tedsorvino
Well-known member
Hi everyone.
I recently found an old digital reverb unit DBX 290.
It has this simple but hard to find 4 pin din AC power supply (attachment).
Simple 9 vAC 20VA (2.2A).
Since the original EU model is expensive and hard to find I made one out of 230v ac primary / 9v ac secondary 20 VA.
But when I used it there was an audible constant white noise blanket particularly audible on louder signals.
It's not acceptable so I guess this is not normal even if the unit is not a great one.
I replaced all power supply filter caps and the same noise is still there.
Needless to say that i used the same leads, same test procedure etc that i'm using with other units with great results.
My question is what could go wrong with a simple ac adaptor since there is no filtering on the external ps unit.
Is it a matter of lower quality ac supply?
I mean do you think that DBX use better quality stuff for its cheaper series?
Is it a matter of current rating since i'm using EU voltage?
Is it something else, somewhere else in the circuit?
If you have any ideas please advice
I attach the simple original supply diagram i followed
I recently found an old digital reverb unit DBX 290.
It has this simple but hard to find 4 pin din AC power supply (attachment).
Simple 9 vAC 20VA (2.2A).
Since the original EU model is expensive and hard to find I made one out of 230v ac primary / 9v ac secondary 20 VA.
But when I used it there was an audible constant white noise blanket particularly audible on louder signals.
It's not acceptable so I guess this is not normal even if the unit is not a great one.
I replaced all power supply filter caps and the same noise is still there.
Needless to say that i used the same leads, same test procedure etc that i'm using with other units with great results.
My question is what could go wrong with a simple ac adaptor since there is no filtering on the external ps unit.
Is it a matter of lower quality ac supply?
I mean do you think that DBX use better quality stuff for its cheaper series?
Is it a matter of current rating since i'm using EU voltage?
Is it something else, somewhere else in the circuit?
If you have any ideas please advice
I attach the simple original supply diagram i followed