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O2 AMP + ODAC - Page 69

post #1021 of 3427

It's my first time hearing of project h.

 

Looks like just a standard O2 PCB inside.  They changed the NJM2068 gain stage op amp for the popular and more-expensive FET-input OPA2134.  OPA2134 has several dB higher (i.e. worse) noise.  Even if the distortion performance were better at the gain used (seems not), the output stage is the "bottleneck" anyway.  Several options for the gain stage were measured by the designer for use in the O2.  Check the blog.

 

I don't see any other changes to the O2 electronics, but I didn't look that hard.

 

You can always change things, not necessarily for the better.  And if you do change for the better, it very well might not sound perceptibly better.

post #1022 of 3427
Quote:
Originally Posted by miceblue View Post
 
Can't you switch out some of the op-amps to get some performance gains in some areas?

 

It might measure better "in some areas." Nothing is more transparent than transparent.

post #1023 of 3427
Quote:
Originally Posted by adydula View Post

The real end of the road lies at a live concert and a good cold beer....

 

lol

 

Alex

 

Alex, this must be  the best post ever on this site!!!

 

I wholeheartedly second it.

post #1024 of 3427
Quote:
Originally Posted by miceblue View Post

I just did some subjective tests using Daft Punk's "Voyager" song (16/44.1 EAC CD-ripped) with the M-100's.

 

1.0x gain:

  • source volume ~ 50% of max
  • O2 potentiometer ~ 8:45 position
  • volume is louder than I would normally listen to music at
  • no background hiss

 

2.5x gain:

  • O2 potentiometer left at ~ 8:45 position
  • source volume left at ~ 50% of max
  • no background hiss (strange, I could have sworn I heard the background hiss earlier.....stopping the music and turning the potentiometer, I can start hearing the background hiss at around the 12:15 position [I did this after doing finishing the testing session])
  • volume is much louder than I would normally listen to music at, so I adjusted the source volume until the volume at 2.5x gain is about the same as 1.0x gain (rough estimate): now source is ~31.25% of max (yeah yeah this isn't objective having the by-ear volume guessing)
  • I don't notice any degradation of the signal with the lower source volume

 

So with the 2.5x gain at a lower source volume, I might be losing bits, but I can't hear it, at least not with the M-100. Having the potentiometer at the 8:45 position is pretty much the bare minimal "angle" before the channel imbalance kicks in for me. So even with the ~50% source volume at 1.0x gain, I have practically no wiggle room for volume adjustment using the O2.

 

i thank you ever so kindly =]

 

Quote:
Originally Posted by Dano91 View Post

The easiest way to explain "why high impedance headphones" will be quoting Beyerdynamic FAQ page:

 

 

 

Quote:
Originally Posted by mikeaj View Post

 

edit:  re advantage of high-impedance headphones

 

Aside from weight of the wiring driver coil, yes, higher impedance means that a certain noise level will transfer less power to the headphones.  Likewise, if the sensitivity is lower, a given power level will create lower sound pressure levels to the ear.  Often times, increasing volume does not scale up the noise as much as it does the signal.  So for higher-impedance and less-sensitive headphones, if you're compensating for lower volume by boosting the signal levels (to listen at equivalent volume as another headphone), there will likely be less noise than for normal listening with another headphone.  You get higher SNR.

 

This is why you could say that sensitive IEMs have some of the most exacting requirements for audio systems.  They'll pick up very low noise levels.  This is one of the reasons why relatively-noisy tube amps are not disasters with high-impedance fullsize headphones—in fact, many people like the combination.

 

In practice, unless you go to the extremes, like sensitive IEMs, noise is probably not an issue.

 

thank you both very much

 

Quote:
Originally Posted by adydula View Post

The real end of the road lies at a live concert and a good cold beer....

