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How to buy an amplifier?

  1. devilduck
    Which specs will an amp need to have to drive the DT-990?

    I can’t find an article that explains this to my ability to understand it.

    I want to buy a cheap amp to use between computer and a pair of DT-990 PRO 250 ohms.

    Actually in this setup:

    Computer to GSX 1000 to New Amp to DT-990

    The GSX1000 is recommended for max 150 ohm headphone.

    I have alredy spent 25% of my monthly income on sound for gaming. So I really need something cheap and good enough.

    I have found some 4 port headphone amps very cheap 20-40 usd.

    Which specs will an amp need to have to drive the DT-990
     
  2. Apatride
    The short version is that if your DT-990 are loud enough for your taste, you do not have to get an amp. Now some people are going to disagree with me here, but I believe that even on easy to drive headphones, the amp can make a difference. My HD-25 sounded much less messy on some busy mids song after I switched the amp of my Fiio X7 for an AM5.
    In this budget, I d go for Bravo Audio if you want something out of the ordinary, otherwise, most Fiio amps will work (I really like my E18 and you can use it with almost any device, including Chromebooks), Creative Labs also have interesting options like the E5 (that I have) but you might as well sell your GSX1000 if you go down that road.
     
  3. Andrey2019
    Hi!

    I also have a GSX 1000 device and sometimes need to connect more advanced headphones to it (like Audio-Technica ATH-R70x - 470 Ohm).

    I use Fiio A5 and I think it is quite cool device. It is relatively cheap (about 100-150$). And as it is small and mobile - you can connect your headphones to any device (player/notebook/phone etc.) that you want.
    And also I really enjoy sound quality while using headphones with this amp.

    So I could recommend this standalone mobile amp. :)
     
  4. yong_shun
    You can consider Creative Sound Blaster X5 or G5. Should not be a problem to drive headphones up to 300 ohms :)
     
  5. ProtegeManiac Contributor
    Easiest way to over guesstimate (that way you'd have some headroom): look at teh sensitivity of your headphone, that's what you get at 1mW given a clean 2V input signal to the amp; for every 3dB step you need to double the previous power input to the headphone amp; work your way up to 120dB (or as close as possible to it). That's the power you'll need including headroom (because you're not literally going to listen at 120dB, even with peaks; gain is also a factor), now find an amp with the lowest THD+N or THD and highest SNR that you can afford that makes that much power at the nominal impedance of your headphone. And if your headphone happens to have a nominal impedance below 250ohms, make sure the output impedance is also low (not a common problem nowadays save for OTL tube amps, which isn't a problem unless you plan on getting low impedance headphones).

    So basically you'll need, very roughly, ~256mW at 250ohms. Now look up amps with around that level of power output and then compare them for the lowest distortion and noise levels.


    Those headphone output distribution amps aren't going to be a lot better than the amp chip on the GSX. They're not exactly like the Schiit Asgard for example with a lumpy power supply surrounded by fat capacitors. Magni3 doesn't need those but it's still an amp circuit with a lot of power and comparatively low noise. On top of that, I'm not even sure the Speaker Out on the GSX1000 is a line level output which is what you need to hook up an amplifier to or if it's a preamp output so you can control the speaker volume from it, so in case it's the latter, it isn't exactly the most ideal DAC for a separate headphone amp.
     
    JediMa70 and PaganDL like this.
  6. PaganDL
    @ProtegeManiac,

    As always, well said.
    Hard to go wrong with this good advice but yes...before anyone says, you never know :)


    @devilduck,

    I agree with @ProtegeManiac regarding the cheap headphone output distribution amps in that price range where for what you need isn't going to make a lot of difference. Though I will say if you willing to spend on something a bit better like Presonus HP 4 if you're still after that kind of distribution system, you will get a decent sound output if your source is good.
    I use the HP 4 myself though more as a inexpensive pass through option rather than a dedicated head amp though I do like the head amp function.
    The GSX amp chip shouldn't be a problem but unless you really need it, I suggest working out what you need via the specs first then go from there.

    Hope you have a great day !
     
  7. devilduck
    Wow - those are the most helpful and precise advice I’ve ever gotten on the inter webs:)

    Kind of wishing I asked before buying :)

    I haven’t received the GSX yet, but if it isn’t powerful enough I will get either one of the amps you suggested or maybe use a big full size amplifier (got a couple lying around) unless of course protegemaniac is right and I can’t.

