Ultra Pimped Alice - my take on a classic DIY design

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homero.leal

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Aug 8, 2015
Messages
80
bxershrts said:
Ah....one last thing -

I will implement a pin socket for the HFEQ capacitor on the pcb until I find one that suits ---using the suggested 8n2 ,3n9 or 2n2 - what capacitor location on the pcb do I socket..?

Thanks for you help,

Hudson

It will be C17.

Regards!

 

bxershrts

Well-known member
Joined
Jan 12, 2015
Messages
49
Hello again ;-) I have assembled the circuit and am ready to calibrate. What is the correct method to calibrate and voltage levels to shoot for?

Thanks
 

homero.leal

Well-known member
Joined
Aug 8, 2015
Messages
80
bxershrts said:
Hello again ;-) I have assembled the circuit and am ready to calibrate. What is the correct method to calibrate and voltage levels to shoot for?

Thanks

Hi!

Voltage reading at SRC_T pad should be 1/4 voltage reading at VCC pad.

This allows to maximize headroom for your mic.

There are other forms of calibration, but they require different equipment.

Regards!

 

bxershrts

Well-known member
Joined
Jan 12, 2015
Messages
49
Thanks for all your shared input.

I have assembled the mic , calibrated it easily - voltages are all in the correct range , the mic is clear crisp and detailed yet there is one problem .

The mic dies with plosives or in close proximity.

At VCC_T voltage drops a whole volt from 11.62 down to 10.34.

At SRC_T Voltage goes up from 2.89 to 5.02 vdc.

Bad Jfet?

Thanks!!
 

homero.leal

Well-known member
Joined
Aug 8, 2015
Messages
80
bxershrts said:
Thanks for all your shared input.

I have assembled the mic , calibrated it easily - voltages are all in the correct range , the mic is clear crisp and detailed yet there is one problem .

The mic dies with plosives or in close proximity.

At VCC_T voltage drops a whole volt from 11.62 down to 10.34.

At SRC_T Voltage goes up from 2.89 to 5.02 vdc.

Bad Jfet?

Thanks!!

It may be a capsule problem. :(  Could you try with a different capsule?

This kind of problem most of the time is due to diaphragm collapsing.

Another thing you could do is replace 9.1V Zener to a lower value (8V?), so polarization voltage is reduced.

Regards!

 

bxershrts

Well-known member
Joined
Jan 12, 2015
Messages
49
Hello again Homero :)

Always appreciate your help and advice.

Yeah...I have tried 3 different capsules and they all do the same thing.

I will try a different zener - good idea!

The polarization voltage sits at about 52.7v and doesnt move when the mic goes dead...perhaps this is too high voltage for all my capsules?
 

homero.leal

Well-known member
Joined
Aug 8, 2015
Messages
80
bxershrts said:
Hello again Homero :)

Always appreciate your help and advice.

Yeah...I have tried 3 different capsules and they all do the same thing.

I will try a different zener - good idea!

The polarization voltage sits at about 52.7v and doesnt move when the mic goes dead...perhaps this is too high voltage for all my capsules?

It's a little bit strange, since 52.7V is not to high polarization voltage.
What kind of capsule do you have?
I have used 60V on some cheap LDCs from EBay and AliExpress, and they work fine.
Are you using the mic in a high humidity environment?
 

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