[LoveKnight]

Mike on Headfonia said that HD598 gets many benefits from mid or high end amplifiers, but be aware he stated that between HD598s and HD650s, the HD650s can up-scale more than HD598s. He used Zana Deux as an reference amplifier. To sum up, if you use high-end tube amplifiers you can find out that HD598s could be too mellow and suitable only for some genres. 
 
Someone said that HD598s do not need separate or inexpensive amps to bring out of them. I totally disagree, I and many other people think by using good separated amplifiers to hear all of their potentials. For me, as I visited a audio store near my house and tried to use my HD598 with many from low to high amplifiers, some amps can make HD598 sings beautifully but some amps do not. By saving money I bought a Fiio E10 but I had tried a Fiio E17 and found out E17 is better than E10 clearly. The instrument separation, the mid, the bass, the transparent are surely better than E10. My E10 however I found it is muddy, not clear, gets harsh with some songs and little bright to my ear.
 
I ordered a C421 OPA2227 to pair it with my HD598 and E10 (using E10 as a DAC only). Hopefully the result will be better, HD598 on my memory should be a little warm and smooth. Next I will be saving money to buy a better DAC such as Dragonfly for example.

 

[NimbleTurtle]

Quote:

Mike on Headfonia said that HD598 gets many benefits from mid or high end amplifiers, but be aware he stated that between HD598s and HD650s, the HD650s can up-scale more than HD598s. He used Zana Deux as an reference amplifier. To sum up, if you use high-end tube amplifiers you can find out that HD598s could be too mellow and suitable only for some genres. 
 
Someone said that HD598s do not need separate or inexpensive amps to bring out of them. I totally disagree, I and many other people think by using good separated amplifiers to hear all of their potentials. For me, as I visited a audio store near my house and tried to use my HD598 with many from low to high amplifiers, some amps can make HD598 sings beautifully but some amps do not. By saving money I bought a Fiio E10 but I had tried a Fiio E17 and found out E17 is better than E10 clearly. The instrument separation, the mid, the bass, the transparent are surely better than E10. My E10 however I found it is muddy, not clear, gets harsh with some songs and little bright to my ear.
 
I ordered a C421 OPA2227 to pair it with my HD598 and E10 (using E10 as a DAC only). Hopefully the result will be better, HD598 on my memory should be a little warm and smooth. Next I will be saving money to buy a better DAC such as Dragonfly for example.

I'm still waiting for the ODA + ODAC to come out... and yeah after I tried the 598s with a tube amp, it felt a little too laidback, which isn't something the 598 needs. It needs to have a bit more speed for those metal genres. 

 

[LoveKnight]

Actually some sentences of my last post were wrong about the meaning because my English is not good. To conclude I think HD598s should pair with expensive amp to bring out of their potentials, but they are still very good with mid amplifiers or with high end DAPs. About pairing HD598s with tube amplifiers someone feels it could be too mellow, sweet to hear but someone could like it. Me, however do not want to pair HD598s with most tube amplifiers.

 

[RudeWolf]

Quote:

[...]To be honest, the whole idea of an incredibly expensive amp requirement to drive "higher tier" headphones such as the HD650 and the HifiMan planar magnetics is easily just as doubtful. How do we know the differences we are hearing between amps are simply a matter of expectation bias? I think people underestimate the degree to which a human brain can affect perception.[...] 

 
Why so? Ok, it doesn't have to be incredibly expensive but these headphones are very specialized loads that need specialized devices to provide good performance. The HD650/600/580 trio together with K701 and high impedance Beyers basically made the dedicated headphone amp. You must keep in mind that there are two problems that a good headphone amp must address. First it must be able to deal with unusual loads that are presented by many higher tier headphones. Let's take the HD650 and HE-500 as good examples from the extreme ends of the spectrum. The HD650 presents a high impedance high sensitivity load and the HE-500 is low impedance low sensitivity. The average headphone amp that's used in most devices is a cheap op-amp with high negative feedback to lower the gain (and distortion). HD650 needs a lot more voltage that the power supply for this op-amp can supply, this is why many portable amps strive for a higher voltage power source. The HE-500 on the other hand needs a lot of current to move the diaphragm which is a difficult task for many amplifiers. Even many common tube circuits aren't that good at supplying current (but excel at voltage gain).
 
Then there's fidelity. A good amp must do the things I wrote above while staying true to the signal supplied by the source. This means using regulated power supplies, extensive filtering, many gain devices so that they are used in very linear manner and much more. Should it be expensive? It depends. If done correctly a truly high end headphone amp does get expensive. And it's not because it needs some exotic parts- it's because of the high standards of manufacture that need to be implemented to make such a device. Take a look here- http://www.sjostromaudio.com/pages/hifi-projects/36-hifi-projects/87-qrv01-headphone-amp this is what in my humble opinion stands for high end. Unfortunately most commercially available products are what I would call "decent enough" or "one could do much worse". Some are plainly laughable. Then there's DIY. What it should be is the pinnacle of technology with all kinds of crazy designs that push the envelope of what's possible electronically. Instead we have an army of parrots that chant the "only the most complex can understand the simple" mantra and upgrade their CMOY's with fatter capacitors. There are truly good and simple designs like Kevin Gilmore Dynalo series but in times like these they often get forgotten because they don't output many watts and require fine tuning to be at their best. Instead we have The Wire that get's lauded as high-end while not being much more than a cheap ticket into the interesting and challenging world of DIY audio.

