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Need advice on first CMoy

post #1 of 8
Thread Starter 

I'm about to order parts for my first DIY CMoy and I have a few questions before I pull the trigger on my Mouser BOM. I'm going mainly off of the Tangent tutorial along with all of the suggested parts upgrades I've found by searching through the forums and looking the JDS CMoyBB parts list. I'm still left with a few questions though…

Since I am a Grado fan, I want to build my CMoy so it's tailored more or less to properly pushing them. I'm using a ~4.7k ohm resistor in R3 for a gain of 3.

1.  Since I'm using only 32 ohm headphones am I ok with using only a single 9V battery or should I use two?
2.  Will this parts list work well for the JRC4556 opamp? I'll probably try some other op amps at a later point, but for now I like how cheap this one is and I hear good things about this paired with Grado headphones.
3.  After reading the virtual ground article on Tangent I've decided to use the TLE2426 rail splitter. If I'm tailoring this for my Grados, should I go with two of them or will the single splitter be ok with the JRC4556?
4.  Are there any other points I should consider for custom tailoring this first CMoy or any parts that I need to add? I think there's enough here to do a complete build on some perf board I'll grab at Radio Shack.

 

While this is largely just a test build, if it turns out well enough I will try to stuff it into a tin and use it primarily with my iPod classic + LOD.

Thanks in advance!


Edited by mawoca - 3/18/13 at 9:25pm
post #2 of 8

JRC4556 benefits from (requires) that you equalize the input offset currents. Read Tangent's article on working with cranky op amps to see how to do it.

 

The extra caps in that article never hurt anyone. 

 

Just build it with an RA-1 style ground with 2*9V

 

Gain of 3 is more than enough for most conventional headphones for most people - even high impedance headphones. Unless you listen freakishly loud you will probably find you are ok with even less! 

post #3 of 8
Thread Starter 
So then I'm basically looking at making a cmoy identical to Fred's RA-1 cmoy. That helps a lot! Thanks!
post #4 of 8

Got a link to Fred's design? 

 

There is a lot to say for the Grado RA-1, when built for parts cost ;) when bought for $400, eeh. 

 

If you do want to stick with the TLE2426, I would use 2 or 3. The current from the op amps has to go somewhere... 

post #5 of 8
Thread Starter 
Here's a link to Fred's assembly instructions for his DIY RA-1 cmoy kit (I hope he doesn't mind). I think it makes enough sense to me that I can build my own off of that.

And here's a link to the kit itself. I would just order the kit with the PCB but I want to make my own layout and learn. It looks like he uses a single TLE2426.
post #6 of 8
Quote:
Originally Posted by mawoca View Post

Here's a link to Fred's assembly instructions for his DIY RA-1 cmoy kit (I hope he doesn't mind). I think it makes enough sense to me that I can build my own off of that.

And here's a link to the kit itself. I would just order the kit with the PCB but I want to make my own layout and learn. It looks like he uses a single TLE2426.

 

Starting off with a nice kit is the way to go, you will most likely end up spending more ordering parts then the cost of buying a pre-built pocket amp.

 

The simple fact is cmoy type chip amps have been built many times over and every single possible layout has been covered on head-fi and other forums so no point in reinventing the wheel.

The real goal is to properly drive headphones so you get the best sound you can out of them. but if you must build one from scratch pm me for a protoboard layout that i use.

post #7 of 8

I used vero board and these instructions

 

http://www.head-fi.org/t/460669/strip-board-cmoy-revisited

 

it was very easy :-)

post #8 of 8
Thread Starter 
That is a great thread smily_headphones1.gif Fred was nice enough to answer some questions I had and I placed an order at Mouser with a fair amount of confidence so now I just need to grab some protoboard from Radio Shack and wait impatiently for a few days.
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