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oliverstoned 
Special Collaborator 
Honorary Collaborator Joined: March 26 2004 Location: France Status: Offline Points: 6308 |
 Posted: June 01 2011 at 13:36 |
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No actually i'm not that rich, i don't own the Stax, but one friend does so i had the chance to listen it quietly and moreover fed by his great system. It's incredibly dynamic and smooth, really push the ears into the brain! It's a fantastic experience but to be honest i'm not very up for indoor headphone listening, i quickly feel claustrophobic or simply tired wearing headphones indoor. I prefer listening to my speaker system indoor and to the high-end portable setup outdoor in the garden or on travel when you have nothing else. That's why i eventually sold back my Senn and the Bijou amp because i quickly got tired of listening headphones indoor. Well, this beautiful class A amp was not as musical as the big valve system. But it's not the same listening experience at all, headphone is much more transparent (on this criteria, a well driven 6XX can compete with big speakers) but is more of a "cerebral" kind of experience and lacks the physical aspect of listening provided by a well working system doing good low and extreme low. The V Can is decent, not excellent but decent and will let you hear more of the 650. No i didn't heard the Orpheus but from reliable source i know that it's a little overpriced and behind the Stax Lambda Signature, very musical but not as dynamic. The potential dynamic from the Stax is unbelievable... The 6XX in itself has a huge potential and the price is ridiculous in this aspect but requires an amp many times its price (at least until today) to express its full potential. And you can keep it a lifetime. 
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The T
Special Collaborator
Honorary Collaborator Joined: October 16 2006 Location: FL, USA Status: Offline Points: 17493 |
Posted: June 01 2011 at 23:49 |
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Thanks Oliverstoned. I always make jokes using your now-legendary "pushes walls" comments but I really appreciate your passion, though sometimes you're not very clear
 . Yep, the V-can is not state-of-the-art but for now will have to suffice. I'll upgrade it later on. Sennheiser makes great headphones so I want to experiment open-back ones, and before going crazy with the Grados and HD800 and Beyerdynamics, the HD650 was the best solution (also available at half price at work). I also want a closed-back one so I'll probably get an Audio Technica or a Denon. I really love headphones. Edited by The T - June 01 2011 at 23:49 |
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oliverstoned
Special Collaborator
Honorary Collaborator Joined: March 26 2004 Location: France Status: Offline Points: 6308 |
Posted: June 02 2011 at 03:53 |
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I'd would be happy to clear any point that was not. Anyway the V can will be a big step up to any "ordinary-integrated output" and i'm looking forward your impressions when you have all you gear and so that you'll be able to compare. I think that you know that your headphones and even your V Can will need some run-in period. So, be patient and let us know how it work then. I don't advice you the HD 800, it's not so great, better go for a killer amp to drive you 650, because like great speakers or valve amp, you can put a lot behind to reach its limits. The Grado is another school, less neutral and dynamic than Senn but very warm and laid back and need a lot of power, in your current/future setup (Marantz CD + Vcan), may be too soft, with the Senn should do a better combo but only listening will tell, as someone said. And i also hope that you'll be abble to compare with a 600 on your future setup.
Concerning Denon, i was very disapointed but Audio Technica is a good brand as well as Beyerdynamic, not that neutral for the latter but very musical. Let us know how it turns in this thread anyway. |
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: June 02 2011 at 05:06 |
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@Teo - please try before you buy. Listen to the V-Can driving HD650's before spending any money. Like Oliver, I have not heard this set up, but I can read and understand specifications - the V-Can is rated at 0.25W into 32 ohms, which equates to 0.026W (26mW) into 300 ohms - while this is a significant improvement on the Marantz h/phone output it is still nowhere near what the HD650s require.
It is better to look for an amp that is designed to drive high-impedance headphones, such as the Pro-Ject Head Box II, which can deliver 60mW into 300 ohms for about the same price as the V-Can.
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timothy leary
Forum Senior Member 
Joined: December 29 2005 Location: Lilliwaup, Wa. Status: Offline Points: 5319 |
Posted: June 03 2011 at 10:39 |
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My headphones are sennheiser hd-595 through a dac, they sound good. My computer speakers are Roland cakewalk ma-7a and they sound and look good.
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: July 16 2011 at 05:24 |
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Now that Teo has bought his V-Can and HD650s and is a happy bunny this thread is pretty much over, so I thought I would delve deeper into this Headphone Amplifier lark to show what the game is all about from a technical point of view. I suggest most people should stop reading as soon as it gets too mystifying/boring as I'm going to be very objective about this and not make any subjective comparisons, and I won't be doing anything silly like recommending brands or models of various amps to anyone - if you want that kind of information, ask Oliver.
