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O2 AMP + ODAC - Page 96

post #1426 of 3453
Quote:
Originally Posted by brainbucket View Post

Hey guys, I built an O2 amp yesterday using components from the official BOM
Quote:
Originally Posted by tintin220 View Post

 

Good observation, but he said he's using a Bifrost as a source, and even at the highest gain, there should not be clipping at the amount he's describing. It's not like he has it plugged into his computer's 3.5mm out and is playing at 10% OS volume. 

 I am not familar with the output specs of the bifrost. I assume it is somewhere close to standard 2vrms. The "official" BOM for the O2 sets the gain 2.5 and 6.5. So yes, if it is built with the "official BOM", then high gain setting will clip horribly.

 

I'm guessing that you misspoke, or don't understand what clipping is and how it is generated in the O2. Clipping comes from driving the gainstage op-amp output above about 7vrms.  (2vrms input) * (6.5 gain) = very bad clipping.  There are various scenarios that could result in brainbucket's amp being on the verge of clipping. It depends on the gain setting of the O2, the output level of the DAC and the setting of the OS software volume control. The result could very easily be exactly what brainbucket posted. The important point is that the O2 is vunerable to clipping with an overly hot source  for the gain used and to fix it could be as easy as lowering the software volume control, if clipping is indeed the problem. 

post #1427 of 3453
Quote:
Originally Posted by bada bing View Post

 I am not familar with the output specs of the bifrost. I assume it is somewhere close to standard 2vrms. The "official" BOM for the O2 sets the gain 2.5 and 6.5. So yes, if it is built with the "official BOM", then high gain setting will clip horribly.

 

I'm guessing that you misspoke, or don't understand what clipping is and how it is generated in the O2. Clipping comes from driving the gainstage op-amp output above about 7vrms.  (2vrms input) * (6.5 gain) = very bad clipping.  There are various scenarios that could result in brainbucket's amp being on the verge of clipping. It depends on the gain setting of the O2, the output level of the DAC and the setting of the OS software volume control. The result could very easily be exactly what brainbucket posted. The important point is that the O2 is vunerable to clipping with an overly hot source  for the gain used and to fix it could be as easy as lowering the software volume control, if clipping is indeed the problem. 

 

No need to be a jerk about it, I didn't know the default gains were 2.5 and 6.5, thought they were 1x and 2.5x.

 

That said, this would be an easy way to test if this is the issue, use the lower gain setting and see if your problem is resolved. If it isn't, bust out the multimeter. The reason I recommended that is I suspect that an incorrect resistor might have been added to the gain resistors, which could of course result in what bada described.


Edited by tintin220 - 5/11/13 at 10:37am
post #1428 of 3453

How is he a jerk about it?

post #1429 of 3453

Bifrost product page says 2.0 V rms out.

 

 

Anyway, before running around or jumping to conclusions, it might be worth checking which resistors were actually installed, and so on.  I mean, who cares about speculating about what might be there and the default (though docs give values for 2.5x and 6.5x, sure enough), when what really matters is what's installed, and that can be easily checked?  While you're at it, you could check the build (there are some troubleshooting instructions and voltages to check out that are diagrammed on the designer's blog).  Actually, if you hear obvious distortion, you could give it a quick whirl through say RMAA or whatever else for a quick sanity check, so long as you have some kind of audio input to run it through.

post #1430 of 3453

Some folks should spend more time on Nwavguy's blog to learn about gain and clipping etc.....

 

Oh my...

 

Alex

post #1431 of 3453
Quote:
Originally Posted by adydula View Post

Some folks should spend more time on Nwavguy's blog to learn about gain and clipping etc.....

 

Oh my...

 

Alex

 

Why should people let a few facts interfere with their presuppositions?.All that hard work learning to speak Audiophilian would be wasted.

post #1432 of 3453
Quote:
Originally Posted by adydula View Post

Some folks should spend more time on Nwavguy's blog to learn about gain and clipping etc.....

 

Oh my...

 

Alex

Honestly, his blog is a big jumble of words. Most people aren't going to go through the many, what would be pages in MSWord, of text he writes and you would get a far more direct answer right here.

post #1433 of 3453
Hey guys, didn't expect so many replies. I did not check the resistances or voltages because I forgot to grab a multimeter from my work. I will when I get a chance, but until then I've played around with it some. If I use the lower gain with the volume maxed out it is a reasonable level and I didn't hear any noticeable clipping. It still does it at the higher gain, but if I lower the the source voltage (using my AK100 right now which should be ~2v at max volume from what I read) it sounds a lot better and gets loud. So I just need to use the software to lower the volume when I use my bifrost I assume?
post #1434 of 3453
Quote:
Originally Posted by miceblue View Post
 
Honestly, his blog is a big jumble of words. Most people aren't going to go through the many, what would be pages in MSWord, of text he writes and you would get a far more direct answer right here.

 

The direct answers you get here are often buried among messages with flowery phrases such as "factors such as sound stage, bass treble response and etc" and other attempts to appear knowledgeable.

 

Overall, the most complete background discussion is from the designer's blog. We also have a few excellent, and knowledgeable, posters here who aren't fooled by audophile-speak. They know who they are. I'd like to thank them.

post #1435 of 3453
Quote:
Originally Posted by HamilcarBarca View Post

 

The direct answers you get here are often buried among messages with flowery phrases such as "factors such as sound stage, bass treble response and etc" and other attempts to appear knowledgeable.

 

Overall, the most complete background discussion is from the designer's blog. We also have a few excellent, and knowledgeable, posters here who aren't fooled by audophile-speak. They know who they are. I'd like to thank them.

