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Pre-amp and Headphone amplifier separates? - Page 4

post #46 of 48
Quote:
Originally Posted by sml1226 View Post

I don't get the argument that headphones are completely different from speakers. I see no difference between a headphone and a full range speaker, really, at least when it comes to amplification. The only difference to cite is an unbalanced wiring scheme... if we assume everyone is using a TRS or some other unbalanced connector. First thing you balance your headphones, you are back to the equivalent of speakers again.

The power demands are substantially lower and sensitivity is much higher, and with the exception of some esoteric designs, headphones are full-range drivers, so you don't have a crossover or multi-amp scheme to contend with. The point is, while you are correct (and I'm not arguing that headphones are "completely different") there are some specific application details that change your amplification requirements just a bit. The ideal speaker amp scheme relies on one amp per channel inside of the system, headphones don't need that, and I'm not even aware of DVC/QVC designs that could benefit from that kind of thing. redface.gif

So if anything, it's simpler than what speakers need. smily_headphones1.gif

Quote:
As far as the common ground issue goes, what happened to the whole path of least resistance thing? The path through the grounds between components will have higher resistance than that of the grounds within the amps themselves simply due to the distance from one amp to the next regardless of your home wiring or power cable wire gauge, therefore a natural tendency to not interact with each other to, at the very least, a minimal extent. The ground they share, if properly done, is also behind a significant amount of filtering if your amplification has a half decent design, so any noise involved in your ground from the power should be blocked out by that as your power supply should be well isolated from your signal and amplification anyway. Having individual filters and supplies for each amplifier board should filter this ground noise out from one channel to the next.

Yes. The point is just that things are not magically isolated because you use multiple outlets, and as you've said, the gains of doing such are minimal with properly designed power supplies in your equipment. wink.gif

Quote:
I'm simply trying to say that there are potential benefits to doing this, and measurable ones for those of you that refuse to listen to an argument unless it's got some numbers in it, and you can't dismiss it as useless and irrelevant simply because it can be overpriced, and it can be just as bad, if not worse, than what you already have.

I'm not being dismissive. I'm being realistic. If you want to talk measurements and science, you don't get to stop with numbers - you have to take it the next step to audibility and preference studies. That's a very deep rabbit hole. basshead.gif

And since you've already dismissed separates for grounding issues, what advantages are there? What potential benefits are there to be had? confused_face_2.gif



Quote:
Originally Posted by johnwmclean View Post

The monoblock concept has merits for high power speaker amps rather than headphone amps due to the large currents involved. Besides the placement of the power amp close to the speakers, to minimise the length of speaker cable, they usually have much larger transformers, and are located away from the pre-amp with little chance of inducing hum/noise into the small-signal circuitry. Each monoblock amp has a separate power supply and ground which are not shared anywhere except at the input common ground (through the interconnect cable, where there is miniscule current). Allows for maximum channel separation. Of course a dual-mono construction in a single chassis could be made to do this, but chassis grounding needs to be common in the latter case.

+1.
Quote:
Originally Posted by googleli View Post

I think many use monoblocks just because generally they have more power output than one chassis amps. I have heard the crosstalk argument too but am not in a position to comment since I don't use monoblocks. But it is the first time I hear people use monos because they want to use shorter speaker cables ... Well... Not sure if that is valid because shortening the distance between the monos and the speakers would mean the necessary lengthening of the signal cables between the preamp and the monos.
Anyway I think the topic is on whether preamps would help with the sound of headphones rather than monoblocks vs one chassis.

Wait what? So because some cable makers want to sell you longer (and therefore more expensive and profitable) cables, that makes something less sound? I don't follow your reasoning. (Note that I'm not even going down the "cable debate" rabbit hole - if you like a given cable, great, but why buy a ton more of it for a single run?)

The advantage to a monoblock for speakers is simple - if you have a speaker that demands a lot of current or is low Z or both, less wire (of any relative gauge) will mean less loss in the cabling. And since XLR/differential drive from the preamp is pretty resistant to noise, running the signal line out by a few yards to amps that drive a foot or two of lead is a lot more rational than a few yards of unshielded line (and with most audiophile stuff, it's not really that heavy (before someone starts in: I don't consider anything smaller than 10AWG heavy)). This is common in PA applications where you can see per-cabinet power demands exceeding 1kW regularly - you don't want to spend a fortune for all of the copper to drive that from across a stadium, but snakes are cheap (by comparison).

The power output thing is also very valid, especially for home equipment that doesn't (and shouldn't, as far as I'm concerned) have forced-air cooling.
Quote:
Originally Posted by johnwmclean View Post

Your preamp needs very low output impedance, and the ability to drive long capacitive interconnect cables without ill effects. Forget unbuffered or passive pre-amps. 

+1.

Quote:
Originally Posted by Quest88 View Post

Notwithstanding the cable argument, going monoblocks certainly isn't about trying to cut down the speaker cable length though in theory it sounds good. 

Wait what? I'm irked by this not because it agrees or disagrees with any data, but because it purports to speak for all people and situations. In other words, for some people, it absolutely is about cutting down cable length.
Quote:
In XLR, the losses and noise rejection would be better than what you incur in speaker cable, hence the common thought.

How does ^ correlate to the first part of your statement? The conclusion does not follow the argument. You first say "no it isn't" and then say "it isn't because it is." Essentially. I'm confused.
Quote:
If anyone sees my setup, they would still see that I use 4m speaker cable even though my monoblocks are right next to my speakers.. there are some reasons for this, but none of which would appeal to those who believe in theories. smily_headphones1.gif

Go ahead and share - no need to be so obscure and distant; I don't think anyone here is looking to fight. smily_headphones1.gif

Quote:
But anyway, steering this back to head-fi, both these arguments don't really apply since cable lengths are relatively short in either case. It's just whether we believe going monoblocks or even dual mono for pre-amp have a benefit, and why are there so few headphone amps that are built this way.

