[MarcJC]

I see all these posts about folks plugging into vintage receivers or speaker amps, as well as headphone amps with ludicrous amounts of power and though cans with high impedance or orthos rejoice in this, is there a general limit? Not just for these power hungry headphones but for more basic dynamic cans and iems as well?

I'm looking into both vintage amps and a modern amp rated at 1000mw output. Though I'm sure my mad dog 3.2s (and one day HE 6 or 400) will be fine, I'm worried about my V Moda m-80 and everyone elses headphones.

At what point do you actually start to blow out the drivers electrically? I'm also curious how amps are measured since volume pots vary output.

 

[MarcJC]

Just finished reading http://archive.is/Nzf7 Which helped in understanding power measurement, but I still don't understand why people claim power output affects sound quality, not just output volume/playback levels. Reading this makes amplification and "driving" Sound black and white in terms of sound quality. Surely mW aren't the only factor (if there IS a relationship between sound quality and amplification. What is this magical number I'm looking for?

 

[SoundFreaq]

Amps are controlled technical chaos. And the best amps refine that into the most usable way. 
 
There's quit a bit to an amp and how it drives a given headphone. Sometimes you can have enough output power, but the amp lacks other things to drive them properly. 1000mW is 1 watt. That is nowhere near too powerful for some of the big guns. In fact, that would be fairly underpowered, depending on other factors. 
 
Other factors that you should research are:
 

1. The relationship between headphone impedance and the amp's output impedance (or Z). The rule of thumb is a ratio of 1:8.
2. A headphone's relationship between impedance and sensitivity. You can have low resistance, but couple that with low sensitivity (db), and you still have a hard-to-drive headphone. For example, the HD800 is rated at 300ohms, and the HiFiMAN HE-6 at 50 ohms, yet the HE-6 is leagues harder to drive. 
3. The amp has to be able to have larger voltage swings to power some headphones. Research your voltage swings. 
4. Understand that impedance varies across the frequency response, sometimes wildly, which can make things very interesting. Most headphone manufacturers report impedance at a given frequency (Hertz), but that is far from the whole story. 
5. Read up on Ohm's law (I=V/R), and understand how an amp can have a high enough output power theoretically, but lack the current or voltage swings to work well. 

 
You have your homework cut out for you : )
 
It's my opinion that you cannot really have too much power unless you are completely imprisoned by no flexibility on the volume pot, or you are forgetful and leave the pot too high when plugging in new headphones. 1000mW is not an incredible amount of power. Some closed portable headphones, like the Sony V900HD handle 3000mW. Most portables don't. But 1000mW is a fine amount to have handy. The Liquid Gold outputs almost 9W per channel. The Abyss recommended power requirements start at 1000mW, or 1W.

 

[MarcJC]

Thanks for the info and precise keywords. Helped a lot in researching so far. So from what I've gathered, that magical sound quality "number" (last bit of first post) I asked about is actually just a coincidentally cleaner signal since one doesn't have to strain an amp or push it closer to its limit. Is that more in the right direction?

 

[SoundFreaq]

Not necessarily. A cleaner signal after going through the amp's circuitry is what determines the quality of the sound, to keep it simple. But the signal being clean has not much to do with what a particular headphone requires in order to be properly driven. That's more impedance, resistance, voltage, current, etc...
 
And a system should be perfectly happy running at 0dB, which is no attenuation of the signal at any point, and is "all the way up." An amp is always amplifying the signal it receives at full blast. All you're doing with the volume pot it adding resistance to the signal before it reaches the amp stage. So theoretically, you're shortchanging it and holding it back when you're at anything other than full volume. 0db is considered the cleanest signal in a particular setup. As you go higher on the volume pot, you're not pushing the amp further, you're simply "un-restraining" it from it's full potential. 
 
You get things like distortion when the signal exceeds 0dB, the drivers can't handle an amp's particular load/are not well matched to the amp, or you have cheap parts in the amp that are not in balance with the system, underrated for the power, or get too hot and malfunction due to poor ventilation. You can melt an amp right down in the right situation. Heck, I've seen amps and speakers catch fire being overdriven, or being poorly matched. 

 

[MarcJC]

I really appreciate everything you've shared so far. Cross referencing the stuff I've been reading now with your answers makes a lot of things fall into place, and a lot of my own questions and doubts answered. I had brought up this question in a separate thread, but I think I can stand behind the conclusion I've come to in confidence. 

