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Review: JDS Labs O2 (Black edition) + O2/ODAC discussion - Page 10

post #136 of 498

If you dont plan on using the batteries, remove them.

 

Batteries like to be charged and discharges over and over and over.....

 

Alex

post #137 of 498

I just purchased a used jds o2/odac combo from someone and I love it but I'm having one issue with it. With some of my higher sensitivity headphones, the volume out of the O2 is simply too much except at very low levels on the volume knob. The problem is that at very low levels the volume pot gives me very uneven volume. By the time I get to where it sounds normal, it's at the absolute limit of how loud I would want to listen. Is there anything I can do about this without changing the gain? It has the default 2.5/6.5 gain on it. I wouldn't really like to change that since I have a wide variety of headphones and the higher gains could be useful to me. Is there a different volume pot that I could use that wouldn't have this issue? 


Edited by AngryGuy - 1/16/13 at 7:03pm
post #138 of 498
Quote:
Originally Posted by AngryGuy View Post

I just purchased a used jds o2/odac combo from someone and I love it but I'm having one issue with it. With some of my higher sensitivity headphones, the volume out of the O2 is simply too much except at very low levels on the volume knob. The problem is that at very low levels the volume pot gives me very uneven volume. By the time I get to where it sounds normal, it's at the absolute limit of how loud I would want to listen. Is there anything I can do about this without changing the gain? It has the default 2.5/6.5 gain on it. I wouldn't really like to change that since I have a wide variety of headphones and the higher gains could be useful to me. Is there a different volume pot that I could use that wouldn't have this issue? 


I'd suggest to lower the source volume to a point where the O2's knob has sufficient variation of volume.

post #139 of 498
Quote:
Originally Posted by AngryGuy View Post

I just purchased a used jds o2/odac combo from someone and I love it but I'm having one issue with it. With some of my higher sensitivity headphones, the volume out of the O2 is simply too much except at very low levels on the volume knob. The problem is that at very low levels the volume pot gives me very uneven volume. By the time I get to where it sounds normal, it's at the absolute limit of how loud I would want to listen. Is there anything I can do about this without changing the gain? It has the default 2.5/6.5 gain on it. I wouldn't really like to change that since I have a wide variety of headphones and the higher gains could be useful to me. Is there a different volume pot that I could use that wouldn't have this issue? 

 

correct me if i am wrong... but didn't nwavguy set the high gain up for lower input sources and not for less sensitive headphones? If you don't plan on using anything but the odac as the source you should never need the 6.5 gain. I cut mine to 1x for use with my BA iem's and the 1x gain is plenty for my hd650. So now I have 1x and 2.5x gain. I would assume that 2.5x gain should be enough to run most headphones. Maybe someone else can comment?


Edited by muad - 1/16/13 at 7:37pm
post #140 of 498
Quote:
Originally Posted by muad View Post

 

correct me if i am wrong... but didn't nwavguy set the high gain up for lower input sources and not for less sensitive headphones? If you don't plan on using anything but the odac as the source you should never need the 6.5 gain. I cut mine to 1x for use with my BA iem's and the 1x gain is plenty for my hd650. So now I have 1x and 2.5x gain. I would assume that 2.5x gain should be enough to run most headphones. Maybe someone else can comment?

You're probably right about this. 

I think I'm just going to try 1x/2.5x. I just need to remove R19 and R23, right?


Edited by AngryGuy - 1/16/13 at 8:02pm
post #141 of 498
Quote:
Originally Posted by AngryGuy View Post

You're probably right about this. 

I think I'm just going to try 1x/2.5x. I just need to remove R19 and R23, right?

Yea, that's what I did. I clipped those two resistors. Very easy to do. 1x/2.5x gain works much better than stock.

post #142 of 498
Quote:
Originally Posted by moshen View Post

Yea, that's what I did. I clipped those two resistors. Very easy to do. 1x/2.5x gain works much better than stock.


Either you can do that, or if you can solder yourself, solder a wire wrap socket instead of the resistors, and then you can just plug in/out the resistors without soldering/clipping.

post #143 of 498
Quote:
Originally Posted by AngryGuy View Post

You're probably right about this. 


I think I'm just going to try 1x/2.5x. I just need to remove R19 and R23, right?

DON'T DO IT!!!!

Clip the 2.5x not the 6X.

The 6.5x is needed for low-voltage sources like ipods and clip+'s when used with higher impedance phones (particularly if using equalisation).

For example, as a loud listener my 32ohm headphones are right at the limit of the pot on the 2.5x gain setting when I set my rockboxed clip+ to 0dbs (with no equalisation).

If I equalize 12dbs at 40Hz ( which gives me a flat bass response at normal listening levels) then this makes the clip+ lower the overall gain to accommodate the equalisation. I run it at -3dbs to give a touch of headroom (0dbs is the limit of gain before distortion sets in as the rockbox developers look up the particular device specs; the extra 6dbs above that is for the gung ho or those who do not seek the nirvana of hifi) then I totally run out of pot at 2.5x.
post #144 of 498
Quote:
Originally Posted by RustA View Post

Quote:
Originally Posted by Currawong View Post

 

When you listen to complex music with the LCD-2s, do you get compression? Whether or not an amp can drive a pair of headphones capably isn't just about the numbers, it has to be able to maintain a linear flow of power to the circuit despite the widely fluctuating voltage it has to deliver.

