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Missing in Action: Low Powered Amps

Discussion in 'Headphone Amps (full-size)' started by mohawkus, Oct 9, 2014.
  1. MohawkUS
    As I am writing this post, the Bakoon HPA-01 I recently acquired is sitting on such a low volume that I'm hearing some channel imbalance yet still too loud, and I am left wondering what is left for us high-end dynamic headphone owners. More specifically those of us with low ohm/high efficiency dynamic drivers. :basshead:

    Are we seeing a repeat of the 'power wars' of the 70s? Or has the high-end market as a whole fully embraced the power hungry planars?

    I'm sitting here reminding myself that the best I have heard my Edition 12s was through the 'simple' headphone circuit of a 1986 CD spinner and that ain't right when one has sampled some high end fair including the Apex Teton and Bakoon HPA-01. What is the future for those of us who sit defiantly in the low-power dynamic camp. Are there enough of us left for manufacturers to take notice? Or should we invest in a pair of ear plugs so that we can listen to our high-end amplifiers without channel imbalance?
  2. tuatara
    Maybe you need something like a Violectric where you can adjust the gain.
    When I purchased my Meier Opera several years ago I had Meier lower the gain so that I could actually get some use of the volume control .  I think he lowered it 6DB which meant I was sitting around 10oclock to 12 on the dial with various Grado and AT phones.
    If you're using a variety of headphones I think a gain switch of some sort is a must.  
  3. ProtegeManiac Contributor
    More people have gone into headphones (due to rising economic capability, and yet even more highly urbanized living, ie shared walls) and orthodynamics are becoming popular and less expensive models are coming out. Hence, many manufacturers come out with amps that can power them as well.

    You can have a low impedance headphone with very high power handling, but if its efficiency is very high, then of course it needs a lot less power to be used within reason. You don't need "low" or "less" power on its own - what you need is low(er) GAIN. My Meier Cantate.2 has a -10dB low gain setting that allows it to drive Grados and even some IEMs (not that they need it, but I tried it just the same; so far the ASG-1.3 and W2, W4 all work with no issues). You can have an amp with lower power but if its low gain is still higher or the same level as the HPA-01 you'd still have a problem.
    In any case it's not like there's a total absence of low power amps - there are a few USB DAC-Amps out there that should have low output, but most of them are USB powered and have no analog inputs, so it requires a computer as a source. The thing with amps that have bigger power supplies though is that you still get better current in case you need it; just get a more reasonable one (I can justify a bit of power, but I do not really advocate using amps that are big enough they might as well drive speakers) that has an easily accessible gain control. My Meier needs to be opened up and jumpers adjusted; the newer models have the switch on the front panel already.
  4. kn19h7
    I don't get those super high power amps either, nowadays unity gain mode is a must-have feature to me for amps.
    Even with hd800, I don't need more than that.
  5. ProtegeManiac Contributor
    Schiit for example argues, "why not?" Easy to say that for the Lyr, it's the same chassis as the Asgard. But then I see a bunch of balanced tube amps as large as a speaker tube amp (at least you can easily stack the Mjolnir over the Gungnir). That's humongous for a desktop system, and if you have a speaker system anyway, the new Cayin tube amps are fantastic with the HD600 (the only one I've tried so far) - I couldn't tell the difference between that and my Cantate.2 when level matched to a sane level, and at much louder volumes the Cayin is a touch warmer and I imagine more "pleasing"  to some (likely a distortion characteristic though).
    In any case as much as I want slightly bigger amps (up to a point), I do see the allure of low power, very low distortion amps driving highly efficient transducers that don't need a lot of current - I mean if I had a speaker system and enough money I'd probably use a Pass Labs passive pre and 10wpc discrete fully Class A amp with 90db+ speakers. With headphone amps though the thing is it's not that difficult to make a roughly 1wpc Class A headphone amp, so from a marketing (not just in "selling" it to people like propaganda, but in understanding the market and what products are more likely to sell) standpoint, that amp with a variable gain will attract more buyers.
  6. kn19h7

    Well. I don't have problem with variable gain, as long as one of the lower gain mode is actually usable, and the amp doesn't need to have lots of vent holes to compensate for "cost-effective" heat dissipation =_=
  7. ProtegeManiac Contributor
    Check the gain level on the Bakoon and its power output against any other low gain amp you look at (forgot how to compute for an estimate of that but if no one chimes in in here you can ask in the Sound Science section). What headphones are those anyway?
  8. MohawkUS
    The headphones are Edition 12s. 99db sensitivity, 40ohm. The current out on the Bakoon is usable on low gain, but voltage has a far superior sound with the Sones. Unfortunately the gain switch is out of the circuit with voltage.

