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Post by imagemaker18 on Jun 2, 2013 12:17:41 GMT
After the initial impressions of my newly acquired O2 that I posted last Friday, I let the amplifier stay powered on to burn-in for about 36 hours. A lot of good things happened following this:  Listening with my modded and active filtered Fostex T50 I noticed a much improved sound stage, much more presence (better rendition of the mid-frequencies), fuller and deeper bass, and a nice smoothing out of the SQ. I don't deny the possibility that my hearing and judgment is vulnerable to expectation, for this is a natural tendency we all have. Our brains tend to alter our perception of SQ as well as that of musicality. One tends to hear what he/she wants to hear. Being trained as a performing classical musician, and expected to be critical and self-critical for the purpose of producing the best possible quality, and getting paid well to achieve it, I tend to believe that I am less inclined to be forgiving or accepting of imperfection, within reason, of course! Frans, please correct me if I am wrong, and I may be completely off on a tangent here, but I do believe that the sonority of electronic components does change after a period of burning-in - some, more than others. I know that if electrolytic capacitors, if left unused for a long period of time, tend to dry out, and need to be powered on periodically in order to "form" them. So, the opposite - powering them for a lengthy period may improve their operation. Again, I may be completely wrong here, but to my ears, the O2 improved considerably after cooking for 36 hours. Please be kindly reminded that the above is based completely on MY hearing, which, as most of us, has aberrations, compensated by very subjective judgement and prejudice! Your mileage may vary!  |
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Post by Rabbit on Jun 2, 2013 12:45:57 GMT
I've been thinking about it since Friday, Israel. I wondered whether the battery was running on low power? (So transients were curtailed?)
I never noticed changes from new or any differences between my new one and the one I borrowed.
Soundwise, I liked it from the start and still do. Chris in Greece described it as thin I think but I didn't find that. (He's the only one who'd said that)
My biggest problem was the quality of the jack sockets which I thought could have been better. One of mine was a bit rickety at the start but over time, it has become smoother and the plugs go in a bit easier now.
Screw plugs are still a problem in that they tend to have a small ridge behind the tip. Normally, the sockets cope with them but the O2 sockets don't. Therefore, I can't easily plug the DT990 into it unless I leave a full sized plug on and use an adapter.
That made me wonder whether there was a really poor connection on one of the jack sockets? (or a dirty connection?)
I've become really fond of mine. I like the power big time and haven't felt that there were problems with the sound at all.
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solderdude
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Post by solderdude on Jun 2, 2013 13:52:52 GMT
About capacitors:
Polar capacitors that have been left unconnected for tens of years need forming of the electrolytes which is the closest to being run in.
One could say 'burn-in' there but it is more that some time is needed for those parts to reach proper operating conditions.
I have revived old capacitors in the past and simply monitor the current to see when it is formed.
Can take a few seconds to hours depending on age, voltage, capacitance, manufacturer, type.
New capacitors, fresh from the manufacturer or that may have been lying around for 1 or 2 years before being sold, need a slight forming but this is a question of a few minutes or less.
Some will argue it takes hours or days but this can NOT be confirmed by current measurements (in the uA or even nA range).
resistors, transistors, semiconductors and 'ordinary' capacitors are not affected by this phenomenon.
Tubes, however, need a certain time to get into 'their zone' because they rely on thermal aspects (emission depends on temperatures).
Also some amplifiers need to reach a certain equilibrium over a period of time to 'set' itself as semiconductors are quite sensitive to temperatures and is for that reason often used as a temp sensor or for thermal compensation.
This doesn't mean that 'setting' is audible and when this effect is 'detected' it is more likely the brain adjusting/altering states than the equipment is.
Both are time related and thus that 'link' is easily made, even when no link is there in reality.
More often than not I have experienced similar things (music/gear sounding different).
When home from work for instance I put on some music on certain gear and don't like it a bit.
Same gear, same music sounds wonderful in the evening and as we speak battery fed and not recharged it is highly unlikely this phenomenon is caused by the equipment involved.
Consider the possibility a similar 'thing' has happened on receipt.
