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How do you get rid of a low frequency buzz?
Old 9th August 2007
  #1
Gear Maniac
 
sr2000's Avatar
 

How do you get rid of a low frequency buzz?

Had a buzz appear on the recordings last night out of nowhere. Spent quite a few hours pulling out cables - testing in different outlets - trying different pieces of equipment. I finally narrowed it down to both Vintech X73i preamps which have a low-level buzz. Since the buzz is on both of them - I can assume the buzz is coming from the power supply? Maybe? I don't know - but I tried plugging it in several different outlets - no difference whatsoever. I also tried moving other cables away from the power adapter so as not to interfere with anything - still have that buzz.

Any suggestions?
Old 9th August 2007
  #2
Gear Maniac
 

if it is on both it would sound like it is the power supply... find someone with one of those and try their supply...
if you are in NY you can bring your two X73 and try them on my supply, that's all I can say
Old 9th August 2007
  #3
Gear Maniac
 
sr2000's Avatar
 

Thanks for the offer marknyc - but I'm in Nashville - does anyone in Nashville have a Vintech X73i so I could stop by and run a quick test?
Old 9th August 2007
  #4
Lives for gear
 

Make sure all of your audio equipment is on the same ground, and always use balanced cables to reduce 60hz hum
Old 9th August 2007
  #5
Lives for gear
 
heathen's Avatar
 

Yeah, it seems it may be a 60hz earth loop hum, if even 1 piece of you gear is connected to a different ground you will get this issue most likely.
Old 10th August 2007
  #6
Gear Maniac
 
sr2000's Avatar
 

Quote:
Yeah, it seems it may be a 60hz earth loop hum, if even 1 piece of you gear is connected to a different ground you will get this issue most likely.
I didn't realize that - I'm going to double-check that next chance I get. I guess the odd part about it is that for the last 3 months I've had no problem whatsoever, yet the issue just popped up out of nowhere.
Old 10th August 2007
  #7
Lives for gear
 
matta's Avatar
 

Sr2000,

Having worked on a fair bit of Neve gear (including a console in your town) I have experienced this before and would hazard a guess it is 1 of 2 things.

1. The PSU itself might be acting up as the same PSU supplies. If you can try and get hold or a new power supply, or borrow one and check this first. Or if skilled enough check the PSU pin outs and check you are getting the correct voltages.

2. The line voltage in your house/studio may be too low for the regs regulate efficiently.

I'm experiencing this now with a custom who I've racked 8 Neve channels for. He works in an area that has pretty unstable power so while the unit was set up for 230VAC operation but some days he is down to 220VAC or below. He can goes for days/weeks or month with crystal clean pres, the moment the line voltage drops below a threshold hum appears across both racks, which in my case each have dedicated PSU's.

A power transformer has generally has 2 windings, a primary and secondary. The primary winding typically goes into your wall/line voltage, in your case say 110-115VAC, using induction this voltage is 'broken down' into a smaller secondary winding which (typically) ouputs a smaller voltage, in the Neve's case +24VAC... BUT if the line voltage drops, so does the secondary winding voltage.

If this happens it is possible that the voltage regulators can't regulate correctly as the voltage differential is too low between the Vin and Vout of the said regulators, thus causing them to 'stress' and the results are often a hum. You want to see at least 27VDC BEFORE regulation occurs.

Remember that these Neve babies are VERY hungry Class A unit running on a single ended voltage so they tend to be more susceptible to these noise problems than say a bipolar Class A/B IC design.

If you can you can, check your line voltage and report back... if you are NOT skilled in doing this I would suggest your tech or electrician do this for you.

I hope that is helpful.

Regards

Matt
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