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-   -   O2: High Performance Portable/Home Amp (http://www.anythingbutipod.com/forum/showthread.php?t=64507)

NwAvGuy 07-30-2011 07:51 PM

O2: High Performance Portable/Home Amp
 
This has been in the works a while. At the request of friends (and a few critics) I've designed my own portable/desktop amp: The Objective2 (O2 for short).

It's a very objective approach (what would you expect from an electrical engineer?) at a low cost "one size fits all" headphone amp. The goal was to show how much performance is possible on a limited budget. It's designed to outperform even far more expensive desktop amps using solid engineering rather than audiophile designer parts or mythical circuit designs.

To put this amp in perspective it will overall outperform everything FiiO makes including the E9 and E11.

For now it's a DIY amp but it's a free open source design and a few commercial companies have already expressed an interest in offering it as a kit, pre-assembled circuit board (no soldering required) and possibly even as a complete amp. Some have called it the spiritual successor to the Cmoy but the performance is an entirely different league (sorry for not being more modest!). Some highlights:
  • Enough output even for difficult headphones like the full size HiFiMan Planars and 600 ohm Beyers (7 V RMS and lots of current). It will drive nearly any headphone from 16 - 600 ohms to "live" levels.
  • Completely silent even with the most sensitive BA IEMs (zero hiss with 131 dB S/N )
  • Near zero ohm output impedance (0.5 ohms)
  • Very low distortion of any kind--some tests push the lower limits of my dScope audio analyzer.
  • ~8 hours battery life for the normal version & ~ 30 hours for the low power version
  • Indistinguishable from Benchmark DAC1 in blind listening tests
  • Switchable gain for use with different source/headphones
  • Unique battery rundown protection
  • DIY friendly, self contained on a single PC board, no surface mount parts
  • Designed for a rugged inexpensive all aluminum case with a pre-made customizable front panel available.
Documenting everything has been a huge project. I've posted 2 articles so far (including detailed measurements) and the third and final article with the rest of the details should be online no later than this coming Wednesday. Bare boards should be available around the end of the month and pre-assembled boards and/or kits could be available as early as September or October.

http://nwavguy.blogspot.com/2011/07/...phone-amp.html

And just to be clear, I'm not selling anything myself, and I don't get a penny of revenue from this design. It's open source hardware licensed under a Creative Commons License.

For the DIY crowd, once I have the final article online, I'll be starting a thread on diyAudio for those interested in building one.

For everyone else, if the O2 is popular, there should be some options in the next few months to purchase it without any soldering or special skills required.

I know many are probably curious about the price, that will be in next article. But as a hint, it was designed to outperform its closest current competitor, the AMB Mini3, in every way including the price.


http://lh5.ggpht.com/-zpzcXtQ25-E/Ti...jpg?imgmax=800

WalkGood 07-30-2011 08:28 PM

Nice job, you’ve peaked my interest, looking forward to seeing/reading more.

axon01 07-30-2011 10:05 PM

Howdy, just checking in, glad to be here..... :)

Axon

Satellite_6 07-30-2011 10:14 PM

"I know many are probably curious about the price, that will be in next article. But as a hint, it was designed to outperform its closest current competitor, the AMB Mini3, in every way including the price."

It looks like the Mini3 is like ~$100, so sounds good!

Come forth to ABI, NwAvGuy's minions. :D

korn_thoughtless6 07-30-2011 10:30 PM

I've been lurking around here for several years and nwavguy's site since he first posted his mini3 review, and I thought I should say how appreciative i am to have found all this knowledge without any of the bs at head-fi. I'm extremely interested in the O2; can't wait until more details are posted. Thanks for both abi and nwavguy's websites, I just wish other sites were this helpful.

NwAvGuy 07-30-2011 11:06 PM

Thanks. I like ABI myself. The Signal-to-Noise ratio here is so much better than at Head-Fi. And I've never had a single problem with, or even know anybody who has, any of the management/admins/mods here.

