Re: NEOTEK: Series 1 Noise Problem

Fri, 02 Dec 2011 09:59:25 -0800 

Hi
If the 192 instructions tell you to lift the negative it suggests that the outputs are not 'transformer like' but a simple amplifier out on the hot and another amplifier out with phase polarity reversed for the negative. With this scenario 'grounding' it will drive signal current into the ground causing possible crosstalk, distortion and maybe even damage to the converter outputs. A 'simple' test for this type of output is to measure a continuous tone signal at a convenient level, say 2 Volts on a multimeter, connected to measure BALANCED (between pins 2 and 3 of an XLR or hot to cold). Now, while monitoring the output level, short one side to ground. With a transformer or 'electronically compensating' output the signal level will not change, or only by a tiny fraction. Shorting EITHER hot OR cold should produce no significant level drop. I suspect that with the 192 outputs you would see a fall of 6dB (Half the original level). In this case you must connect the signal into a balanced input or if you have no choice with an unbalanced input, cut the 'negative' and accept the inevitable signal level loss. With the negative cut you will not damage anything. 
Matt S

On 02/12/2011 17:12, Matt Boynton wrote:
That's what my issue was. Sometimes lifting the shield isn't the answer though. For example, a digi192 suggests on the rear panel to lift the negative wire instead of the shield. Which is different than any other converter I've encountered. I have the studio wired with the shields lifted on the converters so whenever I plug into an unbalanced input on the neotek the signal is 6 db or so lower. To remedy this I'm getting a new converter. 

Matt Boynton
Vacation Island Recording
90 Walton Street
Brooklyn, NY 11206
tel: 347 225 3201
www.vacationislandrecording.com <http://www.vacationislandrecording.com>
On Dec 2, 2011, at 9:43 AM, Tom G <[email protected] <mailto:[email protected]>> wrote: 


Hello Matt,
Interesting. I do have some noise in my left master channel/monitor however it is only the monitoring section. When I mix down to tape or digital the signal is fine. I'll check into this too...I am guessing its more of a power amp and may not be related to my preamp issue. 

Thanks!
Tom
--- On *Wed, 11/30/11, Matt Boynton /<[email protected] <mailto:[email protected]>>/* wrote: 


    From: Matt Boynton <[email protected]
    <mailto:[email protected]>>
    Subject: Re: NEOTEK: Series 1 Noise Problem
    To: [email protected] <mailto:[email protected]>
    Date: Wednesday, November 30, 2011, 3:51 PM

    I had a problem where my speakers had a fairly high frequency buzz in
    them regardless of the position of the control room volume pot. I
    isolated it to the convertors. I ended up lifting the shield wire on
    the ins and outs of the convertors and the buzz was gone. Maybe its
    something similar.
    Matt Boynton
    Vacation Island Recording
    90 Walton Street
    Brooklyn, NY 11206
    Tel: 347 225 3201
    www.vacationislandrecording.com
    <http://www.vacationislandrecording.com>



    On Wed, Nov 30, 2011 at 3:39 PM, Ike Zimbel
    <[email protected]
    </mc/[email protected]>> wrote:
    >
    >  Hi Tom,
    >    Do the channels have to be side by side, or any two at
    random? Does this
    > mean that you are using two and only two pre-amps when this
    happens, or do
    > you mean when it's a pair, like overheads, while using other
    channels for
    > other inputs (IOW, can you only use ONE mic-pre on the Neotek
    at the
    > moment?)? If that's the case, does the problem steadily get
    worse if you use
    > more channels?
    > I very much doubt this is a grounding issue (in the 60hz hum
    sense, anyway),
    > but it MIGHT be an interface issue between the direct outs of
    the Neotek and
    > the input of the converters.
    > Best,
    > Ike
    >
    >
    > On 11-11-30 3:27 PM, Tom G wrote:
    >>
    >> Hello All,
    >>
    >> I have been battling an issue with my Neotek Series 1 console
    on and off
    >> now for about six months. When I use any two preamps (of the
    console) at the
    >> same time, I get a noise on one channel. According to my
    frequency analyzer,
    >> it is approx. 4k and is high enough in gain to make the track
    unusable. When
    >> I use outboard pre's there is no problem whatsoever.
    >>
    >> I thought it may be a ground loop or something similar, but
    floating the
    >> grounds did not help. I'm using SSL converters and it doesn't
    seem to matter
    >> what inputs of the SSL I'm using nor what channels on the Neotek I
    >> use...still the same noise. But only when using two channels
    together.
    >>
    >> Any thoughts? I have not tried completely floating all grounds
    except for
    >> the console. Once I get my tape machine back home and hooked
    up, I am
    >> curious if I get the same result. Although as stated, floating
    the two
    >> channels in question was no help.
    >>
    >> Thanks!
    >> Tom
    >>
    >>
    >
    > --
    > Ike Zimbel,
    > Zimbel Audio Productions Ltd.
    > Toronto
    > 416-720-0887
    >
    > "Studio House Calls". Repairs and upgrades to analog audio
    equipment
    > including: AMEK, dbx, Neve, Neotek, MCI, Soundcraft and more.
    Authorized
    > Warranty service for Allen&  Heath, Clear-Com, Drawmer,
    Soundcraft, SPL and
    > Yamaha. Ask about our RF frequency co-ordination services!
    > www.zimbelaudio.com <http://www.zimbelaudio.com>
    >
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