Well Denons had a pretty audible noise floor even on the Lyr, so I'm not surprised by that. I don't plan on using anything that efficient. I'm just surprised by all the hiss and noise from an HD800, which is 300 ohms with a sensitivity of 102db, which isn't all that efficient, certainly not more than an HD650. Oh well. I guess only one way to find out for sure. I guess I can always pick up another LCD-2 or perhaps I'll try a HE-6, since I have an amp that can somewhat drive them now.
Does anyone know how much current the Mini-X is actually outputting at 38ohms? And 50ohm? and 300ohm?
Just curious if anyone knows how to crunch the numbers on that.
300ohm headphones with a high sensitivity (102db is very sensitive) means it's not that difficult to drive. It's quite easy. 300ohm isn't very much. The Emotiva has high gain, it's a speaker amp, so that's where the sensitivity will pick up, and you'll have noise and hiss. Plus, you're talking about the HD800 which has enhanced treble anyways, so you're looking at even more awareness of the noise/hiss from high gain and high sensitivity. If you want to tone that down, you need to get the resistance to 600ohm or higher even. My 600ohm headphones with bright treble are not exhibiting noise or hiss. But things of lower impedance seem to show it up, when sensitivity is high. I used Beyers for example at 600ohm. When I apply 500ohms to any headphone, the hiss/noise is gone even from super sensitive headphones (like Denons). I think that's the threshold point for my ears at least. They either have to be insensitive (some of the Orthos), or have high resistance to cut down on current. Lower impedance so far, only is hissless/noiseless when insensitive (see HE500, etc). All my high impedance headphones have worked just fine without hiss/noise. But they're all 500~600ohm. Everything lower than that has some hiss/noise when they are sensitive. For example, my balanced Grado has hiss/noise because it's both low impedance and sensitive, yet sounds fine, but I like it especially with 500ohms added because it cuts down on the grain/noise sound, from high gain.
Very rough estimations of output: at 38ohms, the Emotiva is pushing something like 8~10 watts. At 50ohms, something like 7~8 watts. 300ohms, probably 1~2 watts. 600ohm, around 600~700mW maybe. Again, very rough estimations.
So what actually causes the hiss/noise when using a speaker amp with headphones?
Is it that the amp just has too much noise which becomes more obvious with headphones than with speakers.
Is it the typical high gain of the speaker amp magnifiing any noise in the system as a whole.
Or is it an impedance mismatch due to the amp driving much higher impedance loads than it is designed for.
Or is it another reason I have not even thought about or even a combination of the above.
I ask because I am also interested in a speaker/power amp for my headphones,especially but not specifically for the HE6's. I love the way they sound now out of my Master-6 so would not expect a 'cheap' amp to be better so I am looking for something a bit more adventurous and more expensive but I will also like to run other phones, especially LCD2's and very high impedance phones like HD800 and maybe T1's.
However I am concerned about noise levels & fine volume control. As anyone tried attenuators between pre and power amp?
The power amp I am looking at are rated @250 wpc into 8 ohms. I know people are going to say that it's total overkill, maybe even for the HE-6's, but if it sounds really good with no noise issues with a variety of phones then IMO it's no more overkill than $3000 - $4000 headphone amps.
I don't have any low impedance sensitive phones to worry about.
It's the set gain multiplier of the amplifier. For speaker amps, it's usually high, unlike headamps. Think of multipliers on the order of 20x or even 35x or more. Speakers are much less sensitive, and low impedance, so high gain is used.
I get very fine volume control via my pre-amp to my Emotiva for all my headphones, even the most sensitive ones. I don't think you need attenuators between the two. Especially not for the HE6, LCD2, or any 600ohm order headphone for that matter.
If you're looking at a 250wpc amplifier, I would say that you will need resistance some where in your chain, and a pre-amp will help loads on controlling the line level fed to the power amp. You're going to have problems with hiss/noise without enough resistance, or the right headphone with a very low sensitivity (HE6). An HD800 or T1 will sound noisy and hissy from that for sure. The LCD2 might be ok, but it will have very little volume control, because it's really not that hard to drive frankly. I wouldn't go 250wpc for headphones. I wouldn't venture beyond 50~80wpc really. There's literally no point, and you're just adding unnecessary need for resistors, pre-amp, etc, just to control it, and it will only work well on very few headphones, like the HE6.
I've compared the Emotiva to a few entry amps at this point, like the O2 and Magni (which sound virtually the same). Just like with the Asgard and other limited roughly ~1 watt solid state amps, the Emotiva I found to be better in every aspect essentially. I do like the size of the Magni/O2 though. The O2 is ugly and I hate the front control/connections and required use of the 3.5mm jack. The Magni at least is more attractive. Both are good for $100. But I think you get way more value from the Emotiva at twice the price, and way, way more power. If you're thinking Ortho or super impedance headphones or things with really low sensitivity, then I wouldn't look to the Magni/O2. I'd look at a speaker amp. Magni/O2 is for a lower budget, and for headphones that simply won't benefit having serious amounts of current available.
It may not be technically better via sensitive instrument measurement, but to my (and others) very dull and imperfect hearing range, the Emotiva simply sounds better. But I don't subscribe to technical measurement; if you can't hear it, it's not there as far as I'm concerned when it comes to objectively looking at audio.
I've not used the HD800 with it. But just from experience with other headphones, I can highly anticipate that at it's impedance and sensitivity, it will be giving you noise/hiss. You'll want resistance for that. Bright treble headphones that are sensitive probably should steer clear of amplifiers with high gain values as they will nearly always appear noisy/hissy/grainy. The fix is a resistor. Otherwise, simply look to headamps with low gain values.