[proid]

Quote:

Hey guys.
 
DIY related question. How difficult, if at all possible, would it be to increase the current of the amplifier circuitry, ie. to increase the wattage. Is this feasible?
 
All of O2's competitors have greater output power in terms of watts per channel. I'd be interested in a DIY fix to better drive orthos.
 
Cheers!

Very easy, just double the 4556 at the output stage and you get double current output.

 

[Modulus]

Quote:

Very easy, just double the 4556 at the output stage and you get double current output.

 
How much does that component cost? And why isn't that standard practice? Have you heard this configuration?
 
Thanks for your response.

 

[proid]

Quote:

 
How much does that component cost? And why isn't that standard practice? Have you heard this configuration?
 
Thanks for your response.

 
For double current ouput, the added component will cost about 5$. But if you using this configuration, battery can only last half time as before and original O2 is able to drive almost any headphone so it's not necessary.

 

[Modulus]

Quote:

 
For double current ouput, the added component will cost about 5$. But if you using this configuration, battery can only last half time as before and original O2 is able to drive almost any headphone so it's not necessary.

 
There seems to be growing consensus that orthos benefit from higher current, so I thought it could be an interesting modification for these kind of phones. There's been lots of talk of people strapping their cans to speaker tabs and the like. What would happen if you added even another 4556? Would there be degradation of sound?
 
On a related note, what are the copyright restrictions on the O2 design? In terms of modifying and rebranding the design?

 

[MrEleventy]

It's open source so you'll have to follow open source licensing. You can modify and rebrand as well as sell but you can't do anything to limit people from doing the same to your product.

 

[stv014]

You can of course freely modify it for your own personal usage, but the license (Creative Commons Attribution No-Derivs 3.0) actually does not allow for the distribution of modified versions without the designer's permission.
 
Adding more 4556's might not require major changes to the schematics, but you would need to modify the PCB layout, which has been carefully optimized for the best performance, and does not have much space for additional parts. As a quick hack solution, you could just solder the additional chips in parallel onto the existing ones, with the exception of the output and inverting input pins, which for each amplifier should be soldered together and connected through 1 Ω resistors to the headphone output. Note that this modification will increase the DC offset on the output somewhat (because of the doubled input bias current from the 4556 chips), and the power supply section may possibly also need some changes for the doubled current output.

 

[agdr]

Quote:

 
DIY related question. How difficult, if at all possible, would it be to increase the current of the amplifier circuitry, ie. to increase the wattage. Is this feasible?
 
All of O2's competitors have greater output power in terms of watts per channel. I'd be interested in a DIY fix to better drive orthos.
 

 
If you are thinking desktop and not portable, take a look at this one that I came up with:
 
https://drive.google.com/folderview?id=0B67cJELZW-i8VmhVNk5PODNtZnc&usp=sharing   80mm x 160mm PCB -> latest date
 
All DIY that uses 3 of the NJM4556AL (SIP inline version of the NJM45556 instead of the DIP version, but same internals) in parallel on each channel for a total of 320mA usable (after quiescent chip draw) output per channel.  Has +/-16Vdc rails (in one position, +/-7Vdc in the other switch position) for a 14.5Vdc maximum swing vs. the O2's 10Vdc max (10.5V rms vs. 7V rms with the O2).  So it will drive cans that need more voltage swing and/or a lot more current.  4 gain positions vs. 2, 3.5mm and 1/4" out, RCA and 3.5mm input, pre-amp output, clipping indicator, 0.5R balancing resistors instead of 1R, 2 sets of voltage regulators (pre and final low noise LDO), output relay to prevent thumps, 1K pot for low Johnson noise and some other goodies. 

 
I'm not selling anything.  It is all DIY.  The PC board can be made by sending the Gerber file in the link off to a board house like Seeed Studio (4 layer, 160mm x 80mm).  The build involves some surface mount parts, 1206 sized resistors and caps along with the through hole, so a little more involved - and twice as many parts - as the O2.  But similar design with the pot and coupling caps in the middle and gain stage in front.  So far the consensus has been (big discussion in another forum) that it is different enough to be a separate design, not a O2 derivative.  No batteries, no power management circuit, not portable.
 