    I’ be honest and admit I just thought I would connect the gsx to the new amp via the headphone output, use an amp inline between gsx and dt990?

    I can spend more money if I know it is necessary.

    Thanks for all the help - I’ll read through the math part a couple of times
     
  8. ProtegeManiac Contributor
    You can connect it that way and it will still work in the sense that you'll get some sound and louder.

    The problem is that since it goes through the GSX's amp circuit that will already add some noise (and even distortion) to the signal. Your problem there is two fold. First, any amp, even the absolute best ones, will add noise, and will have a little bit of distortion when driving speakers or headphones, which means any amp after it will add more. Second, the signal it's working with already has noise and probably distortion, which means that even with a very low noise, low distortion amp, the signal is already screwed up.

    Of course, you may not necessarily be able to hear the difference, but then again, what's the point of spending a lot of money on the amplifier other than to just make it louder? Chances are switching to very high gain on the GSX might be enough to do that anyway.


    The more money you spend just on the amp, the lower the distortion and noise for the amount of power you can get out of them, but even if these won't add that much noise and distortion that might make the possibly noisy signal audibly worse (or have the distortion compliment each other like a very roundabout way of applying an equalizer), what will happen is that the amplifier's clearer sound with more power just make the distortions and noise in the incoming signal even more audible.

    Now that might not immediately be apparent to you compared to say how I test systems by hitting Play, then Pause, then crank up the volume and then give up on the whole thing if any noise is audible before I even reach 12:00 on the dial, but the thing is, if you can't hear that difference anyway, chances are that other than the possibility of increased output (and that assumes the GSX1000 doesn't have a very high gain mode as on Asus soundcards), you won't notice any other difference over the GSX either.

    Basically if you need a soundcard for gaming, your options are:

    1. Get a high power, low output impedance soundcard like the SB AE-5

    2. Get a soundcard that costs less but has a fixed level line out, like the ZX or ZXR, to hook up to the amp

    3. Get a soundcard that costs less but has an optical output, and hook it up to a DAC-HPamp or to a DAC that you will hook up to an amp

    I'd really recommend just going with the first option if you're not too deep into audio just yet. It's a simpler set up (unless Creative starts screwing around with no driver updates again) and you'll practically get performance on par (ie meaning you're not doing the same noise tests as I do and comparing how the percussion sounds like on one amp vs another on the same headphone) with many amps until you get to the level of, say, a Meier Classic FF, Violectric V281, WooAudio WA6, etc.
     
  9. devilduck
    The reason I went with the GSX 1000 was because I heard a lot of people, here and on YouTube, say that the virtual surround actually works pretty good.
    I really like positional audio, but I am surprised how much better the games I play actually sounds “just” from my DT990’s and a big heavy Onkyo amp/receiver on pure audio setting. All the little details and texture that I was missing before, I think buying a pair of good headphones, at least for me, was a bigger upgrade than going from a GTX 970 to a 1070ti or from 69Hz to 144Hz :)

    I will just use that Onkyo amp if I keep the GSX1000, what I can gather from what you are saying is that my setup won’t be ideal. So why spend more money.

    The GSX does not output VSS (Virtual Surround Sound)through line out, so I would go through headphone jack and as you say that necessarily entails some drawbacks.

    If the GSX doesn’t work out will send it back and get the pci-e solution you mentioned.

    That was the initial plan. But my motherboards pcie-e layout makes it a challenge.

    I had an SB x-if pci card, but it wasn’t compatible and getting rid of the driver was pretty annoying. I also have a Creative Sound Blaster X-Fi SB0460 pci (not e) if any one knows if that is any good. I read reviews but they were very uninformative
     
  10. ProtegeManiac Contributor
    It's great for that, just not for hooking up an amp. Which is why I'd take the sensitivity and response of any headphone I'd use with it into account.

    I'm using a Superlux HD330 with my Xonar U3. Sensitivity seems low at 93dB/1mW, but that's measured at 1000hz; its response at 40hz to 120hz is well above where it is at 1000hz, so at least I don't really have to crank it up just to hear the low frequencies. Using it mostly for Dolby Headphone at max space setting. The U3 can send out an SPDIF signal but I didn't really bother with that from the start.


    That would be your best move at this point other than getting a different soundcard.


    Other soundcards that have a line output can, although the first ones have a software limitation that doesn't send out Dolby Headphone via the FL/FR line output so they can't be used with amps. AFAIK these were fixed years ago. around the time the outgoing models came out, but not sure about the GSX1000.