Headphone Transducers
Headphones are essentially small loudspeakers, being small they are very efficient compared to the big drivers that are fitted into bookshelf or floor-standing speakers but that is generally by-the-by, efficiency is not a prime factor here. Headphone speakers are a small coil of wire in a magnetic field that moves when an electrical current is applied, this movement moves a diaphragm that pushes air in sympathy with the electrical input, thus an electrical signal is converted into a air movement, and our ears detect that air movement as sound. The same mechanism works the other way around - moving air on the diaphragm will move the coil of wire in the magnetic field and induce a current - just like a microphone - in fact I have used microphone inserts as tiny speakers, and I have used small speakers as microphones, and in the good-old-days intercoms did exactly that, using the loudspeaker as both speaker and microphone.
Impedance.
The amount of wire in the coil, the number of turns and the gauge of that wire determines the impedance of the headphone, this impedance determines how much current is drawn for a fixed voltage input -- the amount of current drawn and the number of turns in the coil determines how far the coil will move in the magnetic field and thus how loud the sound will be. More turns of wire means less current is needed for the same movement but more turns mean more impedance which means the current is less for the same voltage in. If this was all nice and linear then it would be a 1 for 1 trade-off, but it isn't: the movement is proportional to the number of turns but the impedance is proportional to the number of turns squared, so if we double the number of turns we get 4 times the impedance so for the same voltage we get a quarter of the current, which results in the half the movement. So to achieve the same movement (air displacement equates to sound pressure level [SPL]) we need to double the voltage every time we double the number of turns in the coil... or to put it another way, double the voltage every time the impedance is quadrupled. As Mr Ohm and Mr Watt will point out, the power in each case is the same.
Ah, you may be thinking, then what is the point of having more turns if we have to increase the voltage? Basically -none, it is all down to application and use - with different "standards" being used historically in different applications.
Headphone speaker impedances come in three broad flavours: low (8, 16, 32 ohms) for domestic use, medium (60, 150, 300 or 600 ohms) for professional (studio) use and high (1.5K ohms or higher) for broadcast use. We can ignore the high impedance h/phones as these are rarely seen and concentrate on the domestic and professional. Simple word-association would imply that the Pro are better than the Domestic, and therefore medium impedance are better than low impedance, but this is not the case - the "Pro" tag may be indicative of better design, construction and perhaps performance (and a higher price ticket), but it is not a direct function of the impedance itself - pro headphones and the h/phone sockets on pro equipment are designed to be compatible, (and so it is with domestic h/phones and domestic equipment). One of the reasons why medium impedance headphones are used in studios is that several sets of headphones can be connected to one amp without affecting the volume of the other headphones.
The low impedance values of the domestic h/phones mean that for a given power lower voltages are needed and this is ideal for portable equipment with 3, 6 or 9 volt batteries and these h/phones are often called "Portable" headphones for that reason, whereas the medium impedance headphones would require more voltage than the batteries can provide and are not suitable for portable use. However, the "portable" tag is a misnomer - the headphone socket on most amplifiers, receivers and CD decks are designed for low impedance h/phones.
This is not to say that domestic amplifiers and CD decks cannot drive medium impedance headphones, they can, but as Teo discovered, they do so at much reduced volume ... because they cannot supply enough volts, or are noisy because of mismatches. For example, the HD650s are 300 ohm, the HD380s are 52 ohms - as the HD650s are 5.7 times the impedance they will need SQRT(5.7) = 2.4 times the voltage to drive them.
Integrated Amps
The headphone sockets on integrated amplifiers come are of two basic designs - the first is the simplest and the commonest - they take the low impedance output that would normally drive the loudspeakers and switch it to the headphones - usually through a very simple one or two resistor attenuator to prevent the 100W of your amp from blowing your head off - this is obviously the cheapest option (for the manufacturer). Since these outputs can normally drive an 8 ohm speaker to 100W then they can in principle produce enough volts to drive medium-impedance headphones, but the simple resistor attenuator may prevent that - it depends on the values and without the schematic it is impossible to know.
The other basic design is to use a dedicated headphone amplifier that is part of the main circuit design. When I scratch-built amps, this is the method I preferred, the designs of these internal dedicated amps are identical to the ones you get in external headphone amps (and just as varied), but more of these later. If your receiver, tape deck or CD player cannot drive loudspeakers directly, then the headphone socket will be of this design - it will be a dedicated amplifier designed to drive headphones. The important consideration here is that in most cases the dedicated amp will be designed for low impedance headphones and still will not be able to supply the voltage that medium impedance headphones need.
