joethearachnid
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Old head on young shoulders.
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Post by joethearachnid on Mar 31, 2013 0:40:08 GMT
I think the difference between Frans and NwAvGuy can be neatly summed up by comparing the o2 to the C.H.AMP. The o2 is a fixed design saying 'This is the best measuring sound, anything else is wrong,' whilst the C.H.AMP is saying 'Measuring well is important, but not everyone likes the same sound so we'll let you change it'.
I take the same view with 'audio religion' as I do with general religion: I don't know what's right or wrong, but I don't ever see why I should forcibly change someone else's mind if they're happy as they are. That said, I heard the o2 at a meet once, listened to one song and the amp caught on one particular distortion and nearly deafened me with a kind of screech of sound. I've never heard anything that bad from that track before or since on any other equipment. Needless to say I stopped the music, thanked the owner for letting me try it and never touched the bloody thing again.
-JoetheArachnid
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chris1967
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Post by chris1967 on Mar 31, 2013 7:52:39 GMT
I agree that for the money we shouldn't be talking about it... it is a hell of an amp...
I think we are talking only because of the hype the designer...
If one gets rid of the batteries and makes small modification to the circuit it will become nicer...
Mike, i recommend you get it in kit form, and then put it in a larger enclosure with nice trafo... and a much better volume pot...
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Post by Rabbit on Mar 31, 2013 8:18:35 GMT
I agree that for the money we shouldn't be talking about it... it is a hell of an amp... I think we are talking only because of the hype the designer... If one gets rid of the batteries and makes small modification to the circuit it will become nicer... Mike, i recommend you get it in kit form, and then put it in a larger enclosure with nice trafo... and a much better volume pot... Oh dear ....... Just asking about the amp to see if it's worth the trouble. Nothing to do with the guy that made it!! Seems I've brought up two more unmentionables now!!! Not really interested in Nwavguy or the ex 19 year old tbh!! Maybe I won't bother with an amp then since I have a Neco. It was only going to be for a review for here anyway but it looks like it'll cause too much fuss! Now I'll get all three arch enemies in one post: Solderdude is the evil twin of NWavguy and their little protege is this 19 year old Solderbabe. In all honesty, I think the CHAMP is probably a way better amp ..... although I've never heard one!!
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chris1967
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Post by chris1967 on Mar 31, 2013 9:16:49 GMT
Ian... i think i have been talking only about the amp, and not the people... the people where mentioned along the thread so i made it clear i will not comment on them... thats all...
It is worth a try it is good... it is worth the trouble... after all it is an inexpensive amp...
Or you can try anything else, if you think it is better...
Saying this yet again i am the only one here that has actually the amp, and had many many hours of listening on it.
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Post by Rabbit on Mar 31, 2013 11:05:30 GMT
No worries, Chris. I have no feelings whatsoever about the characters behind the stuff!! They just seem to pop up out of the blue........ I'll get my hands on one perhaps and keep quiet then!! You always seem to be one step ahead of me with the gear!!!!
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Post by PinkFloyd on Mar 31, 2013 11:14:22 GMT
No worries, Chris. I have no feelings whatsoever about the characters behind the stuff!! They just seem to pop up out of the blue........ I want to know what NWavguy had for breakfast, I want to know where he goes shopping, I want to know what car he drives, is he married?, what are is hobbies?........ erm..... not really
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Deleted
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Post by Deleted on Mar 31, 2013 11:30:18 GMT
Ian If you do intend trying one, and it's a fully built version, not a kit, then JDSLabs may be best. www.jdslabs.com/item.php?fetchitem=o2fullIIRC, there were a few reports about poor soldering by Oliver, but he may have improved since then. As I suggested previously, it should outperform a CMOY due to the buffer I.C. for the output. Also, IIRC, Frans didn't agree with NWAvguy's remarks about output impedance matching for headphones like the K701. With headphones like that, 120 ohms would still be best. Regards Alex
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Post by Rabbit on Mar 31, 2013 12:15:10 GMT
Ian If you do intend trying one, and it's a fully built version, not a kit, then JDSLabs may be best. www.jdslabs.com/item.php?fetchitem=o2fullIIRC, there were a few reports about poor soldering by Oliver, but he may have improved since then. As I suggested previously, it should outperform a CMOY due to the buffer I.C. for the output. Also, IIRC, Frans didn't agree with NWAvguy's remarks about output impedance matching for headphones like the K701. With headphones like that, 120 ohms would still be best. Regards Alex OK, thanks Alex. I understand exactly what you're saying. Thanks for the heads up. My own feeling is that it may work better with iem types because there will be less noise when the vol is turned down. At high gain, input stage could clip
As you say, the other question is the output impedance not really matching too well with the K701 types and yet reports say it's fine!!