And I'd agree with you absolutely here - headphones have extremely low power demands, and relatively short cables to begin with. So you aren't talking about a lot of loss or similar. Going to separates may or may not improve performance in terms of noise and separation, depending on the design, but that's about the only thing you'd get out of it. I don't think there's any reason for it to not work (because it works for speakers, so even if the benefit is less with cans, it's still there), apart from manufacturer reluctance to do anything of the sort, because it cuts into a VERY high profit accessories sector that they've set up. My point is that if you're Acme Inc, and can sell $5 for $5000, why increase your costs to $500? That said, I'm noticing that a lot of more established hi-fi companies are getting into headphones as they become more popular, so I wouldn't be surprised if more true dual mono or even separates designs start to come about (as well as the extreme hobbyist turned entrepreneur offerings from shops like Woo and RSA).

I think a dual-mono scheme is probably the ideal "getting off point" for a headphone amp though, because again power demands are so low, the extra cooling and certification requirements that you gain with a mono are moot. That's also another point to remember - there are established standards and requirements for how much power a device can draw (you can't just run it up to the moon) - 20A is pretty much top-side for anything you can sell for home use (despite audiophiles' willingness to re-wire their in-wall with expensive and bedazzled cables, buy expensive power conditioners, fancy fuses, and even have their mains box re-done, I've yet to see a one of them that will go to 220V for higher current carrying, nor a manufacturer that will oblige). So if you have an amplifier design that needs close to 2kW per channel (which is roughly what you'd expect with a ~1kW Class AB or 200W Class A), you can't make that a stereo amp - it'll never pass UL and nobody will be able to use it. But if they're separate...then you can get around that requirement. Same reason Class D and other switching or rail-modulating designs are getting popular in HT - more power from the same 125VAC outlet. This is along the same reason why your car stereo is 4x50W top-end without additional amplifiers.
Quote:
Originally Posted by wuwhere View Post

A preamp is mostly useful for multiple sources. It has a selector switch. And yes it adds coloration (I can't imagine how it cannot). But if you only have one source and it has a variable output, it is much preferable.

You can add source selection without a pre-amp, and there are some cheap and not so cheap options out there. Most newer DtoAs also accept multiple inputs (like the DACMagic, as a random example). So while I agree with the premise, there are different ways to skin that cat - there is no point in stacking gain stages (that's always a bad idea), especially if it's just to gain input selection. Buy a toggle and use the existing gain stage in your headphone amp, or use a full-size hi-fi component that can drive your headphones. But don't stack a preamp on a headphone amp. smily_headphones1.gif
Quote:
Originally Posted by Quest88 View Post

I find it interesting that since headphones are generally more revealing than most speakers, that it is not thought that a pre-amp actually improves the sound.
I don't think people buy high end pre-amps worth $50k to introduce distortion.. but maybe those of us playing speaker systems are all crazy.

It isn't so much that you're crazy, it's that the power requirements and similar are much different. Speakers have different needs at the end of the day - namely much more power. So to provide that, you need bigger power supplies, more heatsinking, more output devices, etc, and that stuff gets big, heavy, runs hot, and can put out and/or pick up noise. Headphones can generally be driven by a single opamp and run just fine (depending on the headphone of course), so there's no point in overbuilding all of that kit and wasting all of that power from the wall for it. The bigger "separation" that you see with headphone amps is power supply and IA - you don't see that kind of split-up with full-size amps, does that make them inferior as a result? The other thing to consider is that a lot of full-size components try to do a lot of different tasks in one box, they aren't just a single pre-amp gain section and amp output section, they can have tuners, digital decoding, IC control, RIAA preamp, tone controls, EQs, DSP control for everything from noise shaping to the LED displays, motorized mechanical components, etc which are all able to cause (or solve) problems that headphone devices are generally free from (and rely on up-stream hardware to accomplish).

If a headphone amplifier were released with all the features of even a basic stereo preamp or receiver, it would likely benefit much the same as those separates system do from being split apart.
Quote:
If a pre-amp has no difference in head-fi systems, that would be great to know. Perhaps, like I alluded earlier, this is because the current/wattage requirements are much lower on the power section and influence on the pre section is less. Curious to know from those who had really tried.

I'd agree with this and your hypothesis. FWIW, I have run separates for headphones, and in all cases the absolute only thing I ended up preferencing was the generally better volume controls you find on full-size hi-fi components compared to a lot of dedicated headphone amps (like I said, cheap cheap cheap). But using a big'ol stereo amp didn't do a whole lot of anything for me, despite having an ocean of power available on-tap.
Edited by obobskivich - 8/13/12 at 8:40am
post #47 of 48

A benefit of dual separated supplies is the ability break the internal ground connection between supplies, the only ground shared is input at the source, a major plus for ridding ground loops.

post #48 of 48

I have run my HP4 through my Calypso Signature linestage for years and prefer the sound to running source direct. The designer of the amp, Tim De P. states in the manual. "The HP4 has two line inputs, balanced and unbalanced. The choice of which to use is determined by the preamplifier you use and personal choice." Plus, I enjoy the flexibility of using the Calypso's phase control and the convenience of remote volume control since I dont sit within arm's length of the amp. Just my 2 cents on what I perceive to be the actual subject of the thread.

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