 

The one who designed the amp possibly knows more about audio and electronics than all people discussing here on head-fi together... Technical excellence of his amp has even been proved on innerfidelity. So if he claims (on his blog) that the amp is more than suitable for LCD-2, I would definitely trust him. Definitely.

 

However, one should be careful when using batteries... there could be clipping under certain conditions. More info is available on his blog, of course. And that's what I like - you can get all the info you need in order to drive your headphones with near-to-100% confidence.

 

This doesn't answer my question. You don't need an engineering degree to hear compression when listening. It's a simple test for those of us without $10k measuring equipment. FYI, the tests done in various places, with the exception of one I linked, didn't use headphones when they were done, so don't show the linearity of the circuit in actual use. One that did showed that the O2 starts to distort when IEMs are connected, compared to a UHA-6SII which didn't. smile.gif

post #145 of 498
Quote:
Originally Posted by Currawong View Post

so don't show the linearity of the circuit in actual use. One that did showed that the O2 starts to distort when IEMs are connected, compared to a UHA-6SII which didn't. smile.gif

...distort? You mean the frequency curve inaudibly dips, not actual distortion.

This is really academic. No one is going to hear the tiny dip in the O2's driving of a low-impedance balanced armature. The design principle was to aim for audible transparency (which pretty much defines true hifi) not technical perfection, which is in anycase impossible without a true Zero Z (output impedance) which is impossible if I remember correctly.
post #146 of 498
Quote:
Originally Posted by Currawong View Post

 

This doesn't answer my question. You don't need an engineering degree to hear compression when listening. It's a simple test for those of us without $10k measuring equipment. FYI, the tests done in various places, with the exception of one I linked, didn't use headphones when they were done, so don't show the linearity of the circuit in actual use. One that did showed that the O2 starts to distort when IEMs are connected, compared to a UHA-6SII which didn't. smile.gif

 

So what's the conclusion if what you claim is true? That O2 is not perfect from the technical perspective? Well, it's not, you can read it on the author's blog as well... He is very aware of it.

 

I cannot hear any audible distortion with my phones, including IEMs and low impedance phones from Denon or Audeze... The question remains - why do you need an amp for IEMs?

post #147 of 498
Quote:
Originally Posted by AngryGuy View Post

You're probably right about this. 


I think I'm just going to try 1x/2.5x. I just need to remove R19 and R23, right?

I forgot to add that there is an alternative. You could get a splitter with individual volume controls. Seriously useful. Has no audible downsides.

Here's my own:

http://www.head-fi.org/t/627755/short-positive-review-iluv-headphone-2-way-splitter-with-dual-independent-volume-controls
post #148 of 498
Quote:
Originally Posted by mikeaj View Post

It's kind of a gray area.  Yes, it'll continue to charge forever, which is generally not good for the batteries, but once the batteries are at full charge then the current coming in is low enough that it's supposed to be okay.  If you never will use it on batteries, then take them out, but it's probably not a big deal.

 

Quote:
Originally Posted by xnor View Post

From the blog that shall not be named: "The charge current automatically tapers off as they reach full charge and you can leave the AC power connected indefinitely if you want. But if you’re going to use the O2 mainly as a desktop amp for months at a time you should remove the batteries."

 

Quote:
Originally Posted by adydula View Post

If you dont plan on using the batteries, remove them.

 

Batteries like to be charged and discharges over and over and over.....

 

Alex


thank you very much, cheers

post #149 of 498

There is "compression" in the source material....have to be careful here with words...to me being around for a LONG time on this earth things I have learned from this forum and others that the words we use ....well can be interpreteted widely....back to "compression"..

 

When I hear the term in audio I immediatley think of crappy source material...a song that was recorded and the dynamic range was reduced from what the technology would allow....for whatever reason...

 

In electronics like the O2 amp if we are talking about its "compression" to the signal being inserted into it, compared to the signal out....is that the "compression" your talking about?

 

Distortion is another thing...and it is tied to the gain settings and the source amplitude in the O2....

 

For the most part the standard gain settings are just fine....for me with three sets of cans, widely different, I find I never use the 6.5x gains settings with the ODAC and with a much hotter 2.25 Vrms HRT MSii+ asynch USB dac....

 

With AKG 701's, LCD2's anf my Grados....the volume knob is never past the 1pm position....or my ears would bleed. LOL.

 

I can easily get the O2 amp to distort and sound crappy...but you just dont go there....

 

If its one thing that the O2 has an archilles heel its the gain settings implementation because many of us just dont really understand it, what it is, how it works etc...

 

But the real technical beauty of it is that you can dial it in if needed...not like other amps...one new one that comes to mind....that the gain is set....fixed...story over....

 

All the best

Alex

post #150 of 498

I think the input/gain stage of the O2 perfectly fits the rest of the amp and is actually one of its strong points. Other amps clip a lot earlier, like the E9's input at ~2.1 V. That is regardless of the position of the volume control.

 

With the O2 on AC power you can use:

max_gain = 7V / input_voltage

for example: 7V / 2.25V = 3.11x, so any gain setting lower than that is fine

 

max_input = 7V / gain

for example: 7V / 2.5x = 2.8V, so the default 2.5x gain is fine for sources up to 2.8 V

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