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Distorting headphones

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Distorting headphones

Postby Mora___di » Tue Apr 30, 2013 11:58 am

Hi, I work at a music school with a studio for kids and teenagers, mostly rock bands. We have a problem with the headphones distorting when tracking and I am not sure if it is the headphoneamp, the headphones or matching the impedance. When I try to test the headphones for myself, they seem to work loud, clear and undistorted, but whenever there's a band they distort. Of course it's possible that when I'm alone the SEEM loud because they're not competing with an acoustic dumkit.

Setup:
Sm pro audio hp6 headphone amp in the controlroom, foldback is sent to studio via four channels on the multi (i would guess it's probably microphone cable, 6-7 meters), in the studio the performers use 4x Sennheiser hd280, we also have a hd380 wich seem to perform a little better but also distorts to early.

Any idea what is the weak link to achieving louder undistorted volume? It often seems like one side of the headphone is distorting before the other.
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Re: Distorting headphones

Postby Hugh Robjohns » Tue Apr 30, 2013 2:54 pm

I would assume it was the students wanting silly levels to compete with amplified instruments in the studio, and teh Samson headphone amp not being able to deliver enough cleanly.

However, the fact that one side of teh headphones consistently appears to distort before the other implies something amiss with the wiring somewhere.

How exactly are you getting the signals out of the Samson headphone amp, into the infrastructure wiring, and into TRS sockets for the headphones?

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Re: Distorting headphones

Postby Mora___di » Tue Apr 30, 2013 3:20 pm

Thanks for the reply Hugh!
Our multi cable we have fitted with TRS female jacks on one end, and male TRS on the other, plugged straight into the Sm Pro Audio Hp6 (not Samson).

Well, we need quite a bit of volume of course, competing with acoustic drums and amplifiers (normally set a little lower than what would balance against the drums). Do the "ground" on the TRS cables need to be lifted from chassis ground (I assume the female Neutrik TRS jacks in the breakout box is connected to the chassis)?

So most likely the hd280's can deliver the volume, but the amp is to weak for levels competing with a drumset?

Regards
Svein



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Svein
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Re: Distorting headphones

Postby James Perrett » Wed May 01, 2013 11:49 am

The spec on the headphone amp implies that it can output something like 150mW into the 64 ohm impedance of the headphones you are using. So, unless the HD280's are extremely inefficient, you should have more than enough volume.

Where are the volume controls set on the headphone amp and what are they being fed from?
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Re: Distorting headphones

Postby Mora___di » Wed May 01, 2013 8:29 pm

Thank you, I assume you checked the specs for the Sm pro audio Hp6, and not the newer more powerful model Hp6e. The specs for the Hp6 says 300mW @ 32ohms while the newer doubled that to 600mW.

Is it likely to distort easier when all 6 outputs are used, or would their power be completely independent?
should I be concerned by the fact that they chose to double the power of the updated model?

James, the Hp6 gets the signal from a A&H Zed r16, we use the mixers studio outputs (fed from AUX1 and 2). The level on the Hp6 is usually around halfway up, sometimes a little more. Sadly it doesn't have any level or clip indicators.

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