    I'll be honest in that I don't understand exactly what a gain switch does. Where in the circuit is it? Prior to amplification or post? And what effect does it have on sound quality? It seems counter productive to get a bigger amp just to cut the signal with lower gain unless you're looking for wide compatibility. I just want something to drive the Sones so I can deal with a specilized product.
  9. ProtegeManiac Contributor
    You're not "cutting the signal," not damaging it or anything - at best it's in the same context as "cut" in EQ-ing, but in all cases these are more layman short hand than actual technical terms. I forgot the technical explanation, but basically gain affects only the magnitude of the signal amplification, not the output power per se, so you can think of it as a "multiplier." 
    Before you can think it's "throttling" the output though (more like suffocating than mashing a throttle pedal), note that a lot of other applications use gain controls precisely to work with different transducers. Car amplifiers for example take an already pre-amped signal from the master control (either on the receiver or the processor), then still apply its own gain setting, just in case you decided to throw out the passive crossover boxes in favor of an active processor and you'll hook up a 10wpc tweeter to the 75w channels on a 4ch amp. Also, in cases when people report that high gain sounds a lot "better," it could also be higher THD except it distorted more like a tube amp than outright annoying distortion, in case their amp's high gain setting is +XdB (instead of high as normal "0" gain, then a low gain that reduces that signal). Basically, even if an amp is rated at say 1wpc at 0.01% THD, using it on low gain isn't "throttling" the amp, you just end up with for example 250mW at 0.001% THD.
    If you really want a specialized low gain, very low power amp, I'm not sure where to get any of these aside from the USB-powered solutions like the UDAC, which still makes around 25mW or more and some report a lot of channel imbalance with IEMs even on the v2 (not sure about the v3 though). So basically, yeah, going very low power might just mean going for a worse pot than on that Bakoon, and have the same overall problem but this time from a different source, save perhaps for approaching amp builders (like those who build off AMB kits) and ask if they can design an amp that makes about as much power as the integrated chip on a smartphone (5mW), but with less distortion and of course no "cutting" of the gain.
    BTW, you might want to look at the Meier Jazz. Its low gain setting is zero, so no "cutting" of the signal there, but shoot Dr. Meier an email if he's tried it on the Ed 12's. The thing is, it has a digital pot, so channel imbalances are less likely to come from that part of the circuit - you just need to confirm if it's good with the Ed 12 at zero gain.
  10. d1sturb3d
    if you have a pre-amp that has a volume control that is in a resistor ladder network(normally digitally controlled)..you can max the bakoon vol (or even half will do) and control the vol in the pre-amp to avoid channel imbalance..
  11. MohawkUS

    Well that is just the thing, is not using a cheaper amplifier(a question arises whether price is more related to power output or sound quality) not going to limit the headphones? And then comes the added complication of the powerline in my house being rather poor. I used to have a Burson amplifier which developed a noise after sometime and would prefer something with superior filtering(hence the battery powered Bakoon.) Whilst I admit it does seem a bit silly to be asking for beefier power supplies and lower power ratings it is a gap that exists in the market which I don't recall having existed when I first joined this site, that would be around the launch of the HD800 if I remember correctly.

    Don't get me wrong, I'm not looking for something as weak as my phone, which isn't up to the task of driving the ED12s, but something in the hundred-few hundred mW range.

    Of note is the fact that my source may equally be at fault. Volume is not an issue when using my turntable with the phono-amps built into a vintage receiver. I suspect the output must be significantly lower than my DAC, curiously with analog sources the current output of the Bakoon is louder than the voltage. With digital the reverse is true and by quite a large margin.

    Ideally I want as few parts in the signal path as possible hence why I don't want another component in line cutting down the output nor would I prefer a wellrounded amplifier with adjustable gain over a low powered unit. Part of that is just my minimalist nature and part of it the words of others who have heard this pair of headphones. The simpler the circuit the better as one man said, which might help explain what I've noticed with the CD player, I didn't see anything save for a single op-amp by the HP jack when I opened it up. It was a lowly JRC too.
  12. ProtegeManiac Contributor
    Yep. And like I said, a cheap pot may make the channel imbalance worse, even with less power, so long as it has high enough gain along with a crappy enough pot.
    Newer amps that came out since were designed to do well with orthodynamics which were becoming more accessible at the time as well. It's not so much that a "gap" was created since because people simply stopped making them, but more like they didn't make any sort of amps since past a certain price point that didn't have a lot of power. Again, market demands would have informed manufacturers that people would look for high watt per dollar values, so long as it didn't come with downsides like higher THD at that price point, too high price, or too large amps - all of which are more easily circumvented when designing a Class A headphone amp with 1wpc output than, say, a Class A speaker amp with over 15wpc - hence that's what the manufacturers produced. Just look at how many headphones have the same efficiency level as the Ed 12's - that alone is enough to give you an idea of how the market of existing headphones is. The only ones that can compete are the Teslas, but some of them have high impedance.

