O2 AMP + ODAC - Page 41

Heres the O2 black guys!

Quote:

Originally Posted by wolfetan44 

Heres the O2 black guys!

 

Nice! It looks pretty sleek. I was going to order my O2 with a black front plate as well, but I wanted it to match the silver front plate of the ODAC so I ended up getting the standard silver one.

I must admit though, I'm not a fan of all of the O2's inputs being in the front...

Quote:

Originally Posted by miceblue 

Quote:

Originally Posted by wolfetan44 

Heres the O2 black guys!

 

Nice! It looks pretty sleek. I was going to order my O2 with a black front plate as well, but I wanted it to match the silver front plate of the ODAC so I ended up getting the standard silver one.

I must admit though, I'm not a fan of all of the O2's inputs being in the front...

Seeing it in person I think it looks a lot better.

hey guys, wondering where they currently stand with regards to releasing an objective desktop amp or if I can purchase an ODAC/o2 amp in the same chasis
 

Quote:

Originally Posted by mac336 

hey guys, wondering where they currently stand with regards to releasing an objective desktop amp or if I can purchase an ODAC/o2 amp in the same chasis
 

Its on JDSlabs.com go to DAC's and the O2/ODAC amp will be there. I'm not sure I'm allowed to link the website.

thanks.  do you know where he currently stands with designs for an objective desktop amp?
 

does anyone know how many opamp the headphone out section needs? I wanted to try MUSES01 on this for the fun of it, I just dont know how many I need to buy.

Thanks

Quote:

Originally Posted by audionewbi 

does anyone know how many opamp the headphone out section needs? I wanted to try MUSES01 on this for the fun of it, I just dont know how many I need to buy.

There is one NJM2068 in the gain stage, and two parallel NJM4556's in the headphone buffer. However, it is not recommended to "roll" the headphone driver ICs (which were chosen for being the best for this specific application from many possible options tested) unless you really know what you are doing. It could easily make the amplifier perform worse, or even result in oscillation or other problems. It is safer to "roll" the gain stage op amp (preferably using one of the chips tested by the designer, which are known to work without problems), there is just not much point doing it.

Quote:

Originally Posted by stv014 

 

There is one NJM2068 in the gain stage, and two parallel NJM4556's in the headphone buffer. However, it is not recommended to "roll" the headphone driver ICs (which were chosen for being the best for this specific application from many possible options tested) unless you really know what you are doing. It could easily make the amplifier perform worse, or even result in oscillation or other problems. It is safer to "roll" the gain stage op amp (preferably using one of the chips tested by the designer, which are known to work without problems), there is just not much point doing it.

fair enough, I will opt out of it if that is the case, thank you. 

anyone else thinks using 6.5x gain sounds so much better than using 2.5x?

I noticed much sharper sounds, more soundstage, more separtion of instruments, harder bass,

and that's me using eph-100 iem, with 128 kbps radio streaming from winamp shoutcast

Since I had gotten the o2/odac, I was using only 2.5x gain and I was completely content, until I tried 6.5x just out of curiosity and immediately noticed difference in sound.

Things just sounded like it occupied much more space and filled more air space and much more fuller, and overal sounded more airy with more pronunciation of harder to hear instruments. 

At first I thought it was my ear playing tricks, but the songs that I had heard many times sounded, just alot better.

So I proceeded with experimenting with differnt songs, specifically ones with many instruments and of different volume levels.

For obvious reasons I didn't listen to skillrex or some dubsteps, because everything would sound so mushed in to start with.

I listened to some korean ballad, rnb, pop musics, even some classicals,  and  instruments like violin or cello that sounded like it was playing 10 ft away in 2.5x mode sounded like it was playing from 30ft away in

6.5x mode but still managed to sound louder, clearer, and fuller.

I lowered the computer side volume to about 30% so I have more room to fine tune the volume on the o2 side.

Quote:

Originally Posted by despine 

anyone else thinks using 6.5x gain sounds so much better than using 2.5x?

 

 

I noticed much sharper sounds, more soundstage, more separtion of instruments, harder bass,

 

and that's me using eph-100 iem, with 128 kbps radio streaming from winamp shoutcast

 

Since I had gotten the o2/odac, I was using only 2.5x gain and I was completely content, until I tried 6.5x just out of curiosity and immediately noticed difference in sound.

 

Things just sounded like it occupied much more space and filled more air space and much more fuller, and overal sounded more airy with more pronunciation of harder to hear instruments. 

