[Meremoth]

Quote:

You could take a look at this chart
http://www.head-fi.org/t/668238/headphones-sensitivity-impedance-required-v-i-p-amplifier-gain
and then compare with the specs of the amp you want to get

 
 
I have no idea if I'm reading any of this correctly, but it looks like the LCD-3's take 2.5 W's into 48 ohms, maybe?  
 
As far as the amp, I have no idea how to interpret the specs, totally lost there.  Actually, I'm pretty much lost on the whole thing.  Maybe I can find an article explaining how to read the specs.  
 
 
[size=12.800000190734863px]

Manufacturer	Model	S@1V [dB SPL]	Z [Ω]	Voltage [V]	Current [mA]	Power [mW]	Gain [dB]

[/size] [size=12.800000190734863px]

Audeze	LCD-3	102	48	2.512	52.331	131.449	2

[/size]  
 
Amp specs: 
 

1. Frequency Response: +0.01, -0.01 dB (20Hz-20kHz)
2. THD 1 Khz 150 Ohms: 0.0016%
3. IMD CCIF 15 Ohms: 0.001%
4. IMD SMPTE: 0.002%
5. Noise (ref 400 mV): -105 dB
6. Max Output (33 Ohms): 613 mW
7. Output Impedance: 0.54 Ohms
8. Crosstalk (15 ohms): 65 dB
9. Channel Balance (max volume): 0.6 dB
10. Gain: 2.5x and 6.5x
11. Volume Potentiometer Taper: 15A or 3B
12. Case Dimensions (mm): 108.50 x 80.00 x 29.50 (excludes jacks)
13. Case Dimensions (inches) = 4.27 x 3.15 x 1.16" (excludes jacks)
14. Battery Run-time: 6-8 hours
15. Weight: 11 oz, with batteries 

 

[Brooko]

OK - so I'm pretty confused now.
 
I took mikeaj's advice, and conducted a little test tonight.  I used my Q701's and my DT880 600 ohm.  I don't have an SPL meter - so I had to carefully volume match as close as I could by ear.  I used iTunes with no EQ (I'd usually use Foobar - but I wanted to be as close as possible to the iPhone, so figured 'why not').  So was the test conducted using proper volume matching - no.  Was it sighted - yes.  Hardly convincing or scientific so far huh
 
Rather than use FLAC - I used aac256 for both set-ups as personally I can't tell the difference from lossless anyway.  I'll also add that I have low level permanent tinnitus - and definitely no golden ears.  I'm well aware of my personal deficiencies - and have no problem with the fact that my hearing is likely not as good as many who frequent these fora.
 
Anyway - I tried to use tracks that I know fairly intimately, and also some that highlight different parts of the sonic spectrum.
 
Set-ups were:
 

• PC (iTunes) > optical > NFB-12 > high gain and about 10-11 o'clock on the pot > DT880 600 ohm
  VS
  iPhone > DT880 600 ohm (volume at roughly 80%+)
   
• PC (iTunes) > optical > NFB-12 > high gain and about 9 o'clock on the pot > Q701
  VS
  iPhone > Q701 (volume at roughly 60-70%)
   

Again - all of this was done sighted, and I don't have a switching box - so it might have taken me about 5-10 seconds to switch between devices.
 
After a lot of testing 40-45 minutes my observations:
 

1. Bass on both headphones wasn't an issue - on either set-up.  It sounded pretty good actually - even on the 600 ohm Beyers via the iPhone.  Via the NFB-12, bass hit and definition was (to me) slightly better defined - but we aren't talking major (night and day) differences.  Surprised me actually.
2. On most of my modern music there didn't appear to be any issues with peaks (no clipping I was aware of)
3. Only issue I had was when I switched to classical and I started running out of headroom with some Tchaikovsky.  Had to turn the volume up with all set-ups, and with both iPhone set-ups I got audible distortion - guess this is clipping right?  On the NFB12 - I was at 1 oclock with the Beyers and about 11 oclock with the AKGs (both sounded fantastic on the desktop set-up).
4. AKGs in upper mids and treble lacked a certain 'something' in some tracks when unamped.  Hard to describe.  Not as clear / lively.  Wouldn't discount this being placebo though.  Again differences not large.

