different op-amps for a cmoy

[choweee]

hi all,

so i built a cmoy this summer for use with my grado 225's to find no change in sound. i thought it was because grados are low impedance, so i set the gain to 3.

i thought it was a waste of a project because nothing changed in terms of sound, but then it just occured to me that i remember someone mentioning how different op amps will change the sound slightly. i figured it would be worthwhile to try to see if i can get a sound i like, seeing as how op-amps are pretty cheap, and i have a working cmoy built with a socketed op-amp.

so can anyone give me a quick summary of different popular op-amps and their characteristics? thanks!!!

 

[Ozymand]

A good resource is Tangent's homepage, where he did a rundown of a lot of popular op-amps in a Cmoy-like circuit (his is different from the bog-standard Cmoy, so your results may vary).

You can find it here:

http://www.tangentsoft.net/audio/opamps.html

Also look thorugh the entirety of the audio page he has, lots of good information in there! Good luck!

 

[Earwax]

Another vote for Tangent's page. In addition, there's this thread

 

[tangent]

Quote:

no change in sound

Aside from changing op-amps, you might want to just try listening more carefully. If you were expecting a dramatic sound change, like you get when engaging the "3D" processing on some home theater receivers, you will definitely be disappointed. A low-end amp like a CMoy is good mainly for refinement, not dramatic changes.

 

[andjules]

many believe that with Grados you need more current to get them to perform well (as opposed to voltage/gain amplification) - see the Szkeres amp on headwize.com. and check this out:
Quote:

Grados are different from most high-end headphones in that they have a relatively low impedance (32 Ohms). Most others are in the hundreds of Ohms. Top of the line Sennheisers run as high as 600 Ohms. This means that Grados require more current than most headphones, therefore, general purpose headphone amps can have trouble providing appropriate power to Grados. This changes the sound quality rather than the volume—an important distinction. My Cmoy amp could drive the Grados plenty loud, but wasn't providing optimally high current handling.

from http://www.feistworks.com/ben/a47/default.asp

does your CMoy run on one 9v or two?

 

[ECM]

when i built my first cmoy for my Grados, i too didn't notice much difference. it wasn't until i used a high current chip that i could really differentiate between my PCDP and my cmoy.

i used a njr4556 dual op amp. it's really affordable and sounds pretty good with low z cans like grados.

the most dramatic change came when i built a Szekeres amp. this sucker will provide all the current the grados need. it's simple to build and sounds amazing.

 

[skyskraper]

for me cmoy was "yeah this isnt bad, sounds a bit different" then the pimeta was build and i was like "woah sweet mother of jesus, my cans sound like THIS?"

to put it mildly, you might want to trade up

i was hesitant at first for the extra cost, but the result was more then worth it. next stop, ppa.

 

[jpr703]

I started with a Pimeta and immediately noticed a huge difference in the sound of my 225s. The improvement over the out-of-the-jack sound was huge.

I'm hoping that Santa will bring me a Gilmore Lite this year. I've heard so many good things about it, especially in terms of its synergy with Grados.

 

[Syzygies]

Quote:

Originally Posted by skyskraper for me cmoy was "yeah this isnt bad, sounds a bit different" then the pimeta was build and i was like "woah sweet mother of jesus, my cans sound like THIS?"

I bought an Altoids CMoy on eBay from http://www.evilfire.com/, to tide me over before I start building my own. Taking Tangent's advice, I'll start with a Pimeta.

I hear both a distinct sonic improvement over the iPod, and plenty of room to improve. Some of my headphones really need the volts, it's that simple. Also, lots of detailed "punch". I own from decades ago a once-expensive used Stax electrostatic rig, extremely difficult for anything to compete with (except I can't fly with it!) BUT it has an overall silky effortlessness to its sound. This is a lie, sound isn't effortless. Sound bespeaks to incredible violence at the small scale, as physical objects go through rapid changes. An amp/headphone combination should convincingly convey the illusion that this physical violence is indeed taking place in the room. Here, the CMoy has a punch that the Stax don't quite have, even if in some objective sense the Stax rig is infinitely better.

For want of better words I hear a mild high frequency haze on anything with complex harmonics. However, this gets MUCH better as the amp warms up/breaks in. For a travel day, it would actually make sense to run the amp overnight first as prep. To state the obvious, people should give amps long break-ins before judging them.

 

[james902]

i'm not an experienced audiophile,

but my cmoy definitely sounds different. i really didn't notice the difference until my 3rd 9v battery. which means, i had to listen for 100+ hrs. i use the standard op2134. to me the music sounds something like... broader/wider than my laptop sound card. perhaps this is what people call "soundstage". I can't really define it better than that. perhaps someone else could. I can't even imagine how the addition of crossfeed and/or another amp would make me feel.

and my cmoy is paired with an ety.

 

[skyskraper]

i was underxagerating

the cmoy is well solid, my microcmoy is still rocking along nicely

especially with cheaper earbuds. i love my pimeta though, and am completely wrapped up in it atm

i can't wait to try a ppa or something else of a similar standard