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dodgy cable/interesting sound effect. why?

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dodgy cable/interesting sound effect. why?

Postby hooty2 » Fri Jul 20, 2018 12:46 pm

Hi all,
just had friend in to play his midi compositions from his ipad into my pc...real time time via cables.
Ipad headphone out...mini trs to x2 RCA phono joined with connector to...x2 RCA phono to
1/4" mono Jack plugs..into analogue ins 1/2 on RME UFX/-10dBV....( no long cable available)

We got a max level of -30dB with anything that could make things louder in ipad activated etc.

The sound: no centre image, a ghostly image outside speakers...seemingly coming from my diffusor panels at the mirror points (wev'e been through that one..:)).

The guy bumped the lead at the ipad and there was a sudden burst of sound that cut out and the centre image returned briefly. ....replacing the cable from the ipad with similar (mini trs/RCA) solved the problem.

Can anyone say what physucs gave the ghostly image?
cheers
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Re: dodgy cable/interesting sound effect. why?

Postby blinddrew » Fri Jul 20, 2018 1:21 pm

hooty2 wrote:The sound: no centre image, a ghostly image outside speakers...seemingly coming from my diffusor panels at the mirror points (wev'e been through that one..:)).
That sounds like classic Stereo-TRS out to mono-balanced-TRS in, but that doesn't make sense given the set-up you've described. I'd be tempted to check the headphone socket for some small bit of debris that's stopping the jack going all the way in.
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Re: dodgy cable/interesting sound effect. why?

Postby Hugh Robjohns » Fri Jul 20, 2018 1:24 pm

You were sending an unbalanced stereo signal into a balanced mono input -- or some minor variation along those lines depending on what bits of your bodge lead and adaptors were working at the time!

Central image content disappears as the differential input cancels common mode signals, leaving just the wide-panned sources and any spatial effects like reverb.

H
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Re: dodgy cable/interesting sound effect. why?

Postby hooty2 » Fri Jul 20, 2018 2:14 pm

Ok....but what confuses me is...the cable replacement was the same cheap and cheerful type as the one rejected....
Also...can a balanced mono jack 'look' like an unbalanced one.
?
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Re: dodgy cable/interesting sound effect. why?

Postby Tim Gillett » Fri Jul 20, 2018 2:44 pm

Even with just headphones a poor or no sleeve connection can give you no centre channel. You hear "Left minus Right".

Carefully cleaning the plug and socket can sometimes fix it, which relates to what blindrew said. Make sure the plug is in all the way, or can go in all the way.
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Re: dodgy cable/interesting sound effect. why?

Postby Hugh Robjohns » Fri Jul 20, 2018 2:59 pm

It was probably some odd combination of plugs not being inserted completely, or not making proper connection in the socket... You'd have to draw it all out to figure out the possibilities.

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Re: dodgy cable/interesting sound effect. why?

Postby hooty2 » Fri Jul 20, 2018 7:05 pm

:oops: thank you...he's poking about in his ipad and i'm doing what the man said.
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Re: dodgy cable/interesting sound effect. why?

Postby James Perrett » Fri Jul 20, 2018 10:27 pm

Almost certainly no sleeve connection on the iPad output caused by a worn headphone socket, a thin connector or an intermittent joint.
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