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Any idea at all how the AD8656 OPAMP compares to the AD8620? - Page 2

post #16 of 23
Thread Starter 
Quote:
Originally Posted by ClieOS View Post

By non-portable, I mean you actually need to use D3 with an USB power supply of some sort since D3 doesn't have any internal power supply (battery). Seems to me that you are going the long way to solve a simple problem, which the effort might out-weight the result. Anyway, good luck to your experiment.
External power is via USB. It can even be powered via a computer or whatever other device it is plugged into (and the filtering seems to be sufficient enough for me so far, though if I run into a noisy device, as I said though, there are USB "battery packs" which use lithium-ion batteries and I have more than one even. These are actually overall more convenient to deal with than powering a CMoy with either the quite large AAAs or AAs packs or 9Vs that have to be recharged on a frequent basis and I kind of wish I could use one of them with the CMoy instead except that to get enough voltage I'd have to put them in series or something which actually would be more inconvenient.) My computers, netbook, PS2, and TVs all have USB ports on them that supply sufficient voltage for the D3 (which requires very little on its own in fact) so none of them even need anything like that battery pack. In fact, I can't think of any devices that I own where I can actually use the Fiio D3 that don't have USB. If anything, its power supply is actually far more convenient than the CMoy's...

Anyway, this thread is meant to be about the sound of two different OPAMPs, not about how portable the Fiio D3 is or whatever. Actually, let me put it this way. What if I were considering another amp such as the iBasso D-Zero with its AD8656? My current CMoy has been fried, so I'm going to have to get another. Along the way it doesn't hurt to investigate if I can find ANYTHING that even remotely approaches what I had with this. Most are much too expensive (too bad, I saw that JDS Labs has a "C421" with an option to get an AD8620, but it's $184 and I just don't think I can afford anything close to what it would cost even used right now) and really I can't afford even the D-Zero right now, but it doesn't hurt for me to at least consider it given how much easier it would be to deal with than a CMoy. (Especially given that it has a built in rechargeable lithium polymer battery and can also be powered via USB sources...) The thing is, the AD8620 in that CMoy "just fits" for me right now. It's just exactly what I needed and wanted. (Or more accurately was since the CMoy is now fried.) I don't want something that's just good, but something that suits me like that AD8620 did.
Edited by Nazo - 6/4/12 at 6:52pm
post #17 of 23
Originally Posted by justin w. View Post

the AD8656 shouldnt be used with over 5.5V

 

the AD8620 has a minimum voltage of 5V, but is not designed to run at voltages that low.  it's not a rail to rail output type op-amp and you'd have almost no voltage swing left at 5V

 

great example of why amps that allow op-amp rolling are a terrible idea

 

The Leckertons seem to run it just fine ...


Edited by kiteki - 6/4/12 at 7:11pm
post #18 of 23
Quote:
Originally Posted by Nazo View Post

Anyway, this thread is meant to be about the sound of two different OPAMPs, not about how portable the Fiio D3 is or whatever. Actually, let me put it this way. What if I were considering another amp such as the iBasso D-Zero with its AD8656? My current CMoy has been fried, so I'm going to have to get another. Along the way it doesn't hurt to investigate if I can find ANYTHING that even remotely approaches what I had with this. Most are much too expensive (too bad, I saw that JDS Labs has a "C421" with an option to get an AD8620, but it's $184 and I just don't think I can afford anything close to what it would cost even used right now) and really I can't afford even the D-Zero right now, but it doesn't hurt for me to at least consider it given how much easier it would be to deal with than a CMoy. (Especially given that it has a built in rechargeable lithium polymer battery and can also be powered via USB sources...) The thing is, the AD8620 in that CMoy "just fits" for me right now. It's just exactly what I needed and wanted. (Or more accurately was since the CMoy is now fried.) I don't want something that's just good, but something that suits me like that AD8620 did.

As I have said, D-ZERO with its AD8656 doesn't impress me much. If anything I think a cmoy with AD8620 and sufficient voltage sounds better. Since you are hunting down another cmoy, JDS's cmoyBB with the AD8620 and 18V option should be in your list. If you ever wanted to spend that much money on D-ZERO, the smart thing is to spend a bit more and get the FiiO E17 instead since it will probably have everything you want, plus better sounding. Anyway, back to AD8656 - with everything said, I just don't see it being as good as AD8620 if other things are equal. But then again, you are making a compromise so maybe you could be happy about it. AT least you know it will be better than the stock opamp in D3.


Quote:
Originally Posted by kiteki View Post

The Leckertons seem to run it just fine ...

That's because Leckerton's amps (both UHA-4 and UHA-6 variants) are all running on +/-6V with true ground and designed with AD8610 in mind. Regardless, Nick has began to offer OPA209 as stock, at least for the upcoming UHA-6 MKII and likely his future amp as well. If you look at JDS's C421-AD8620, it runs on even higher +/-7V. That's good reason why these amps sound far better than cmoy with an underpowered AD8620.
post #19 of 23
Thread Starter 
I can give the CMoy more power, that's really not such an issue, but I still have to say that I find it hard to believe that it was so underpowered if it wasn't producing ANY signs of it such as clipping or etc. Anyway, whenever I can get a new one I'll go ahead and provide ~12V of power (8xAAAs) which should at least be safely above the minimum.

Anyway, I'll just stick with the CMoy for now then. I'll go ahead and order another AD8620 (really it's not that expensive from the Chinese sellers on eBay, it's just the length of time it takes to get one that bothers me) and try to get a decent CMoy.

On the up side, my E6 is working again (it suffered a long swim in water a long time ago and despite all my efforts to fully clean and dry it out I suspect there's still some hint of dirt or something in there messing up the switches or something) and it always sounded pretty good at least. It's not an AD8620, but it does apparently use the AD8692 (well, I guess you'd know that already, lol) which seems to at the very least be pretty good.
Edited by Nazo - 6/5/12 at 12:51pm
post #20 of 23
Do note that it is quite possible to get fake (remarked from other cheap opamp) or repurposed (2nd hand scraped from other electronics) opamp from China.
post #21 of 23
Thread Starter 
I guess I'm going to have to take my chances in this case. I don't really trust myself to solder the chip right now and even with the slightly better shipping it's still only $15 this way. Up to now the seller has had great ratings anyway. I doubt that a fake could sound half as good as the real thing, so it should be blatantly obvious if it is.
post #22 of 23
Originally Posted by ClieOS View Post

Do note that it is quite possible to get fake (remarked from other cheap opamp)

 

Do you know where to find the die of the OPA627 so you can open it up and check if it's real?

post #23 of 23
You can get some sophisticated measuring tool to compare the performance of the opamp in your hand to the same opamp from a credible source (Farnell, Mouser, manufacturer, etc), but that's just indirect comparison. Besides, even the same opamp model can performance slightly different coming from different batch, especially for lower end stuff. Many times manufacturer also remarks the same opamp to different name (mainly better torrence opamp get marked a better name while lower torrence of the same model opamp get marked a lower name so they can sell the premier stuff on a higher price).

As for the actual design of the die, that's trade secret. Even if it is patent, it will probably still going to take a laboratory of equipments and a lot of work to take away the shell and compare the inner. If verification can be easily done, we wouldn't have seen so many fake opamp flowing around.the open market.
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