[ilikepie]

Ok so ive decided to make a comy amp for my soon to be dt-770's becuase im bored and have nothing better to do. I read through some threads about cmoys and i pretty much picked out all my parts. I still have a few questions though. For the wires does it really matter which kind of wires i use? I have a bunch of old ethernet cables that i use for wires. Theyre copper and pretty thin. Same thing about solder, does it really matter? I have some cheap radio shack 60/40 solder. And how small of a tip should i use? Anyway this is my parts list from digikey:

493-1098-ND CAP 0.47UF 50V ELECT VR RADIAL
2P10247-ND CAP 470UF 16V ELECT FC RADIAL
4.75KXBK-ND RES 4.75K OHM 1/4W 1% METAL FILM
100KXBK-ND RES 100K OHM 1/4W 1% METAL FILM
10.0KXBK-ND RES 10.0K OHM 1/4W 1% METAL FILM
1.00KXBK-ND RES 1.00K OHM 1/4W 1% METAL FILM
OPA2132PA-ND IC DUAL FET HI SP OP-AMP 8-DIP
AE7313-ND IC SOCKET .300 8 DIP GOLD
P2U4103-ND POT 10K OHM 12MM HORZ MET BUSHING
2238K-ND STRAP BATTERY 9V I-STYLE 4"LEAD
CP-43502PM-ND CONN JACK AUDIO 3.5MM 4COND
226-1041-ND KNOB BLK GLOSS.50"DIA .250"SHAFT

Is there anything im missing or should change? Also should i use 2x9v or is 1 enough?

 

[Garbz]

Of course it matters. Ordinary cables do not blow a hole in your pocket. It is not the same if you come out on top.

Audiowise however you will not notice any difference not in a CMoy and arugeably not in any other amp but I will not go there. Cat5 is a fine choice just remember if you use solid core cat5 that it snaps easily and can not handle stress.

Same with the solder. "Silver" solder not only will give you no improvment over 60/40, 60/40 is also cheaper, melts at a lower temperature, is much easier to work with, and far less likely to give you a dry solder joint.

 

[ilikepie]

So are there any problems with the stuff i picked out? Should i use 2 9v batteries or 1?

 

[thedoctor]

Quote:

Originally Posted by Garbz Of course it matters. Ordinary cables do not blow a hole in your pocket. It is not the same if you come out on top. Audiowise however you will not notice any difference not in a CMoy and arugeably not in any other amp but I will not go there. Cat5 is a fine choice just remember if you use solid core cat5 that it snaps easily and can not handle stress. Same with the solder. "Silver" solder not only will give you no improvment over 60/40, 60/40 is also cheaper, melts at a lower temperature, is much easier to work with, and far less likely to give you a dry solder joint.

^ i'm sure there'a a quantum physics theory somewhere to counter that post.

FWIW, build your first CMOY according to the article and don't even consider audiograde yet. best of all, just use any stock, jellybean parts that you could get cheap. the cheaper the better.
you'd most probably get into problems building it (or making it work). and then you'll just forget about it once you move to a better design.

Quote:

Originally Posted by ilikepie So are there any problems with the stuff i picked out? Should i use 2 9v batteries or 1?

is that the stuffs recomended by the article? at least tangent's article on the CMOY amp is good enough to get followed without leaving any parts. make sure you read that.
1 9V is enough. 2 is even better. 3 is too much. for an initial amp, just use one.

 

[ilikepie]

Yeah all that stuff is exactly from tangents list except the caps. People reccomended bigger caps for better peformance. How would i get audio grade? Better caps, new op amp, and tuning the gain? Whatever the gain is.
And im definately sure its gonna take me a while to put it togther. And burn my self a couple dozen times

 

[thedoctor]

Quote:

Originally Posted by ilikepie Yeah all that stuff is exactly from tangents list except the caps. People reccomended bigger caps for better peformance. How would i get audio grade? Better caps, new op amp, and tuning the gain? Whatever the gain is. And im definately sure its gonna take me a while to put it togther. And burn my self a couple dozen times

there's not much you could do to a CMOY. doubt you could hear any difference going with 470uF or 1000uF or 2000uF. the stock suggested BOM is as good as it is. the gain tuning is discussed in the article, and have little to no impact on the sound quality.

 

[Pars]

Your first item (493-1098-ND CAP 0.47UF 50V ELECT VR RADIAL) won't do. This is an electrolytic cap, and electrolytics should be avoided for coupling caps (some like BlackGates in the application, but we won't go there

). Something like 3019PH or EF1105 would work well. Polypropylene would be the best for this application, but physical size is a problem. Take a look at something like 495-1298-ND, but verify sizing before you order. The BC MKP 416 series are very good caps, something like BC2083-ND would be a good choice if you can fit them.