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post #151 of 771
I would have to say NO, the 400 ohms is just way too high and the voltage requirements for those phones is too high.

It is not so much a matter of Watts, but what is important when driving high impedance headphones is the voltage output of the amplifier.

To drive high impedance loads like 400 ohm headphones you have to deliver higher voltage to get the power to the phones.

The MARK IV can deliver 150 mWatts into 16 ohms.

Doing a little math the MARK IV will put out 1.55 Volts RMS.

The voltage output of amplifiers doesn't change much throughout an amps rated load range ie 16 - 10,000 Ohms for the MARK IV.

Now with 2 Watts RMS into 400 ohms, you'd need 28 Volts RMS.

The math doesn't lie.

You need one heck of an headphone amplifier to drive those phones to 2 Watts.

In fact most Power Amplifiers that drive 8 ohm speakers put out around 28 Volts so you could probably run those phones directly from a small power amplifier.

If you do do this, you are doing so at your own risk!!!!

But it is very hard to drive 400 ohms and get any kind of power without high voltage amps.

For sure battery powered headphone amplifiers could not drive them UNLESS the headphones are VERY efficient, but it sounds like they are not.

The MARK IV would put out 6 milliWatts into a 400 ohm load, 75 milliWatts into 32 ohms, and 150 milliWatts into 16 ohms... see the pattern.... for every double the impedance (ohms) you get half the power.

If your headphones were 119 dB per milliWatt then they would work, but my guess from what you've said is that they are much lower efficiency.

hotaudio40
post #152 of 771
Quote:
Originally Posted by hotaudio40 View Post
In fact most Power Amplifiers that drive 8 ohm speakers put out around 28 Volts so you could probably run those phones directly from a small power amplifier.
I've got two old Beyerdynamic DT-100's (400 Ohm) at a thrift.

Would it be possible to in any way damage the amp by driving these directly from the speaker outputs of a e.g. a 40wpc/8Ohm amp?
post #153 of 771
You'd be far more likely to damage the headphones...

If you start with the volume at zero, and work your way up to a comfortable level...

Most, if not all commercial amplifiers have fuses in them or some sort of protection.

I'm 99.9% sure you could do that without damaging the amp.

But I make NO recommendations that you try!

And if you do try, YOU DO SO AT YOUR OWN RISK!!!

Please let us know how it goes.
post #154 of 771
I've got a bunch of old low-wattage amps picked up at fleamarkets and such, so I'll try it out one of these days. Thanks for the tip!
post #155 of 771
thank you, others also suggested the desktop amp, I will try it with a Sonic Impact T-amp after balance mod...

the specs are:
Transducter Types: Dynamic moving coil low-frequency system; Fixed-charge electrostat high-frequency system
Frequency Range: 16 Hz to 25000 Hz
Crossover: 4000 Hz, 6 dB/octave
Nominal Impedance: 400 ohms, each channel
Sensitivity: 1.6 Pa/volt
Normal listening level requirements: 0.64V (1mW) for 94bB SPL (approx. 1 Pa), „IHF Sensitivity” rating 0.5V (63mW) for 112dB SPL (approx 8Pa)
Sound Pressure Level for <= 1.0 THD: 104dB (200 to 2000Hz)
Maximum Continuous Input (per chan.): 9V (200mW) approx. 117 dB SPL
post #156 of 771

A little more testing

So I've had the HotUSB1 for a few days now and am back in my apartment. I haven't been keeping an exact count, but I'd venture the DAC has at least 30 hours (probably closer to 40, but I would rather under than overestimate) on it. Since I'm not getting any work done (I swear, my book will be finished in 09--if I can't get these last few chapters done in a year I'm switching careers ) I figured I might as well A/B this DAC with my onboard. And remember, all of this is in my inexpert opinion.

Listening with:
Foobar w/ ASIO > Onboard 'Sigmatel HiDef' sound / HotUSB1 > Ultrasone HFI 2200. Volume at normal "active" listening. Both songs are MP3s @ 320k

The short version:
If you're using a laptop buy yourself an external dac. That's all. I don't care if you buy this dac (though, at its price point I doubt you'll beat it) or something else. Really, just do it.

The long version:

First song: Pain of Salvation - Used, track 1 from the Perfect Element

Onboard:
Immediately (as the song opens with some loud chords) I'm hit with some harsh guitars. The bass guitar sounds a bit thin. Highs sound brittle. There's a bit of distortion going on towards the end of the opening. I get some glaring distortion (this time from the cymbals) at 1:05. In the "Getting used to pain" pre chorus there's more distortion on both the low and high ends of the spectrum. By this point I really, really want to stop using the onboard sound--and there's still 4 minutes left to sit through!

The guitar solo @ 2:40 starts out promisingly, as the song relaxes a bit here. As the rhythm section gets busy again and the backing vocals enter (starting softly with a build) the onboard goes to hell. I start hearing cymbal distortion and a general lack of definition. The end of the song isn't terribly offensive, but if you made it this far I have pity on your ears.