 

I think our numbers are more numerous than they appear. Many just don't post often, myself included, because our comments tend to draw a crowd of angry cable loving, blind test hating "audiophiles". A quick look at my post history will show you how some of my recent conversations here have gone...


Edited by tintin220 - 5/11/13 at 8:09pm
post #1436 of 3453

If I get a O2 ODAC is it possible to disable the DAC and just use the O2 AMP with PC soundcard as DAC?

post #1437 of 3453
Quote:
Originally Posted by grandpatzer View Post

If I get a O2 ODAC is it possible to disable the DAC and just use the O2 AMP with PC soundcard as DAC?


first of all, you can get a standalone O2. however, if you do get a combo then yes, you can use the 3.5mm input and use your pc soundcard. question is whether or not your pc can give a line out? if you want to send the signal through the headphone jack to the O2 youll be "double amping", and depending on your pcs amp, youll probably get a not so good result...

post #1438 of 3453
Quote:
Originally Posted by adamlr View Post


first of all, you can get a standalone O2. however, if you do get a combo then yes, you can use the 3.5mm input and use your pc soundcard. question is whether or not your pc can give a line out? if you want to send the signal through the headphone jack to the O2 youll be "double amping", and depending on your pcs amp, youll probably get a not so good result...

 

My PC has a Xonar DX soundcard, I think it has no OR weak amp, so this can be a problem if DX has built in amp because of "double amping"?

I might invest on a Creative Titanium HD or Z because those are more recommended for competitive gaming.

 

So basicaly I would connect Xonar DX to O2 ODAC then headphones to O2 ODAC?

So because the O2 ODAC Usb is not connected it is disabled?! 

post #1439 of 3453
Quote:
Originally Posted by grandpatzer View Post

 

My PC has a Xonar DX soundcard, I think it has no OR weak amp, so this can be a problem if DX has built in amp because of "double amping"?

I might invest on a Creative Titanium HD or Z because those are more recommended for competitive gaming.

 

So basicaly I would connect Xonar DX to O2 ODAC then headphones to O2 ODAC?

So because the O2 ODAC Usb is not connected it is disabled?! 


errrrr pretty much yea. im almost certain you can use the analog in of the combo and not use the odac if you wish... as for the soundcards i really have no comment. im unfamiliar with pc soundcards. just know that if your using a headphone jack, that means that the signal has already been amped and whatever noise or degradation that the soundcards amp may have added to the signal will also be amplified by the O2.

post #1440 of 3453
Quote:
Originally Posted by brainbucket View Post

Hey guys, didn't expect so many replies. I did not check the resistances or voltages because I forgot to grab a multimeter from my work. I will when I get a chance, but until then I've played around with it some. If I use the lower gain with the volume maxed out it is a reasonable level and I didn't hear any noticeable clipping. It still does it at the higher gain, but if I lower the the source voltage (using my AK100 right now which should be ~2v at max volume from what I read) it sounds a lot better and gets loud. So I just need to use the software to lower the volume when I use my bifrost I assume?

 

You don't need to check voltages or bother troubleshooting, if that's the case.  If you used defaults, that's the gain stage clipping on high gain (if fed a signal higher than a 1.08 V rms sine wave), as mentioned previously.  That's how it works.

 

You could either just use low gain all the time, lower the source voltage, or lower the gain.  O2 can handle about 7 V.  With low gain of 2.5x and source voltage of 2 V, meaning up to 5 V max, there's not much room to go higher than that.  If you plan on keeping source volume at max, you could just move the values to 1x (remove resistor) and 3.5x or so (no less than 600 ohms; 1000 ohms brings you down to the 2.5x you have now).  Resistors to change are R17 and R21 for low (switch out), R19 and R23 for high (switch in).

 

 

 


Quote:
Originally Posted by grandpatzer View Post

 

My PC has a Xonar DX soundcard, I think it has no OR weak amp, so this can be a problem if DX has built in amp because of "double amping"?

I might invest on a Creative Titanium HD or Z because those are more recommended for competitive gaming.

 

So basicaly I would connect Xonar DX to O2 ODAC then headphones to O2 ODAC?

So because the O2 ODAC Usb is not connected it is disabled?! 

 

Nah, actually the O2's input jack itself is the switch.  If you plug something in, it disconnects from the ODAC.

 

Or at least, that's how it's supposed to be.  I didn't verify myself.

 

Unless you're using CMSS-3D or whatever processing Creative offers these days, or especially EAX (rare for current titles, if I'm hearing things correctly), I wouldn't think there's much substance to claims about gaming audio.  The way you get significant changes is to change the bits that get sent to the DACs.  If you're not doing software processing that changes those bits, it's just about DAC performance, and that's a small blip in the grand scheme of things.

 

 

 

Quote:
Originally Posted by adamlr View Post


errrrr pretty much yea. im almost certain you can use the analog in of the combo and not use the odac if you wish... as for the soundcards i really have no comment. im unfamiliar with pc soundcards. just know that if your using a headphone jack, that means that the signal has already been amped and whatever noise or degradation that the soundcards amp may have added to the signal will also be amplified by the O2.

 

A lot of times, double amping is really no big deal.  I mean, it's a lot easier for an amp to drive a line input (thousands of ohms impedance, thus low current and so on) than it is for that amp to drive some actual headphones.

 

And DX I think is like D1, which has ~100 ohms output impedance.  It's supposed to be a normal line output that's driven by some high-quality audio op amp that's not particularly some high-current output part.  It's not really much of an amp in the sense that most people are talking about.


Edited by mikeaj - 5/12/13 at 8:32am
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