DBX 290 reverb processor noise

[tedsorvino]

There's a remote possibility the low audio tone (138Hz, not 277Hz I mentioned earlier) is coming into the device rather than being generated by it.
Running it standalone in a different location may eliminate this, but probably not, actually.

I also can't believe this was how it left the factory, unless there is now some kind of grounding issue, and the noise is generated within a earth loop or some such.
Or just that your gain structure is bad, resulting in a lot of noise overall, but that sounds unlikely too.

It's my third reverb unit. Used same leads. Same location. Same everything. Yamaha spx and boss rv rack just do the trick flawlessly. So obviously a dbx unit problem

 

[tedsorvino]

There is an input noise gate which comes before the reverb (not the gate for gated reverb) check that this is on. The Small and Large buttons are pressed simultaneously until their LEDs light - then the first four room type buttons are used to select the gate threshold. If only room is lit, your gate is off - if all four are lit you are at the highest noise threshold. See if the noise you are hearing switches off when you have the highest threshold. If it does then the noise is pre reverb and is either coming in from external source or possibly is being generated by the opamps in the pre stages.

Good tip and of course since they are putting an internal noise gate, they were suspecting something (op amps prone to noise maybe)

 

[tedsorvino]

With any reverb I never pass the full original audio through the unit as an insert but send to it from an Aux send bringing it back into the mix on its own channel(s), full wet, reverb sound only - thus eliminating any artefacts from the unit itself in the original signal.

Of course. That's the way i'm using time shifting effects most of the times. Parallel. It's not my first reverb unit. In my life i've owned more than 20. Some are fantastic. Yamaha, Roland and Lexicon are great . Some Yamaha (R 100) were noisy too. I also love noisy tube spring reverb tanks. But ...different horses for different courses,

 

[RoadrunnerOZ]

Good tip and of course since they are putting an internal noise gate, they were suspecting something (op amps prone to noise maybe)

The actual noise figure for this unit without the gate is pretty good - the noise gate is to suppress externally introduced noise - but it’s the last point of entry into the digital reverb system so a good identifying post for any noisy components in the pre stage with no signal input - if the noise goes away with the gate closed then it’s in the pre stage - however if it’s loud enough to open the gate even at max threshold then you wouldn’t know without using a scope. Easiest way is to track the signal through from the input - all 4558’s - with a scope or a signal probe to the A/D input.

 

[tedsorvino]

Finally it was one of the 5 dram chips. After following RoadrunnerOZ advice and help, I replaced all 5 with cheap chinese current ones and it worked. And then by removing 1 after the other and using the old ones, i found the faulty original one. Just one faulty d ram chip.