    You can just get a Xonar U3 and use its 3.5mm to toslink adapter to hook it up to something like a Modi3, then hook that up to something like a Magni3.
     
  11. devilduck
    ok so I just got my GSX 1000 - and it sounds like crap on both Phillips SHP 9500 and DT990.....

    The SHP9500 are 32 Ohms and it can't even drive them, I am so disappointed right now.

    Tried it directly with both cans and it just just lacked the low end. It sounded tinny and the highs were grating my brains out.

    Also tried double amping and that brought back the bass but it sounded like reverb and just really really bad....

    The positional thing works, when sounds are coming from behind you it sounds like it is actually behind you.

    Don't know wether to get my money back or keep it and find some headphones that work with it.

    There wasn't any noise when no sound was being put through, but it sounded hollow and cave like. I turned the reverb off, in fact I turned everything off except the 7.1 function, then I tried the eq settings but nothing made it anything other than horrible sounding. And I am not experienced in audio, my ears are not finely tuned to pick up small imperfections.

    Later today I will try them with some gamings headsets and some Jabra and Phillips bluetooth headphones via jack, to see what they sound like on less good headphones
     
  12. Apatride
    What you are describing sounds a lot like what I experienced when using a line-out instead of headphone out on a previous system. You might want to look into this.
     
  13. ProtegeManiac Contributor
    Impedance almost exclusively only affects power delivery, and there's always a trade off. Very generally higher impedance is a consequence of designing a driver with higher efficiency without making as many trade offs in the response curve - look at how the HD580/600/650 and K701/702 are mostly comparable in response width and curve (save for the relatively early roll off on the K701) but the AKGs have 62ohms and 93dB/1mW while the Sennheisers have 300ohms and 97dB to 98dB/1mW. Grados particularly the original and the "i" series don't make this trade off as they have 32ohms and sensitivity in the high 90s (the e-series is now at 99dB/1mW), but the curve is spiky and rolls off too soon (the upper bass boost is what makes them seem livelier than the K701, or any of the others for that matter). Obviously this doesn't apply as much to newer driver designs like the HE400S at 22ohms, 98dB/1mW, but even the HD660S has slightly lower sensitivity than the HD650 (they're gambling on how headphone amps nowadays won't have a problem due to high output impedance and have really high power output to offset that, but without getting too low to need totally beefy current delivery).

    What I would assume to be the main problem with the GSX is the output impedance because even Sennheiser's high end amps have high output impedance (something that they wouldn't really need to worry about if the amps were designed for the HD600/650 and HD800; and not as much even on the HD700 and HD660S), although usable power ie while it may not clip THD+N needs to stay well below audible range, is likely also a problem.


    Your speaker amps assuming they don't have those weaker separate output driver stage but controlled by the preamp circuits on the headphone output will have a lot better current and voltage delivery than most (not all) USB-powered amp circuits, particularly one that also has to run a DAC and DSP chip (assuming it even has a real DSP chip that does the processing and not a chip that the software will recognize when installed, but that software is t he actual DSP running off the CPU).


    Is it just with the speaker amps? Because to some extent the more positional audio you apply the more it will tend to sound like that since it's trying to sound like it's in a room but obviously you can't just override physics. This is why most DSP software and chips have variable levels of room simulation, but of course the minimal level practically just tries to not get all the audio locked deep inside your head.

    If those are HT receivers they might have their own DSP adding that reverb through the headphone output. Disable that on the receivers if they are.


    If it works well enough that sounds seem like they're coming from the rear the positional audio is probably set to max. See if there's a variable setting for it.


    Turn off the surround simulation. If it's only slightly better the analogue circuit is the problem. If it's vastly improved then it's the DSP setting, considering you can actually hear rear channels. See if it has a variable setting.

    That cave like sound is a natural consequence of trying to get around the physics of using two channels to sound like five, even worse in a dynamic environment and not for example an audio recording that was exclusively done to play on 2ch headphones instead of 2ch speakers.


    That depends on how much time you have to get a refund. Do you have time to order several headphones? If not might as well try a Xonar U3 and something like an AudioGD NFB-11, although if you do check if there are a lot of U3's that you can order within your country and order it when the NFB-11 gets there that way you won't run out of time to return it in case that's a problem (the NFB-11 will be coming from China unless you buy used from somebody near you).
     

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