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**Hifiman HE-400 Impressions and Discussion Thread** - Page 1027

post #15391 of 21783
Quote:
Originally Posted by money4me247 View Post
 

cable twisting question. hey anyone else notice having to screw in the cable causes the cables to have a lot of tension & the cable gets all twisty? i'm just worried about the long-term stress of having the cable all strainy-twisty like that.

 

Yes, after owning the HE400 for almost a year I have realised why people say the cable connectors are a bad design.

post #15392 of 21783

Quote:

Originally Posted by nicholars View Post
Quote:
Originally Posted by money4me247 View Post
 

cable twisting question. hey anyone else notice having to screw in the cable causes the cables to have a lot of tension & the cable gets all twisty? i'm just worried about the long-term stress of having the cable all strainy-twisty like that.

Yes, after owning the HE400 for almost a year I have realised why people say the cable connectors are a bad design.

 

**solved!** you just twisty your cable the other way 3 times before you screw em in! hahaha... imma genius =P

post #15393 of 21783

Hey guys, I have a quick question that I would really appreciate a solid explanation to! 

 

I saw the following quote on a forum:

Quote:
The Bravo amps are suitable for high impedance and low efficiency headphones only.
The HE-400 won't work well with the V3, as they are low impedance, high efficiency headphones.

The poster then goes on to recommend the Little Dot 1+ as it "can handle low impedance, high efficiency headphones." I was wondering how true those comments are. I compared the specs for both amps & their impedance, and they appear about the same to me. Am I missing something?

 

Bravo V3: Out-Put Impedance: 20~600 Ohm

Little Dot 1+: Suitable Headphone Impedance: 8 - 600 ohms [Note: they do NOT state the actual output impedance]

HE 400: Impedance: 35 Ohm, Sensitivity: 92.5 DB

 

If someone can answer this question, it would be much appreciated! :) I am also wondering how would you go about matching the headphone impedance w/ the amp impedance... it just needs to be within that range right? I would love to hear a more technical explanation of all the specs :normal_smile : thanks & cheers

 

Bravo V3 full specs (Click to show)
In Put Power DC24V
Input Sensitivity 100mV
Input Impedance 100KOhm
Out-Put Impedance 20~600 Ohm
Gain 30dB
Frequency response 10Hz-60KHz +/- 0.25dB
Signal/Noise Ratio >90dB
Dynamic range 84.6dBA(300 ohm) 89.8dBA(33 ohm)
THD 0.016%(300 ohm) 0.45%(33 ohm)I
MD + Noise: 0.045(300 ohm) 0.42(33ohm)
Dimension 79mm (D) X 130mm (W) X 44mm (H)
Input Stereo RCA x1, Stereo 3.5mm x1
Output Stereo 6.35mm x1

 

Little Dot 1 Full Specs (Click to show)
Frequency Response: 10HZ - 50KHz (-3 dB)
THD+N:
0.2%: 1Vrms @ 1000Hz
0.6%: 3Vrms @ 1000Hz
1.0%: 5Vrms @ 1000Hz
Signal-to-Noise: 92dB
Suitable Headphone Impedance: 8 - 600 ohms
Input Impedance: 50K ohms
Power Output:
150mW @ 300 ohms
300mW @ 120 ohms
800mW @ 32 ohms
User variable gain settings: 6.5x or 3.25x
Power Consumption: 15VA
post #15394 of 21783
Quote:
Originally Posted by nicholars View Post
 

 

I cannot be bothered to argue with you because it has been said 100000x on these forums but most "AV receivers" like you said, have cheapo high ohm headphone chip amplifiers, not connected to the main amplifier with a resistor. I researched it myself and tried various ones myself... The key is you said "AV receiver" which typically do not have good headphone jacks. Yours might... I do not know... But either way it is not very good advice, stop making misleading one liner comments and there will be no problem.


Have you read through this thread?

http://www.head-fi.org/t/338299/many-av-receivers-stereo-integrated-amps-do-not-use-opamp-powered-headphone-jacks

 

Lots seems to be said on many subjects that is not necessarily accurate for all cases.

post #15395 of 21783
Quote:
Originally Posted by money4me247 View Post
 

Hey guys, I have a quick question that I would really appreciate a solid explanation to! 

 

I saw the following quote on a forum:

The poster then goes on to recommend the Little Dot 1+ as it "can handle low impedance, high efficiency headphones." I was wondering how true those comments are. I compared the specs for both amps & their impedance, and they appear about the same to me. Am I missing something?

