[raoultrifan]

Soundstage increased a lot, better bass extension, trebles sound now with much more details...etc.

Kidding, of course...couldn't help myself, sorry.

Short answer: NO, I wasn't noticed any improvements, but it would probably be very difficult to improve something to Objective2 with ease. After all, O2 is measuring perfectly with sine-wave signals on inputs and I'm glad after doing the above mods I was able to make it measures almost perfectly with square-wave input signals too.

O2 is lacking a more powerful output buffer to drive planars or really low sensitive cans, otherwise...it's the perfect headamp for most headphones out there. However, it can easily drive my Fostex T50RP mk3 planars, but also the 600-ohms Beyers, so I really have no complains.

Maybe in an A/B test with 2 identical O2's I could be able hear some difference between my modded O2 and the original O2, but otherwise...my ears are not feeling a really difference, sorry. However, from my previous experience with the MUSES01 and 02 in Voltage-gain stage, but also with the Burson SS V5, I've notice a bit of increase in soundstage, but be aware of their price.

Also, the background noise is a tad lower now with the OPA1652, tested with sensitive cans (Beats Solo2 and AKG K550), O2's gain @ 3.7X and volume knob to the max (nothing connected to O2's inputs!). Also the DC-transients are lowered too when powering ON and OFF the O2. In case you want to try SOP8 opamps, feel free to follow https://www.head-fi.org/threads/make-yourself-soic8-to-dip8-adapter-56k-warnings.89714/ or similar threads. Personally, I was using DIP8 socket instead of the small PCB + pins and I had the OPA1652 mounted on top of the DIP8 socket and get it soldered (some small wires were added too, also flux was used).

 

[439598]

It might measure perfectly with a fixed sinewave (and square wave now thanks to you) but what about actual music with actual headphones? there was a huge difference when ABXing with and without those additional supply caps , even at low volume at 1x gain with efficient headphones like the M50 and AD2000X. Does the oscilloscope/testing device provide a realistic load for the amp?

 

[raoultrifan]

Neutral/analytic sound is usually good for professional applications and studio monitoring. This way you're sure the sound you get into your headphones is as close as possible to the original music. If you like a bass boost or a V-shape sound you could choose a different headmap, based on headfiers fellows recommendations of an iFi with bass-boost perhaps.

In case you like a "warm-sounding" headamp, then bear in mind that this usually means phase-shifting on sine-waves and time-delay, rounded edges on the square-waves; check the below pics of my Matrix M-Stage HPA-3B, a powerful balanced/single-ended Class-A headamp that sounds warm, pleasant, tube-like and less-fatiguing:

Matrix M-Stage HPA-3B

20Hz square-waves (phase-shift)

vs.

Objective2

20Hz square-waves


Matrix M-Stage HPA-3B

20kHz square-waves (time-delay and rounded edges/corners)

vs.

Objective2

20kHz square-waves

My own conclusion:
- Matrix HPA-3B sound more pleasant to my ears, although I'm aware that is not accurately reproducing the original sound.
- Objective2 sound a bit...clinical, too neutral and with DSD music re-mastered from original analog tapes sounds very good, instead with digitally recorder music sounds...too neutral perhaps (I'm aware that is actually the original sound, no matter my own taste).

 

[raoultrifan]

[...] even at low volume at 1x gain with efficient headphones like the M50 and AD2000X. Does the oscilloscope/testing device provide a realistic load for the amp?

You could use a higher gain for the O2 if you like, but feel free to check Tyll's measurements for the headphones you like, then compare O2's specs if match the RMS level wanted.
The loads I've used are purely resistive, but O2 is not oscillating easily, so no worries here. You can also check Tyll's measurements too.

 

[439598]

I should take some measurements with and without them to see whats really going on, hopefully a PCs microphone input is high quality enough.

 

[439598]

you were right, the opa1688 are very very good, better than everything else... no contest. also picked up a opa1612 for the voltage gain, unquestionably better than the LM4562, more neutral, more detail, no flaws whatsoever.

after replacing them it turns out the negative regulator has a different pinout to the positive regulator explaining the 'problem' (Im an idiot) , but they were replaced with 15V regulators so it wasnt a waste. cant say I notice much of a difference with 15V rails, I think it would only matter for extreme volume listening.

 

[ThanosD]

Hello, I know this thread is not particularly active, but I have problem. I want to build the O2. I have found all the parts, except the Wall Adapter. I cannot find a suitable one. JDS labs sell one with EU plug, but I cannot order from them, as they are from US, and the shipping to EU is just too much. Mouser also does not ship the adapters mentioned in the BOM spread sheet. So, do you have any idea where I could find one? EBay would be great, but any supplier from EU will do it.

 

[439598]

Hello, I know this thread is not particularly active, but I have problem. I want to build the O2. I have found all the parts, except the Wall Adapter. I cannot find a suitable one. JDS labs sell one with EU plug, but I cannot order from them, as they are from US, and the shipping to EU is just too much. Mouser also does not ship the adapters mentioned in the BOM spread sheet. So, do you have any idea where I could find one? EBay would be great, but any supplier from EU will do it.

head n hifi, they are the EU O2 builders:
http://www.headnhifi.com/components/power-supplies/power-supply-15v-ac

I dont think you can get them on ebay or at least its impossible to search for them, you just get AC-DC adapters.

really its just a 15V AC transformer in a wallwart enclosure and barrel connector cable. you will find plenty of suitable 15V transformers on mouser but you would have to wire them up your self

 

[ThanosD]

head n hifi, they are the EU O2 builders:
http://www.headnhifi.com/components/power-supplies/power-supply-15v-ac

Well, that was fast. Thanks a lot for the fast reply. I guess I can start ordering parts now.

 

[439598]

Well, that was fast. Thanks a lot for the fast reply. I guess I can start ordering parts now.

np, just check the edit I added

 

[ThanosD]

np, just check the edit I added

Yeah, searching for them is impossible. Regarding the other thing, I thought that to, but I believed that there is a reason why those particular adapters were suggested. I imagined they would have some kind of circuit, to make them more suitable for an audio device (I don't really know much about electronics yet). I wouldn't have any problems just wiring a simple transformer though. I guess something like this could work?

 

[439598]

Yeah, searching for them is impossible. Regarding the other thing, I thought that to, but I believed that there is a reason why those particular adapters were suggested. I imagined they would have some kind of circuit, to make them more suitable for an audio device (I don't really know much about electronics yet). I wouldn't have any problems just wiring a simple transformer though.

nope no difference, they are very convient and safer for beginners though.

 

[ThanosD]

nope no difference, they are very convient and safer for beginners though.

If you can, check my post, I added a link at the end. Would this work?

 

[439598]

If you can, check my post, I added a link at the end. Would this work?

yes thats fine but its need to be minimum 13W according to JDS labs

 

[ThanosD]

yes thats fine but its need to be minimum 13W according to JDS labs

Oh ok, thanks a lot again for the help,and have a good night