 
So now I have to eat my words from the previous pages - I'd love to go back and edit what I originally wrote, but I spoke up without volume matching previously - so I need to publicly admit how wrong I was.
 
 I think in a blind test properly volume matched - I'd be lucky to tell the portable from the desktop set-up on most tracks.  There is no huge deficiency in the music - and the only real issue is with music that requires more volume  - that the iPhone struggles to reach.
 
I must say - I now have an even bigger respect for both my iPod Touch and iPhone as a DAP.  I guess I'll still need either a small amp for Mum to go with the K701 and her classical - or a better player.  If she was into classic rock that wasn't too dynamic - I honestly wouldn't bother with an amp after what I've learnt tonight.
 
Anyway - thanks all for the help.

 

[xnor]

Quote:

 
I have no idea if I'm reading any of this correctly, but it looks like the LCD-3's take 2.5 W's into 48 ohms, maybe?  
 
As far as the amp, I have no idea how to interpret the specs, totally lost there.  Actually, I'm pretty much lost on the whole thing.  Maybe I can find an article explaining how to read the specs.  

Amp specs: 
 

1. Frequency Response: +0.01, -0.01 dB (20Hz-20kHz)
2. THD 1 Khz 150 Ohms: 0.0016%
3. IMD CCIF 15 Ohms: 0.001%
4. IMD SMPTE: 0.002%
5. Noise (ref 400 mV): -105 dB
6. Max Output (33 Ohms): 613 mW
7. Output Impedance: 0.54 Ohms
8. Crosstalk (15 ohms): 65 dB
9. Channel Balance (max volume): 0.6 dB
10. Gain: 2.5x and 6.5x
11. Volume Potentiometer Taper: 15A or 3B
12. Case Dimensions (mm): 108.50 x 80.00 x 29.50 (excludes jacks)
13. Case Dimensions (inches) = 4.27 x 3.15 x 1.16" (excludes jacks)
14. Battery Run-time: 6-8 hours
15. Weight: 11 oz, with batteries 

 
The impedance is about 48 ohms, and they take 2.5 volts (RMS) to reach about 110 dB SPL, or 131 milliwatts. (131 mW = 0.131 W)
 
 
The amp can output more (613 mW) into a more difficult load with 33 ohms. The O2 is a bit picky about gain, but if you run it with the wall wart and the ODAC you can calculate the max gain with 7/2 = 3.5x.
 
Even if you just use the low gain (2x) you will still get more power than you'll probably need: P = V^2 / R = (2*2)^2 / 48 = 333 milliwatts. (The 2*2 are the 2 V input from the DAC times the 2x gain.)
 
If you listen to dynamically compressed music you might even be fine with 1x gain. (From the table the recommended gain is about 2 dB, that's about 1.26x so very close to unity gain.)

 

[Joe Bloggs]

A nitpick: assuming constant voltage swing for different loads, the amp should output more power into a lower impedance load. From 613mW into 33ohms I calculated a max voltage swing of 4.5V, which would supply 421mW into 48ohms. Of course usable voltage swing should increase a bit with increasing resistance so this is a pessimistic figure. Still plenty enough.

 

[Meremoth]

So if I'm interpreting what you guys are saying correctly, the O2 has plenty enough power for the LCD-3's, yeah?  
 
As far as the gain is concerned, with the LCD-3 + O2/ODAC, do you recommend the stock gain of 2.5x & 6.5x?  If not, what custom combination do you guys think would be best?  
 
I don't understand DAC specs at all, but I'm assuming there shouldn't be any issues with the ODAC and LCD-3 either, correct?  
 

1. Freq. Response: +/- 0.1 dB
2. THD+N 100 hz 0 dBFS: 0.0029%
3. IMD CCIF 19/20 Khz –3 dBFS: 0.0011%
4. IMD SMPTE –1 dBFS: 0.0004%
5. Noise A-Weighted dBu 24/44: -102.8 dBu
6. Dynamic Range –60 dBFS A-Wtd: -111.1 dBr
7. Linearity Error -90 dBFS 24/44: 0.0 dB
8. Crosstalk 0 dBFS Line Out 100K: -93.5 dB
9. Maximum Output Line Out 100K: 2.0 Vrms

 

[miceblue]

Quote:

So if I'm interpreting what you guys are saying correctly, the O2 has plenty enough power for the LCD-3's, yeah?  
 
