Now,I'd like to make yet another digression. I will get back to the subject of this thread later on.
There is yet another, well known approach to construct a high power Hi-Fi amplifier employing LM3886 Chips. Here is an example on a snapshot below. I have used two boards using three LM3886 each, bridged with the use of AD134 based unbalanced to balanced converter. The both boards have a mirrored signal at the output making the output voltage double, when outputs are connected. Doubling the voltage creates four times higher power output.
With the use of +/-32V power supply, this configuration yields 200 W into 8 Ohm load.
There is yet another, well known approach to construct a high power Hi-Fi amplifier employing LM3886 Chips. Here is an example on a snapshot below. I have used two boards using three LM3886 each, bridged with the use of AD134 based unbalanced to balanced converter. The both boards have a mirrored signal at the output making the output voltage double, when outputs are connected. Doubling the voltage creates four times higher power output.
With the use of +/-32V power supply, this configuration yields 200 W into 8 Ohm load.
Well, I haven't got that far. I have abandoned it based on preliminary tests: why bother with distortion tests if the amplifier doesn't satisfy the most basic quality criteria? After preliminary tests I have found square wave response quite odd even at 1kHz, at 20 kHz response was horrid. After inspecting component values I've suspected that 47pF capacitor was too large. Replacement with 10pF improved response, but just slightly.
Then I wanted to find solution in many previous threads about BPA-200/150/100 which are the same thing. What I found is, that there were no serious attempts to measure/verify BPA design indicating that all these designs were done assuming everything will be OK. Because LM3886 itself guarantees success? There is a Youtube video about the board from #21 praising its sound. Is that guy deaf?
The YISHENG board from #1 is the right choice. More expensive but great. I use it for midrange section of a threeway system and as a standalone amplifier. And I am not Snake Oil Customer. Cheap things can be great too bout not this time.
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All I see is the designators aren't all oriented the same way, a couple overlap, and one is under the mounting bolt! Not very professional, this was a board designed in a hurry.
Also the rigid array of passives speaks of no understanding of electronic layout.
There appear to be type-II ceramic caps (coffee-coloured) in the signal path too. Now that's bad bad news and will bash the board's performance to rock bottom immediately, type-II caps have high distortion including cross-over distortion and should only be used for supply rail decoupling in an audio circuit. It might be the case these are all non-critical if in the servo circuit, but if its repeated all over that board it won't give good performance.
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