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Old 4th October 2011, 12:18 PM   #1211
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Default 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
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Old 4th October 2011, 12:20 PM   #1212
AndrewT is offline AndrewT  Scotland
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Do you mean output offsets?

As far as I know the bias inside a chipamp is not adjustable.
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Old 4th October 2011, 12:44 PM   #1213
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Quote:
Originally Posted by tryonziess View Post
Does anyone know why Jeff Rowland choose the inverted mode on this amp.
I believe they want to avoid common mode distortion.

The trimmer of each 3886 is used to adjust output offset.
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Old 4th October 2011, 01:39 PM   #1214
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Quote:
Originally Posted by tryonziess View Post
Can anyone offer up a method for adjusting the bias trimmers on the BPA300.

Tad
Look at post 1136#
BPA300 Round 2
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Old 17th January 2012, 06:15 PM   #1215
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Default Order PA150 circuit boards

Can I still get four (4) of the PA150 latest group buy? Let me know.
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Old 13th November 2012, 06:22 AM   #1216
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I would like to get 4 boards also, are there any available?
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Old 15th November 2012, 01:13 PM   #1217
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Who's interested in PA150 /BPA300 group buy?

Details here:
PCB 3xLM3886 (PA150) 150W
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Old 15th November 2012, 01:16 PM   #1218
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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
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Old 27th November 2012, 10:18 AM   #1219
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Unhappy 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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Old 28th November 2012, 12:57 AM   #1220
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Default BPA 300

GOTCHA..! Problems fixed, I must not mixed different batch of lm3886t , three of themmust be in one batch number...it's sound good enough to my modified jbl lx-6
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