Dedicated Amps
Dedicated headphone amplifiers are designed to drive headphones, the type of headphones they can drive is dependant upon the design, some have a gain switch that allows low, medium or high impedance headphones, some can only drive one type and some are set somewhere between low and medium so they can drive both, but those will be louder for low impedance h/phones than for medium impedance ones. As a general rule, portable headphone amps for medium (Pro) headphones will have two or more 9v (PP3) batteries in series to get the needed voltage while others use two amplifiers in Bridge (BTL) configuration to drive both sides of the speaker connection.
Output Stage Configurations
The output stage that feeds the headphone has three basic designs that generally determine how the circuit works, the simplest is called Class A - this is not a measure of quality but a classification of the transistor (or valve/tube) configuration - The next is Class B - which is the commonest in any high power amplifier, and finally Class D, which is becoming more popular, especially in portable equipment and in ICE amps for cars. There is (obviously) a 4th class of amplifier (called Class C) but this cannot be used for Audio as it is an RF amplifier using tuned circuits.
Class "A"
This is considered (by audiophilists) to be the top-dog of audio power stages, but it is horribly inefficient, uses a lot of power to produce a relatively low-power output, runs hot, can be very non-linear if the biasing is wrong and can produce a lot of harmonic distortion, it also requires a large capacitor on the output to produce a usable frequency response - Class A amp can be good, but that's not guaranteed. Simply put, this has one transistor (or FET or valve/tube) driving the speaker and the transistor (or FET or valve/tube) is always conducting so even when there is no signal present it supply current is still being drawn. Basically you don't get a lot of power out of a Class-A amp and it is pretty useless for portable equipment ... a Class A amp running off a 9V battery would not drive the higher impedance (32, 52 ohm) domestic headphones too well and the high quiescent current would drain the battery very quickly. Class A amps can be transistor, FET or valve (tube) and even though the circuitry is simple, with very few components compared to Class B or D, they command disproportionately high prices because audiophilists like them. True Class A amps are pretty rare.
Class "B" (and "AB")
This is also called push-pull since it uses two transistors (or FETs or valves/tubes) to drive the speaker - one transistor drives the positive cycles of the signal and the other drives the negative. The advantage of this is that when there is no signal neither transistor is working so the quiescent current is practically zero, the disadvantage is that the change-over from one transistor to the other may not be perfectly matched and this results in crossover distortion. However, simple circuitry has eliminated that from designs and has done for many decades now so this is not a problem - these amplifiers are called Class "AB", but in reality they are just Class "B" that are biased differently. Most dedicated headphone amplifiers use Class "B" or "AB" amplifiers in their output stage.
Class "D"
Class D is basically digital and is common in a lot of portable equipment and in some portable headphone amplifiers such as the FiiO E1, 2, 3 etc. and it's a fair bet that the amps in Bluetooth headphones will be Class D. This design uses Pulse Code Modulation working much like a lamp dimmer, switch-mode power supply or motor speed controller - in headphone amp designs the inductance of the coil in the speaker acts as the low-pass filter of the high-frequency digital "carrier" signal - the advantage of these is that no power is wasted in the amplifier itself as the drive transistor is either fully on or fully off. Obviously the presence of an HF carrier signal (even when far above the audio range) is psychological barrier for some. The main disadvantage is the circuit is very complex for a home-build unless dedicated Class D amp chips are used. For high and medium impedance headphones (and automotive ICE systems) Class D amps are often driven in bridge configuration to achieve the required votlage swing, this is designated as BTL (Bridge Tied-Load) on some advertisements and sometimes called Class "T".
Conclusion (if any)
With any hifi system, it is a case of ignoring the advertising spiel and the audiophilist hyperbole and trust your ears. Class A amps are not necessarily better than Class B, valve/tube amps are not necessarily better than transistor, descrete transistor amps are not necessarily better than monolithic ic amps and analogue amps are not necessarily better than Class D amps. Edited by Dean - July 16 2011 at 06:15 |
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Mr ProgFreak
Forum Senior Member
Joined: November 08 2008 Location: Sweden Status: Offline Points: 5195 |
Posted: July 16 2011 at 05:54 |
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^ Awesome breakdown of the different amp types. Nothing mystifying about all of that IMO, more like de-mystifying!
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TheGazzardian
Prog Reviewer 
Joined: August 11 2009 Location: Canada Status: Offline Points: 8670 |
Posted: July 16 2011 at 10:56 |
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Dean, thank you for the time you spent writing that out, I don't think I understood it all 100% but I still got enough to understand a more now.
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Headphones and amps...
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The T wrote: