BPA300 mono block finished and measured

Just finished one BPA300 mono block and used RMAA to do some measurement.

DSC05448.JPG


RMAA result :

rmaa1.jpg


More photos and details can be found at my site :

http://www.shine7.com/audio/bpa300.htm
 
Very nice indeed :nod: and you have swedish RIFA caps also :drink:

I see also that you have used SMT parts, I like it! :up:

I haven't check your pcb layout in details but it look near 100% perfect. The most critical part is the grounding since you have many amperes.

Is it possible to show as the performance of sound card alone?

Can you also show us the graphs from RMAA? The LM3886 is producing very low numbers I must say.
 
nice work

i think you have a bit of a.c. leakage which needs attending. if you look at the spectrum analysis -- you have 2 bumps -- one at at 50Hz and another at 100Hz -- you might want to figure a way of getting the hot a.c. wiring away from the gain stages -- i found that when I did this the low level distortion went down several 0.001%s -- twist the a.c. leads a bit more tightly and tack them to the bottom of the chasis with tie-wraps.

It might be too late now -- but I would move the trafo to the center of the box.
 
consider mounting the driver board on the left SIDE of the cabinet, away from the large filter cans. You can rig an L-Bracket to do this.

You have what appears to be a common mode choke on the chassis floor (or is this a choke in the capacitor ground connection to limit the turn-on current surge?). If it's a common mode choke, it could be mounted on the rear of the chasis where the mains come in.

No harm in using microphone cable to route the signals (if you don't have microphone cable, you can use CAT-5 cable with one of the conductors grounded.) I would also use CAT-5 cable for the power of the driver board -- it's pretty flexible and can be tacked to the bottom of the chasis.

When you perform tests with a distortion analyzer put the chasis cover on ;) Dress your leads so that power is at right angles to signal.
 
jackinnj said:
You have what appears to be a common mode choke on the chassis floor (or is this a choke in the capacitor ground connection to limit the turn-on current surge?). If it's a common mode choke, it could be mounted on the rear of the chasis where the mains come in.

I connected the PCB ground to the chassis ground / AC main ground thru a choke and a 10ohm resistor in series, the 10ohm can minimize the current flow between the power amp and other equipment, and thus reduce hum. The choke is intended for filtering out the HF noise from the AC ground. I have been searching for a perfect gounding scheme but it seems everyone's grounding method is different.

I am sure the 10ohm here helped a lot to reduce the 50hz hum, but not too sure about the effect of the choke.


jackinnj said:
No harm in using microphone cable to route the signals (if you don't have microphone cable, you can use CAT-5 cable with one of the conductors grounded.) I would also use CAT-5 cable for the power of the driver board -- it's pretty flexible and can be tacked to the bottom of the chasis.

I am currently using shielded twisted pair for signal, which I think is similar to a microphone cable, right?