 

Bravo V3: Out-Put Impedance: 20~600 Ohm

Little Dot 1+: Suitable Headphone Impedance: 8 - 600 ohms [Note: they do NOT state the actual output impedance]

HE 400: Impedance: 35 Ohm, Sensitivity: 92.5 DB

 

If someone can answer this question, it would be much appreciated! :) I am also wondering how would you go about matching the headphone impedance w/ the amp impedance... it just needs to be within that range right? I would love to hear a more technical explanation of all the specs :normal_smile : thanks & cheers

 

Generally, for low impedance headphones like planars, you want as close to zero output impedance as possible. Less than 1 ohm is good.

 

With those two amps you mentioned, the Bravo doesn't specify an output power at all and has a high output impedance (not good), the Little Dot has 800mW @ 32 ohms (should be enough), however, it doesn't specify an output impedance at all. If its high, it won't provide enough current which planars love (before it voltage clips). Personally I wouldn't get either of them. If you want one in the $100 range, get something like the magni.

post #15396 of 21783
Quote:
Originally Posted by mlxx View Post
 
If its high, it won't provide enough current which planars love (before it voltage clips). 


I don't think this is accurate, at least without qualification... Are you saying that amps with a high output impedance, by design, cannot deliver enough current to drive planars? Vintage receivers are doomed to voltage clip? All that matters is how powerful the amplifier is. I know I'm the odd one out for using a speaker amp with resistors, but this setup is essentially the same as many receivers. And it doesn't clip because there's a lot of power. My CMOY had an output impedance close to 0 ohms, and it clipped really easily with the HE-400. Probably because it didn't have enough power. 

EDIT: I'm not debating that the output impedance of an amp forms a voltage divider. All else equal, a given amp will have less power if its output impedance is increased. However, output voltage can be as high as you want at any given impedance as long as source voltage is high enough. 


Edited by manbear - 12/21/13 at 1:07pm
post #15397 of 21783
Quote:
Originally Posted by manbear View Post
 


I don't think this is accurate, at least without qualification... Are you saying that amps with a high output impedance, by design, cannot deliver enough current to drive planars? Vintage receivers are doomed to voltage clip? All that matters is how powerful the amplifier is. I know I'm the odd one out for using a speaker amp with resistors, but this setup is essentially the same as many receivers. And it doesn't clip because there's a lot of power. My CMOY had an output impedance close to 0 ohms, and it clipped really easily with the HE-400. Probably because it didn't have enough power. 

 

 

I am saying that particular amp that I was talking about with a high output impedance and only barely enough power probably will. That's why I was referring to the output impedance in combination with the power output. As we spoke about before, a speaker amp is a different kettle of fish. It needs the resistor in there for protection or it has enough power to damage headphones.

 

Quote:
Originally Posted by manbear View Post

 

EDIT: I'm not debating that the output impedance of an amp forms a voltage divider. All else equal, a given amp will have less power if its output impedance is increased. However, output voltage can be as high as you want at any given impedance as long as source voltage is high enough. 

 

Sadly headphone amps don't have an endless supply of voltage, usually its about 10V (more for balanced). If you have a high output impedance you will be wasting it and it will clip faster.


Edited by mlxx - 12/21/13 at 1:36pm
post #15398 of 21783

Ok, returning to the Little Dot 1+, it uses op amps for voltage amplification and its recommended headphone pairing range is "Suitable Headphone Impedance: 8 - 600 ohms," so I think its safe to guess that it has a low output impedance. 


I took your statement somewhat out of context, but still, if someone likes the sound of a particular high impedance amp, the high impedance isn't necessarily a problem. One can afford to waste some voltage in many cases. Maybe the amp will get loud at 1 o'clock instead of 9 o'clock. Doesn't matter.

As long as an amp doesn't clip, there is no reason that an output impedance of less than 1 ohm is preferable for the HE-400. The 1/8th rule is pointless when the impedance is flat with respect to frequency. You just need enough power (not even that much, really). A 10 V headphone amp could have an output impedance of 130 ohms and still put out ~120 mw, which is what I am getting from my 20 V amp and 300 ohm resistors. It doesn't clip at any volume I can stand. 

For a 10 V headphone amp going to the HE-400, what is gained by having an output impedance of <1 ohm versus 130 ohms? The only thing I can think of is that you could play at unsafe volumes without clipping... I guess that's important for some? IDK. 

post #15399 of 21783

Well there is more to it than just being loud enough. A headphone can be loud enough but still sound like crap because it isn't being driven well, even if it doesn't clip (that is not to say that everything with a high impedance will sound like crap but with planars its more likely the case). If you have a high output impedance the amplifier will struggle more to supply the current into a low impedance, that is just a fact. Also, planars have a flat impedance response as you said. When they say "Suitable Headphone Impedance: 8 - 600 ohms", a dynamic headphone could be specified as "8 ohms" (they usually specify only nominal impedance) but it could have a lot lot higher impedance over the frequency range so it might drive those well but it doesn't follow that it can drive say an 8 ohm planar well that is always at 8 ohms. Going for less than 1 Ohm is a good rule of thumb, my amp has 2 Ohms that doesn't mean I should throw it out.

post #15400 of 21783

I don't have any problems with low output impedance, but restricting oneself to low output impedance rules out a lot of amps that one might enjoy. Like Vali over Magni, or most any vintage receiver, for example.