Basically, I had wanted to purchase a series of two cable conversions/adapters to connect the amp I'll be ordering this week to run the OUTPUT (amplification) stage in balanced. My fallback would have been to run this as a single ended, single cable input which, I now assume, will be very bad since the headphone out of my audio interface is not a fixed output line out. Running the amplifier out of that line will introduce the signal to two sets of amplifiers, and on top of that, I have doubts about the amp inside the interface. 
 
Second, I now know that running an RCA > XLR > ibasso cable conversion is not only expensive, but pointless. The input receives no benefit of common noise rejection, nor the signal potential behind a pure XLR connection ( from http://www.head-fi.org/t/713669/adapter-safety-question-ibasso-xlr-ic-to-adapter-rca-male-xlr-female ). So, to avoid the problem of two stages of amplification, I intend to use a simple dual RCA Phono > TRS cable on an output that isn't linked to my main volume pot, straight into the ibasso as a single ended connection. That single ended input, carrying a L/R signal regardless, should still pass through all four opamps of the ibasso PB2 so long as my headphone is connected to the balanced output. 
 
As a result, though I won't have a truly balanced configuration, I will still be able to receive the full amplification potential of this amplifier, instead of only half of it had I plugged my headphone into the amp's single ended, 1/4" port.
 
I think (and hope) I understand this a little more clearly now and that the conclusion above is valid. (- whatever degree of noise is amplified in the balanced output stage from the single ended input)

 

[SoundFreaq]

  I really appreciate everything you've shared so far. Cross referencing the stuff I've been reading now with your answers makes a lot of things fall into place, and a lot of my own questions and doubts answered. I had brought up this question in a separate thread, but I think I can stand behind the conclusion I've come to in confidence. 

Basically, I had wanted to purchase a series of two cable conversions/adapters to connect the amp I'll be ordering this week to run the OUTPUT (amplification) stage in balanced. My fallback would have been to run this as a single ended, single cable input which, I now assume, will be very bad since the headphone out of my audio interface is not a fixed output line out. Running the amplifier out of that line will introduce the signal to two sets of amplifiers, and on top of that, I have doubts about the amp inside the interface. 
 
Second, I now know that running an RCA > XLR > ibasso cable conversion is not only expensive, but pointless. The input receives no benefit of common noise rejection, nor the signal potential behind a pure XLR connection ( from http://www.head-fi.org/t/713669/adapter-safety-question-ibasso-xlr-ic-to-adapter-rca-male-xlr-female ). So, to avoid the problem of two stages of amplification, I intend to use a simple dual RCA Phono > TRS cable on an output that isn't linked to my main volume pot, straight into the ibasso as a single ended connection. That single ended input, carrying a L/R signal regardless, should still pass through all four opamps of the ibasso PB2 so long as my headphone is connected to the balanced output. 
 
As a result, though I won't have a truly balanced configuration, I will still be able to receive the full amplification potential of this amplifier, instead of only half of it had I plugged my headphone into the amp's single ended, 1/4" port.
 
I think (and hope) I understand this a little more clearly now and that the conclusion above is valid. (- whatever degree of noise is amplified in the balanced output stage from the single ended input)

 
Glad to help! And you learn fast and well. The parts I highlighted, you nailed, are absolutely correct. 
 
You're not going to be able to get a truly balanced, amplified signal, until you have quad mono output stages. There would be some way to craft that together with some custom soldering, adaptors, and ingenuity, and then at that point you're basically building an amp! But you would need a whole other set of matching amplification to round out fully balanced, +/- and left and right. 
 
Your curiosity has you on a creative, inventive path. Not to mention you will learn a lot, and already have. You now have a better understanding of some of this stuff than many around here : )
 
Keep up the good work. 

 

[MarcJC]

I can't put into words how much my wallet and I appreciate your input! I'll deal with the unbalanced input until I have a better source than my recording interface, but for now, at least my Mad Dogs will have, at the very least, the full power of the amp in power alone (which will help since my my x3 and e11 do nothing much for them), given the PB2s claimed 32v swing and max 2500mW output.
And about the bit about making an amp, to be honest, the reason I picked the PB2 is because I fully intend to swap out the opamps/buffer combos, and later, when I have more experience, personalize it even further.
Again, you have my thanks. You've been a great guide and teacher :>