[PachmanP]

I'm looking to build a Cmoy and I'm seeing that some use dual channel opamps while the origional at headwize uses two single channel. Being in a circuit theory class I'm at the point with a small amount of dangerous knowlegde and I just don't see how a dual channel opamp works. They don't appear to have any extra needs which is what I would think you'd need for an extra channel. So I guess my question is how do they work or do differently than a single channel opamp? Then tangentially is there a sonic benifit to using a dual channel over two singles or vis versa? Thanks.

 

[Fresno Bob]

try this its what im building along with a mint right now. http://tangentsoft.net/audio/cmoy-tutorial/

 

[PachmanP]

Yeah have that tutorial and comparing it to the origional Chu Moy article is what raised my question. Thanks though

 

[Syzygies]

Datasheets are your friend. Find an op amp available both dual and single from Mouser or Digi-Key, and download the datasheets, stare at the pinouts. You'll answer your own question in more detail than we possibly could.

The extra pins on single chips offer options most circuits don't use. More importantly, it is felt that there are some advantages to keeping the channels on separate chips to avoid crosstalk, but people have trouble hearing any difference in practice on e.g. PIMETA.

You'll never hear any difference on a CMoy.

My biggest beef with dual op amps is economic. If you start to have many different op amp sets around, and many different amp boards around, it's twice as expensive to keep chips mounted both dual and singly.

Case in point: I have $40 in OPA627's mounted on a Browndog adapter to look like a dual DIP-8 op amp. Now I can never use these on my PPA or M³ amplifier boards. That was truly dumb of me, I should have seen it coming.

 

[Fresno Bob]

Most of the c-moy that i have seen built have one op-amp and the amp is a dual based amp some may add buffers to the amp. if you want you could use two single based amps. which if im not misstaken one controls the left and the other controls the right. the reason for single op-amps is the left and right are built in. hope this babel of mine has help some. im sure some of the more better builders will add to this. or correct this.

 

[PachmanP]

Cool from the looks of pinouts on the datasheets it's just two opamps in one chip. Offest appears to be lost though but I guess it's not a big deal. Thanks again. Looks like I'll get a dually to keep size to a minimum.

 

[Clutz]

Quote:

Originally Posted by PachmanP Cool from the looks of pinouts on the datasheets it's just two opamps in one chip. Offest appears to be lost though but I guess it's not a big deal. Thanks again. Looks like I'll get a dually to keep size to a minimum.

AFAIK the dual op-amps are just two op-amps in one chip. One advantage to using a dual op-amp (such as the OPA2134) versus a single op-amp (such as the OP134) is that using a dual opamp chip reduces the number of chips required. The advantage of using two single opamps as opposed to a dual op-amp has to do with thermal interference which occurs when two opamps are in the case casing. I don't know what that means- I just know that's what most people say.

Hope that is useful.