Plus bigger isn't always better. Even if Head-Fi didn't suffer from so many other problems, the sheer size is just about impossible to navigate and keep up with unless you have a spare 10 hours a day. The scale here is much more user friendly.

If anyone has questions about the O2, please just ask?

Mikerman 07-31-2011 09:37 AM

The reference to "mythical circuit designs"--love it.

Thanks--a great and interesting effort! Will enjoy seeing this as things go forward.

The DarkSide 07-31-2011 12:41 PM

Man!!! I want someone to SELL me one - I'm a "hands-off" kinda guy,...unless you want toast with that!!! Great job bro, luv this thing!

axon01 07-31-2011 02:03 PM

Quote:

Originally Posted by The DarkSide (Post 566350)
Man!!! I want someone to SELL me one - I'm a "hands-off" kinda guy,...unless you want toast with that!!! Great job bro, luv this thing!

I'm going to build the portable but I'd like to buy a nicely cased desktop model, as well.

Confispect 07-31-2011 03:33 PM

Interesting profile name. :eek::o:rolleyes:

Nice amp I'm definitely interested.

dfkt 07-31-2011 03:38 PM

Looking forward to the schematics and the price list - and hope I can get all the needed stuff in Europe as well.

NwAvGuy 07-31-2011 03:52 PM

Quote:

Originally Posted by axon01 (Post 566371)
I'm going to build the portable but I'd like to buy a nicely cased desktop model, as well.

Did you find the bits about the same board slipping into a taller aluminum case allowing adding 1/4" headphone jacks, RCA inputs, etc? I'll be making the CAD file(s) available for that version as well. You can just send them to Front Panel Express as is, or you can add your own tweaks, lettering, etc.

I'm curious if there's any sort of consensus on what people would like in the bigger version?
  1. RCA inputs on the back (even though that means ordering two panels instead of one doubling the cost)?
  2. Two 1/4" jacks instead of just one (in addition to the 3.5mm jack)?
  3. Install the board "backwards" to put most everything on the back and just have a panel mounted "off board" volume control and 1/4" jack on the front?
  4. For option #3 above, can the power switch stay on the back? (the O2 idles at 0.5 watts power and can be left on 24/7).
  5. Also for option #3? does the front need a panel mounted Power LED?

axon01 07-31-2011 04:16 PM

Quote:

Originally Posted by NwAvGuy (Post 566386)
Did you find the bits about the same board slipping into a taller aluminum case allowing adding 1/4" headphone jacks, RCA inputs, etc? I'll be making the CAD file(s) available for that version as well. You can just send them to Front Panel Express as is, or you can add your own tweaks, lettering, etc.

I'm curious if there's any sort of consensus on what people would like in the bigger version?
  1. RCA inputs on the back (even though that means ordering two panels instead of one doubling the cost)?
  2. Two 1/4" jacks instead of just one (in addition to the 3.5mm jack)?
  3. Install the board "backwards" to put most everything on the back and just have a panel mounted "off board" volume control and 1/4" jack on the front?
  4. For option #3 above, can the power switch stay on the back? (the O2 idles at 0.5 watts power and can be left on 24/7).
  5. Also for option #3? does the front need a panel mounted Power LED?

Thanks for the info..... I'm also following the blog now.

If you had to just guess, off the top of your head, what do you think it would cost, parts and all, to put your amp in a GS-1 case?

Also, is there any benefit to the desk model running off clean battery power and trickle recharging like the portable?

Is there a downside to putting the transformer in the same case, like the GS-1, as long as the case is big enough? How susceptible is the O2 to interference from a transformer?

Satellite_6 07-31-2011 04:20 PM

I kind of like the backwards idea. . . with a 1/4" jack, volume control, and LED at the front. It seems weird to have everything at the front by default, but I guess that's for simplicity.

NwAvGuy 07-31-2011 05:20 PM

Thanks Satellite, and to Axon01, there's no real benefit to running on batteries. If it's strictly a desktop amp, I would leave them out entirely.