 

lol

 

Alex

beerchug.gif

you inspired me to get up and fetch a beer 
                                                                                                                       

 

as for the O2 being the end of the road, excluding electrostatics, i can easily believe it (and i say "believe" rather than "agree" because im not nearly informed enough to make such a claim). "wire with gain" is exactly what im looking for, and in this thread, i imagine everyone else is aswell. however, other things are to be considered when choosing an amp, such as channel imbalance, which is in my very humble opinion, the only issue with the O2, though im confident that once iv changed my gain options, and start using unity gain, this will no longer be an issue at all (due to the more-to-the-right position that unity gain will require).

HOWEVER, marketing schemes and such are pretty powerful, and for the life of me, i cant imagine staying with the O2 when i eventually have enough money for real TOTL gear, and im sure that ill get atleast an asgard, knowing full well that i dont actually need it. kinda ashamed of admitting it, but i never lie.

 

 

unrelated question: why cant i power headphones with the odac? i can control its volume digitally, why not use it for sensitive, efficient headphones? ive never tried it due to the massive warning jds labs has printed on the instruction manual that comes with the odac (yes i read it, for me its part of the fun of getting new stuff - being geeky about it beyersmile.png). will it "underpower" the headphones? will it damage them? will it damage the odac?


Edited by adamlr - 2/21/13 at 6:47am
post #1025 of 3427
Quote:
Originally Posted by adamlr View Post

unrelated question: why cant i power headphones with the odac? i can control its volume digitally, why not use it for sensitive, efficient headphones? ive never tried it due to the massive warning jds labs has printed on the instruction manual that comes with the odac (yes i read it, for me its part of the fun of getting new stuff - being geeky about it beyersmile.png). will it "underpower" the headphones? will it damage them? will it damage the odac?

 

More or less, you can, but not recommended.

 

ODAC doesn't have electronics dedicated to driving headphones.  The electronics are built to just be a line driver and feed an amplifier's line input (which is in the thousands of ohms and thus doesn't require much current, unlike headphones).  Actually, the line driver is integrated inside the DAC chip for the ODAC, and specs are not publicly available.

 

It's possible that with low-enough levels and the right headphones, the sound could be okay when directly driving headphones.  Depends on what it's really like internally.  Practically, if you plugged in some low-impedance headphones and cranked the volume, it would probably start to distort badly early.  Sometimes for the right building, you can use a hammer as a wrecking ball, but that doesn't mean you should...

 

It won't damage the headphones and it probably shouldn't damage the ODAC.


Edited by mikeaj - 2/21/13 at 8:18am
post #1026 of 3427
Quote:
Originally Posted by mikeaj View Post

 

More or less, you can, but not recommended.

 

ODAC doesn't have electronics dedicated to driving headphones.  The electronics are built to just be a line driver and feed an amplifier's line input (which is in the thousands of ohms and thus doesn't require much current, unlike headphones).  Actually, the line driver is integrated inside the DAC chip for the ODAC, and specs are not publicly available.

 

It's possible that with low-enough levels and the right headphones, the sound could be okay when directly driving headphones.  Depends on what it's really like internally.  Practically, if you plugged in some low-impedance headphones and cranked the volume, it would probably start to distort badly early.  Sometimes for the right building, you can use a hammer as a wrecking ball, but that doesn't mean you should...

 

It won't damage the headphones and it probably shouldn't damage the ODAC.

cheers!

post #1027 of 3427
Quote:
Originally Posted by adydula View Post

If I thought I was missing something I would not have sold my Asgard, or my Lyr or my SOHOii, and after listening to a lot of others....I am not missing anything with the O2.

 

That said there is nothing wrong with wanting a amp that costs more, has billet aluminum casings, wrap around victorian moldings, gold plated contacts, NOS tubes, and on and on and on....its your bucks...

 

Some folks like the coolness factor and must have their amp in red, or blue or yellow....LOL...

 

You put a O2 next to a Burson or a Vioelectric amp and the O2 looks like the skinny kid at the beach...but in this case the sand doenst get kicked against the O2, it holds its own.

 

To me its the absence of colorations, straight wire with gain...

