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kingof12



Joined: 09/04/10
Posts: 54
hum noise whrn phantom power engaged.Any way of solving?
      #1032880 - 10/02/13 11:40 AM
I have two sdc mics going into a dav bg1u preamp output of which goes into a patchbay and then out to inputs on my motu 828mkiiconnected to laptop. The priblem is that after about 30 minutes the mics pick up a low frequency hum. I thought it was the mics but have recently bought two new sontronics stc 1 and the problem persists. I am using balanced cables. There is not a problem when i use a mic that doean't need phantom powe. It seems toht worse when a signal is introduced to the microphone.. So in other worda the hum is present but flairs up when you sing or play into the mic and then settles down to it's oruginal volume when you stop. I have tried the mics directlyinto the motu 828 preamps with the same cables and there is no problem. I have therwfore put this down to something wrong with the phantom power supply on the dav bg1u. Am I right to deduce this? Dows anyone know what the problem might be? Anyo e have any solutions? Any advice much appreciated

Sam


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Hugh RobjohnsAdministrator
SOS Technical Editor


Joined: 25/07/03
Posts: 21714
Loc: Worcestershire
Re: hum noise whrn phantom power engaged.Any way of solving? new [Re: kingof12]
      #1032884 - 10/02/13 12:15 PM
Sounds like there might be a heat-related problem with the DAV power supply. I'd have it serviced.

hugh

--------------------
Technical Editor, Sound On Sound


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kingof12



Joined: 09/04/10
Posts: 54
Re: hum noise whrn phantom power engaged.Any way of solving? new [Re: kingof12]
      #1032894 - 10/02/13 01:47 PM
Right thanks Hugh. If that is the problem it's annoying as only had the Dav about a year. Surely these units sgould last longer than that. Could my rack or the position of the unit in the rack be causing this. My rqck os a 4U made.of mdf. Have you any idea of how much will it cost me to fix a prob like this? Again any advice appreciated.


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Hugh RobjohnsAdministrator
SOS Technical Editor


Joined: 25/07/03
Posts: 21714
Loc: Worcestershire
Re: hum noise whrn phantom power engaged.Any way of solving? new [Re: kingof12]
      #1032900 - 10/02/13 02:33 PM
Quote kingof12:

If that is the problem it's annoying as only had the Dav about a year. Surely these units sgould last longer than that.




Yes... but sometimes electronics components just fail. I'd contact DAV directly and discuss the problem with them -- I'm sure they'll get you sorted out very quickly -- and probably as a warranty job.

http://www.davelectronics.com/contacts.htm

Quote:

Could my rack or the position of the unit in the rack be causing this.




It's not very likely, but it would be easy to check. Just remove the DAV from the rack (you'll have to anyway to get it fixed), and try using it away from the rack to see if the problem persists.

hugh

--------------------
Technical Editor, Sound On Sound


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ef37a



Joined: 29/05/06
Posts: 6762
Loc: northampton uk
Re: hum noise whrn phantom power engaged.Any way of solving? new [Re: kingof12]
      #1032901 - 10/02/13 02:45 PM
Quote kingof12:

Right thanks Hugh. If that is the problem it's annoying as only had the Dav about a year. Surely these units sgould last longer than that. Could my rack or the position of the unit in the rack be causing this. My rqck os a 4U made.of mdf. Have you any idea of how much will it cost me to fix a prob like this? Again any advice appreciated.




How many posts have you seen here and in other forums where equipment of this quality has failed? Almost none because it hardly ever does but just because something rarely fails it does not mean that it can't.

Because of the usual "zero" failure rate of their goods, high end equipment firms are usually very magnanimous about out of warranty servicing. Indeed, they generally want to know what has gone wrong themselves!

If I had to put a tenner down on it I would say "dry joint" (unfortunate but 'it'appen) or a dodgy regulator chip.

Dave.


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kingof12



Joined: 09/04/10
Posts: 54
Re: hum noise whrn phantom power engaged.Any way of solving? new [Re: kingof12]
      #1032908 - 10/02/13 03:19 PM
Okay thanks to you both for taking the time to reply. I have been in contact with Mick Hinton of Dav electronics and he has confirmed thqt he will fix the unit under warranty. He suggested it might be a smoothing capacitor on the phantom power. Is it unreasonable for me to ask DAV to cover my postage costs?

Thanks


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ef37a



Joined: 29/05/06
Posts: 6762
Loc: northampton uk
Re: hum noise whrn phantom power engaged.Any way of solving? new [Re: kingof12]
      #1032911 - 10/02/13 03:36 PM
"Is it unreasonable for me to ask DAV to cover my postage costs?"

IMO yes. The retailer is responsible for the goods he sells and initial contact should be with them. They might decide to stand the carrige costs but AFAIK they are not obliged to.

Dave.


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Hugh RobjohnsAdministrator
SOS Technical Editor


Joined: 25/07/03
Posts: 21714
Loc: Worcestershire
Re: hum noise whrn phantom power engaged.Any way of solving? new [Re: kingof12]
      #1032918 - 10/02/13 05:05 PM
Quote kingof12:

Okay thanks to you both for taking the time to reply. I have been in contact with Mick Hinton of Dav electronics and he has confirmed thqt he will fix the unit under warranty.




Good. I thought he might -- and it's impressive that you got a reply on a Sunday, too. That's service above and beyond!

Quote:

He suggested it might be a smoothing capacitor on the phantom power.




Yes, quite possibly -- I'd have guessed at either that or a faulty, possibly overheating regulator.

Quote:

Is it unreasonable for me to ask DAV to cover my postage costs?




Yes. It's over a year old, after all. If he's feeling really generous he might ship it back for free if you pay for the shipping to him and ask really nicely.... but to be honest, I'd count the shipping costs as a reasonable trade off for the excellent service in responding to you today and fixing it for free.

hugh

--------------------
Technical Editor, Sound On Sound


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kingof12



Joined: 09/04/10
Posts: 54
Re: hum noise whrn phantom power engaged.Any way of solving? new [Re: kingof12]
      #1033054 - 11/02/13 03:24 PM
Okay thanks. I think i have just had bad luck with the dav bg1u and art pro vla ii and a zoom r16 all bought from new and all developing problems. I always read the documentation and take care to not misuse the equipment. The vla and zoom r16 were imported from the usa so i had problems with warranty despite them being only a few months old. I would just like to get everything working so i can get on with recording and writing music! I also inherited a teac a6010 reel to reel which needed a service which i had to drive to leeds to get sorted as there is no one who specialises in fixing recording equipment in cumbria where i live.

Thanks for your advice Hugh and Dave.

Sam


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