It's just a CMoy isn't it? (With a different arrangement for the gain?)
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chris1967
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Post by chris1967 on Mar 31, 2013 12:28:37 GMT
No worries, Chris. I have no feelings whatsoever about the characters behind the stuff!! They just seem to pop up out of the blue........ I'll get my hands on one perhaps and keep quiet then!! You always seem to be one step ahead of me with the gear!!!! no problem Ian... it is by coincidence that i have some of the gear we are talking about... there is so much that i want (and i don't need){and i don't have the money to buy...}... I have the JDSlabs version... If you don't want it portable i would recommend you have Mike tinker with it and make it desktop... i suspect it will be much better than the battery powered one... Sorry Mike... didn't really want to give you extra homework...
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Post by Rabbit on Mar 31, 2013 12:34:14 GMT
Chris, if the batteries are NOT inside, does an adapter power it up, or are the batteries like a buffer? ie: they supply the power while charging up.... if you see what I mean? Here's the gain thing I've been talking about from the handbook - just found it!! Distortion Cause: O2's volume control resides between its input and output stages. Some combinations of headphones and line‐level sources can overdrive the O2's input stage. Refer to NwAvGuy's blog for thorough explanation.
Solution:Use low gain, or switch to a high voltage AC adapter.
A bit more:
On Battery Power – At 2.5X gain the O2 can handle 1.8V and at 6.5X it can handle 0.7V (most LODs are 0.5V).
Using the default Low Gain setting of 2.5X it’s extremely unlikely the O2’s input will be overloaded by any reasonable fixed output source. But it could happen at higher gain settings. If you plan to use more than 2.5X gain, especially with an unusually high output source, see the Maximum Input section.
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chris1967
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Post by chris1967 on Mar 31, 2013 15:59:00 GMT
The adapter is AC and is used to charge the batteries... but it also works without the batteries inside just with the AC adapter. (With the batteries inside it does work like a buffer yes.. careful also as it does not have a charging protection circuit, thus it may ruin your rechargeable batteries if you have it always on power...)
I am not exactly sure how it is implemented but to get it to sound better is to get rid of the charging circuit altogether.
Also if i would buy it again i would not buy it in an enclosure since it has all the connections in front, and input is only a mini stereo jack... out is also mini jack... the ac adapter input is in front...
I would put it in a a larger enclosure, nice volume pot (maybe large blue Alps, or better) proper rca inputs at the back, large headphone jack... and a mother of a toroidal to keep input voltage steady...
I have always used it on low gain, never had to go more than half and a bit... it may overload if you connect to headphone out from a mp3 player if you have the volume (of the mp3 player) cranked full etc... always prefer line out.
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Post by Rabbit on Mar 31, 2013 17:12:02 GMT
Thanks Chris. I wondered about everything on the front panel. I thought perhaps it's like that so it's possible to put it into a shoulder bag or something, facing upwards for the plugs.
NwAVGuy seems to think the charging is pretty safe:
The battery specs say you can charge a NiMH battery at 1/20 the battery capacity indefinitely. Higher than that and you’ll cook the battery, and much lower will take forever to charge. That limit is about 10 mA for the O2’s batteries. A resistor can be sized setting the charge current well under that (about 6 - 7 mA) when they’re fully charged which helps prolong the life of the batteries when the amp is left plugged in. But, even better, the charge current in the O2 is proportional to the battery voltage. This speeds charging compared to a constant current source. The maximum current is around 50 mA if the battery is completely dead which is still a safe value. So no constant current limiting IC is required. It’s also dirt cheap and takes up very little board space.
So he uses AC not DC adapters. Maybe I'll see if I can get my mits on one then? It seems it's just a CMoy though really with a different arrangement for the gain and a very low output impedance. It also puts over 1/2 watt into 32 ohms which is loud!!
I'll start sending begging letters out......
After a little checking;
It puts out a lot of power but ......
The batteries don't act as a buffer. It will work with the batteries taken out, straight from the power supply. NwAVGuy might be wrong about the charging in his article. I think it's best to unplug once they are charged. The distortion thing is less likely on the low power setting, but gets a little close at high power so if you have a high output CD player, you'd need the amp on the low setting perhaps to avoid clipping.
Is it just me or do you find some of the statements he made a little bit odd for an EE? a) The perfect amp? (basically, it's a CMoy) b) The battery can be left charging safely. c) The output impedance statement - is that right? d) The amp outperforms other amps costing 3 to 4 times the price.
