O2 AMP + ODAC

[AsianBatman]

I'll be using the ODAC as my main source for quite some time yet. I don't know about the Senn's, I'm torn between them and Grado's.

 
I was once torn also. Still want to own a pair of Grado's though and do plan on investing in a pair down line, just to quench my curiosity.  Was hoping for a 325i or something above that. 

 

[Solrighal]

I was once torn also. Still want to own a pair of Grado's though and do plan on investing in a pair down line, just to quench my curiosity.  Was hoping for a 325i or something above that. 

I was also looking at the 325 bit for me it's a lot of money. £300 here. It would have to sound very good indeed because it's ugly as sin, uncomfortable & poorly built. I suspect the Senn might come first. I don't suppose you're in a position to compare the HD600 with the AKG Q701?

 

[AsianBatman]

I was also looking at the 325 bit for me it's a lot of money. £300 here. It would have to sound very good indeed because it's ugly as sin, uncomfortable & poorly built. I suspect the Senn might come first. I don't suppose you're in a position to compare the HD600 with the AKG Q701?

 
Not a solid comparison. Had the chance to audition a friend's Q701s for a night. I preferred the sound and comfort of the HD600. The Q701 was too analytical for my taste and exploited some of my lower quality tracks. 

 

[Solrighal]

Not a solid comparison. Had the chance to audition a friend's Q701s for a night. I preferred the sound and comfort of the HD600. The Q701 was too analytical for my taste and exploited some of my lower quality tracks. 

I've heard that complaint before. These are my only reference you see. The details are incredible but there are times I'd prefer a bit more warmth. Not often mind, with the ODAC & O2 these are luscious but, as you imply, with the "right" recordings.

 

[agdr]

Reaching the right power is one thing, but having sufficient current going through a low-impedance/efficient headphone is another. I don't know the current limitations for the O2's op-amps, but planar magnetic headphones are current-demanding. You might not have the same bass slam as with an amp of higher current output.

 
Yeah that is the problem.  With the O2's 7Vdc peak swing on batteries you would need 7v / 33R = 212mA per channel.  The O2 can only handle around 120mA per channel with the standard NJM4556A chips.
 
Headphones like that are one of the reasons why I designed the O2 booster board.  The output chips are good for up to 250mA on peaks.

 

[r010159]

Yeah that is the problem.  With the O2's 7Vdc peak swing on batteries you would need 7v / 33R = 212mA per channel.  The O2 can only handle around 120mA per channel with the standard NJM4556A chips.

Headphones like that are one of the reasons why I designed the O2 booster board.  The output chips are good for up to 250mA on peaks.

Thanks for this bit of information. Now I understand the real advantage for using the booster board. Not just for a subtle change in fidelity.

 

[Solrighal]

"Booster board". That's twice now. What's this all about?

 

[adydula]

you can get details on the booster boards at diyaudio....
 
There is also a thread on this site as well....
 
fyi
 
Alex

 

[AsianBatman]

Great help...
Much appreciated...
 
Thanks....

 

[Solrighal]

you can get details on the booster boards at diyaudio....

There is also a thread on this site as well....

fyi

Alex

Cheers.

 

[Solrighal]

Following on from the earlier group-think on power supplies and current I've just managed to get my paws on this...

http://www.maplin.co.uk/p/maplin-10w-linear-acac-multi-voltage-power-supply-n58at

Does it make a difference? Hmm...

I feel a lot better though

 

[adydula]

I have used most all of the adapters and none really make any real world discernible difference to me.
 
I can understand how one might feel a lot better though!!
 
A.

 

[Solrighal]

I have used most all of the adapters and none really make any real world discernible difference to me.

I can understand how one might feel a lot better though!!

A.

It's just a placebo isn't it? To be honest if you knew the trouble I actually went to to source that supply you'd be seriously impressed. The company I bought it from did avert thing they possibly could, at 3 different stores and on their website, to thwart my attempts to get it.

It turned out there's some new European Directive being enacted which effectively outlaws all AC - AC adapters currently on sale. I have no idea why.

 

[agdr]

Thanks for this bit of information. Now I understand the real advantage for using the booster board. Not just for a subtle change in fidelity.

 
Along with double the otuput current, the no-thump headhone relay, and the indicator LEDs the other truely hard-and-fast benefit is the ability to run the O2 at +/-15Vdc for the rare 600 ohm low-sensitivity headphone where the O2's standard +/-12Vdc power supply won't produce enough volume.  The O2's standard output chips could overheat at +/-15Vdc, depending on specifics of the load, due to the small DIP8 package type.
 

It's just a placebo isn't it? To be honest if you knew the trouble I actually went to to source that supply you'd be seriously impressed. The company I bought it from did avert thing they possibly could, at 3 different stores and on their website, to thwart my attempts to get it.

It turned out there's some new European Directive being enacted which effectively outlaws all AC - AC adapters currently on sale. I have no idea why.

 
Hey you definitely get an "A+" on part sourcing!  I had completely forgotten about that EU power efficiency directive.  They want all power supplies to be switchers, that run at 100kHz - 1mHz or so, which are more efficient than transformers.  They also can produce switching noise so audiophiles have typically avoided them.  It can definiltey be done though - JDS Labs C5 headamp has a switcher in there and he's shown me the FFT of the output.  It is completely free of switcher noise.

 

[Solrighal]

The one I bought can be set to a few different voltages, 15V being the max. I went with 15V since the one supplied as stock was 15V. Did I do the right thing?

I've also just ordered another geek improvement which I'm sure is gonna make this sound like the dogs. I have a new machined aluminium volume knob en - route from New Yawk!

I have to thank ali-pacha for that idea. Shipping is costing me 4 times the value of the knob, lol.

I also finally found a use for those silicon bands that Fiio ships with their units. I'm using two of them to keep the ODACXL/O2 in a neat wee bundle.

There's only one wee tweak I want to perform but one thing about this project of mines has a significant sway over my choices. Namely - the design ethos behind the O2. I've got the models of both that gave stereo RCA sockets. This is great but creates some problems for me...

All my interconnects are 1.0m long and generally pretty stiff. They look ridiculous.

I need a very short stereo RCA interconnect. I can't find any online ready made so I've put the feelers out to Toxic Cables. They can make them short enough and flexible enough to allow them to be tucked in discretely. Toxic Cables are not cheap and this causes me dilemma number one - I'm not prepared to spend more on the cable than the O2 itself cost me.

Even if Toxic can do it cheap enough there's dilemma number two. The ethos behind the O2 and (to a lesser extent) the ODAC is transparency and neutrality. To this end I can hardly use an overtly coloured cable which is what I believe silver brings to the party (Toxic like silver).

Am I mad? Discuss.