1

AB528 Microphone preamplifier / Re: Noisy/Clicky

« on: September 04, 2023, 11:46:54 AM »

Thank you for your reply!
After more testing of the AB528, the noise/crackling only appears when the v48 is on.


Does the preamp work apart from the noise? - Yes

Does the noise level depend on the position of the pot? - Yes

Does it depend on the gain switch position? - Yes, the noise increase when the gain is increasing

What is the DC voltage on Q5 collector, taken on the heatsink? Should be about -0.5V. - The DCV is 0.

Check that all your electrolytic caps are in the correct direction. - All are correct.

2

AB528 Microphone preamplifier / Noisy/Clicky

« on: August 19, 2023, 05:14:18 PM »

I just finished my second ab528.

There is a crackling, irregularly noise. 
The diode on the front panel is lit solid green.
I have done all other tests, changing cables, changing slot in my 500- rack. but still there. 

3

AB528 Microphone preamplifier / AB528-Test guide?

« on: October 16, 2022, 11:20:04 AM »

where do i find the test guide for the ab528?

4

AB528 Microphone preamplifier / AB528

« on: October 04, 2022, 10:07:18 PM »

My next step in the build is the three Relays. They are 10 pin relay and there is 10 holes in the PCB, BUT two of the holes have no metal ring to them. Do i solder them anyway or do i skip the two last pins on the relay?