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BPA300 Round 2

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#1,201
chrapladm said:
I think so Bob. Because 15-20db would be insane for me. I was told along time ago to use rms power and atleast an amp that can deliver 3db more for headroom. SO I would need 5000 watts per speaker for my subs and to have 17.5-10db more WOW!!! that would be a LOT of power. I thought I was crazy. But I understand what you are saying Andrew T.

Now my speakers I am building Bob will be very efficient. A similar speaker combo has a 105db rating.
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if you are proposing to use 105dB/W @ 1m speakers then simply subtract 10 to 15dB from my earlier example.

-15dB ref 5000W = 158W.
But, how did you come up with 5kW?
5kW into 88dB/W @ 1m speakers would give ~120dB @ 2.5m listening distance for a stereo pair. That is insane !

95dB speakers and 100W of power is more than most would want/need for any domestic occasion.
 
#1,202
Covering the last octave has always been about displacement but I also need wattage. So for my subs I need rms power. (2500 watts) Then with an added L/T circuit I will need more wattage but will just stick with 2500. Then wanting to have 3db headroom that puts me at 5000 watts. Now I will have amps that will coast by 95% of the time. Transients aren't that long but I have enough power to reach all peaks in reserve power at reference volume plus.

Now for the 105db speakers thats a whole other game.
 
#1,203
I don't use the MyRefs with the Denon 7.1. That is a completely different system with its own internal power amps. I switch speaker leads to the DIY LM3886 builds when I listening to two channel stereo music. I rediscovered the simplicity and accuracy of straight-up stereo once I combined the MyRefs with my current speakers. I now feel most of the DSP action/options in receivers is really unnecessary when the "amp - speaker" combination is a proper match and of sufficient quality. The "Sunflower" speakers I built are open back for the mid-range and provide all the room ambiance I need - reflects the production goals of the source material.

In "Audiophile" listening the only thing I might add form time to time is the Carver C-1 preamp with its "Sonic Hologram" capabilities.

If you want to develop a 5/7.1 system with your own builds, there is a thread dedicated to that concept elsewhere on this forum.
 
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#1,206
This is how the boards are fixed to the heatsink. I should've use a less thick clamping bar, but that's what I had in hand.
 

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#1,208
You and those Rifa's. If I had them I would show them off too. We just do not have a full compliment supplier here in the U.S. at affordable prices for those monsters. Even if you find them overseas the shipping will kill you.
Things are looking really nice so far. How you liking all that aluminum tapping? Ain't it fun.

Tad
 
#1,209
tryonziess said:
You and those Rifa's. If I had them I would show them off too. We just do not have a full compliment supplier here in the U.S. at affordable prices for those monsters. Even if you find them overseas the shipping will kill you.
Things are looking really nice so far. How you liking all that aluminum tapping? Ain't it fun.

Tad
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I got the RIFAs from Elfa.se, P/N is 67-685-92. The cost killed me, you're right. But because the amplifier is being made for a friend, he pays 😉 :

Net value................ 250,80 EUR
Freight cost............. 20,00 EUR
Taxes.................... 67,70 EUR
---------------------------------------
Gross value.............. 338,50 EUR


I managed to don't make any tapping (lucky me) 😛 I made "fake holes", don't know the name in english. See the attached picture.
 

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#1,211
Adjusting individual bias on BPA300

Can anyone offer up a method for adjusting the bias trimmers on the BPA300. In the past I was not able to get much real change while turning the Bourns resistor. Alexw88 in his original article was able to get overall bias to less than .09 volts total.

Does anyone know why Jeff Rowland choose the inverted mode on this amp.

I have my old boards completely stuffed except for the trimmers which I forgot to order, duh. I will add this into a tri-amp setup and see, or listen, to what happens.

Tad
 
#1,218
Ladies and Gentlemen

Let me put all the informations in one and a right place (group buys).

Basing on alexw88's (shine7.com) experience, I've created my own project of PA150 (3xLM3886). It has been modified a bit, the size has been reduced, and some other tweaks have been made. I'd like to share the project with you (below). PDF file with switchable layers, try it! I'm gonna order the PCB soon, if anyone wants to grab a couple of PA150 PCB, let me know. Of course, tweaks still can be done before the order.

PCB layout:
http://airproject.drl.pl/PA150v18.pdf

Power supply up to +35/-35 VDC. LM3886 datasheet.
Details: PA150 - 3x LM3886 PCB assembly guide
PA150 - 3x LM3886 PCB assembly guide

I has been well tested by alex88. Testing and measurement:
DIY BPA300 6x LM3886 300W audio Amplifier

It is still the same project, except the capacitors which were moved from the bottom to the top, C10 (10u) replaced with wima (better solution), and some downsizing.

Anyone who is interested, just give me your e-mail address and I will send you some details.

Of course don't hesitate to ask questions 🙂
 
#1,219
bpa 300 gainclone

Dear marlowson,

recently I am trying to re assemble my long time never touch project, my bpa 300 alex wong (3xlm3886) , during test i found 1 of my lm3886 very hot,compared to 2 others, when i checked it broken , and i change with new lm3886 (picture attached) why its still very hot (from pin 3 i measured 16vDC at output) compare with the old 2 lm 3886, but when i assembled only using 1 lm3886 (non inverted configuration refer to chip amp.com design, it is works fine and i am tested to my speaker and tested for hours, was there any mismatch or diferrent configuration of pin of these new batch of lm3886 (serial number JM06ARE3)? realy need your help bro!

Thanks
 
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