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Old 6th Dec 2017, 12:25 pm   #1
fronker
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Default Noisy headphone jack - Amplifier

Hi I posted the following on a turntable forum I read but didn't really get too much help that I can follow. Wondering if anyone here can help?

I've got an Arcam Delta 60 amplifier. I noticed recently that if I put a pair of headphones (AKG K451: these ones https://www.amazon.co.uk/AKG-High-Pe.../dp/B005LBQ7BY) into the amp headphone socket there is a strong white noise on any input.

I don't think this is noticeable from my speakers.

Any ideas if this is normal with this amp / old amps in general, or does it indicate a problem somewhere within the amp?

Thanks.
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Old 6th Dec 2017, 1:07 pm   #2
Nuvistor
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Default Re: Noisy headphone jack - Amplifier

It appears that those headphones have a microphone, does it have a standard 3 ring stereo plug or the 4 ring type, the extra ring for the microphone?
What impeadance are the headphones, many for use with phones are 32 ohms, what does the amplifier require?
The thought about the microphone is that the extra ring may be not making the connections correctly.

Just some thoughts, I could be way off with them.
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Old 7th Dec 2017, 6:27 pm   #3
Grubhead
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Default Re: Noisy headphone jack - Amplifier

Try another pair of headphones. If the noise is still present on them it could be in the headphone amp part of the circuit.
But I think Frank is right, about the microphone. Unless the jack is a standard one it won't connect right.
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Old 8th Dec 2017, 8:07 am   #4
tri-comp
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Default Re: Noisy headphone jack - Amplifier

Quote:
Originally Posted by Grubhead View Post
If the noise is still present on them it could be in the headphone amp part of the circuit.
The head-phone output of this amp is taken directly from the speaker-outputs through 2 x 330-Ohm resistors.
This is not going to generate any noise so it must always be there and go unnoticed when using speakers only or the clearly unsuitable headphone used causes self-oscillation in the output amp. circuit.
The latter is, however not likely as the headphone is isolated from the outputs by the 330-Ohm resistors so even a dead short of the signal to ground is harmless.
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Old 8th Dec 2017, 11:08 am   #5
Nuvistor
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Default Re: Noisy headphone jack - Amplifier

Its quite possible that the noise as always been there and not noticed but I have had problems with 3.5mm plug and sockets cause unusual noises with headphones.
Always more difficult diagnosing problems at a distance.
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Old 8th Dec 2017, 5:58 pm   #6
dseymo1
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Default Re: Noisy headphone jack - Amplifier

How loud is the 'wanted' signal?
If you have to turn the volume to near minimum for a normal listening level, you will inevitably hear some noise too; it's easy to attenuate the output if that's the case.
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