As far as the gain is concerned, with the LCD-3 + O2/ODAC, do you recommend the stock gain of 2.5x & 6.5x?  If not, what custom combination do you guys think would be best?  
 
I don't understand DAC specs at all, but I'm assuming there shouldn't be any issues with the ODAC and LCD-3 either, correct?  
 

1. Freq. Response: +/- 0.1 dB
2. THD+N 100 hz 0 dBFS: 0.0029%
3. IMD CCIF 19/20 Khz –3 dBFS: 0.0011%
4. IMD SMPTE –1 dBFS: 0.0004%
5. Noise A-Weighted dBu 24/44: -102.8 dBu
6. Dynamic Range –60 dBFS A-Wtd: -111.1 dBr
7. Linearity Error -90 dBFS 24/44: 0.0 dB
8. Crosstalk 0 dBFS Line Out 100K: -93.5 dB
9. Maximum Output Line Out 100K: 2.0 Vrms

Power-wise yeah the O2 should be just fine. DAC-wise it doesn't really matter. You can even get a Schiit Modi instead of the ODAC for less money.
 
I use the 2.5x/1.0x gain options. The 1.0x was enough for the LCD-2 I tried. *I tend to listen to music at low volume levels*

 

[xnor]

Quote:

As far as the gain is concerned, with the LCD-3 + O2/ODAC, do you recommend the stock gain of 2.5x & 6.5x?  If not, what custom combination do you guys think would be best? 

As I wrote above, O2's max gain before clipping with a wall wart and the ODAC is about 3.5x. The default high gain of 6.5x is meant for portable sources that output up to or below 1V like iPods.

 

[Meremoth]

The headphones I will be using are low impedance (at least I think they are) full sized headphones (AD900X & LCD-3).  

And if I understand what you guys are telling me, high gain settings are really only for portable sources and/or high impedance headphones, correct?
 
So, as long as I'm using the ODAC with the headphones mentioned above, a low gain setting should be fine?  The amp/DAC on your music source (PC, iPhone, TV, bluray/cd player) etc.) will be negated by the O2 + ODAC, correct?
 
1x/2.5x is a standard low gain option for the JDS Labs version, but they allow custom gains.  Do you guys recommend 1x/2.5x as my low gain option, or should I go with a more specific setting?  
 
And it seems 1x would imply an amp isn't needed at all, right?  But I assume, even on a 1x setting, the amp will still improve the sound quality of the headphones, correct?  
 
 
Thanks for all the help, fellers, I really appreciate it.  

 

[ab initio]

Quote:

The headphones I will be using are low impedance (at least I think they are) full sized headphones (AD900X & LCD-3).  

And if I understand what you guys are telling me, high gain settings are really only for portable sources and/or high impedance headphones, correct?
 
So, as long as I'm using the ODAC with the headphones mentioned above, a low gain setting should be fine?  The amp/DAC on your music source (PC, iPhone, TV, bluray/cd player) etc.) will be negated by the O2 + ODAC, correct?
 
1x/2.5x is a standard low gain option for the JDS Labs version, but they allow custom gains.  Do you guys recommend 1x/2.5x as my low gain option, or should I go with a more specific setting?  
 
And it seems 1x would imply an amp isn't needed at all, right?  But I assume, even on a 1x setting, the amp will still improve the sound quality of the headphones, correct?  
 
 
Thanks for all the help, fellers, I really appreciate it.  
 

