Official U87 "AI" Booster Conversion Board - Build and Support Thread

JMPGuitars

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Apr 30, 2018
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Today I was bored, so I figured out that if I mount C5 horizontally on the back of the PCB, the PCB would fit in the budget body with the blue PCB version of the U87.

Obviously I decided to test it before connecting to a functional mic. I seem to have similar problems to others in this thread that have gone unanswered. Is this project abandoned?

I didn't use R8 or R9, so I have R3, R5, and R6 on the PCB. R8 is bridged across all 3 vias.

With a source voltage (bench PSU) of 12V, I had only 10V on the Vout. I saw somebody else with a similar issue, and higher voltage was suggested. I raised the bench PSU to 24V, and then (I believe it was) the diodes started smoking. They're very shiny now, and look a little melted maybe.

Assuming these boards aren't completely abandoned, maybe somebody should post a functional layout/schematic of this board in use with the U87 project?

Thanks,
Josh
 

Matador

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Apologies I missed this.  It isn't defunct, it's just that not many people seemed interested in the PCB. :)

I still have my 4 prototypes, and I can measure them.  There isn't much to debug here, as there are only a handful of components and 99% of the circuit is handled within the chip itself.  However if you need some test voltages I can measure them for you.
 

JMPGuitars

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Apr 30, 2018
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Matador said:
Apologies I missed this.  It isn't defunct, it's just that not many people seemed interested in the PCB. :)

I still have my 4 prototypes, and I can measure them.  There isn't much to debug here, as there are only a handful of components and 99% of the circuit is handled within the chip itself.  However if you need some test voltages I can measure them for you.

Test voltages would be great, thanks.

Question- how much of an output increase does this give the U87?

Thanks,
Josh
 

JMPGuitars

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Apr 30, 2018
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RuudNL said:
Output level is linear with the polarisation voltage.
Incresing the voltage from 46 to 60 volts will mean 2,3 dB gain.

How does that 2.3dB gain translate to real world use? If a 3dB increase is double the power, and 10dB is double the volume, how does that gain in this case affect the real world perceivable output level? Will I need only 2.3dB less increase on my preamp?, or would I need 2/3rd less preamp boost based on power?, Or 25% less based on volume?
 

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