The brain is a funny thing.
IMO this same phenomenon is responsible, just like anticipation is, for a LOT of burn-in stories or stories about mains being polluted during the day and less so in the evening.
I do NOT say this is ALWAYS the case but it is a likely scenario that is often disregarded.
I sometimes do wonder how many people (often) experience similar things.
gear/music not sounding good at all and later on, while nothing but time/emotional state has changed, the same gear/music sounds great.
And I do mean considerable differences and not 'marginally small'.
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Post by imagemaker18 on Jun 2, 2013 14:00:29 GMT
I've been thinking about it since Friday, Israel. I wondered whether the battery was running on low power? (So transients were curtailed?) From the start I never ran it on batteries alone. It was always plugged into a power outlet while playing. My initial problem was not with the transients at all. They were all there. Just dry and clinical at the start. No longer the case. It has now become much more musical. Perhaps yours may have been powered a bit longer than mine before shipping, and due to variations in quality control of components, especially in electrolytic capacitors, mine sounded initially dryer than yours. I also recall reading similar comments elsewhere, in addition to RG. I did not intend to sound negative in my initial impressions, but tried to be as brutally honest as possible, based on MY hearing, of course. And, as I warned then, my impressions were subject to change with notice, and my last post was just that. I still like my Project Sunrise better, however, and will continue using it at home. It simply is more musical and three-dimensional, with more depth and power. But I do want to come across as being very impressed, especially now, with this little giant, so much that if I can get past some of the present demands on me, I would love to go ahead and build one myself, and give it to one of my sons! I agree with you there! I am wondering when they will actually give out! The tinkerer in me is already thinking of replacing them before too long with some better quality Neutriks or such. I also prefer the 6.3mm phone plug. Most of my HPs have top quality 6.3mm phone plugs. Funny you should mention this! I keep a can of DeOxit handy, and believe it or not, I sprayed my mini-plugs before testing the amp - something I periodically do, especially with mini-plugs, which are more prone to poor contact simply because of the smaller surface areas involved. |
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Post by Rabbit on Jun 2, 2013 14:20:53 GMT
The reason I mention the sockets Israel is that I did once have an amp go 'sour' on me. I felt that there was something wrong but wasn't exactly what it was. I thought that a component was starting to break down and then suddenly a connection broke. However, now you've suggested it, I went between my Horizon and O2. I too prefer the Horizon without a doubt. It's fuller and has more 'oomph' in its sound. I guess I don't expect that full blooded sound from a portable and so don't look for it. I kind of regard it as a portable only rather than a home amp. I tried it with the DT990 actually and it does kind of clean up its sound in comparison with the Horizon, but the Horizon does indeed sound more 'musical.' The O2 is better than the Neco though. That's worse in this respect. |
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Post by solderdude on Jun 2, 2013 14:42:32 GMT
There actually is a technical reason for that.
It has to do with the way a tube 'distorts'.
In SS amps huge amounts of gain is used that is being controlled/reduced (instantaneously and constantly) and this produces an excellent linearity.
Thus with 5x gain 1.0000 mV comes out as 5.000mV and 1.000 V as 5.000V.
Tube amps like the Indeed thingies, Ember, e.t.c. have NO overall feedback PLUS the tubes are used on voltages that are lower than they were intended for which adds to this non-linearity.
When low amplitudes are applied think 1.000mV (with the same 5x gain) an output voltage of around 4.999x mV will be present as for small signals the non-linear overall gain curve is pretty linear. With higher amplitude levels distortion increases as the gain is NOT as linear as SS is. In case of tubes the 2nd harmonic the most prominent and higher harmonics are also increasingly smaller in amplitude. so 1.000V becomes 4.98x V or so (illustrative and not actual numbers)
When solely looking at the numbers the O2 (most SS designs) perform much better due to the great linearity and it actually is MORE accurate in amplification (as NwAvGuy elegantly explains as well).
Since the FR spectrum of music has the biggest amplitudes in the lows (bass) there is also the biggest amount of distortion in those frequencies where the finer nuances all consist of very small amplitudes and thus are reproduced quite accurately without audible harmonics.