It uses the larger (than the O2) B4-080BL case, or can use 2 boards end-to-end in a longer B4-160BL case, which then easily holds an ODAC on the back board.  The back board just has the PSU section populated in the 2 board option, while the front board has everything but the PSU populated.  In one of the folders in the link there are CAD files for the front and back panels which can be sent off to outfits like Proto Panel (the one I used) or Front Panel Express.  The panel hole measurements are all also in a spreadsheet there to self-drill the panels that come with the case.  The BOM lists all the Mouser numbers and some cross references to Digikey, Farnell, Allied, and others.

 

[Modulus]

@stv014
Thank you for the very useful information.
 
@agdr
Wow. You've done an incredible amount of work on that, it's very impressive. Definitely adds some good features to the minimal O2 design. I've always felt the O2 is somehow just 'not quite right'. It seems conflicted whether to be a portable or desktop rig. I have no interest in portable audiophilia beyond good buds, and I'm sure most people are using the O2 as a desktop solution.
 
In my opinion the front AC plug, the unnecessary battery circuit and the lack of current (to preserve battery, as mentioned by another member) are problems. I am interested in building an amp that deals with these as efficiently as possible. But circuitry diagrams are scary 

. 

 

[miceblue]

Quote:

Quote:

 
DIY related question. How difficult, if at all possible, would it be to increase the current of the amplifier circuitry, ie. to increase the wattage. Is this feasible?
 
All of O2's competitors have greater output power in terms of watts per channel. I'd be interested in a DIY fix to better drive orthos.
 

 
If you are thinking desktop and not portable, take a look at this one that I came up with:
 
https://drive.google.com/folderview?id=0B67cJELZW-i8VmhVNk5PODNtZnc&usp=sharing   80mm x 160mm PCB -> latest date
 
All DIY that uses 3 of the NJM4556AL (SIP inline version of the NJM45556 instead of the DIP version, but same internals) in parallel on each channel for a total of 320mA usable (after quiescent chip draw) output per channel.  Has +/-16Vdc rails (in one position, +/-7Vdc in the other switch position) for a 14.5Vdc maximum swing vs. the O2's 10Vdc max (10.5V rms vs. 7V rms with the O2).  So it will drive cans that need more voltage swing and/or a lot more current.  4 gain positions vs. 2, 3.5mm and 1/4" out, RCA and 3.5mm input, pre-amp output, clipping indicator, 0.5R balancing resistors instead of 1R, 2 sets of voltage regulators (pre and final low noise LDO), output relay to prevent thumps, 1K pot for low Johnson noise and some other goodies. 

 
I'm not selling anything.  It is all DIY.  The PC board can be made by sending the Gerber file in the link off to a board house like Seeed Studio (4 layer, 160mm x 80mm).  The build involves some surface mount parts, 1206 sized resistors and caps along with the through hole, so a little more involved - and twice as many parts - as the O2.  But similar design with the pot and coupling caps in the middle and gain stage in front.  So far the consensus has been (big discussion in another forum) that it is different enough to be a separate design, not a O2 derivative.  No batteries, no power management circuit, not portable.
 
It uses the larger (than the O2) B4-080BL case, or can use 2 boards end-to-end in a longer B4-160BL case, which then easily holds an ODAC on the back board.  The back board just has the PSU section populated in the 2 board option, while the front board has everything but the PSU populated.  In one of the folders in the link there are CAD files for the front and back panels which can be sent off to outfits like Proto Panel (the one I used) or Front Panel Express.  The panel hole measurements are all also in a spreadsheet there to self-drill the panels that come with the case.  The BOM lists all the Mouser numbers and some cross references to Digikey, Farnell, Allied, and others.

Woah....that's freakin awesome! Very nice job with that!

 

[tdockweiler]

Do you think it's possible for a powered USB hub (attached to a massive surge protector) to degrade the sound of a DAC?
 
I had this weird problem with the V-Moda M80 today where when used with the O2 it had very bloated bass and the low mids were too forward and fatiguing. When I switched it to another amp it was perfect (no bass roll-off on the amp).
I took the powered USB hub out and the M80 now seems fine on the O2. It was like whatever was screwing up the O2 wasn't getting through on the other amp. Bizarre.
 
