Sony MDR 7506 impedance questions - experts please advise...

[danieln]

Hi everybody,

Based on the recommendations from this forum I bought the Sony MDR 7506 and I am quite happy with them. I have a problem though: when I listen to them through my Yamaha HTR 5140 receiver, which has a headphone output impedance of 300 ohm, there is pretty loud hiss at low volume. I also have a pair of Porta Pros. Both the Sonys and the Porta Pros are rated at 60 ohm. Well, when I listen through the Porta Pross, the above mentioned hiss is 90% gone. I forget the sensitivity ratings, but I stronlgy believe that the sensitivity alone cannot explain this difference.
I would appreciate any advice on the following:
What's causing the hiss? The receiver is very quiet when listening through speakers or Porta Pros. Would 300-600 ohm headphones help? Some AKGs, rated at 600 ohm, look pretty good. The better Senns, rated at 300 ohm, also look good, but they are pricey. What do you recommend? I have a very broad range of material that I use my headphones for - from movies to Mozart to rap.
By the way, I find the Sonys more detailed than the Porta pros, but to me, the upper mids seem pretty harsh. The Porta Pros are more "liquid" and sweet, but less revealing, and they are somewhat lacking in the midrange - the bass and treble are a bit exagerated. Another quibble I have with the Sonys is that they are uncomfortable - yes, I know about the Beyer pads and I am going to get then soon.

 

[joelongwood]

Unfortunately I cannot offer an explanation for the fact that there is a hiss through the Sonys..........but I can tell you that you are not alone. My V6s pick up any hiss or noise that is present in any piece of electronic equipment, whether it be a CDP or an amp. They are very revealing headphones.

 

[Tim D]

Speaker/Headphones do not ever make hiss(unless active, i.e. builtin amp). It is the fault of the receivers which I will still say, and continue to say, are some of the worst hardware to source a headphone jack, beaten out by only mini-systems.

It is also nice to always have a pair of uber-elctronically revealing headphones as it will ensure that future hardware that you buy is hiss-free. Typically it isn't uncommon to see people who wonder why they buy a new pair of speakers/headphones and wonder why there is hiss all of the sudden and blame the speakers/headphones. This HISS or electronic noise was ALWAYS there, it is just being revealed now due to both impedance and sensitivity issues as well as just the revealing nature of different headphone/speakers.

You can either upgrade your source and amp such that it delivers clean signals...or buy certain headphones that aren't uber-revealing of electronic noise (variety of either high impedance phones that are typically less efficient).

Oh yah I always forget to mention...sometimes its just the recording. Sometimes people forget that too.

 

[Dusty Chalk]

Quote:

Originally posted by danieln ...I bought the Sony MDR 7506...when I listen to them through my Yamaha HTR 5140 receiver...there is pretty loud hiss at low volume...I find the...upper mids seem pretty harsh.

You just answered your own question. There was a thread where Vertigo-1 was talking about his Sony's through the RKV and the hiss problem, and the problem with the Sony's is that they are very forward, so if there's hiss in the same region, it will be very forward.

 

[danieln]

Thanks a bunch for your explanations and suggestions.

Joe - I am also using the Sonys with a rather crappy CD-Rom, a HP 9100 R-W, and there is no hiss. The Yamaha beats the HP hands down in terms of sound quality. So I cannot believe that it's got anything to do with the phones or with the receiver - it's rather some kind of mismatch between them, and I believe the most likely culprit is the impedance (but then, why it's not there with the Porta Pros?).

Tim - of course any passive headphones don't "create" sound, they merely reproduce it. But when I listen to my "big" system - 4 JBL 610s for main speakers and surrounds, JBL HLS center, and a Mission 10" powered sub, there is no hiss in any mode (stereo, Prologic or Dolby Digital). If I would choose a single word to describe the Yamaha's sound, it would be "clean". With the Sonys, even with the receiver volume at minimum, and everything else turned off (no source), the hiss is there. When turning the volume up from minimum (7 o'clock) to what would be pretty loud (10 o'clock) if I used a source of sound, the hiss does not get louder. Only after 10 o'clock the receiver's noise takes over.

Dusty - are you saying that the midrange being harsh is causing the hiss? I doubt it, it sounds like a much higher frequency to me.

Thanks again for your replies.