[Guardian]

Can someone who has a hi-end stereo system use the same amp s/he uses to power the speakers for a hi-end pair of headphones? Is there any advantage to using a dedicated headphones amplifier instead of a 'normal' power amp?

 

[Duncan]

You can... yes (looking at AKG-K1000 and Sony MDR-R10) but as a general rule you'd have to have a whole lot of resistance at the output point else... 50 watts going into a 1 watt max headphone... not only would the volume probably make you deaf instantly... but you'd also kill the headphones... without question

 

[Guardian]

So there is no fundamental difference between the circuitry of a headphone amp and a power amp? It is only that the latter is much more powerful than is necessary for headphones? The sound of a headphone amp is not geared specifically towards headphones listening in any particular way?

 

[Duncan]

A headphone amp is to all intents and purposes a pre-amp.. but there have been some units made that plug into the speaker terminals of power amps... namely the R10H... but they don't seem to exist anymore... only on the wishlists of MDR-R10 owners...

 

[Guardian]

Okay, thanks for your help. I'm still coming to understand the actual role of different parts of a sound system.

 

[bangraman]

Presumably this is just one huge resistor...
But still, I'm intrigued.


http://www.stoneaudio.co.uk/stoneaud...asp?product=93

 

[Hirsch]

The ASL UHC-Signature will allow a headphone to be driven by speaker outputs, and should be currently available.

The Grado HP-1 came with a diagram showing how to make an attentuator (using resistors) to drive headphones from power amps.

 

[mkmelt]

A power amplifier or integrated amplifier or receiver can all be good headphone amplifiers. Usually, inline resistors are installed in series with the headphone output so that the volume control can be adjusted over a wide enough range to allow the user to finely control the sound level. Without these resistors, the volume would come on too strong, too soon, as you turned up the volume control so you would have a difficult time adjusting the setting so that it was not all the way off, or too loud.

Most solid state (transistor) amplifiers can't deliver full power when used as headphone amplifiers because they were designed to deliver their rated power and frequency response into either a 4 ohm or 8 ohm load. Most headphones have a higher impedance, at least 32 ohms, and quite a few have rated impedances of 100 - 300 ohms.

When using speakers, it is common to speak of an amplifier's ability to deliver current into a load. When using headphones, it is voltage rather than current that is the limiting factor. To deliver rated power into a high impedance load, an amplifier needs to be able to provide a wide peak to peak voltage capability of 25 or 30 volts or more. Many solid state amplifier power supply designs just can't provide the needed voltage swing, while many tube amplifiers can and do operate this way.

For this reason, tube amplifiers are generally better at delivering power into higher impedance loads, say 120 ohms or 300 ohms, and can drive this type of headphone to higher volume levels than many transistor amplifier designs. This is usually only significant when dealing with high impedance headphones, some Sennheiser models such as the 580 and 600, or moderately high impedance and low sensitivity designs such as some of the AKG series headphones such as the model K1000 earspeaker.

The K1000 earspeaker is a headphone with a moderately high impedance (120 ohm), and low sensitivity (74 db/100mwatt) that proves too much for many solid state amplifiers. While there are exceptions, many solid state amplifiers just can't drive these headphones to normal volume levels whereas there a many tube amplifiers that are fully capable of driving the K1000 to full volume.

 

[PinkFloyd]

Quote:

Originally posted by bangraman Presumably this is just one huge resistor... But still, I'm intrigued. http://www.stoneaudio.co.uk/stoneaud...asp?product=93

Would be interesting to get a peek under the bonnet wouldn't it?

 

[robo7]

Many Solid state Headphone amps (Headmaster, Gilmore's, SDS, META42, Ray-samuel's HR2...) are built like a small delicate version of a Speaker amplifier.

The relevant differences are 3:

gain - speaker amp 15-40. headphone amp 1-11.
supply voltage - Speaker Amp of 20W/8ohm will have some +/- 25v (100w/8ohm +/- ~50v) etc.
headphone amp - from +/-5v(szekeres) to +/-24v (Borbely).
At the output stage of speaker amp you can find high power devices.

Headphones request less power to make sound, much less.
Why is that?
1. they are more sensitive than loudspeakers,.
2. headphones are closer to the ear.

Speaker amplifiers are more powerful(too powerful) and more sensitive than H.phone amps.

remember: Power = V x I or V2 / R

from the equation it is clear that to get more power you need either higher voltage or lower impedance.

to drive a 32ohm Grado or a 300ohm HD600 (same sensitivity assumed) to the same volume level we need about 3 times current on the grado or 3 time the voltage on the HD600.
Quote:

Most solid state (transistor) amplifiers can't deliver full power when used as headphone amplifiers ...

Almost any speaker amp will surpass any headphone amp on power delivery terms, because of higher supply voltage and the ability to push higher current into a load.

Hope this helps.

Robo

 

[Guardian]

Thanks for your informative posts, everybody. I have a very clear understanding of the difference; it should have been obvious to me before. Thank you.

The reason I asked this question was that I wondered what people who listen frequently to both loudspeakers and headphones do in their systems--I wonder if they use a dedicated headphones amp separate from their power amp or not.