In my experience, EE's tend to be quite tight lipped and don't make big claims like 'the perfect amp'. They tend to shrink back if anything!!!
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chris1967
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Post by chris1967 on Mar 31, 2013 19:24:45 GMT
The amp is very powerful and as i said above drives all my phones well, and loud.
It is not wise to leave it always on charge.
I always use it on low gain... i never had to use high gain.
a) the perfect amp it is not... never mind the opamps... it sounds very good. b) it can be left overnight but no more if you want to preserve battery life. c) yes it is right d) it does sound very good and i could not hear much difference between it, and my Musical Fidelity M1 HPA (i have sold it since, and have no regrets)... the M1 had a bit more body and headroom, a little... it is a good show for the O2 and a bad show from the M1,... so the statement is true depending with what you compare it with...
It does sound a little thin, i am repeating this, and it may sound bright with some headphone combinations... it certainly is better to be partnered with warm lush headphones...
It compliments my Sennheiser HD650's very nicely... sounds ok with my Anaxilus2 moded HD800's... before the mod it was too bright. Never liked it with AKG Q701... perfect with HiFiMAN HD-300...
That's why i don't want to talk about the person, because he has a lot of absolutely correct things in his blogs, but too much self appraisal... it does not though diminish the fact that the O2 is a good amp at the price it is sold...
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Post by Rabbit on Mar 31, 2013 20:11:58 GMT
I must admit, I'm very curious. The K701's would be bright because the output impedance is way too low for them Chris. The Senns are probably a little brighter too.
The K701's are better at 120 ohms output impedance. Tried that with my Panda and they work best with that amp and output impedance imo.
The output impedance according to some shouldn't be more than 1/4 the impedance of the headphones I saw....
So for 32 ohm headphones, an 8 ohm output impedance max? However, that's not true with the K701.
I'll find one eventually .........
I'll sniff around.
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chris1967
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Post by chris1967 on Apr 1, 2013 5:44:25 GMT
It is not a matter of output impedance Ian... the amp sounds a little thin.
I am no electronic, but the output impedance story, should be implemented with good powerful amps... in small cheap designs it might create more problems than it solves.
The consensus in this forum about the K/Q 701/702 to be used on amps with 120ohm impedance maybe sonically better, but some amps may run out of steam. It has been discussed before about why and what of this old (professional?) industry standard.
I have an outboard adapter (currently at 120ohm) that i do all these tests by ear, you can make one to test A/B which sounds best for you and see what it does to your amps gain.
On the other hand i don't fancy the k701 sound (with filter or without).
Good sniffing!!
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Post by Rabbit on Apr 1, 2013 9:34:13 GMT
Most amps do run out of steam with 120 ohm out Chris.
Basically, I'm on the look out for a portable that is capable of driving the T40/T50 reasonably well.
The Neco isn't really up to it. While you get a sound and all that, the T40 needs quite a lot of current to be available and I'm wondering if this little beastie would give it enough to sound good. (Not just get a sound!!)
The bright part is possibly good news with the T40 and it puts out a lot of power. Short battery life, but hey, if it drives the T40 properly - fine.
I don't understand why those op amps sound thin. They're not bad ones. Pretty standard.
Some amps go thin when they run out of steam - but I don't think that's the case with this one. Low output impedance can raise the top a bit but it's not normally a massive change.
I know that people will say it's fine with a T40, but I'm talking about driving it properly and not just getting sound though. I can use the Fiio E5 and get sound from the T40, but I wouldn't call it a great sound!!
One is on the way. I am quite curious about the 'thinness'. Can't see why.
Won't have it for a little while though since work calls and I'm away for a week next week, so perhaps a couple of weeks time, I'll get to hear one.
I'm taking your advice, Alex and avoiding Solderbabe of Exeter. (Unless he offers one for review) His version is different in that the power supply CAN be left in safely.
So Oliver, if you want one reviewed, get in contact with the Rabbit!!
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Post by PinkFloyd on Apr 1, 2013 9:42:02 GMT
May be a long shot but have you tried one of the BaNZAI amps with the T40 Ian?
