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alexw88 29th September 2005 07:40 AM

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

RMAA result :

More photos and details can be found at my site :

peranders 29th September 2005 08:05 AM

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.

Mad_K 29th September 2005 09:51 AM


Looks very nice!

Do you have holes in the top/bottom of your chassis?

Looking forward to hearing about your listening impressions when you get your other channel up and running..

alexw88 29th September 2005 10:14 AM

P-A, thanks for your comment!

PCB layout :

The sound card itself has THD of 0.0015%, so the THD measurement is very close to the limit of my sound card. I think the BPA300 can actually have a better THD at high wattage.

Mad K, my chassis has many holes on the side and top :

alexw88 29th September 2005 10:17 AM

P-A, the RIFA caps is capable of delivery very high current, I accidentially shorted one fully charged 47000uF with a screw driver, a very big spark occured and the steel screw driver had a big dent on the surface!

I love them! ;)

peranders 29th September 2005 10:31 AM

Have you shaked the RIFA'a? Lot's of fluid inside them.

tobias_svensk 29th September 2005 10:38 AM

Wow! impressive build & pcb's :)

jackinnj 29th September 2005 11:13 AM

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.

alexw88 29th September 2005 03:41 PM

Agreed that the AC line can be twisted tighter and should be placed away from the PCB, I think I will try to re-wire it later, may be to go in between the 2 PCBs?

Moving the transformer is a bit difficult...

alexw88 29th September 2005 04:00 PM


Originally posted by peranders

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

This is the soundcard loopback test :

I can see the soundcard has distortion at 2k and 3k, about -100dB.

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