[Solrighal]

I have a couple of newbie questions if you do not mind me asking

After turning on the O2 amp, should I delay plugging in the headphone cable until the amp "warms up"?

Also, should the O2 be placed on top of a cover to prevent damage to the wooden desktop it is on? I have heard that amps can damage wooden desktops due to the amount of heat generated.

This is my first headphone amp and I have started using it tonight. So far I have noticed that the sibilance of the DT-990s has been greatly reduced. I like that very much. I wonder if it would be adequate for a pair of AKG k712s or similar models.

Can I ask you what DAC you're using?

 

[XIX47]

Can I ask you what DAC you're using?

Sure, since I am going to do quite a bit of gaming, I have a SB Z as a DAC. The built-in amp of the SB Z is not powerful enough to drive the headphones, hence why I bought the O2 amp. I do have plans to listen to orchestra/acoustic music in the future as well.

 

[Whitecitadel]

Finally got my o2 together this afternoon, sounding good!

Zorrofox does your volume knob sit flush with the panel? I fitted the retaining nut which looks like it should sit under the vol knob but it's proud just wondering what a pre-built looks like (as there from the same place)

 

[Solrighal]

Finally got my o2 together this afternoon, sounding good!

Zorrofox does your volume knob sit flush with the panel? I fitted the retaining nut which looks like it should sit under the vol knob but it's proud just wondering what a pre-built looks like (as there from the same place)

The volume knob was the only part of Walters work which jarred with me. I was able to see the assembly underneath the plastic knob.

I ordered two of these and received them within 10 days...


https://www.mayflowerelectronics.com/shop/customization-and-accessories/aluminium-volume-knob/

They do the job beautifully.

 

[adydula]

I have the new "AGDR" ODA Version 2.0 up and running, playing wonderfully here.....I am waiting on a tool to complete the front panel alignment for the holes drilled for all the jacks, switches etc...
 
Here are some pix:
 

Fig 1: The venerable O2 on the left the new ODA in the middle and one of my external ODACS on the right.
The rear RCA jacks allow for a second DAC if you want via RCA jacks and you can easily compare dacs with the press
of the input selection switch second from the right,.

Fig 2: Lots of room inside for mounting an internal ODAC if you want as well as other
options that you can include in your ODA.

Fig3: Size Differences.

Fig 4. Simplicity

Fig 5: Will put feet on the ODA in the near future.

Fig 6. Preliminary Pilot holes.

Fig 7. Back Panel, RCA inputs, On/Off Switch and the AC Power input.

Fig 8. Ready for Case.

Fig 9.Playing music!!
 
More to come...
Alex

 

[headwhacker]

Looking nice, I hope a commercial version appears soon. 

 

[Xenophon]

Congrats! Enjoy. How does it sound (strange question in the objective context but you know what I mean)?

I saw the other build pics but am struck again by the high component density on the board. Not a good project for a first build.

 

[adydula]

Hello,
 
Thanks...this project has been a very good one for me....I was waiting on someone to grab the design and re-invent the amp in a desktop version with a 1/4 jack and RCA plugs etc.
With this design we get that an much more.
 
I have listened to it for about 4 hours and have made comparisons to the venerable O2.
 
Being an analytical person I hate to make verbose generalizations but my gut is telling me its as good as the O2 for sure and maybe better....I am going to find a helper to do some real double blind testing....like the O2 designer would approve of.
 
We all are biased and that includes me as well.
 
I was blown away at the first sounds....and the fact that I have to go back a forth with the O2 and "really try to hear differences" is a good thing....
 
Its not a first time build for sure, but its very well documented now by AGDR at DIY...the build instructions are really good now.
(the hardest part is the SMD parts and soldering) This does take a steady hand and patience.
 
There are a lot of options and "customizing" if you desire and how they would fit your particular needs.
 
To some this may be a bit confusing....but all the explanations are there it takes some time to digest etc..
 
Not all options have to be done or included, like bass boost, pre-amp out etc..
 
Its a keeper here, and I will post my objective and subjective impressions soon!
 
All the best
Alex

 

[HaVoC-28]

Waiting for the carrefully level matched comparison + ABX / Blind test . 