 
The headphones you mention are listed here: http://www.head-fi.org/t/668238/headphones-sensitivity-impedance-required-v-i-p-amplifier-gain#post_9529378
 
2.5x should be enough voltage gain to get your LCD-3s up to dangerously loud volumes. The gain setting will specify how much voltage gain the amplifier can provide. In the case of lower impedance headphones, the voltage requirement isn't so much the problem, rather the current requirement becomes the limiting factor. Low quality amplifiers may lack the ability to source sufficient current to inefficient low impedance headphones. In the case of the O2, even at 1x gain setting where there isn't a change in the voltage in provides, it can provide a lot more current than a low quality headphone out. You also need to consider the output impedance of the amplifiers in question. When using low impedance headphones, it is usually preferable to have very low output impedance in the amplifier. Again, I believe the O2 offers sufficiently low impedance that it should play nicely with the headphones you mention. You should be fine with the 1x/2.5x option on the O2. Unless of course you want your headphones really really really loud!

 
Cheers

 

[uchihaitachi]

Quote:

The headphones I will be using are low impedance (at least I think they are) full sized headphones (AD900X & LCD-3).  

And if I understand what you guys are telling me, high gain settings are really only for portable sources and/or high impedance headphones, correct?
 
So, as long as I'm using the ODAC with the headphones mentioned above, a low gain setting should be fine?  The amp/DAC on your music source (PC, iPhone, TV, bluray/cd player) etc.) will be negated by the O2 + ODAC, correct?
 
1x/2.5x is a standard low gain option for the JDS Labs version, but they allow custom gains.  Do you guys recommend 1x/2.5x as my low gain option, or should I go with a more specific setting?  
 
And it seems 1x would imply an amp isn't needed at all, right?  But I assume, even on a 1x setting, the amp will still improve the sound quality of the headphones, correct?  
 
 
Thanks for all the help, fellers, I really appreciate it.  

I have the 2.5x ODAC and O2 as well as the LCD-3. 2.5 is more than enough

 

[Joe Bloggs]

I have the 2.5x ODAC and O2 as well as the LCD-3. 2.5 is more than enough

What I don't get though is why one would set two gain settings so closely spaced. If just going by volume knob travel, I'd be fine with full blast on low gain corresponding to 12 or even 10 o'clock on high gain. That would be like what, 1x and 12x?

Of course the question is whether the amp can take it, as it has to amp to the full multiplier before being attenuated by the volume control. As xnor mentioned the max gain before clipping with the ODAC is 3.5x. So how about 1x and 3.5x?

 

[uchihaitachi]

Quote:

What I don't get though is why one would set two gain settings so closely spaced. If just going by volume knob travel, I'd be fine with full blast on low gain corresponding to 12 or even 10 o'clock on high gain. That would be like what, 1x and 12x?
 

I never understood either....

 

[xnor]

2.5x = about +8 dB
3.5x = about +11 dB
 
so it's not an earth shattering difference.
 
The high(er) gains are only useful for weaker sources like DAPs. If you don't use such devices or have headphone with high sensitivity or listen at lower levels you don't need high gain.
 
 
1x and 2.5x are not far apart, I agree, but most amps don't allow gain to be configured to lower than unity gain (ODA project @diyaudio makes this possible iirc) so you could have something like 0.5x (= -6 dB) for low-impedance/high-sensitivity cans and 2.5x for the rest.

 

[ProtegeManiac]

Quote:

Originally Posted by xnor /img/forum/go_quote.gif
 
The high(er) gains are only useful for weaker sources like DAPs. If you don't use such devices or have headphone with high sensitivity or listen at lower levels you don't need high gain.

 
It also depends on the amp settings. With the 70x cans I can push my amp to full at default (low) gain, which is -10db, and it's not blowing my eardrums off; normal listening with the HD6xx/800 is around 12:00 to 1:00 on the dial, on the SR60/225/RS1 it's around 10 to 11; Westone 2 at around 10:00 too. This default low gain is -10db, with "high" gain at 0db attenuation. After trying this out and not having any Grados, or IEMs that would need it, I set it to "high" gain and left it there permanently (internal jumpers, no external switch - yeah, I know, bummer). Input signal BTW is USB, and AFAIK, the USB DAC outputs close to 2v, since perceived levels aren't too far from a regular CDP when I tried it out (chances are the perceived loudness of it may be more because of the more solid "slam," as NAD calls it, on the 545).