[drexman]

what is a suitable AC/AC adapter for europe 220V? specs, brands..?

 

[mikeaj]

Quote:

what is a suitable AC/AC adapter for europe 220V? specs, brands..?

 
It should output between 13.5V to 20V with no load.  200 mA or higher is okay.  400 mA and maybe like 14V or higher output is preferred if you're driving insensitive lower-impedance headphones like some of the planar magnetics models.

 

[symphonic]

I have a couple of laptop power supplies that are around 15 V, I think - these should do the job, right?

 

[wje]

Quote:

I have a couple of laptop power supplies that are around 15 V, I think - these should do the job, right?

Are they AC (alternating current) adapters?  Keep in mind, the DC adapters won't work.

 

[mikeaj]

It's almost undoubtedly DC...and yes, AC/AC adapters are more difficult to find.  The point is that the board itself contains most of the power supply, which does the AC/DC conversion to generate the positive and negative rails.

 

[wje]

Quote:

It's almost undoubtedly DC...and yes, AC/AC adapters are more difficult to find.  The point is that the board itself contains most of the power supply, which does the AC/DC conversion to generate the positive and negative rails.

OK, I'm not a pro when it comes to the Objective 2... just a happy owner.  However, I did come across a thread on DIYAudio, I believe where a user wanted to use a DC adapter.  In order to do so, it meant that some internal modifications to the amp itself had to be applied.  While the AC power supplies / adapters are harder to locate, it still seems like less of an issue as opposed to messing with the original design of the amp itself.  Just my .02

 

[Willakan]

Yup, using a DC adaptor is considerably more trouble than it's worth IMHO.

 

[ChickWhite]

If you really wanted to use a DC adapter, you would need to find one with +/- 12V outputs which would then require a different power connector on the O2.
 
If you wanted to use a single supply DC adapter, then you would need to do some major work on the O2, adding some sort of switcher to provide the negative supply. It will put noise on the O2. Unless you really know what you are doing, don't do it. If you do do it, I would be willing to bet that you have seriously compromised the noise floor of the O2.
 
The regulators on board are linear regulators. They do not generate any high frequency hash of their own.  It is far cheaper  to just order an AC to AC adapter from Mouser.  If you really can't find one, go to your local electronics part store/e-tailer and buy a stepdown transformer that will provide anywhere from 12Vrms to 20Vrms at 200 mA. Put it in a box with AC cord and AC out plug to match the AC in on the O2.With the specified 12V regulators 14Vrms out will handily do the job. The higher the voltage, the more heat you are going to generate. I actually have a 12V 400mA rated transformer. It's output under load from the O2 (charging batteries and playing fairly loudly with Sennheiser HD600's) is 13.8V RMS. Just enough to keep the regulators from dropping out of regulation. Under those conditions, the regulators barely feel warm to the touch. 

 

[symphonic]

AC/AC it is then - I didn't realise that it was doing the conversion on board. I'll save the other DC supplies for T-amps. Thanks for the info guys.
 
Quote:

If you really wanted to use a DC adapter, you would need to find one with +/- 12V outputs which would then require a different power connector on the O2.
 
If you wanted to use a single supply DC adapter, then you would need to do some major work on the O2, adding some sort of switcher to provide the negative supply. It will put noise on the O2. Unless you really know what you are doing, don't do it. If you do do it, I would be willing to bet that you have seriously compromised the noise floor of the O2.
 
The regulators on board are linear regulators. They do not generate any high frequency hash of their own.  It is far cheaper  to just order an AC to AC adapter from Mouser.  If you really can't find one, go to your local electronics part store/e-tailer and buy a stepdown transformer that will provide anywhere from 12Vrms to 20Vrms at 200 mA. Put it in a box with AC cord and AC out plug to match the AC in on the O2.With the specified 12V regulators 14Vrms out will handily do the job. The higher the voltage, the more heat you are going to generate. I actually have a 12V 400mA rated transformer. It's output under load from the O2 (charging batteries and playing fairly loudly with Sennheiser HD600's) is 13.8V RMS. Just enough to keep the regulators from dropping out of regulation. Under those conditions, the regulators barely feel warm to the touch. 