 

[Whitecitadel]

The volume knob was the only part of Walters work which jarred with me. I was able to see the assembly underneath the plastic knob.

I ordered two of these and received them within 10 days...


https://www.mayflowerelectronics.com/shop/customization-and-accessories/aluminium-volume-knob/

They do the job beautifully.

Ok so probably as designed, if I turn it one way it's louder, the other quieter, does what I need so far

Will trawl RS and farnell at some point and see what local options are.

 

[Solrighal]

Ok so probably as designed, if I turn it one way it's louder, the other quieter, does what I need so far

Will trawl RS and farnell at some point and see what local options are.

I checked for local options too but found nothing satisfactory. Good luck.

 

[adydula]

I set the levels with a SPL to 85db with a 1Khz tone.
 
I went back and forth between the O2 and ODA.
 
Even though this is not blind testing.....which I still intend to do, after I get it in the case and buttoned up..
 
I was able to come to a conclusion that they both sound pretty much the same.
 
The ODA will be sent out to be measured objectively soon.
 
I used Brian Broomberg's "Wood" cd for wonderful bass.....for checking an amps bass tonality this is a great reference.
 
The bass was as good as the O2's, not any less IMO.
 
I could go on and on about how great it sounds, but the same that has been said by me about the O2 pertains here as well.
 
Great stuff sounds great, crap sounds like crap!
 
Its dead silent at all gain positions (all 4) with the volume cranked up to full roatation.
 
So far  I am the only person that has one of these ODA's  except for the designer AGDR.
 
There is another being built in process overseas I believe.
 
As soon as my reamer arrives I will finish up the front panel holes and get it in the case and do some double blind testing.
 
Alex

 

[adydula]

Ok here is my first set of results doing a real double blind test with a helper.

All that had to be done once the level sets were done was to swap the headphone jack from the ODA to the O2 etc or not! (I choose a level that produced 95 db) enough to make the cans really sound "good" or "loud" etc.

I did a run of 10 samples.
(I used Eva Cassidy's "Ain't No Sunshine" for the test.)

I was not able to successfully pick out either amp to any degree of certainty.

Half the time I was wrong half the time I was correct....but I was never really sure.

It was very hard to detect which one was playing and any differences....very easy to get confused.

This tells me that the amps are very very close, and that's a good thing.

To maintain the same sonic qualities of the O2 is no easy feat to me...to be as transparent and as good as the O2 is awesome.

I have to give kudos to my wife who ran the switching or not switching!!

I also spent an hour just listening, really listening to really low level in he background instruments to see if the resolving was nay better on one or the other. Same conclusion, its all there in both of the amps.

Ok so I am very happy that the ODA to me soncially seems from the same sonic "tree" that the O2 is.

No for some listening!

Alex

 

[Xenophon]

Thanks for your impressions and the testing (and thanks to your wife, I know how mine would roll her eyes were I to ask her to run the double blind test  
 
It'd be interesting to test the new version vs the old with some headphones where I feel the O2 delivers only marginally good performance such as the HE-500 and (the most extreme and in fact unfair case) my HE-6.  I'm tempted to purchase one myself but at 479 USD + the price of the ODAC + import duty and 21% VAT it's no longer in the realm of 'bargain', especially if I have to build a power supply for it (am in the EU) and a bit of a large bet for a blind purchase  because I'm not convinced it'll be able to drive the two cans in question satisfactorily, never mind what their formal specs say.  Of course I could probably sell it on if I didn't like it.
 
Hmm, gotta sleep on this one for a while.

 

[adydula]

Hey, I understand that....
 
I don't have any HE's around and don't know of any one near me etc.....but I will ask around.
 
The "other" version" may be better, but I would pm agdr directly and ask him.
(other version that being with higher rail voltages etc).
 
In one of his posts he recommends the Beta for those types of cans...
 
I have around $250 in this so far, with me doing the labor and having the good fortune of haning it work the first time.
 
The gain switch was defective but that was replaced.
 
We have one final small (2) resistor change to reduce the heat on IC11.
 
That should be it  for awhile!
 
All the best
Alex