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Post by Rabbit on Apr 1, 2013 10:37:15 GMT
Yes Mike. The Morph. I wish now that I'd kept the two battery version though. Mind you, I was never keen on the battery arrangements inside. The Neco works ok but I just want something that gives plenty of current for the T50/T40. It goes into clipping on peaks with the T40 attached. Even the Aune S2 is working at 50% on the volpot to get a healthy output. Sounds good though. Looking for something with kick ass power for mobile use (or movable rather than portable)so I can double up the T40 as a workhorse as well as a home headphone when stuck in a hotel!! You're not far off the mark with the Banzais's either. The O2 is a posh CMoy, that's all. That's also why I'm so curious about this guy being an EE. He's designed a CMoy with a slightly weird gain stage to lower noise for iems but in the process has also introduced the (Lowish) likelihood of 'clipping' with anything that puts out a healthy amount of power at every volume since the gain is before the potentiometer. (In order to lower noise) Most EE's I know would say don't bother for an iem let alone put a box this size on the front and yet he claims that it's also good for medium impedance, less sensitive headphones like Senn 650 etc. Now he's blown away, perhaps it's actually possible to look at it without the nonsense and hype that went with him more in retrospect - although I am suspicious of JDS Labs selling it with his continued claims. Mind you, I hope he is right and it turns out to be the best amp under £300 - £400 as he claims. (3 to 4 times the cost of the amp is where it comes out he said!!) I like the idea that he's built something without boutique parts that delivers real power and all that but he's also a bit liberal with the claims for an objective EE. Another option is the Zigis amp plugged in or the bigger one he's introduced with three batteries, but I wasn't too happy with the charging arrangements on that so I decided to wait a while on that one until someone suggested the O2 might deliver. The little one plugged in is prone to mains noise but can go as high as 30v. Perhaps I should get a box to take say three or four 9v batteries like Mick has and plug the Zigis in. The T40 or T50 are great for monitoring but they also have the advantage of changing the lead so I can stick on a lead with a mini jack and plug in to a portable as well when I'm away. The jacks on mine have totally cleaned up now and never play up.
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Post by PinkFloyd on Apr 1, 2013 20:18:16 GMT
Yes Mike. The Morph. I wish now that I'd kept the two battery version though. Remind me of your details ;-)
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Post by Rabbit on Apr 1, 2013 20:55:23 GMT
It's OK thanks, Mike. One is being sent to me to have a listen when I get back in a couple of weeks or so. It has a lot of power so I'm just curious as to whether it drives the T40 and T50 properly. I'm all over the place at the moment.
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mrarroyo
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Our man in Miami!
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Post by mrarroyo on Apr 3, 2013 9:50:37 GMT
I wonder if the X-Can V3 at 1.5 watts would drive the T50's properly?
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Post by Rabbit on Apr 3, 2013 10:07:48 GMT
V2 is ok Miguel (especially with Little Pinkie), but the Fostex really are current hungry. The standard T50 is more sensitive and is ok - just. It's the modded T40 that needs more and sends amps just over their maximum. The modded headphone is certainly flatter sounding and more even, but it is also less sensitive and because it's really flat, you can play a lot louder without a problem. It just seems to grow more naturally and gets closer.
The Neco goes into audible clipping on peaks. The new Aune amp has to be pretty high and imo is close. I need it around 12 - 1 o clock for the t40.
The O2 supplies a lot of power in comparison to most portables which is why I'd like to try it. Plus the fact it's pretty cheap as well.
Battery life is only 8 - 10 hours from two batteries.
It just means that I could have really good sound while away from home with a pretty small set up. I like the modded t40 so much that I've even bought a posh case for it so I can carry it around!!
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Post by Deleted on Apr 3, 2013 11:00:21 GMT
V3 drives modded T50 with no problem. An ordinary EAC ripped CD is playing loud at 28dB on the scale on the volume knob. I tried the Dr Chesky test disc, which needs more power on any of my amps and at 8dB on the volume the drum solo is devestatingly loud and superb. At your listening levels Miguel you'll have no problems with T50s on a V3
My manual for the V3 says 'typically 1 watt'. The Xcans (V1) 100mw into 40 ohms, I can't find the V2 manual just now but I think its 200 or 250 mw. V8 is 1.3 watts and is driving the HE6 pretty well, though with the knob well rotated so T50 would be great with it. It's the only one of my amps that can drive the HE6. Syd
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Post by PinkFloyd on Apr 3, 2013 12:13:48 GMT
The AUNE T1 has MORE than enough welly for my T50RP..... it would blow your head off if you went past 12 o' clock
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chris1967
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Post by chris1967 on Apr 3, 2013 19:30:40 GMT
The O2 is not portable... it is transportable, since you need an AC adapter with you.
I cannot agree with he term "posh c-moy", are all opamp amps c-moys?
It is so powerful that you will cause ear damage trying to clip it into the Fostex...
Have you looked at other alternatives such as the new fiio e12 (which is fantastic by the way...) since you are looking for a portable amp? it is smaller very powerfull (880mw @ 32ohm) as well nicer and recharges from any usb charger or pc/mac?
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