 

Alex


You have to remember that after the first watt, even a 6 watt lyr offers *only* 6-9 dB of additional headroom over a 1 watt amp. I consider the O2 a Half-Watt amp, so 9-12 dB gain from say, a lyr, only makes it to "twice as loud" as the O2, while the power output may put my phones at risk.

 

While I am at it, why don't headphone manufacturers supply information about RMS and Max Power inputs into headphones?

 

Of someone *really* needed to go so crazy loud, I would start looking at the efficiency of the phones' themselves! Hell, the other day I was thinking about how nice it would be to have a 100 watt version of my amp rather than the 50 watt version. Then I remembered that other than a tiny bit more headroom, I am ultimately not taking much of a step up.


Edited by MrMateoHead - 2/22/13 at 9:09am
post #1028 of 3427

Hi.

I am currently enjoying my ODAC + O2 with HD600 but I have a small problem.

With ODAC set to 50% in windows, O2's gain 2.5X and volume knob at about 9-10am it's still too loud for my liking.

 

I want to change my O2 gain settings. Now I have 2.5X (gain switch out) and 6.5X (gain switch in). I would like it to be 1X (Gain switch off) and 2.5X (Gain swtich in).

Which resistors I need to swap / remove to achieve it? 

Thanks.

post #1029 of 3427

R17 and R21 correspond to gain switch in the out position.  For 1x(unity gain) you can leave these empty.

R19 and R23 is for gain switch in position.  For 2.5x you want 1K OHM resistors in those spots.

 

You could go the easy route and just clip the resistors in R19 and R23.  That will give you 2.5x with the switch out and 1x with the switch in.

post #1030 of 3427

Thanks. I am going to try it right now. 

 

Edit: Works exactly as I wanted. Thanks.


Edited by ProTofik - 3/2/13 at 8:40am
post #1031 of 3427
Quote:
Originally Posted by ProTofik View Post

Thanks. I am going to try it right now. 

 

Edit: Works exactly as I wanted. Thanks.

Glad it worked out for you.  You're welcome and enjoy!

post #1032 of 3427

Is there something wrong if I have foobar set to 100% (0.00dB) volume, windows set to 100% volume and O2 with 2,5x gain 9 o'clock and it sounds comfortable? 10-11 o'clock is a bit too loud for my liking. I'm using 32ohm signature DJ.

post #1033 of 3427
Quote:
Originally Posted by Stratok View Post

Is there something wrong if I have foobar set to 100% (0.00dB) volume, windows set to 100% volume and O2 with 2,5x gain 9 o'clock and it sounds comfortable? 10-11 o'clock is a bit too loud for my liking. I'm using 32ohm signature DJ.

 

Depends on the source output level, but that seems very typical.  Are you thinking that the amp is too loud?  If you want, you can change the other setting to 1x by clipping resistors, and just mentioned previously in the thread.

 

Most people don't actually need (> 1) gain unless they listen louder, have inefficient headphones, and/or have higher-impedance headphones.

post #1034 of 3427
Quote:
Originally Posted by mikeaj View Post

 

Depends on the source output level, but that seems very typical.  Are you thinking that the amp is too loud?  If you want, you can change the other setting to 1x by clipping resistors, and just mentioned previously in the thread.

 

Most people don't actually need (> 1) gain unless they listen louder, have inefficient headphones, and/or have higher-impedance headphones.


ok thanks :) I was just worried if I've missed something. Feels good so I think I'll pass playing with DIY stuff for now. 

post #1035 of 3427
Quote:
Originally Posted by mikeaj View Post

Depends on the source output level, but that seems very typical.  Are you thinking that the amp is too loud?  If you want, you can change the other setting to 1x by clipping resistors, and just mentioned previously in the thread.

Most people don't actually need (> 1) gain unless they listen louder, have inefficient headphones, and/or have higher-impedance headphones.

...or are using ipods or clip+ as a source, in which case 6.5x is a good idea. I'm quite bemused at the advice for clipping the 6.5x to leave only 1x and 2.5x. Unless you really know that you will never use an ipod or clip+ or similar then you likely need the 6.5x.
Edited by lorriman - 3/4/13 at 1:19pm
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