 

 

 

At first I thought it was my ear playing tricks, but the songs that I had heard many times sounded, just alot better.

 

So I proceeded with experimenting with differnt songs, specifically ones with many instruments and of different volume levels.

 

For obvious reasons I didn't listen to skillrex or some dubsteps, because everything would sound so mushed in to start with.

 

I listened to some korean ballad, rnb, pop musics, even some classicals,  and  instruments like violin or cello that sounded like it was playing 10 ft away in 2.5x mode sounded like it was playing from 30ft away in

 

6.5x mode but still managed to sound louder, clearer, and fuller.

 

 

I lowered the computer side volume to about 30% so I have more room to fine tune the volume on the o2 side.

Nope. I read somewhere recently that the 6.5x gain actually starts clipping sound on the O2. 6.5x gain just adds excess background noise for my headphones when I used it so I just took out those resistors.

Yeah right here. I'm not 100% sure if it's true or not though:

Quote:

Quote:

Originally Posted by Dano91 

Quote:

Originally Posted by imackler 

 

Nope. Just your normal 9-10 pm. I really thought it was the headphones falling apart (HD650), but it was the ODAC/O2 combo. I felt better when JDS Labs confirmed it was a known issue. For me, I felt the HD650 needs the dynamics of high gain; low gain is fine, and I was perfectly happy with low gain with the HD600. But if you use an Ipod line out as source, you don't have the issue becaues of output impedance of ODAC... or something like that. 

I wouldn't call it an issue. To put it simply, O2 amp is not designed to be used with 6.5x gain if dac with high output is connected. (ODAC has 2V output).

6.5x gain is for sources like ipod..

 

More technically, on AC with 2.5x gain max input is 2.8V. With 6.5x it's around 1.1V

On battery with 2.5x it's 1.8V and with 6.5x only 0.7V.

 

So with 6.5x gain you are overloading the input stage of O2, which translates to clipped sound.

 

Quote:

Originally Posted by miceblue 

Nope. I read somewhere recently that the 6.5x gain actually starts clipping sound on the O2. 6.5x gain just adds excess background noise for my headphones when I used it so I just took out those resistors.

Yeah right here. I'm not 100% sure if it's true or not though:

ya I remember reading several replies on that issue, that's why I was only using 2.5x, but to me things are on a completely different level at 6.5.

Do you have the o2/odac combo or do you have them separately? I think  I read somewhere that may be the cause

Quote:

Originally Posted by despine 

Quote:

Originally Posted by miceblue 

Nope. I read somewhere recently that the 6.5x gain actually starts clipping sound on the O2. 6.5x gain just adds excess background noise for my headphones when I used it so I just took out those resistors.

Yeah right here. I'm not 100% sure if it's true or not though:

 

 

 

ya I remember reading several replies on that issue, that's why I was only using 2.5x, but to me things are on a completely different level at 6.5.

 

Do you have the o2/odac combo or do you have them separately? I think  I read somewhere that may be the cause

I have them as separate units.

The volume knob on the O2 is after the gain stage, so if the input is high and the gain is high, then it can exceed the amount the amp can handle. You get clipping, no matter what you set the volume to. On most audiophile amps, the volume control operates before the gain. That solution has worse SNR but avoids clipping if the source output is high and amp gain is also high.

If used with ODAC, which outputs standard Redbook ~2V, default gains really ought to be like something between 3-3.5x for high and lower than that for the low (I'd say 1x). If you use ODAC with O2 set at gain above 3.5x, any max-volume signal (or if gain is higher, than some things below that as well) will be clipped at the peaks. That is, with all software volume controls turned to max, if there's a peak in the track that reaches the max, the ODAC will output a signal that will be clipped by the O2 set at gain above 3.5x. In most music releases these days, it reaches near the max all the time. Frequently, on most every beat. If software volume control is turned down, then you'll be cutting everything down to a level below the max the ODAC can output, and you can avoid clipping even on 6.5x gain or whatever.

When the designer decided upon the default gains, it was envisioned (maybe in some sort of distorted fantasy land?) that most people using the O2 would be DIYers making one for themselves and thus setting the gains for themselves, and/or people were going to use this thick large palm-sized amp as a portable / transportable and primarily use portable sources like iPods and phones with weaker outputs that need more gain to reach the same levels. On the other hand, you could call it some kind of modesty (har har?) in not expecting the O2 to be as big a success as it is now among non-DIY users.