Wouldn't an 8 ohm planar be easier to drive than a 35 ohm planar? Or a dynamic with impedance greater than 8 ohms at certain frequencies? Sensitivity being equal of course. The LD 1+ seems to have more power into lower impedance loads... Anyway, most devices with opamps in the output stage,  such as the 1+, have very low output impedance due to the impedance of the opamps. 

post #15401 of 21783

Never always easier; always different.  A pair of speakers that are 4Ω are usually harder to drive than ones that are 8Ω.  You need more and more current the lower the impedance.

 

Head-fi member Purrin has been having problems finding the right match for the new 16Ω Audezes.  He likes Vali in general but doesn't like it with the new Audezes.


Edited by TMRaven - 12/21/13 at 3:33pm
post #15402 of 21783
Quote:
Originally Posted by manbear View Post
 


Wouldn't an 8 ohm planar be easier to drive than a 35 ohm planar?

 

No.. not for a high impedance amp, its harder, that's the whole point.

 

Vintage amps have enough power to send headphones to hell (and your ears) so they will work fine as they do.

With regards to the LD 1+, I have no idea what its output impedance is so I don't know.

If a headphone amp has a higher impedance than the headphones themselves, (for low impedance planars)  then for sure start looking at something else. Things are not always straight forward, sometimes its a suck it and see approach.

post #15403 of 21783
Quote:
Originally Posted by mlxx View Post

 

No.. not for a high impedance amp, its harder, that's the whole point.

 

Vintage amps have enough power to send headphones to hell (and your ears) so they will work fine as they do.

With regards to the LD 1+, I have no idea what its output impedance is so I don't know.

If a headphone amp has a higher impedance than the headphones themselves, (for low impedance planars)  then for sure start looking at something else. Things are not always straight forward, sometimes its a suck it and see approach.


Your comment about 8 ohm planars was in reference to the Little Dot 1+, if I read your post correctly. The Little Dot has more power as headphone impedance decreases, at least down to the 32 ohms in the published specs. I suppose that whether that trend continues into lower and lower impedances depends on the output impedance of the amp. I don't know its output impedance either, so it's pointless to continue talking about. But I am not debating that an amp will become less efficient once headphone impedance is less than output impedance. That is obvious. 

The issue is that one shouldn't always "for sure start looking at something else" when that happens. We have been over the exceptions. 

 

post #15404 of 21783
Quote:
Originally Posted by manbear View Post
 



Your comment about 8 ohm planars was in reference to the Little Dot 1+, if I read your post correctly. The Little Dot has more power as headphone impedance decreases, at least down to the 32 ohms in the published specs. I suppose that whether that trend continues into lower and lower impedances depends on the output impedance of the amp. I don't know its output impedance either, so it's pointless to continue talking about. But I am not debating that an amp will become less efficient once headphone impedance is less than output impedance. That is obvious. 

 

The issue is that one shouldn't always "for sure start looking at something else" when that happens. We have been over the exceptions. 


I was just pointing out that just because it says it works down to 8 Ohms (as you had said) that doesn't mean it will necessarily work with 8 Ohm planars (or 32 Ohm planars for that case). I can't be exact about the LD, I don't know its specs, so I was just giving an example as to why it would say that in the specs.

 

Also just because it has its max power at 32 Ohms in the specs doesn't mean all will be fine. Depends how much current it can supply. You can have lots of voltage and very small current and still measure lots of power but that is not ideal for planars.

 

It also starts to get less efficient after the amp output impedance is >0. It gets really bad after its greater than your headphones impedance.
 

If you want to get amps whose main job is to to heat up resistors (because that is what will happen) by being mismatched, go for it. Sure the Emo can do it, but most headphone amps can't.


Edited by mlxx - 12/21/13 at 6:02pm
post #15405 of 21783

@mlxx & @manbear & @TMRaven,

 

thank you all for the interesting information. i don't think i necessarily completely understand everything that was said so far, but i found the entire discussion very helpful to read.

 

I haven't noticed any sonic issues when pairing my HE400 w/ my Bravo V3 tube amp, so I am satisfied. Was just a bit worried that I was missing out on something if my amp was inadequate. Perhaps I will try a different SS amp in the future to see if that is the case.

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