Originally Posted by enJr
i am thinking about building a cmoy. i wandered around the internet and read bunch of stuff.
seems that there was a guy, nwavguy, who did an awesome home amplifier called objective 2 (which is currently sold on jds labs web page, i am sure most of you aware of), which is a nice objective by the way. he also did some measurements on a standart cmoy with a flawed design.
i know there are lots of better desings, but they are too complicated to build (it would be bothersome to bug) or they are no portable (objective 2 for example)
i am thinking about morphing those two. i mean cmoybb and standart cmoy with jrc4556ad.
it is like this with 82nF//22k bass boost: image
any ideas how it is gonna turn out? any insights would be great.
His measurements on the Mini3 were seriously flawed and then got worse from there. He was trying to discredit the CMoy after smearing the Mini3, but like all very simple circuits, it tested quite well - at least for the things he tested, those which he considered important. There's a lot more to it than that.
Regardless, a CMoy is great fun and performs like a champ, especially with high-impedance phones, which is the basic reason Chu Moy invented it. In the DIY-world, though, the CMoy is sort of a rite-of-passage. All of us who've been here awhile recommend Tangent's excellent version and tutorial as a first build:
It will pretty much give you priceless experience in almost every area of DIY: soldering, wiring, picking parts for making up a BOM, even case work (hint: a paper hole punch can do a number on mint-tins). Except for the opamp, Tangent even wrote the tutorial so that you could pretty much purchase everything at the local Radio Shack.
P.S. I would stick with the opamps that Tangent recommends. An OPA2134 or 2132 will give spectacular results, doesn't cost an arm and a leg, and you can always change it out later.
P.S.S. Note that you if you go through a legitimate DIY resource such as Tangent's, the entire principles of gain are discussed and options for using different resistors to obtain different gains are clearly spelled out. There is no trumped-up "gotcha" with an isolated CMoy that happened to be built with no-gain.