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O2 AMP + ODAC - Page 188

post #2806 of 3771
Quote:
Originally Posted by Whitecitadel View Post

 

Its not just a portable battery power device, its the o2 running on battery as well, my understanding from the designers site is that 6.5x is there for low voltage inputs when running on battery (EDIT: Running o2 on battery I mean). A red book standard device with 2v output like the odac on a desktop PSU is going to be nowhere near needing that kind of gain is my understanding.

 

O2 running on batterys has nothing to do with it, it does however create another problem where the max voltage swing on the outputs is reduced which you may run into with power hungry headphones like the HD600 series.  If anything you are forced to use a lower gain setting when running on batterys.

post #2807 of 3771
Quote:
Originally Posted by Whitecitadel View Post
 

Just came back from lunch and building security had my package from Stefan! :D

 

Read the o2 ODA thread - interesting. Did you mean to include a link to your separate build thread Xenophone?

If and when I get around to it, I'll certainly do so.  But not now, don't have the time at present while my job keeps me in India.  I have a vision of me hopping from business hotel to business hotel lugging along a soldering station, cutters, pliers and a bagful of tiny components to keep me occupied at night :-)  Hopefully I'll be able to stay in Europe for a couple of years starting next summer and then some serious electronics tinkering is certainly on the agenda.  For now I relegate myself to reading up on the design -really interesting as you know- and kowtowing to guys like Adyula who are courageous enough to play pioneer and debug things.  

post #2808 of 3771
Quote:
Originally Posted by mcandmar View Post
 

 

O2 running on batterys has nothing to do with it, it does however create another problem where the max voltage swing on the outputs is reduced which you may run into with power hungry headphones like the HD600 series.  If anything you are forced to use a lower gain setting when running on batterys.

 

Thanks for correction - too much late night reading and mixed issues there then.

 

Considering adding LED to my odac (going in separate B2-080), seen diagrams to use the second signal ground and the pad near the coil - assuming the 10mA or so from the USB 5v rail is inconsequential to the performance of the ODAC? Anyone else using LED on their odac?

 

Hands up that its partly as it will look smart under the o2, but also useful to indicate its powered up as my desk is a bit busy with stuff and its not always clear if something is not working as expected.

post #2809 of 3771
Quote:
Originally Posted by Whitecitadel View Post
 

 

Thanks for correction - too much late night reading and mixed issues there then.

 

Considering adding LED to my odac (going in separate B2-080), seen diagrams to use the second signal ground and the pad near the coil - assuming the 10mA or so from the USB 5v rail is inconsequential to the performance of the ODAC? Anyone else using LED on their odac?

 

Hands up that its partly as it will look smart under the o2, but also useful to indicate its powered up as my desk is a bit busy with stuff and its not always clear if something is not working as expected.

 

Use a large resistor (20-30k) and high efficiency LED (5k-10k mcd). This will result in current consumption well below 1mA.

Reply
post #2810 of 3771
Quote:
Originally Posted by jseaber View Post
 

 

Use a large resistor (20-30k) and high efficiency LED (5k-10k mcd). This will result in current consumption well below 1mA.

Thanks for tip!

 

I had to order some thinner solder earlier (I mainly solder connectors usually, decided to get something a bit more delicate and easier to control for the o2/odac) so I already picked out a 3mm in red with integral resistor rated 8mcd a max If 10mA.

 

I will test it on 5v PSU with DMM first to see what it pulls if not look for something high efficiency with large resistor as you suggest. I intentionally looked for low mcd LED as I didn't want to light the room with it, didn't think to get high efficiency with large resistor...

 

By the way, really like the JDS o2 panel design with the symbols not lettering :bigsmile_face: sadly international shipping and UK import made it not a cost effective option for me.

post #2811 of 3771

My ODA is  coming right along. got most of the 1206 SMD resistors installed, not as bad as it looks but does take awhile and you have to have a steady hand and really know how to solder....

 

I hope to have my 24 vac 1.8 amp adapter in tomorrow from Mouser and be able to apply power to check stage 1 of the power and relay action....

 

There is a lot of discussion at DIY audio on options and new stuff that have come into being since the V2.0 of the ODA have come about...if your at all serious about this amp you should go over there and follow the thread...I don't want to post in several sites etc...most of my experience is over there under the headphone area and the ODA thread.

 

Discussing voltage swings and gain and options...depending on what your cans are etc..

 

Moving Right Along..

 

Alex

post #2812 of 3771
Looking forward to your ODA progress.
post #2813 of 3771
Quote:
Originally Posted by Zorrofox View Post

I've got a question. When I bought my O2 I opted for gains of 1x/3x on the advice of a kind forum member. These gains work superbly with every pair of headphones I've tried. In fact, I've never had to use 3x gain, even with my HD 650's or my Q701's.

So why are the "standard" gains always 2.5x/6x? It looks like overkill to me.

If I listen to Rammstein as loud as I can take it (and far louder than I need it) the volume will be around the 4 o'clock position with the HD650's. Using the M -100's I'd be lucky to need to go past 1 o'clock.

So why do they use 2.5x as the low gain standard? I also seem to remember reading years ago that it's better to use more of the volume range (or something, I can't remember).