 

 

[glenda]

Quote:

I've been rocking my o2 for about two weeks.  Still waiting on my front panel from a group buy, but it sounds and performs like it should.  I'm using a a pair of HD 25-1 II.  I'd heard that they were a bit sibilant before from a lot of reviews, but I never heard it until I started using the o2 to power my cans.  I still love my HD 25's, but I can definitely hear them as they really are now.

Found this thread as I was looking for an FPE template to finish up this O2 build,  man this post doesn't inspire a lot of confidence. " My headphones weren't sibilant before but now with the O2 they are?"

   Kinda makes you think maybe just maybe headphones in general aren't design for an instrumentation type amplifier like this.  Oh well I'll finish it up and be able to hear for myself soon enough.
 

 

[Br777]

Quote:

The PCB is the board into which some ~80 components go into.  If you get a PCB, it has all the holes drilled in already and all the points wired together as needed.  To have a working amp, you need (1) PCB, (2) components soldered into that PCB, and (3) power source.  Power can come from two 9V batteries or from certain suitable AC/AC wall transformers.  If you use rechargeable batteries and the transformer, the circuit will charge the batteries.  It can charge batteries and operate at the same time.
 
There is a complete parts list (bill of materials) you can find, and it's possible to just copy + paste the list from mouser and order them, at least in the US.  They also stock suitable AC/AC transformers.  Parts can also be gotten elsewhere.
 
 
To assemble it, you need to obtain all ~80 components and the PCB, and solder the correct component into the correct holes marked for it.  There's no particular order--though as usual, starting from the smaller components first makes more sense--thus, no real instructions needed.  Solder them all in and it's done.  There are some extensive tips and troubleshooting advice on the blog, though.
 
Cost of ~80 components + AC/AC adapter is just under $30 before shipping.  PCB is about $10 before shipping.  Rechargeable batteries cost about $10.  If you'd rather not solder it yourself, JDS Labs offers the PCB + all components (all soldered in, so assembled), for $95 plus shipping.  You still need to get the AC/AC adapter if you buy the completed board from JDS Labs, but they do supply the batteries.
 
 
If you want an enclosure and front panel, those need to be gotten separately.

 
JDS sells fully assembled, and cased O2 amps - http://www.jdslabs.com/item.php?fetchitem=O2Full
as does epiphany acoustics for ya'll UK types - www.epiphany-acoustics.co.uk.
As does (at least i think he still does) "MRSLIM" via the diy audio forum -  http://www.diyaudio.com/
 

 

[shadow419]

Quote:

Found this thread as I was looking for an FPE template to finish up this O2 build,  man this post doesn't inspire a lot of confidence. " My headphones weren't sibilant before but now with the O2 they are?"

   Kinda makes you think maybe just maybe headphones in general aren't design for an instrumentation type amplifier like this.  Oh well I'll finish it up and be able to hear for myself soon enough.
 

Don't be scared of a little sibilance.  I actually like the sizzle in the highs better this way.  My motherboard onboard sound card, while pretty quiet, has very little power and rolled off the highs a bit. The EDM and rock I listen to definitely sounds better now.
 
And there's a difference between not being sibilant, and not being able to hear the sibilance.  The HD 25-1 II's have been called slightly sibilant in nearly every review I read before I bought them.
 

 

[LizardKing1]

The sibilance sounding good is just like tube distortion! It doesn't matter if you like it, it's still not part of the intended music. An amp shouldn't be creating it. If an amp creates te most gorgeous eargasming sibilance ever, then no matter how much better your music sounds this way, the amp is flawed.

 

[shadow419]

Quote:

The sibilance sounding good is just like tube distortion! It doesn't matter if you like it, it's still not part of the intended music. An amp shouldn't be creating it. If an amp creates te most gorgeous eargasming sibilance ever, then no matter how much better your music sounds this way, the amp is flawed.

Well it's a good thing the amp doesn't make the headphone sibilant, as it's not imparting it on any of my other headphones.  The HD 25-1's are sibilant.  

 

[Willakan]

Headphones make amplifiers sound sibilant, not the other way around!
 
(Unless you have a really crap amp, I suppose)