Why headphone amps?

I listen mainly on headphones, largely because I think they are more cost-effective than speakers, giving more acoustic information for the same cost. I am told by dealers that in my circumstances I really ought to use a headphone amp rather than the socket on an ordinary amp- but I auditioned one at a dealer and noticed no improvement over using the headphone socket of my ordinary amp. I also could not really understand the high prices, as I'm sure a headphone amp cannot require the expensive components required to supply high power to loudspeakers. I use a very old amp, a Cambridge Audio P25, believe it or not, though I have owned more recent amps and discarded them because the P25 sounds better, to my ears. In fact the sound that I am listening to right now (into low impedance 'phones) I find really superb, and I can't imagine it can be much improved (though of course one has imagined that quite a few times before and been badly wrong!). Now are all these dealers and hi-fi mags correct, and I'm missing out? Or are headphone amps a reaction to built-in modern headphone amps that are not up to the same standard as those of a previous generation? And if so, why so expensive? One can buy a decent enough phono stage quite cheaply (I have a cracking one for the P25), but even the cheapest headphone amp costs much more. From where I'm sitting, it looks as though one is having to spend for a headphone amp as much as one would pay for a whole integrated amp just to get the same quality that yesteryear was available from integrated amps for no extra cost.

On advice from the industry, some people used to simply put a couple of resistors to a speaker socket and get good enough sound, apparently. Cheaper than a Graham Slee, anyway! I'm sure it can't be that simple, but I'm equally sure I don't understand the reason.

 

It can depend on the headphones. Some are quite difficult to drive with low sensitivity, low impedance or both.

As far as I know there are two common ways to make a cheap headphone output used on amps. One is to use a resistor network and feed from the main amp output. Actually this can sound very good if the main amp is of quality. The other way is to use an op-amp (a little low level amplifier chip), something like an NE5532. These can deliver the power most headphones require and are incredibly low distortion and noise. A lot don't like to drive impedances much lower than 600Ohms though, or distortion increases quickly.

In my experience some cheap op-amp designs can be a bit crap and weedy. But some can be quite decent, like the one in the Behringer SRC2496. Driving from a power amp output has been very effective for me, working well with a Cyrus 3 in to AKG K701's and a Cayin KT88 valve amp in to AKG K1000's. The only downside here is that its a bit of a pin in the arse with cables, connectors and switches. The Op-amp output from the Behringer sounds as good as the amp output of the Cyrus though, so that was used most of the time, but I did do the comparison to check.

Studios do indeed often use a normal power amp to drive headphones, but that's not 100% to do with quality as much as convenience of being able to connect more and more without worry of running out of juice. They use 600Ohm headphones so they don't need a resistor network (the high impedance means they draw less power for a certain output voltage).

A dedicated design should be better than an op-amp or a power amp with resistors but how much I'm not sure. I've not been very convinced by my experiences given that the best headphones I have heard are AKG K1000's and they are made to run off a normal power amp. I can see the point maybe for nice little valve based amp, where it can add some sweetness to the sound.

Sorry for the long post... been drinking! :beer:

 

Don't forget those of us who don't have headphone outs on our amps!

It does depend on a number of factors though; your amp may already have a great headphone out, or your headphones might not be very revealing or vulnerable to changes in amplification.

 

Oh, I agree, there is no alternative for those without that facility. But then I ask myself, why not that facility? Take the modern Cambridge budget amp, basic, but well reviewed.

"Smashing little job, sir, just £70. No phono stage, of course. Want a phono stage? Here's one for £20, sir, complete with mains supply. No probs..... What? You want to listen on headphones, sir? That will be £100."

"Wow! That's more than the main amp! But it will sound like the bees knees, at that price?"

"Well, no sir, it will sound like..."

"£80 down the drain."

But my whole amplifier, which was forgotten in the loft for at least a decade, was bought centuries ago as a budget entry level amp, and I'd be lucky to get £15 for it on eBay today (though I wouldn't part with it for £150). With Grado SR80s it produces the same quality as a headphone amp costing over £100. The very same cans, from the same CDs.

It may be that scavenging accountants put a stop to any but basic expense applied to headphone circuitry, if they countenance them at all, and that many modern amps give dire results with cans. I still don't see why that puts prices of headphone amps so high, though. It's not as though it can all be put down to economies of scale, as the price of the separate phono stage shows.

 

Also remember that adding a headphone output to an amp is not going to cost anywhere as much as making a dedicated headphone amp as you then need to have a separate case, power supply, PCB and so on. All of this is already in the cost of the existing amp so you get better value I guess.

 

Correct- it must add just a few quid to add on a 'phone socket, but you know what accountants are. But how does one explain how those items listed cost £100 when associated with a headphone amp, but just £20 with a phono stage?

 

Did one have a more fancy case?

Not all headphone amps are expensive. Look at the pro sector. Sorry for the long link.

http://www.studiospares.com/browse/...rice,name&setsortprice=ascending&setpagenum=1

 

Exactly. Look at the pro sector. Headphone listening costs £2.79 per channel in a studio, but £50 per channel in a home. Now if a £100 home single headphone amp works to studio quality, the case must cost £94.42!

 

a little dot headphone amp from ebay doubles up as a room heater.

If you ever wondered what picking up a red hot brick felt like, nows your chance...

 

What are the best portable dac/ headphone amp combinations around right now? Preferably discrete

 

wedding oneself to a headphone setup with no tone control would be regrettable