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Best sounding cheep op-amp for CMoy's? OPA2227, OPA2228, AD8066...other? - Page 2

post #16 of 106
I didn't find the AD8397's soundstage very narrow, personally; it seems to perform more happily when not using a 'ground channel' in my experience.

IMO, most op-amps are not really suited for this type of application. If you're running at 6V, use an OPA2365 or AD8397. Up to 12V, you could either try the ADA4899-1 or the OPA656 I guess, though make sure to use the Ib cancellation on the 4899 if you use that. Those are single channel op-amps. If you're more sophisticated, and feeling very adventurous, you could try the AD8099 but it takes more effort to get it stable. It needs external comp (think NP0 SMD cap) to run below gain 15, but will go down to gain 2 with such comp. Would need ample bypassing and a non-standard feedback loop. Fun chip, though, and has an Ib cancellation circuit to get it down to 100nA or so. However, it's not for beginners.

I thought that AD825 was decent; I guess you could try that *shrug*.

Also make sure, whatever you use, that you have proper rail bypass so you can get optimal performance. Just because the thing isn't squealing and burning up doesn't mean it won't benefit from implementing proper supply design. For adaptors, I'd use either the ones made by Aries (or something similar), or maybe the ones Per-Anders makes as those would make bypassing easier.
post #17 of 106
Originally Posted by Joshatdot View Post
Ahh yeah, but I would like the op-amps changeable.
You can stack those on top of other DIP8-socket == changeable.
post #18 of 106
Originally Posted by Filburt View Post
I didn't find the AD8397's soundstage very narrow
Dito. The soundstage is one of the best. It's both wide and deep yet accurate (i.e. it sounds narrow when it should, unlike e.g. LM6171/72 and LM4562). It's tremendous more impactful than AD8620, which I found to be lean and bass shy, even in front of a buffer. I've never heard any opamp close to 8397 when it comes to slam, punchy bass and impact. It's major flaw is it's "shouty" - very in your face and demanding.
post #19 of 106
Some more info... I tested the chips in a Cmoy with tweaked version of AB virtual ground, and also having their single version (lika OPA134PA against OPA2134PA) - as a "my own idea" buffered virtual ground, with AD8397 on the channels side. As I could realize the influence from both sides, I described both.

Regarding AD8397 - its soundstage is very close, but huge and deep. You feel like you could grab the drummer's stick, being amongst the instruments. It sounds a bit bright and damped, lacking a bit of transparency, however smooth and intimate. I agree with NelsonVandal, it's impact is out of range of any regular op-amp. If you need a true amp for bigger cans, use AD8397 or buffer your op-amps with BUF634s or discrete buffers. Otherwise it does not make much sense beyond IEMs. Im exaggerrating, but follow the idea.
post #20 of 106
Originally Posted by jcw122 View Post
majkel, what is used to let two single channel op amps work in a dual channel setup? Like what adapter would I buy for that?

http://cimarrontechnology.com/index....WPROD&ProdID=9 Is it this?

There are some better but I dunno where. You need 2*SO8 to DIP8 op-amp adapter. I saw ready kits including 2*AD825 and 2 small electrolytic caps, with DIP8 pinout. It was an accessory for CD player tweakers.
post #21 of 106
You could etch your own... or a group buy of an olimex-made pcb would also work
post #22 of 106
If you're exploring cheapie opamps, you may also want to give the jrc2068 a try. A bit more neutral than other jrc/njm parts.
post #23 of 106
I think it would be worthwhile if the op/amp reviewers would include the name of the headphones they used in their reviews and also the capacitance of the power supply and input capacitors in their CMoys.

post #24 of 106
Joshatdot: I have to revise my recommendation for the AD823. depending on your interpretation of cheap, the AD8066 really might be better. The AD823 is 3.2$ cheap, the ad8066 5.2$-cheap. if you intend to make complete kits, this really is a cost/performance tradeoff. the ad8066 really seems to be clearer, with better separation. but with higher current draw, and it will be more prone to oscillation because of its speed
post #25 of 106
Thread Starter 
I think I'll go for half OPA2227 & half AD8066 w/Soldered 8-DIP Socket
post #26 of 106
Thread Starter 
One other thing, what would be a good general Gain setting for either 2227 or 8066? Gain 11, Gain 6, other?
post #27 of 106
For single 9V battery it is stable and comfortable to have gain of 5~6. With two 9V batteries you can go 11 to better satisfy high impedance heaphones (lower impedances don't need much voltage).
AD8066 is for sure better than AD823. The latter is harsh and noisy.
post #28 of 106
Thread Starter 
my CMoy PCB is built for dual 9v batts, but could be used for a single.
post #29 of 106
I don't understand why you would use the OPA2227. Distortion is quite high above a few KHz. It's really designed to be used in DC or low frequency applications. The 8066 is...better I guess, but I still wouldn't recommend it.

Honestly, I'd say the most cost effective solution is just to use AD8397s for these if you're planning to hand them out to people. It's inexpensive and, really, it isn't particularly difficult to use. Just do proper bypassing and it should be plenty stable. The 8066 and 2227 are far inferior in load driving capability and you're pretty much inviting much higher distortion by using them. I'm not trying to be flippant about it (I'm not upset or anything :P), but the choices people make for their CMoys to go with chips like the OPA2227, I think, contributes greatly to the later impression people come to that they'll benefit tremendously from buying a commercial portable amp.
post #30 of 106
On the other side, who want's to compete to Mini3, XP-amp or PINT? Better do something unique.
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