As the harmonic distortion is an ADDITION to the original signal this means HARMONICS (thus not the original signal) are higher and as harmonics determine the 'sound' of instruments. The bass portion is 'affected' most as the amplitudes, and therefore the non-linearities, are the biggest in a music signal.
The higher the frequency is the smaller the amplitude, the less alteration and added harmonics.
Thus also dependent on the overall volume and we hear 'more' with increasing volume.
With tubes there is 'flattening' of the tops and this means the amplitude of the original signal will be smaller and because it is 'flattened' the harmonic contents of that signal have a relatively high amount of harmonics.
For this reason the instrument appears to sound more like the same instrument but with tad (or hint of) realism as it were as an instrument by itself also has (the same but differently spread over the FR range) harmonics.
So in essence when listening to non feedback triode amplifiers we are listening to the original signal + added harmonics.
Since ALL instruments have harmonics by themselves there is a slightly bit more 'instrument' coloration present in those amplifiers.
It's something a lot of people like and 'purists' that ONLY want the original signal and nothing but the original signal hate as it is an addition and not the original.
It's the same as vinyl vs digital.
Digital is closer to the original recording but some people prefer the coloration ADDED by the way vinyl is made and reproduced.
Taste/musicality versus technically correct.
Both sides have their own fan-boys.
Pick your poison...
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Post by Rabbit on Jun 2, 2013 14:52:46 GMT
Of course. I completely forgot, Frans. We're not comparing like with like. I forget that I'm listening to a tube tbh. I know it's there looking at me but I just don't see it.
I like both really. I find SS can make a good 'mouthwash' after a dirty old tube!!
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Post by imagemaker18 on Jun 2, 2013 15:14:57 GMT
Thank you, Frans, for your sane and sobering explanation of the myth of "burning-in"! With all its imperfections, the human ear never ceases to amaze me! If judged by a standard other than scientific, it actually comes across to me as indeed perfect in its own way, paradoxically BECAUSE of its imperfections!  Connected to that magnificent machine, the human brain, it has the ability to filter and color whatever it perceives, depending on pre-programming applied by the owner! Your post, based on scientifically measured and proven facts, helps in understanding how powerfully each of us can be influenced by expectations, prejudices, and physical differences, as well as sales pitches by inflated floor-walker salesmen at stereo shops!  Your post made me think about the famous work of Helmholtz - "The SENSATIONS of Sound". It is important to note that he did not name his book "The SOUND", but instead presented SOUND as a living phenomenon, because without perception it means nothing at all! All the scientifically measured technologically perfected SOUNDS are worth nothing unless perceived and sensed by a living being with imperfect hearing! I find this beautiful and well worth contemplating! So, thanks again for setting me straight, and reminding me that, as a musician, I can be somewhat opinionated, and I should leave unanswered questions remain unanswered! Too many variables! Cheers! Israel |
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Post by Rabbit on Jun 2, 2013 15:21:45 GMT
What a brilliant post Israel.  |
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Post by imagemaker18 on Jun 2, 2013 15:26:31 GMT
What a brilliant post Israel. Thank you, Ian! |
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Post by imagemaker18 on Jun 2, 2013 15:58:16 GMT
There actually is a reason for that. It has to do with the way a tube 'distorts'. In SS amps huge amounts of gain is used that is being controlled/reduced (instantaneously and constantly) and produces excellent linearity. <snip> When looking at the numbers the O2 (most SS designs) performs better and it actually is MORE accurate in amplification (as NwAvGuy elegantly explains as well). <snip> Pick your poison... As a musician, who has toured a lot and played in various auditoriums around the globe, I tend to pick a little more intoxicating "tube poison". To my ears, while I am amazed at the accuracy of SS sound, and like it a lot for what it is, I think it should be appreciated as a separate "art form", for this is definitely NOT the SQ that one perceives while attending a live concert in an auditorium with its own peculiar distortions, depending on seat location. I am especially often bothered by the highs as