And yes you could build the power supply alongside the amp in a big enough box--especially if you used a small toroidal transformer (as in the GS-1). There are some nice heavy and sufficiently large DIY audio chassis on eBay for around $50. Some even come with a matching volume knob, etc. But you're on your own to figure out all the connectors/controls/etc.

In terms of hum and noise the measurements might be slightly worse but it should still be way below the audible threshold even with BA IEMs. You could just use an AC transformer and feed the board at the power jack input, or a dual (bipolar) full-wave DC power supply and feed the raw DC to the O2's onboard regulators.

As for price, I have a good idea, but I'm hoping to nail down the PCB price from at least one of the vendors interested in offering it. That's one of the most expensive parts of the project so it makes a significant difference.

And to dfkt, most everything is available from Farnell and their various subsidiaries. Even what's known as Front Panel Express in the USA has a location in Berlin (Schaeffer AG) that can accept the same files for the panel(s). There might be one or two parts you have to go elsewhere to buy. And, unlike Mouser, Farnell even sells the Box Enclosure case.

Of course there are the special triple diamond buffer discrete op amps in the O2. They use proprietary transistors which have been aged in liquid nitrogen for 6 months to improve their sound. The modules have to be installed so the transistors are oriented towards the North Pole to be compatible with the earth's magnetic field. These op amp modules are only available for NwOpAmpGuy.com (no relation to me). ;)

dfkt 07-31-2011 05:29 PM

Quote:

Originally Posted by NwAvGuy (Post 566396)
And to dfkt, most everything is available from Farnell and their various subsidiaries. Even what's known as Front Panel Express in the USA has a location in Berlin (Schaeffer AG) that can accept the same files for the panel(s). There might be one or two parts you have to go elsewhere to buy. And, unlike Mouser, Farnell even sells the Box Enclosure case.

Excellent info, thanks NorthWestern(NewWave?)AudioVideoPerson. I will look into those.

Quote:

Originally Posted by NwAvGuy (Post 566396)
Of course there are the special triple diamond buffer discrete op amps in the O2. They use proprietary transistors which have been aged in liquid nitrogen for 6 months to improve their sound. The modules have to be installed so the transistors are oriented towards the North Pole to be compatible with the earth's magnetic field. These op amp modules are only available for NwOpAmpGuy.com (no relation to me). ;)

I sure hope those op-amps roll off the treble above 10kHz by 6dB/oct, otherwise they won't sound 'musical' and 'foot tapping'.

SpaceTimeMorph 08-01-2011 12:57 AM

Quote:

Originally Posted by NwAvGuy (Post 566396)
Of course there are the special triple diamond buffer discrete op amps in the O2. They use proprietary transistors which have been aged in liquid nitrogen for 6 months to improve their sound. The modules have to be installed so the transistors are oriented towards the North Pole to be compatible with the earth's magnetic field. These op amp modules are only available for NwOpAmpGuy.com (no relation to me). ;)

If it doesn't have the unobtanium shielding to prevent pion radiation from affecting the music then I don't want them.

...;)

axon01 08-01-2011 09:29 AM

Another interesting 2 battery design. How does this stack up against the O2? Measurements Here (I think the red painted opamps might be AD797s)

http://www.6moons.com/audioreviews/emmeline/strip1.jpg

NwAvGuy 08-01-2011 10:16 AM

O2 vs SR-71
 
I don't think the SR-71 has battery protection (someone please correct me if I'm wrong?) which is a big deal in my opinion. It could damage your headphones (and also the batteries).

It costs quite a bit more than the O2 and, based on the Stereophile measurements, the O2 will generally match or outperform it. JA only tested down to 150, and in one case 100 ohms. What about 25 ohm Denons? Or 60 ohm AKG K701s? Or 38 ohm HiFiMans? I have a feeling the O2 will easily better the SR-71 into those sorts of impedances.

It's (mostly)surface mount which has the advantage of making it smaller than the O2 but that also makes an amp much less DIY friendly.

fnzeee 08-01-2011 05:10 PM

Can hardly wait!
 
This looks exciting....standing by to build one.


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