I have a Fender Mustang V2 amplifier, and two kinds of headphones:

1. VModa Crossfade M100 (with embedded microphone, and just one connector)
2. Ordinary headphone + microphone with separate cable and connector for the microphone

When I connect the ordinary headphone's speaker connector to the amplifier, I get an awful hiss noise, and the guitar/amp sound is weakly superimposed on it.

When I connect the VModa Crossfade M100, I get no sound at all, unless I keep the VModa's connector plugged in partially. I guess this because the connector also has a microphone output, which is coaxial, so there may be an earthing problem.

Can someone suggest a connector for the VModa, which might solve the problem?

Cellphone headphones (the ones that have 3 rings on the jack) sometimes are wired differently than standard headphones, i.e. the rings are in different order, that would explain the second problem (tried it myself, you actually have to hold the jack plugged about 1/2~3/4 way in to get them to sound the way they suppose to).
Try the other pair on something different maybe the "ordinary headphones" are just broken.
Get yourself a set of Sennheiser HD201's.

They'll be far better than what you're trying to use and are extremely cheap.
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