[Zacabeb]

I use my AKG K-501's with a Yamaha RX-V2500 receiver that I purchased the other day, and before then with an old Yamaha DSP-A1000 amplifier. One thing I've noticed is that on my new receiver, I must raise the volume quite high on the scale.

I should mention that in both those amplifiers, the headphone output is independently powered and tapped shortly after the volume control, not tapped from the power amp as some claim most receivers do. The headphone amplifier circuit in both the DSP-A1000 and RX-V2500 are quite similar in design and built around the same basic op-amp, so there seems to be nothing obviously "cheaper" about the new one.

So, the question is: How does the headphone amps in Yamaha mid-range amplifiers/receivers stand up to reasonably priced standalone headphone amps, and would it be worth getting one? If so, what would you recommend for the AKG K-501?

[TameRacingDriver]

A headphone amp will definitely benefit the K501 as its a difficult to drive headphone. I'd recommend an amp with full bodied bass and smooth treble - a tube amp such as the Singlepower PPX3 or similar would do them well - or a PPA with the appropriate opamps and optional bassboost circuit would probably help with the lean bottom end of the K501. I'd expect any such dedicated headphone amp to offer superior performance to a receiver.

[Zacabeb]

What would be the sign of a headphone amp in a receiver being inadequate to drive a certain pair of headphones? Since I listen mostly "non-audiophile" recordings, it is difficult to judge by ear what are characteristics of the recordings and what are characteristics of the headphone amp in my receiver.

I'm concerned that if I buy an inexpensive headphone amp, I'm relly going to get someting not too dissimilar from what's already built into the receiver and not notice much difference aside from placebo... which would not be worth the money. I already know that the op-amp used there (NJM4556) is used in at least one dedicated headphone amplifier.

The Singlepower PPX3 looks respectable, but it is unfortunately about three times the price I'm willing (well, able) to spend on a headphone amp.

[TameRacingDriver]

This is the problem with headphone amps. Its difficult to find that many models to audition, least of all the best bargain ones. I guess the only thing I could suggest is going to your local hifi dealer, and either asking if you could audition one at home, or audition one there against a similar receiver, however many of the models that your hifi store will stock will either be pretty poor - the likes of the Creek and Project Headbox, or expensive - Graham Slee Solo, MG Head, Naim Headline, or both expensive and poor value - Musical Fidelity X-Can, Sugden Headmaster. It should however, give you an indication as to whether you feel it will make a difference. The best amps tend to be those of a broadly "DIY" origin, at least in terms of performance for a given price - the Headsave Classic, PPA, META or similar amps tend to fit in with this philosophy.

As for telling apart the characteristics of receiver against dedicated amp, I am going to massively generalise here, but generally, a receiver will give what may seem at first listen to be a warmer, bassier sound than a headphone amp, but in reality, the bass will lack definition, the "warmth" will in fact be muddiness, almost like listening with a bag on your head, and the overall sound will lack detail and richness, and sound fatiguing - headphone amps tend to make a big difference to the soundstage of your music.

Now, if you are happy with the sound you get, why change? Headphone amps mean different things to different people, and I must say that I've had lots of headphone amps, and most have been a big disappointment, many of which are sometimes not a clear improvement. It really is your call, but if you have a good source, then your K501's are revealing headphones and will benefit from an amp.

As for the quality of your recordings, I mostly listen to trance and techno and I still feel that my headphones benefit from my headphone amp over using my stereo amp, and my headphones are probably not even as revealing as yours (although I have not heard yours) - but the fact is, most good quality headphones can reveal as much detail as speakers costing up to 10x the price given the right partnering equipment.

[avanzato]

I bought a Tsinghua headphone amp off eBay before Christmas and it's brought a worthwile upgrade to my Ergo headphones. I mention it here as from what I can make out of the Chinese instructions several AKG models were used in it's developement. Slight mechanical hum from the transformer but you can't hear that with the phones on. The sound from the amp is clean, detailed, silent when it's supposed to be and good bass, IMHO. Only cost £105 and is worth looking out for.