I'm trying to figure out what caused this because it shouldn't be the O2s fault but something else weird going on.
 
Nothing else on that powered hub attached. Maybe it's just a bad hub (it's a Belkin). I'm using very short high quality cables too ($10 ones).
 
I should point out that the differences are barely noticeable on my Q701 and HD-650. Mostly it's on headphones that are closed and with a little bass emphasis.

 

[MrEleventy]

Do you think it's possible for a powered USB hub (attached to a massive surge protector) to degrade the sound of a DAC?

I had this weird problem with the V-Moda M80 today where when used with the O2 it had very bloated bass and the low mids were too forward and fatiguing. When I switched it to another amp it was perfect (no bass roll-off on the amp).
I took the powered USB hub out and the M80 now seems fine on the O2. It was like whatever was screwing up the O2 wasn't getting through on the other amp. Bizarre.

I'm trying to figure out what caused this because it shouldn't be the O2s fault but something else weird going on.

Nothing else on that powered hub attached. Maybe it's just a bad hub (it's a Belkin). I'm using very short high quality cables too ($10 ones).

I should point out that the differences are barely noticeable on my Q701 and HD-650. Mostly it's on headphones that are closed and with a little bass emphasis.

... How are you powering the O2 via a USB hub? Isn't it wallwart or batteries only?

That aside, the M80s don't really gain anything from amping. I've ran them from a multitude of amps and never noticed a change vs just from the source itself. Just enjoy them as is.

 

[tdockweiler]

Quote:

... How are you powering the O2 via a USB hub? Isn't it wallwart or batteries only?

That aside, the M80s don't really gain anything from amping. I've ran them from a multitude of amps and never noticed a change vs just from the source itself. Just enjoy them as is.

I'm using a wall wart for the O2. No surge protector.
 
I actually just got the M80 today and my only good setup right now is on my PC. I haven't used a portable player in months really. I have a Clip+ and two Ipods I'll test them with later.

 

[MrEleventy]

Ooooooohhhhhhh. Ok, I think I understand now. You're saying that plugging and unplugging the hub from your computer is effecting the O2. It kinda sounds like something isn't grounded and getting into the O2. If the hub uses a seperate usb cord, try to find one with a ferrite bead and see if that does anything.

 

[BenF]

Quote:

Do you think it's possible for a powered USB hub (attached to a massive surge protector) to degrade the sound of a DAC?
 
I had this weird problem with the V-Moda M80 today where when used with the O2 it had very bloated bass and the low mids were too forward and fatiguing. When I switched it to another amp it was perfect (no bass roll-off on the amp).
I took the powered USB hub out and the M80 now seems fine on the O2. It was like whatever was screwing up the O2 wasn't getting through on the other amp. Bizarre.
 
I'm trying to figure out what caused this because it shouldn't be the O2s fault but something else weird going on.
 
Nothing else on that powered hub attached. Maybe it's just a bad hub (it's a Belkin). I'm using very short high quality cables too ($10 ones).
 
I should point out that the differences are barely noticeable on my Q701 and HD-650. Mostly it's on headphones that are closed and with a little bass emphasis.

Powered hub can definitely affect the sound, if it doesn't provide the correct voltage/current - 5v/500ma

 

[tomb]

Quote:

Powered hub can definitely affect the sound, if it doesn't provide the correct voltage/current - 5v/500ma

It depends on the power supply quality of the hub, the power demands of the DAC, and the voltage regulation capability of the DAC.  These things are all variable.  If the DAC is limited on its own capability of regulating voltage, then a powered hub may make things worse, because the powered hub's voltage supply may be from a cheap, switching supply.  If the powered hub is from a high-quality power supply, then it will make things better.  On the other hand, if the power demands of the DAC are high, but onboard voltage regulation is great, then a sufficiently powered hub may make a lot of positive difference - especially if a laptop is in the equation (never enough power).  An in-between DAC (low-power, but poor voltage regulation) may be at the complete mercy of the power supply - either PC or powered hub.  Even the cable may have effects when it comes to the power supply.