HotUSB1:
The intro is handled with much more class, it doesn't feel like I'm being beaten over the head with a loud guitar. The music is pushed back a little bit, no obvious distortion occurring. The bass guitar is clearer, the highs more realistic/live sounding. The distortion at 1:05 is gone, as it the pre-chorus distortion. Drum dynamics feel much better--that might be just in my mind, but since the HotUSB1 has a better bass response I don't think so.

There are some small keyboard details pre 2:40 solo that are much clearer on the HotUSB. Again, the solo sounds great, but this time the drums/backing vocal build doesn't distort. Again, the increase in drum detail here (due to the lack of distorting drum cymbals) is quite nice.

Song 2: Agalloch - A Desolation Song, track 9 from The Mantle

Onboard sound:
Something different: acoustic guitar, accordion, mandolin, and whispered (ish) vocals only. No drums to get distorted, my ears are thankful .

Much nicer this time around. The guitar is very much upfront. Accordion feels a little buried, the whisper/croak of the vocals are a bit too close, so it sounds more like he's whispering in my ear. The mandolin sounds nice, if also slightly buried. Overall, I can't really complain about this onboard audio's presentation of this song--it doesn't do anything glaringly wrong.

HotUSB:
The accordion sounds more balanced with the guitar through the HotUSB. Or rather, the guitar is pushed back a bit, as are the vocals. There's more air through the external dac. Again, the mandolin sounds nice, and a bit more forward--it's actually a little more discernible during the 2nd verse under the vocals. The effects at the end of the song sound a bit more full, too.

The differences between onboard and the HotUSB are much less dramatic for this song, however, the HotUSB is still better--if I was casually listening I probably wouldn't notice, but paying attention I feel that I could pick out the HotUSB in a blind test.

I'll stop it here, as I feel it'll simply get redundant. David's HotUSB1 is a nice step up from onboard sound. Are there better DACs out there? Sure, but you can't buy them for $50. For a first/budget/laptop setup the HotUSB1 makes sense. Don't expect miracles, but then again, it changed an unlistenable Used into something quite nice for me.
post #157 of 771
Hi to all, specially to Dave!

It looks like this is the first post of 2009 here, so... HAPPY NEW YEAR to everyone!

Well, just to tell another HOTUSB1 is on his way (to Madrid, Spain). With the actual rates and the free shipping offer, it cost me just 50 euro and I wanted to have some alternative for the M-Audio Transit I use at office so...
post #158 of 771
I plan on getting one from him really soon too josep so hurry up and give us a review when you get it

And happy newyear!
post #159 of 771
I also just ordered a HotUSB1. I asked Dave a question before I bought it, and he answered promptly. I bought the amp off ebay at 12:05 AM. At 12:21, I received an email from Dave saying the item was ready to ship and would be out the next morning. I have to say, I've never experienced service this good.

Oh, and by the way, I really applaud your efforts to answer questions here on Head-fi. This is a great resource, and reading through the thread answered a lot of questions that I would have asked you.

Keep it up, Dave!
post #160 of 771
Quote:
Originally Posted by graj08 View Post
I bought the amp off ebay at 12:05 AM. At 12:21, I received an email from Dave saying the item was ready to ship and would be out the next morning. I have to say, I've never experienced service this good.
1+

I received Dave's email saying "it will ship today" 20 minutes after completing the ePay buy. Guys, it is january 1st. Astonishing. It deserves a great success.
post #161 of 771

Noob DAC question

Sorry for my ignorance, but does the DAC convert all formats to analog, or only lossless files?
For example, I use iTunes on my computer which has mostly lossless and 256 aac VBR files. Would this DAC convert both formats to analog?
post #162 of 771
Yes.
post #163 of 771
Well first of all Happy New Year to everyone

And this is by far the best forum out there for anyone looking at headphones or other audio related equipment.

Everyone on here seems very honest, open, and helpful!

I really enjoy this stuff as much as you guys all do, but it is your enthusiasm which fuels me to work even harder

I really enjoy reading the feedback and the different articles on here and elsewhere!

If you guys are happy with my products then I am more then happy to make them for you!

Here's to a great upcoming year for all !!!

hotauido40
post #164 of 771
Quote:
Originally Posted by peanuthead View Post
Sorry for my ignorance, but does the DAC convert all formats to analog, or only lossless files?
For example, I use iTunes on my computer which has mostly lossless and 256 aac VBR files. Would this DAC convert both formats to analog?
The DAC really has no idea what format or codec the source file is using. That's the job of the software player on your PC (in your case iTunes). The software player reads the format and sends the data out the USB port to the DAC. The DAC builds the analog signal. As long as your PC can see the DAC as an audio output device you are good to go. I can tell you that on my XP system, the hotusb1 was recognized with no additional drivers - it was literally just plug 'n play.
post #165 of 771
Thanks!
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