0 or 120 ohm output?

0 ohm is definitely preferable for low impedance cans like Sonys and Grados. You never want the output impedance of your amp to be higher than that of your headphones. If you had 300 ohm Sennheisers, for example, you could use the 120 ohm outputs, but not with 70 ohm Sonys and 32 ohm Grados.

sometimes you sacrifice the source impedance to reduce source hiss.

my ety er4-p sound amazing with the adition of a 100 ohm resistor pair...

i have not tried the extra resistor with the grado's because they dont hiss with my portable amp. kind of weird. the "elcheapo" cans i initally tried it on (25 ohm free with portable type) also sounded ok with the resistor cable.

I'm fairly certain that I've read (on head-fi and something from Sennheiser) that the Senns are designed for a 0 ohm output--perhaps someone with more technical know-how than I can say for certain.

Oh sure, you can use the Senns with the 0 ohm output, and as you say, it is often preferable to do so. I was just saying that it's "okay" to use the Senns with a 120 ohm output, but not so much with Grados and Sonys.

i'd say the opposite.

look at the spec sheets for the comon buffers, and opamp chips (where used with no buffer.) most dont particularly appreciate driving a load less than 100 ohms.

"I'm fairly certain that I've read (on head-fi and something from Sennheiser) that the Senns are designed for a 0 ohm output--perhaps someone with more technical know-how than I can say for certain."

It could be true. I tried a HD600 with an amp that had a relatively high impedance becasue it doesn't had any feedback applied around its output stage (and also had a coupling capacitor) and the bass was very boomy. However this phenomeon is not unkonwn in the world of speakers. Some prefer high damping factor (very low output impedance), others sound best with non-feedback designes. It is a question of how good is the driver self damped (mostly mechanically). Good mechanical damping does not need high damping factor (low output impedance.) This translated to our case means that Sennheisers probably need electrical damping as well.

On the other had I had a tube, non-feedback amplifier and my HD600 was not boomy with it and others are using it with such amplifiers with great results.

So ultimately my conclusion is, that the Sennhesiers do not like the big coupling capacitors some circuits have. (The amp which made it sounding boomy had a 4.700uF coupling capacitor). However it had no problem with high impedance phones (and the corner frequency was down at 0.5 Hz.)

Uhh...it became a bit long, sorry.

"look at the spec sheets for the comon buffers, and opamp chips (where used with no buffer.) most dont particularly appreciate driving a load less than 100 ohms."

That is the problem for the given chip, those phones usually need as low output impedance as low you can get

An IC in itself could be oscillating if loaded with too low impedance. Or worst they current limit will make the sound harsh and you think it is the phone what you hear

Here's a quote from Jan Meier's site regarding this:

Normally a headphone amplifiers has a very low output impedance which gives the amp tight control over the headphone action. However, many headphones have been sonically optimized to be driven by an output impedance of 120 Ohm. This output impedance is an international standard.

It is a unique feature of CORDA headamps that they have two headphone-sockets, each having a different output impedance. Thus always an optimal output impedance can be choosen.

I've tried many headphones with the HA-2 and have yet to find one that sounds better from the 120 Ohm output. I seem to recall Jan saying that he preferred the 120 with his DT931s, but that was years ago and I may be wrong.

Your rebuttal does not make too much sense in the context of the discussion. I don't think you're talking about the same thing we're talking about. You're talking about what kind of load the amp wants to see. We're talking about the output impedance of the amp (in other words, what kind of "load" the headphones want to see). Different issue altogether. The main point of debate here is "what output impedance is "better" with headphones of different impedances?"

But since you brought up that point about the impedance of headphones and the load they present on the amp, I say you should never drive low impedance headphones without buffers. And when I say use buffers, I mean use multiple buffers per channel (like the PPA, which uses quad Intersil buffers per channel). Not only does this increase the current handling capability, but reduces the output impedance of the amp. Believe me, with quad output buffers per channel, you can drive headphones of any impedance.

Yes, it was the DT-931. I have the DT-831 which benefits dramatically from the use of a 120 ohm adapter......without it, it is far too bright. Painfully so.
With the adapter, the sound is much more balanced.

My MDR-V7 sounds better out of the 120 ohm out. It's highs can be really piercing.

Do you happen to know the output impedance of the amp to which you were adding the additional 120 Ohms? As you likely know, the effect of using the adapter with an amp having a 0 Ohm output might differ considerably from one already having 120.

You should use whichever one sounds better with you. Higher impedence has different effects on different phones. On most dynamics headphones, it reduces bass damping, and results in more bass quantity, with a slightly looser quality. On some Sonys, like the SA5000, it makes no difference at all (other than volume). Sony has some internal electronics that make them insensitive to changes in amp impedence. Canal phones with balanced armature drivers will have increased treble output with higher impedence, basically the opposite of dynamic headphones.

Personally I use the 0 ohm output, and correct the bass rolloff (or treble screech) with an equalizer. The exception is for the Shure E3c, which I use with the 120 ohm output. Just my preferences, though.


gerG

They sound better to me on the Sugden Headmaster and the RKV, but I have no idea what their output impedance is. All I know is that I can now listen to the DT-831......and actually enjoy them.