recorded by close miking, and reproduced faithfully by SS. Even if one has a front row seat in a fine auditorium, the HF as well as all the rest of frequencies, are never perceived in the same way! The sound produced by the performers quickly changes quality as it travels even as little as 10 feet into the audience seats! A live concert listener would have to literally sit close (within a foot) in front of every single musician to perceive the type of close-miked, faithfully reproduced SS SQ, which is quite impossible in real life! A tube amp with its "friendly" distortion is closer to reality IMHO, for it smooths out some of these weird creations by some sound engineers, focused on super-accurate rendition of sounds that are never heard by the live concert listener! Many HiFi aficionados also tend to forget and ignore the fact that a concert hall is full of distortions, caused by wall and stage shell reflections, which in effect give that particular auditorium it's sound character (good or bad). Even the great acoustics of famous halls like Carnegie Hall, the Concertgebouw, Frank Lloyd Wright's Grady Gammage Auditorium in Tempe, Arizona, The Academy of Music in Philadelphia, and many others in effect have their individual characters defined by their peculiar distortions as generated by these reflections. Every hall, good or bad, has its individual acoustical physiognomy, or face, with its own characteristic imperfections. Some faces are prettier than others. Pick your poison! So, the unanswered question is "Which one do you pick?" I pick musicality anytime! My favorite poison! Thanks again for another reality check, Frans! |
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Post by Rabbit on Jun 3, 2013 16:04:56 GMT
Frans, the power of suggestion is strong. Now you have reminded me that the Horizon is a tube amp, I could swear now that I'm hearing the richer sounding bass region moreso and the O2 does seem very 'clean' or even 'clinical'.
I think Israel is latching on to the 'clinical' way that it presents sound. Actually, it's something that I feel very strongly with the Neco and the 86** op amps. I think that the twin brother states that differences can't be heard between op amps but I'm sure I can pick out the 86** series.
To me, they seem to be so clean and squeaky, that I kind of lose interest in the music. Norman's old Govibes were the same and he fitted the very same opamps.
I still find the added warmth from tubes very comforting and musical as well.
Bass is puzzling on a headphone. My ears detect much more bass in live situations whereas a headphone seems to make the music sound much further away and 'thin'. I've always felt that and the simple process of adding more bass doesn't do it. They just become muddy.
Perhaps it's just the room size missing and the lack of space for the music to wallow around in. To some extent, maybe a valve with its added harmonics kind of gives more of that impression which is why Israel feels that it's closer to reality? (Me too actually)
Mind you, the idea that an orchestra or a rock band emanates from little 2 inch speakers perched close to your ears does get it more into perpective.
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Post by solderdude on Jun 5, 2013 18:41:46 GMT
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Post by Rabbit on Jun 28, 2013 10:43:46 GMT
You know, I've been having a really good listen with my HD650 this morning on the O2 and it really isn't a bad sound at all. No veil. Clean. No fat bass sounds either. That got me curious, so I went to Jan Meier's site to have a look at the output impedance section where he actually shows the Beyer DT931 and HD600 on the end of 470 ohm out and 150 ohm out. It shows them both becoming more flat in the bass region at the lower impedance so maybe the low output impedance of the O2 is counterbalancing the sound of the HD650 too. It really isn't at all bad ..... and from a portable amp too. Output Impedance ComparisonA red O2!! |
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Post by deireleire on Nov 29, 2013 10:11:33 GMT
Does anybody has the O2 Low Power Option Kit (2x Texas Instruments TLE2062CP (replaces U3 and U4) 1x - Burr Brown OPA2277PA (replaces U1))? I was thinking of buying it, since I'll be using the O2 mainly for travelling.
BUT it will powering the T50RP (50 Ohm).
There are some trade offs: RESPECTABLE performance with 50 Ohm hp's, more noise more distorsion.
What does that mean in SQ? Will there be SQ loss or will only affect numbers (not hearable ranges)?
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Connected to that magnificent machine, the human brain, it has the ability to filter and color whatever it perceives, depending on pre-programming applied by the owner! 
