[rembrant]

I'm sure this will seem elementary to you guys. Where should I connect Input ground in a Cmoy amp with a rail splitter. I'm thinking it should be isolated from output ground. Maybe connected to supply ground? This amp is nothing special it has no ground channel or anything like that.

I'm sorry for the dumb question but I have only ever built single supply devices and I have never really had to think about it before. As of right now, I have input ground connected to the ground plane along side output ground in my layout. I had planned to order some boards tomorrow and I just wanted to be sure before I pulled the trigger.

 

[deltaydeltax]

I've seen the fewest problems when attaching directly to the filter/supply cap grounds. Some of the Philips IC amps will even oscillate if each ground pin isn't grounded in this fashion.

 

[rembrant]

So I should have the input ground connected to the negative of the battery and the rest of the circuit grounds to the ground plane?

Just to add some more info. I have one 470uf cap before the TLE. The output of the TLE is connected to the ground plane and V+ and V- are connected to the ground plane with a .1uf ceramic.

 

[MisterX]

Input ground should connect to the ground plane

 

[deltaydeltax]

Attach it to the caps where your "virtual ground" is created. I'll try to draw a diagram later.

It will definitely need to end up on the ground plane as MisterX says.

Right at the filter caps is usually what I've seen work best. If it can't be done, then so be it. You may have a decent working amp without going this far.

 

[NelsonVandal]

Quote:

Originally Posted by rembrant /img/forum/go_quote.gif I'm sure this will seem elementary to you guys...

Grounding issues are certainly not elementary to most of us. For an amateur it's not easy to understand, and even proffessionals seem to disagree about a lot of issues. Some advocate star ground and some a ground plane. Some active and some passive ground. I'd suggest you look at some schematics and layouts. Looking at your CMOY amp, maybe you'd be better of using two electrolytic capacitors - from negative rail to ground and from positive rail to ground. You should definately have two small ceramic caps from rails to ground, as close to the opamps power pins as possible.

 

[rembrant]

I don't have the room for that. Have you guys seen my PCB layout? And oh yea the ceramics are right on the pins.

The board size 1.4"x1.325" with all through the hole parts. I'm trying to fit this one in a small space. Supposedly, the TLE can source up to 40ma. The data sheet says 80ma. Do you think the opa2132 is gonna need more than that?

My first PCB design. - Page 4 - Head-Fi: Covering Headphones, Earphones and Portable Audio
Post #32 is the most updated layout as of this morning.

 

[NelsonVandal]

Quote:

Originally Posted by rembrant /img/forum/go_quote.gif I don't have the room for that. Have you guys seen my PCB layout? And oh yea the ceramics are right on the pins. The board size 1.4"x1.325" with all through the hole parts. I'm trying to fit this one in a small space. Supposedly, the TLE can source up to 40ma. The data sheet says 80ma. Do you think the opa2132 is gonna need more than that?

Yes I've seen your board. I'm a bit curious where you're going to use this amp. An analog volume control is essential to me mainly because of convenience. If you're using a DAP or portable CDP with digital volume control, I think you're going to experience a lot of noise with 11 x gain. If you're using anything but low efficient high impedance phones, the noise will drive you crazy.

It's not so much what OPA2132 needs, but what's returned from the headphones, but yes I think 40 mA is plenty enough.

 

[rembrant]

I guess you guys don't own a PSP. While its audio out sounds quite good, its volume level is very low. To put it into perspective I have been using a head banger with it for the last year or so and I don't find myself turning the volume down at all. The only other use this will have is on my desk next to my PC. Because my PC is also my home theater, I have a switch box and analog volume control that I use to switch my output from the front L/R speakers to my amp. I am planning on putting this in a very small tin so it fits in my pocket easier. The PSP is quite large and consumes most of my pocket space.

This is the tin I have designed this amp to fit in.

With three of these cells in series for power.
http://www.all-battery.com/productim...o-3-7V-150.jpg
Or these. I haven't decided yet.
http://www.all-battery.com/ProductIm...7V-15C-450.jpg