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Review: JDS Labs O2 (Black edition) + O2/ODAC discussion - Page 11

post #151 of 497
Quote:
Originally Posted by lorriman View Post


...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.

 

Technically that's distortion, but almost everybody means "non-linear distortion" when they talk about distortion.  Mild FR changes are not non-linear distortion, as you say.  I wouldn't be confident enough to say "inaudibly dips", but I think it's at the level where it's not worth losing sleep over.  That said, it's a bigger deal than some other things that audiophiles worry about.

 

Many devices have lower output impedance.  0 output impedance is like 0 distortion or 0 noise—impossible, as you say... unless you find me a wire with 0 resistance and much more.  It's meaningless in the grand scheme of things.  Most of it on the O2 comes from the output resistors, which are there mainly for safety / matching of the cheap output op amps.  A small tradeoff, like many things.

 

 

 

If you wanted, you could adjust the gain on lots of other DIY amps, some commercial ones too.  Though beware of instability.

post #152 of 497
Thread Starter 
Thanks guys, I'm learning a lot from my own thread, I might actually change mine to 1x and 6x gain, 2.5 is too high.
post #153 of 497

Kool!!

 

Thanks for starting the thread...its good to see us all learning etc...

 

Alex

 

smily_headphones1.gif

post #154 of 497

Is there any use for the 6.5x gain if I will only ever use an odac with it?

post #155 of 497
Quote:
Originally Posted by muad View Post

Is there any use for the 6.5x gain if I will only ever use an odac with it?


With the ODAC, maybe not.

post #156 of 497

Now that the proper power requirements and schematics have been taken care of, how about some pics?

 

Show your sources, docks, LODs, mini cables connected to the O2.  I've already posted a couple but have to bling her up for the next go around...

 

Cheers!!!

post #157 of 497
Quote:
Originally Posted by lorriman View Post

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.

Woah that's a lot of volume. o.0

I usually have my Clip Zip at -25 dB, 1.0x gain on the O2, with the volume knob as my volume adjustor, hooked up to my 36-ohm headphones (according to Innerfidelity's impedance measurement).

 

Is the 6.5x gain thing true? I occasionally use my O2 with my Clip Zip, but not very often and I have the 2.5x/1.0x gain options.

 

 

 

Quote:
Originally Posted by HeatFan12 View Post

Now that the proper power requirements and schematics have been taken care of, how about some pics?

 

Show your sources, docks, LODs, mini cables connected to the O2.  I've already posted a couple but have to bling her up for the next go around...

 

Cheers!!!

I don't have a LOD at the moment, but I'll probably get one from Amazon soon whenever I order something to get the "spend $25 get free shipping" deal thing.

Anywho here are my setups.

 

^ Does anyone have a recommendation for a shorter mini USB cable? I don't like the length of the one that came with the JDS Labs O2, I don't like bending my cables very much (I tend to keep the cable as close to its original position as possible), and I don't want to lose sound quality (if the AC charger was carefully chosen, perhaps the USB cable was carefully chosen as well?).

 

 


Edited by miceblue - 1/17/13 at 8:22pm
post #158 of 497
Quote:
Originally Posted by miceblue View Post

Woah that's a lot of volume. o.0
I usually have my Clip Zip at -25 dB, 1.0x gain on the O2, with the volume knob as my volume adjustor, hooked up to my 36-ohm headphones (according to Innerfidelity's impedance measurement).

I've noticed that some of my friends usually set the clip to -24db when I would set it to between -9db and -15db (no equalisation). Others set it to my level. One of the -25db-ers told me that any higher was painful!! So that's not because they are quiet listeners; it's their volume/pain threshold (at least in that particular case). So, going on a conservative estimate, that's a 9db difference which is quite a lot. AFAIK, I'm not deaf. I had an ear test when I was a kid and had fine hearing. Progressive deafness usually affects the midrange the most, but listening to a sine generator rising from 100Hz to 12Khz on my etymotics (legendary flatness), I can't hear a volume difference; so I doubt I am deaf.

It would be interesting to know more about this difference. I'm going to test one of my -24db friends today to see if they have better hearing or are just more sensitive to pain (I suspect the latter because in this person's case they are very sensitive to physical pain-play, like how chaps punch each other for fun, or, in a boring chemistry lesson, my best friend and I would stab each other in the legs with biros to try to alleviate the boredom; that's a total no-no with this person).

If the latter then that would have a profound affect in relation to the loudness/frequency curves and necessary bass equalisations (to get flat bass all the way down to 20Hz from headphones that trail off in the lower regions as most do). In order to get the same bass response as myself they would have to go for even more than 12dbs gain at 40Hz. I've noticed from frequency/sine-tone testing that at low volume there is a 30db perceived difference between 100Hz and 30Hz which, which reflects those curves. Of course, with their volume so low, they are not going to get distortion with a 30db bass boost; except from a poor equalizer (like ipod nano 2 or Windows Media Player 11; both utterly awful).
Edited by lorriman - 1/18/13 at 12:33am
post #159 of 497
Quote:
Originally Posted by lorriman View Post

Quote:
Originally Posted by miceblue View Post

Woah that's a lot of volume. o.0
I usually have my Clip Zip at -25 dB, 1.0x gain on the O2, with the volume knob as my volume adjustor, hooked up to my 36-ohm headphones (according to Innerfidelity's impedance measurement).

