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dbx 286 s
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Thread My Preamp emits a buzzing noise.

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TartanKiwi

TartanKiwi

1 post
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First post
1 Posted on 05/12/2018 at 15:47:26
As the title says, my pre amp emits a buzzing noise. It comes straight from the DBX 286s, not from the headphones or mic it is plugged into.

The set up is as follows.

BP40 Audio Technica into
DBX 286s preamp into
Steinberg UR12 interface into
PC.

So, When I got the piece, I unwittingly plugged it straight into the wall or multibox to be exact. it takes 110 volts. In NewZealand where I live our out puts are 240 volts. I almost blew the thing up however luckily it survived. I took it into an electrical shop to get a transformer. The only piece that fit the bill was an 120 volt piece. It worked! However, now it buzzes. The mic does not pic it up and the thing still works as intended but it is starting to grate at my ears. Would this be because the transformer is 120 volts and not 110? Could it be the brief encounter with 240 volts has slightly degraded the components of the DBX, or something else.

I'd love to get some insight on the matter!


Cheers.
Steve Skies

Steve Skies

5 posts
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2 Posted on 09/14/2018 at 09:14:45
Check that its not a ground issue and or faulty connections on the inside (check the soldering of components). Though i would advise taking it to a specialist to get it checked out.

Steve Skies @ Sirius Sound Studios. 

https://www.facebook.com/siriusstudiosfr/

https://www.linkedin.com/in/steve-skies-b41707170/

angelie

angelie

350 posts
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3 Posted on 09/16/2018 at 07:49:26
Hey,

Sorry to hear you almost lost your equipment.
And that my response is a bit late.
I didn't noticed this post....


I think with the transformer a capacitor or two has been blown up / damaged.
These things can handle some voltage but if you feed them to much voltage... they die.

Capacitors function is to make the dc voltage after a diode bridge smoother. To much fluctuation in the DC voltage causes a hum in the signal amplifiers...

If one or more capacitors are damaged you will hear a hum / noise from the equipments output because the dc voltage is no longer smooth enough..

I expect the capacitors right after the diode bridge or even the one directly over the mains input is gone...

- Angelie

It's not about what you got to use ....    but how you use what you got...

[ Post last edited on 09/16/2018 at 13:30:52 ]

AudioFantastic

AudioFantastic

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4 Posted on 05/23/2022 at 07:48:25
Quote:
I expect the capacitors right after the diode bridge or even the one directly over the mains input is gone...


I have the same problem with buzzing DBX286A (that's "S" in its older reincarnation). Almost no experience with soldering, but willing to give it a go. Would you be able to provide some additional details?

Here is the general schematic from the user manual:
dbx.png

Actual service schematics are available here: https://dbxpro.com/en-US/product_documents/286a-project-1-schematicszip

I am not sure about the exact revision of mine as it's not written anywhere outside. It has the following marking on the side: DBX286A-EU 100592 Sep 99
This strongly suggests the latest, A4 revision.

@angelie, could you give an idea of which capacitors need to be replaced with what? :) Will post photos of its PCB, etc.

[ Post last edited on 05/23/2022 at 08:00:57 ]

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