    Since you're concerned about your power line anyway and would prefer battery power, then you might want to ask in the Portable Amps section; if you'll be using a computer anyway then you can just use a battery-powered DAC-Amp. It may not the the same quality as the Bakoon in the sense that as an alternative to for example a 200wpc Unico integrated you can blow a lot less of that money on a 15wpc Pass Labs Class A amplifier and a matching passive preamp, but no need to suspect it will absolutely just suck. Your primary concern should be whether it hisses or has channel imbalance, so use the Shure SE535 as a reference. If a portable DAC-Amp doesn't hiss nor have a channel imbalance with that, then go check it out. My Ibasso D-Zero on low gain has zero issues on my Aurisonics ASG-1, which has a 127db/1mW efficiency. It needs about one scroll of the volume control from one side to the other (not the full revolution, just the visible part) to go loud enough and has no channel imbalance.
    In addition to the D-Zero I mentioned above, try the D42 Mamba (USB input, Android compatible) and D12 Anaconda (optical input) as well. Ibasso's site is down for now the meantime though but there are review threads here, just use the search function.
    That or you're listening to loud digital recordings. Even audiophile recordings joined the loudness wars; my vocal albums are even louder than Smashing Pumpkins and Fall Out Boy. If you use a portable DAC-Amp for digital and then use the Bakoon for your analog source then you might alleviate the problem - portable DAC-Amps with the exception of a few as well as current DAPs have a line out signal well below 2volts. Noticeably louder than an iPods but still noticeably softer than, say, a lot of DACs (many of which output 2.2v actually).
    Or you can even try using their line out, bypassing their amp circuits and sending the signal out, to feed a signal to the Bakoon.
    The gain might really be high on that one.

  13. kn19h7
    There do exist some nice amps with proper low gain mode, like Phonitor 2, Lehmann Linear etc. Both include unity gain mode.
    Well, maybe I am seeing things in an opposite way of yours, or maybe we are really looking at things in different markets =_=
  14. ProtegeManiac Contributor
    Sorry, I didn't elaborate. Just as an example, the HD600 is rated at 97dB efficiency, 300ohms; OP's Ed 12 is only 2dB more efficient, but his is 40ohms. Even amps that make more power at 300ohms than 32ohms likely makes more power than he needs, although of course I did discuss with him low gain settings as well as how, as much as the HD600,* HD650,* and even the K701 for example are out there, my point was that manufacturers try to squeeze out as much power as they can as they can, which can be done without a lot of distortion nor huge heatsinks with modern designs.
    That makes those amps, right down to the $99 Magni, compatible with a "wider range of headphones," but the thing is they are targeting more the ones that are harder to drive. Like I posted previously though it's not so much that they ignored the more efficient ones outright given low gain or unity gain designs, but the OP seems to have some resistance to doing things that way (like the oft noted resistance to using EQ I suppose). In any case, some Schiit and Meier amps for example can do well enough on IEMs despite being designed primarily for the likes of the HD600 and LCD-2 - my Cantate can drive IEMs surprisingly well, and I just don't because I don't see the point (with the IEM anyway).
    In any case, I do have to admit my interest is piqued by the Ed.12. The PM-1 was acceptable with my SGS3 (heck, even a lot better than my ASG-1, save for isolation), so now I'm insanely curious about how the Ed 12 is with the AK120 MkII.

    *Although if you really think about it, 2dB isn't as small as it looks, considering 3dB is technically twice as loud; and when impedance is considered with them, then overall the Ed 12 is far easier to drive. Then again, like I've posted above, if it is that easy to drive, then no need for an exotic amplifier with a huge power supply since there are decent, properly-designed, modern amplifiers that won't have anywhere near audible distortion at the amount of output the Ed 12 will need unless its impedance swings wildly from nominal (does it?) and hence requires a beefier power supply design. The bigger question is whether such amps' pots and gain settings would work with how efficient it is, which is why I suggested looking into amps for the SE535 as a reference for a quiet amp that won't have channel imbalance issues.
  15. MohawkUS

    Yes, I am showing resistance to resistance. :p I'm not sure how intelligent it is, but I am stubborn about it. Just the same I don't like buying things with features I don't use which is part of my reluctance in using DAC/amp combination units. The other side of that coin is in that I have analog sources and such devices rarely have analog inputs. When they do, they lack analog outs(which makes comparing to other amplifiers difficult.) I had that problem with the Burson 160DS I used to own whereas I wanted to avoid using its amplifier after I got my first pair of Ultrasones, the PRO2900.

    As of the moment I think I am right where I started, if I want the ideal amplifier for my headphones I need to be looking into people who do custom work. And that implies tube amplifiers as that seems the specificity of most custom designers and they are typically lower in power.

    In a twist of irony, I've been using vintage receivers for my headphone amping needs for the past year. The kind old enough that the HP amps are running right off the speaker outputs with some resisters in line, the kind old enough that they were produced before hp jacks were standardized necessitating reversing the RCA cables to get things playing in the correct channel. Channel imbalance is the least of your worries with 40yr+ old pots on 'as is' vintage equipment. I would really like to get off of that and have something running as direct as possible, plus if I am not mistaken amps run more linear the less they are being pushed.

    As a final note the ED12s are not the most sensitive pair of headphones that I've had here. The Beyerdynamic T90 take the throne there, being easily driven(to the same extent) as my speaker amps off of a Sansa Fuze. 102db/250ohm. On the other side of things was the HE-6 which sounded lackluster with everything I have on hand.

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