Headphone Issues

[coach086]

I have recently bought a set of Sony MDR V600 headphones for use with my Warwick Blue Cab 60 practice amp. When i plug them into the headphone out i get really loud hiss. When i plug them into my ipod, there is no hissing, so I know there is nothing wrong with the headphones.

Could there be something wrong with the headphone out or the amp in general? I bought it new less than 12 months ago and haven't had any other issues with it. It seems to get slightly better if i EQ out all the treble, but its still really noticeable and I would like to avoid doing this for obvious reasons. Could it be something to do with the 1/4'' to 1/8'' adapter used on the headphones? I tried a different one to the one supplied with the headphones but the hiss was noticeably louder.

I play an '08 Mex J Bass, and seem to have this problem regardless of whether I am using pedals or plugging straight into the amp. I've also tried a number of different cables and I still get the hiss.

Sorry about the lengthy post, any help/ideas would be much appreciated. Thanks!

 

[RickenBoogie]

That sounds like a real drag. I don't have a clue what could be going wrong, but just in case, do you still have warranty time on the amp?

 

[coach086]

Yeah it is, I still have warranty time left. Looks like I'll have to ship it off to get looked at, unless anyone has any bright ideas?

 

[Underworld]

I may have found your problem. According to the Warwick user manual, the headphones used with that amp need to be a minimum of 200 ohms impedance.

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However, those Sony headphones are rated at only 45 ohms.

 

[coach086]

Yeah, this is true. Thanks for pointing this out, I never would have thought of that. And you think the impedance of the headphones being too low is the cause of the hiss? I have no idea about these things. Just kinda assumed that any headphones would work with any amp.

 

[Rick Auricchio]

1. Do you hear the hiss without an instrument plugged in?

2. Do you have the amp's input gain cranked? That'll add hiss.

3. As Underworld said, definitely try different phones.

If all else fails, stand in front of a guitarist's amp for several hours. You'll no longer hear hiss after that.

 

[rbonner]

OK look, yes the impedance of the headphones is the problem with your amplifier... The headphone amp section amplifier circuit DC path is completed when you plug the phones into the amp. When you plug in the low impedance set the amp RUNS TOO MUCH POWER. If you would have plugged an 8 ohm set in the headphone amp would have probably blown itself out.

I have run into this problem before and used this cheap fix.

Go to Radio Shack. Buy a 150 ohm 2 watt resistor, and a couple audio connectors. Make up a series circuit where the resistor is INLINE with the headphone speaker lead.

When you plug this little adapter into the line, the AMP will run several watts less and the hiss will subside.

The other option, find a set of 200 ohm headphones. But I think my little adapter would be a lot cheaper.

Me? I'd install the resistor INSIDE THE AMP in series with the center pin of the headphone jack. But that's just me.

Problem fixed.

I use a set of Sony MDR-V700 headphones on my ham rig. I paid $180 bucks for them 10 years ago. Sony makes a nice set of phones but the darn things are susceptible to RF getting into the headphone cord as its not shielded. That created a whole bevy of different problems for me to sort out with mine.

BOB

 

[coach086]

Thanks for the advice Bob, much appreciated