace out your wiring and check the way you've wired the transformer.

Here's the story.
ok at first, i connected the ground (pin1) to the mic Body, now the hum when i'm touching the mic are disappeared.

The hum seem at the same level of the signal...
i reversed the polarity on 100uF+1uF, was wrong.. Less (little bit) Hum..
I saw also (omnipressor site, Steve) that can be an error on the scheme for the heater polarity inverted..but i didn't understand..seems correct.
Now i'm think to change the trafos in the PSU, have to be Toroidal?
i've got normal..

:?
Sob..
Hummmmmmmmmmmmm...

Finally works!!!
the problem was on PCB , there was an error (a ground disconnected from the heater to the ground..
:twisted:
But now it work, the sound is good also with cheap china capsules..
thanks Jacob for this project.
A payed dinner for you, the next time you'll come in Italy.
:grin:
Regards, Corrado

Great Duka,

Do we get to see some pictures ?

[quote author="tamtamstudio"]
A payed dinner for you, the next time you'll come in Italy.
:grin:
[/quote]

I hope I'll be able to get that someday! I absolutely love Italian food..

:grin:

Jakob E.

And now spaghetti and champagne...


http://homepage.mac.com/tamtamstudio/PhotoAlbum10.html

:green:

Whoa, Those mics looks fantastic! :shock:

Jakob E.

Like my spaghetti... :thumb:
Hehehehe..
I'm near to the end for 1176.. i'm waiting for frontal panels..
I will send you also the pics from my SSL clone..
My rack is expanding..

Was this using one of Labs' boards? I noticed the broken connection on the board, but didn't know if that was going to be a problem.

Daniel

:?:

it's right that we must connect
the ground and the Heater 0v together ?

:?:

Yes, the heater 0V, the chassis ground, the HT 0V, and the audio ground has to be connected. Preferably in the microphone.

ok thanks Jakob,

i have a little ground noise problem...
so it's perhaps the solution

Those mics look fantastic! How did you make the mic cases? Also, which cheap Chinese capsule did you use?

The capsules was bougth from Ward, some months ago.
The console is Control24 from digidesign/Focusrite.
:wink:

[quote author="gyraf"]Yes, the heater 0V, the chassis ground, the HT 0V, and the audio ground has to be connected. Preferably in the microphone.[/quote]

Hi Jakob
I make a ground on mike chassis, but where I will connect ground on PSU chassis. I connected mains earth near euro conectors.
Thanks in advance
Duka

in order to attenuate my 50Hz noise.
i plan to change the wire mesh 12x12holes/inch to 18x18 or more

i have put some aluminium foil over the head of the mic
and after be sure of the good electric contact
i have test the noise improvement...
(test with and without led :wink: )

but the difference is very little, and the humm still audible.
any problem in my method ?

i have test 1001 ground & earth connections
and the actual design is the better i have found.

the noise is not a buzzz at 50Hz full of harmonic (100Hz, 200Hz...)
but only a humm at 50Hz, it's not a very big hum, but it's nevertheless too high for a "professionnal" microphone. :?

here is a comparaison between the noise
of the TLM103 and my G7.

http://img.photobucket.com/albums/v439/jazzy_pi/noisetlm103-g7.gif

Black : my G7
Red : Neumann TLM103

unfortunately the 120Hz noise is my PC. :?
(it's at the same level on the two graph but the black line mask the red line.)

we can clearly see the 50Hz pic, and little harmonics.

i have the .wav if anybody can share it ?