 

[NimbleTurtle]

Quote:

 
Why so? Ok, it doesn't have to be incredibly expensive but these headphones are very specialized loads that need specialized devices to provide good performance. The HD650/600/580 trio together with K701 and high impedance Beyers basically made the dedicated headphone amp. You must keep in mind that there are two problems that a good headphone amp must address. First it must be able to deal with unusual loads that are presented by many higher tier headphones. Let's take the HD650 and HE-500 as good examples from the extreme ends of the spectrum. The HD650 presents a high impedance high sensitivity load and the HE-500 is low impedance low sensitivity. The average headphone amp that's used in most devices is a cheap op-amp with high negative feedback to lower the gain (and distortion). HD650 needs a lot more voltage that the power supply for this op-amp can supply, this is why many portable amps strive for a higher voltage power source. The HE-500 on the other hand needs a lot of current to move the diaphragm which is a difficult task for many amplifiers. Even many common tube circuits aren't that good at supplying current (but excel at voltage gain).
 
Then there's fidelity. A good amp must do the things I wrote above while staying true to the signal supplied by the source. This means using regulated power supplies, extensive filtering, many gain devices so that they are used in very linear manner and much more. Should it be expensive? It depends. If done correctly a truly high end headphone amp does get expensive. And it's not because it needs some exotic parts- it's because of the high standards of manufacture that need to be implemented to make such a device. Take a look here- http://www.sjostromaudio.com/pages/hifi-projects/36-hifi-projects/87-qrv01-headphone-amp this is what in my humble opinion stands for high end. Unfortunately most commercially available products are what I would call "decent enough" or "one could do much worse". Some are plainly laughable. Then there's DIY. What it should be is the pinnacle of technology with all kinds of crazy designs that push the envelope of what's possible electronically. Instead we have an army of parrots that chant the "only the most complex can understand the simple" mantra and upgrade their CMOY's with fatter capacitors. There are truly good and simple designs like Kevin Gilmore Dynalo series but in times like these they often get forgotten because they don't output many watts and require fine tuning to be at their best. Instead we have The Wire that get's lauded as high-end while not being much more than a cheap ticket into the interesting and challenging world of DIY audio.

Thanks for the input. It's good to learn these things from a more experienced person. How do we know if a high end headphone is getting enough voltage (HD650) or getting enough current (planar magnetics)? From what I know, achieving high listening volume has no relationship between sufficient amount of voltage/ current being inputted right? 
 
I haven't learned anything about negative feedback yet... will do so tomorrow. What is your opinion of the O2 amp? 

 

[RudeWolf]

You can always use the Ohms Law to derive any variable if you know the other two- http://www.ohmslawcalculator.com/ohms_law_calculator.php
 
Just keep in mind that these calculations are very simplified in relation to real world performance. Amplifier (actually PSU) performance can vary when driving different loads. In a good design this variation is negligible.
 
In my experience amplifier performance can be detectable by ear to some extent. Insufficient voltage gain results in clipping (clipping performance is an often overlooked amplifier parameter). Not enough current results in decreased dynamics. The funny thing is that without hearing something that is better you won't be able to detect these things. I used to be okay with how my E10 drove the HD650, then I built a Dynalo/Sigma22 amp which made the HD650 a vastly more neutral headphone. No more upper bass/lower mid hump and a ton of treble. Was I happy before? Sure! Am I happy now? You bet!
 
For me an universal way how tell if an amp is good means listening at low volume. There should be no loss of dynamics.
 
P.S. I'm just a newbie that has read the very basic stuff. Also I went through a reverse polarity accident when building my Dynalo which decimated all transistors so I had to learn the circuit in and out to find out what's wrong. On top of that I also had some very knowledgeable folks helping me with this.

 

[RudeWolf]

As for O2... I don't really know. I might build one just for schiits and giggles to compare it with Dynalo but other than that... The circuit is very boring and the rumor is that sound follows the trend. I have a bad feeling that we aren't measuring the stuff that really matters or interpreting in a way that it tells us something that matters.
 
I'll just tell you one thing- an acquaintance of mine who designs his own power amps only by meters (the guy doesn't even own any speakers) saw the O2 schematic and whilst smiling told me that "I wont say anything".

 

[Digital-Pride]

Really enjoying the current discussion.  Keep up the good work guys.

 

[tdockweiler]

Quote:

Mike on Headfonia said that HD598 gets many benefits from mid or high end amplifiers, but be aware he stated that between HD598s and HD650s, the HD650s can up-scale more than HD598s. He used Zana Deux as an reference amplifier. To sum up, if you use high-end tube amplifiers you can find out that HD598s could be too mellow and suitable only for some genres. 
 