 

Hi,

 

1x/3x is the optimum when using the O2 with the ODAC only. The reason is that the ODACs 2V output as per redbook standard would overload the O2 input stage for higher gains even on AC power. Overloading the input stage results in clipping with terrible sound and a chance to fry your phones.

 

You can calculate the max permissible gain by dividing the O2s max. output voltage of 7V on AC power or 4.5V on low batteries by the input voltage of your source. In case the O2 on AC power and the ODAC it's 7V / 2V = 3.5. Please note that turning down the O2 volume pot will not prevent it from clipping with excessive gain - only turning down the volume of the source works,but that means using the dreaded software volume for ODAC due to no hardware volume pot, which might or might not result in a loss of resolution depending on bit rate.

 

Higher gain options are available since not all users use redbook compatible sources, especially mobile stuff tends to have max output voltages of less than half of redbook standard...

 

Joachim


Edited by jring - 4/29/14 at 4:06am
post #2814 of 3771

Helpful...Thanks for sharing.

post #2815 of 3771
Here is something that relates to the DAC. This has to do with integer mode which is the passing of audio information to the DAC. It looks like if integer mode is properly implemented, there should be no audible difference between it being off or on. This has to do with converting audio data from higher resolution format to that of lower resolution using dithering. Since the DAC supports using 24-bits internally, and players like J River are using 64-bit audio information internally, there will be no difference. The conversion should be trivial in this case. Even if DSP effects were being used in the player, the conversions between integer and float data should not lose information.

The only other reason for integer mode would be to address latency issues which involve the timing of audio information to the DAC. This is not a problem with audio players. Even if it was, the data is being buffered at the USB interface to the DAC anyways.

Apparently the push to implement integer mode with the various players is more for marketing purposes than for technical reasons. And if there is actually a difference, the software developer really screwed something up that is meant to be simple.
Edited by r010159 - 4/29/14 at 10:58am
post #2816 of 3771

Well I got all the parts sorted and resistors on last night, took a while to get going with decent flow through to other side as my soldering is a bit rusty! Glad I bought a decent temp controlled iron in a sale recently with a small tip as the pads for the 1/8w resistors are quite small. Checked few online tutorials, think my theory is good need more practice - any tips welcome!

 

Blog says 3x gain should be 750Ohm resistors as a pair, but head'n'hi-fi supplied 715Ohm as part of their gain resistor bundle (which was comprehensive covering all the blog gain options and more it seems) - these sound about right for 3x gain right?

 

Calculation:

High Gain Ratio = 1 + R16/R19

= 1 + 1500/715

= 3.09x

 

 Voltage Gain in dB = 20 * Log(Gain Ratio)

= 20 * Log(3.09)

=9.8dB

 

Have left out R17/R21 for 1x gain on low.

 

Surprised how long its taking to assemble, probably just me checking every component before installation and its properly in before I snip legs and move on. Suspect the caps will be quite fast to do, the IC sockets a bit fiddly, then just need to tackle the ESD sensitive bits - but I have grounded mat and wrist strap in a draw somewhere to take care of that.

 

Fingers crossed it works on power up! :)

post #2817 of 3771

I had a question about the ODAC. How does the ES9023 chip objectively perform compared to the ES9018 chip? I know the latter is much more expensive and is used in high end DACs. Any thoughts?

post #2818 of 3771
Quote:
Originally Posted by PTom View Post
 

I had a question about the ODAC. How does the ES9023 chip objectively perform compared to the ES9018 chip? I know the latter is much more expensive and is used in high end DACs. Any thoughts?

 

I can't say I have heard both, but if it helps the ODAC designer wrote on his blog in the comments for the post "odac-may-update":

Quote:
Ultimately, the ES9023 properly implemented, is an audibly transparent DAC. The window glass is completely clean. There are no perceptible flaws. It's not possible to get the glass perceptibly cleaner. While the ES9018 or ES9012 might even better measurements, I honestly don't believe they can improve on the sound quality when listening blind.

 

HTH

post #2819 of 3771
Speaking of "transparency," the O2 is supposed to be transparent compared to the DAC1 PRE. People make the claim that it's supposed to follow a "wire with gain" kind of model, but in recent listening tests I haven't found that to be the case.

MacBook Pro (X volume level) -> V-MODA Crossfade M-100
versus
MacBook Pro (X volume level) -> O2 (maximum on the volume knob, unity gain, AC powered) -> V-MODA Crossfade M-100

Were the theory of a "wire with gain" true, I should hear no difference between the above setups, no? I find the MacBook Pro's headphone out to sound much more coherent and transparent than through the double amping. Through the double amping, the bass becomes woolier and more bloated, and the treble subdued a bit. Instrument separation becomes more blurred and it just sounds less transparent to me.
Edited by miceblue - 5/8/14 at 1:35am
post #2820 of 3771


Try that with any other amp.

 

Try that with the vmoda driving the o2.

 

The setup and conclusions your assuming are not correct at all.

 

 

 

Whitecitadel...are your sure u need 3x gain? What cans are you going to drive?

 

Alex


Edited by adydula - 5/8/14 at 5:18am
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