my A12 make HISS

[goldcut]

Hi Tim

I have my A12 for now 1 years or so, used a lot, really liked it. Now since 1 week, it is unusable, it make terrible hiss.

It happens 1 minutes after i power up the rack, (i guess when components gets hot enough), and then it last forever. The gain, the output trim, the 48v switch and the phase switch doesnt affect the hiss. It make it at the same volume regardless of the gain selected, it also make it when the gain is at 0.

here is a mp3 a record of that hiss.

http://www.lafusion.net/a12.mp3

thanks!
Mathieu

[tpryan]

First, verify that the DC voltages are correct at the op-amp pins. Also measure the DC voltage at the op-amp output. If the supply voltages are correct and DC offset is close to 0v then it's possible the op-amp has failed. Let us know what you find.

[goldcut]

thanks Tim

voltage at the op amp pins:

between 3 and 4 = 18V
.. 4 and 5 = -18V

.. 6 and 5 = -18V
.. 6 and 4 = 0V
.. 6 and 3 = 18V

.. 5 and 3 = 36V

everything seem normal, can it be the OP AMP?

[tpryan]

Do you have an op-amp to swap? If not, contact sales@seventhcircleaudio.com for return authorization and we'll test it.