Someone said that HD598s do not need separate or inexpensive amps to bring out of them. I totally disagree, I and many other people think by using good separated amplifiers to hear all of their potentials. For me, as I visited a audio store near my house and tried to use my HD598 with many from low to high amplifiers, some amps can make HD598 sings beautifully but some amps do not. By saving money I bought a Fiio E10 but I had tried a Fiio E17 and found out E17 is better than E10 clearly. The instrument separation, the mid, the bass, the transparent are surely better than E10. My E10 however I found it is muddy, not clear, gets harsh with some songs and little bright to my ear.
 
I ordered a C421 OPA2227 to pair it with my HD598 and E10 (using E10 as a DAC only). Hopefully the result will be better, HD598 on my memory should be a little warm and smooth. Next I will be saving money to buy a better DAC such as Dragonfly for example.

 
Somehow I can't get the E10 as a dac to sound amazing with the line out. I don't know why. If I do the "bad" thing and use the headphone out to my amp it sounds great. It's clearer and has better controlled bass and a larger soundstage. Much more balanced. Guess it's like double amping. My Micro amp can pretty much drive anything, so it's not a lack of power.
 
The line out seems to make the mids MUCH MUCH more forward and compresses the soundstage. This makes no sense at all!
 
I haven't tried the 598 enough straight from the E10. Just 10 minutes and something seemed a bit off.
 
The E10 using the line out doesn't sound very neutral at all. Yet it measures perfectly flat. I guess measurements are not everything right?
 
What makes things worse is that the E10 makes my DJ100 sound perfectly balanced. Straight from the E10.  If I use line out, it's much worse and not caused by my amp.
My DJ100 and Q701 sound amazing with the E10 as a dac though.
 
Guess I need to try the ODAC. Currently trying to sell my HRT to try and fund the purchase of one. Hopefully it's as uncolored as they say..to my ears. Fingers crossed.

 

[palmfish]

Headphones aren't specialized loads. They act the same as any loudspeaker, only they are 1000X easier to drive.
 
The Sennheiser HD 598 is rated at 102dB sensitivity. That's a lot of volume for not very much power. And even at it's lowest impedance (50 ohms at 1kHz), it takes a very small amount of current to properly drive (a fraction of an amp). For example, listening to a pair of HD 598's at a "comfortable" average volume of 80dB and allowing for peaks as high as 90dB (10dB is more dynamic range than most recordings contain) requires 60 mV and 1.2 mA. An iPod easily provides this with no audible distortion.

 

[RudeWolf]

Sure, the HD598 isn't the worst kind but are you sure that an iPod will be able to deal with the 300Ohm peak at 100Hz? It will go plenty of loud but the FR will get distorted because of this. 

 

[palmfish]

Quote:

Sure, the HD598 isn't the worst kind but are you sure that an iPod will be able to deal with the 300Ohm peak at 100Hz? It will go plenty of loud but the FR will get distorted because of this. 

That impedance spike centered at 100 Hz probably explains why the 598 isn't as lush and bassy sounding as some other popular headphones. For people who like the 598's signature, it's a good thing. But for the sake of discussion, if you must have your 100 Hz bass reproduced at 90dB peaks, then your amp would need to produce 130mV and .5 mA. Still just a small fraction of the output capabilities of an iPod.
 
You linked an ohms law calculator above. You also know the sensitivity and impedance of the HD 598. Therefore, you surely already know that an amp only needs to provide a fraction of a milliwatt to power these Sennheisers to ridiculous volumes.

 

[RudeWolf]

Fair enough. Then tell me, why did I hear such difference when going from an E10 amp stage to a full fledged Dynalo? Keep in mind that I'm not a high volume nut- I drove my HD650 at 30% on the E10 and on a similar volume position on a Dynalo. I can't help but to think that there's something else beyond loudness for an amp to produce. Damping factor? Nah, damping can't give me more treble.

 

[stv014]

Quote:

 
That impedance spike centered at 100 Hz probably explains why the 598 isn't as lush and bassy sounding as some other popular headphones. For people who like the 598's signature, it's a good thing. But for the sake of discussion, if you must have your 100 Hz bass reproduced at 90dB peaks, then your amp would need to produce 130mV and .5 mA. Still just a small fraction of the output capabilities of an iPod.

 
Impedance peaks do not need more power or voltage. To avoid frequency response anomalies, you need an amplifier with low output impedance (unless the headphone was designed for some specific high source impedance, like the old 120 Ohm IEC standard). At ~100 Hz, the HD598 needs less power, i.e. the same voltage but less current; that makes sense, as the driver is resonating at this frequency, therefore its efficiency increases.

 

[palmfish]

Impedance peaks do not need more power or voltage. To avoid frequency response anomalies, you need an amplifier with low output impedance (unless the headphone was designed for some specific high source impedance, like the old 120 Ohm IEC standard). At ~100 Hz, the HD598 needs less power, i.e. the same voltage but less current; that makes sense, as the driver is resonating at this frequency, therefore its efficiency increases.

I agree that a low output impedance is desirable and will likely minimize frequency response anomalies (it gives the amp a "tighter grip" over the headphones). But it may or may not eliminate them because the changing load requirements still require swings in voltage and current from the amp, which may or may not result in audible changes. Impedance is only one factor that comes into play between an amp and a transducer.