I've noticed that some of my friends usually set the clip to -24db when I would set it to between -9db and -15db (no equalisation). Others set it to my level. One of the -25db-ers told me that any higher was painful!! So that's not because they are quiet listeners; it's their volume/pain threshold (at least in that particular case). So, going on a conservative estimate, that's a 9db difference which is quite a lot. AFAIK, I'm not deaf. I had an ear test when I was a kid and had fine hearing. Progressive deafness usually affects the midrange the most, but listening to a sine generator rising from 100Hz to 12Khz on my etymotics (legendary flatness), I can't hear a volume difference; so I doubt I am deaf.

It would be interesting to know more about this difference. I'm going to test one of my -24db friends today to see if they have better hearing or are just more sensitive to pain (I suspect the latter because in this person's case they are very sensitive to physical pain-play, like how chaps punch each other for fun, or, in a boring chemistry lesson, my best friend and I would stab each other in the legs with biros to try to alleviate the boredom; that's a total no-no with this person).

If the latter then that would have a profound affect in relation to the loudness/frequency curves and necessary bass equalisations (to get flat bass all the way down to 20Hz from headphones that trail off in the lower regions as most do). In order to get the same bass response as myself they would have to go for even more than 12dbs gain at 40Hz. I've noticed from frequency/sine-tone testing that at low volume there is a 30db perceived difference between 100Hz and 30Hz which, which reflects those curves. Of course, with their volume so low, they are not going to get distortion with a 30db bass boost; except from a poor equalizer (like ipod nano 2 or Windows Media Player 11; both utterly awful).

Well I have -25 dB as the maximum volume level while riding on the bus, so that might be something to take-in to account. While walking around campus I lower it to -30 dB. At home, if I listen to my Clip Zip, I have the volume set at -60 dB. I'm kind of afraid to know what my threshold of pain is, but I know that with -25 dB at 1.0x O2 gain with 36-ohm headphones with the volume knob at the max volume, music is pretty loud to me while on a noisy bus.. >.>

 

Oddly enough, or perhaps by coincidence, my sense of touch pretty sensitive too (I would say my sense of touch and hearing are my most sensitive senses). Hearing is a mechanical/electrical process via mechanotransduction so maybe that has to do something with volume sensitivity (just pondering out loud, it's probably not the case).

 

I have yet to do frequency/sine-tone/pink noise testing since I'm not quite sure how to do it but I have read about the equal loudness contours.

 

Interesting stuff.

 

John at JDS Labs recommended I use the 2.5x/1.0x gain since I tend to listen to music at low volume levels, which is why I was asking about the 1.0x/6.5x gain thing. I can't really imagine using the 6.5x gain. XD


Edited by miceblue - 1/18/13 at 1:20am
post #160 of 497
Quote:
Originally Posted by miceblue View Post

John at JDS Labs recommended I use the 2.5x/1.0x gain since I tend to listen to music at low volume levels, which is why I was asking about the 1.0x/6.5x gain thing. I can't really imagine using the 6.5x gain. XD

With such extraordinarily low-volume listening (to my mind) it does make sense to choose 1x/2.5x . Then again, if you were to get a 300ohm headphone (HD600?) and clip+ with +30dbs 30Hz bass equalisation reflecting the loudness contour for a low volume listener, if that's how it works which remains to be seen (and with which the clip+ automatically lowers the overall gain by 30dbs), even you might run out of pot at 2.5x.
Edited by lorriman - 1/18/13 at 1:45am
post #161 of 497
Thread Starter 
i think its best to have 1x and 6.5x as i might get some quite hard to drive headphones in the future, which mau need the 6.5x gain, 1 and 2.5x are too close to be of any use to me i think
post #162 of 497
Quote:
Originally Posted by randomkid View Post

i think its best to have 1x and 6.5x as i might get some quite hard to drive headphones in the future, which mau need the 6.5x gain, 1 and 2.5x are too close to be of any use to me i think

 

The best thing is to use "Optional Gain Resistor Pin Sockets" = you can have whatever gain you want whenever you want... Search on the blog for more info.

 

If you do not have an option to do it, use 1x and 2.5x since 6.5x is too much for 99% of headphones. For ODAC users, 6.5x is even more out-of-reality.

post #163 of 497
Thread Starter 

using an iPod, rockboxed, i used 6.5 on beyerdynamic T1 and the likes, 1 is fine for most headphones in my opinion, especially if you used ODAC, then 6.5 for ipod and hard to drive headphones.

post #164 of 497
Thread Starter 

more pics:

 

Toxic cables DIY silver LOD, plus Toxic cables SPC DIY headphone cable

 

 

 

post #165 of 497
Using expensive "silver" cables with the Objective 2… oh the irony!
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