Why do some amps drive headphones better than others?

ChopperChas

Super Member
So, I have several pairs of headphones that are relatively difficult to drive. iPod gives very little volume, and... well, amps don't fare much better. My orthodynamics are really tough, but even my Koss HV/1 and AKG K250 aren't particularly easy to drive. I have a 65wpc Pioneer SA-720 integrated amp that should be able to drive any of those just fine.... but they all sound like crap. Especially the orthodynamics. I can get a respectable volume, but the bass is distorted badly. My thoughts were that any kind of receiver or small amp should be able to drive a pair of headphones... but I'm obviously mistaken. The only amp I have that does a good job is my Toshiba SC-665 power amp/SY-665 preamp system in my office. It's also 65wpc, but on that system, all my headphones shine. The orthodynamics especially - I can drive them to ridiculous volume, and the bass is clear and sharp and undistorted all the way up to the limit at which I can bear.

So what is it exactly that is going on here? Does the Pioneer have a different amplifier for the headphones? If I build a little adapter that takes speaker level outputs and attaches them to a 1/4 headphone jack, would that be able to drive my orthodynamics without distortion? For that matter, would a 12wpc receiver be able to drive my orthodynamics that way? Or no?

Thanks!

Charles.
 
My orthorynamics are based on the Yamaha YH-2 drivers, and those are rated 150 ohms and 3 watts, btw. The Pro-50's / AKG K250 I believe are 600 ohm electrostatic hybrids, 200mw. The Koss HV/1s are 150 ohm too. Don't know the wattage rating on them though. None of these sound good on the Pioneer, when given some serious volume. All sound great on the Toshiba though.

Charles.
 
Im guessing your Pioneer doesn't have a dedicated headphone amp to start with. Many integrated amps and receivers just use a set of resistors right off of the ouputs. It sounds like the Toshiba has a better impedance match. Look up the manuals, they should state the impedance and output of the headphone jack. I have a pair of old 600 ohm Pioneer headphones and a pair of 60 ohm headphones that seem to work fine with a Pioneer SX780 I have on the bench right now.
 
Hmm, so basically I could bypass the resistors and get better output from the headphones?

Maybe I'll build a box to convert speaker output to a headphone jack, and that'll let me use full power to drive these orthos.

Charles.
 
Hmm, so basically I could bypass the resistors and get better output from the headphones?

Maybe I'll build a box to convert speaker output to a headphone jack, and that'll let me use full power to drive these orthos.

Charles.
So, I have several pairs of headphones that are relatively difficult to drive. iPod gives very little volume, and... well, amps don't fare much better. My orthodynamics are really tough, but even my Koss HV/1 and AKG K250 aren't particularly easy to drive. I have a 65wpc Pioneer SA-720 integrated amp that should be able to drive any of those just fine.... but they all sound like crap. Especially the orthodynamics. I can get a respectable volume, but the bass is distorted badly. My thoughts were that any kind of receiver or small amp should be able to drive a pair of headphones... but I'm obviously mistaken. The only amp I have that does a good job is my Toshiba SC-665 power amp/SY-665 preamp system in my office. It's also 65wpc, but on that system, all my headphones shine. The orthodynamics especially - I can drive them to ridiculous volume, and the bass is clear and sharp and undistorted all the way up to the limit at which I can bear.

So what is it exactly that is going on here? Does the Pioneer have a different amplifier for the headphones? If I build a little adapter that takes speaker level outputs and attaches them to a 1/4 headphone jack, would that be able to drive my orthodynamics without distortion? For that matter, would a 12wpc receiver be able to drive my orthodynamics that way? Or no?

Thanks!

Charles.
Hi Charles: New to Karma but longtime headphone user/builder. I noticed your mention of AKG K250; I have AKG 240 dual driver, 300 ohms per side. They have had a reputation for being hard to drive as well as Ortho's. My latest build dedicated headphone amp. has an impedance switch w 2 ohm; 65 ohm & 120 ohm; so you can match the phones to the correct impedance. Ortho dynamics require an extremely low impedance drive. My modified & equalized Fostex T50RP's are great on the low ohm setting but suffer a large drop in level when switched to 65 ohms & even more on 120. My AKG 240's & other dynamic driver phones do not suffer the same loss in level as the impedance is changed.
For that reason I do not recommend trying to drive Ortho's with an amplifier designed to drive speakers.
 
I've always wondered why the newer headphones don't interact well with vintage amps and receivers. Back in the seventies the Koss 4a was what everyone I knew had and without a preamp, fact is......I don't remember headphone or phono preamps being available for the customer. But, everyone I knew had the larger Marantz receivers....
 
Neither of the OP's amps has a dedicated headphone amp, both take signal from speaker outputs via resistors. Looks like it's 2 resistors in series (100+150 Ohm) in the Pioneer, a single resistor (330 Ohm) in the Toshiba.

You could try a speaker to headphone level adapter on the Pioneer, but that would improve things only if there is a problem in the Pioneer with either these resistors or the headphone socket itself (dirt, oxidization).

Most vintage amps (even low power ones) drive vintage orthos without problems and with good bass. I have 4 such headphones, they do not have a problem with high output impedance. One is a clone of Yamaha YH-2 orthos. So the reason could be simply that the Pioneer is generally not as good as the Toshiba, or it distorts due to some sort of failure, and you hear it better with orthos. The distortion/bad SQ could just as well be caused by the Pioneer's preamp section.
 
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Im guessing your Pioneer doesn't have a dedicated headphone amp to start with. Many integrated amps and receivers just use a set of resistors right off of the ouputs. It sounds like the Toshiba has a better impedance match. Look up the manuals, they should state the impedance and output of the headphone jack. I have a pair of old 600 ohm Pioneer headphones and a pair of 60 ohm headphones that seem to work fine with a Pioneer SX780 I have on the bench right now.
Often the cd player has a better headphone driver than the preamp, amp or receiver it's hooked up to!
 
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