Talk:CMoy

Cmoy is a myth
the so called "cmoy design" is just an ordinary op-amp circuit you find in the chip's datasheet. There's no "design" here as such. It's just the normal way to connect an op-amp for audio. — Preceding unsigned comment added by 92.40.217.7 (talk) 00:19, 5 January 2024 (UTC)

OP Amps
The text is misrepresenting the content of the reference. The reference merely states that a cmoy is not a good tool for evaluating op amps as some will work, and some wont. Not that the cmoy design is inherently flawed. 83.251.155.224 (talk) 16:38, 25 June 2015 (UTC)


 * Please reword to be as clear and neutral as possible. Thanks!  •  Sbmeirow  •  Talk  • 00:15, 26 June 2015 (UTC)


 * Well that's that then! 83.251.155.224 (talk) 15:37, 30 June 2015 (UTC)


 * For an unspecified reason the changes clarifying the issue were reverted, as a result I've tried to change the language of the original sentence to better reflect the source while trying to preserve the original intention (that using the wrong op-amp will lead to poor performance). There are many variations of the CMoy amp using various op-amps (which may be used correctly) so I'm not inclined to dig up sources to clarify even further but I'll try to explain somewhat informally here: the original CMoy design uses a particular op-amp and it implements it almost exactly as the datasheet recommends, that is, the circuit is well suited for the intended op-amp. The problem is there's an incorrect belief that op-amps are largely interchangeable with no modifications needed to the circuit (this belief is true of the larger audio world, not just CMoy), and as a result people have recommended using jellybean components like the Texas Instruments TL072 and found that it performs really badly. The issue is of course as the source points out, you should not take one example of one implementation of an audio related product (like an op-amp) to declare it bad; the Ti TL072 performs badly in a standard CMoy design for two reasons, the first being that the Ti TL072 requires a higher voltage than the 9v the CMoy supplies (technically +9v and -9v for up to 18v differential but this is instead to get a virtual earth not to provide 18v) and secondly that the Ti TL072 is not suited for low impedance circuits (such as driving headphones directly), this neither means that the CMoy is a bad design (as the original sentence HEAVILY implied) nor that the Ti TL072 is bad, it merely means that using a Ti TL072 incorrectly, such as in a CMoy amp, means that it will perform badly. To really drive the point across, here is a page detailing the usage of various op-amps with an almost stock CMoy design: https://tangentsoft.net/audio/opamps.html and the relevant part: "Bottom line, this chip [a Ti TL072 variant] does not like to drive low impedances. I've heard members of this op-amp family distort even at the chip's full operating voltage of 30V. I'm not talking about minor problems here — I'm talking about crunchy, ugly, obvious distortion. Therefore, I recommend using this chip only under duress, and then only if you're willing to give it a fairly high supply voltage.". And as a final addendum there are CMoy designs that have resistors between the op-amp and the headphones, which may make chips like the Ti TL072 more suitable (given that you increase the voltage by say having a power supply that plugs into mains providing say 15-30v rather than 9v batteries), although they're more likely intended for superior op-amps which also incidentally have trouble being used in low impedance modes, however these are some of many CMoy variants and quickly start to stray from the original design. Hope I've clarified the situation to anyone reading. Cheers. 94.175.26.148 (talk) 14:05, 26 November 2016 (UTC)