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panson_hk 12th August 2011 04:53 PM

LM3886 parallel
 
Anyone seen more than three 3886 in parallel? Make sense?

Michael Bean 12th August 2011 05:09 PM

In theory, yes, but as more amps are added it becomes harder to control output voltage offsets and current sharing. Whether or not it makes sense depends on what the design objective is.

Mike

pacificblue 12th August 2011 08:56 PM

Makes no sense, because there are too few speakers around with 1 Ohm coil impedance or less. A few car subwoofers maybe, but they are better off with class D amps anyhow.

If it has been done, then most likely by Rowland Research. They just love bridging and paralleling LM3886s and TDA7293s by the numbers.

abraxalito 14th August 2011 01:04 AM

I have four TDA2030A in parallel, but they're much lower current than 3886. Even if bridged, I reckon four LM3886 in parallel is overkill assuming the design is adequately heatsunk. If there is some other unusual constraint on the design, then 4 * LM3886 might be a goer in limited situations.

AndrewT 14th August 2011 09:57 AM

a BPA400 might make some sense in that each chip would not have to supply as much current into the 8ohm speaker and thus there could be some performance improvement.
But, in my view it is totally nonsensical to parallel chipamps when the LME498xx series of chip driver ICs are available.

panson_hk 15th August 2011 06:05 AM

Quote:

Originally Posted by AndrewT (Post 2671415)
a BPA400 might make some sense in that each chip would not have to supply as much current into the 8ohm speaker and thus there could be some performance improvement.
But, in my view it is totally nonsensical to parallel chipamps when the LME498xx series of chip driver ICs are available.

I think LM3886 on-chip protection is an advantage compared to LME498xx based amp. It is also much cheaper.

abraxalito 15th August 2011 06:17 AM

Yeah, both good points - a third is there's no worry at all about biassing schemes.

panson_hk 15th August 2011 06:34 AM

Quote:

Originally Posted by Michael Bean (Post 2669637)
In theory, yes, but as more amps are added it becomes harder to control output voltage offsets and current sharing. Whether or not it makes sense depends on what the design objective is.

Mike

I experience the difficulty of DC offset adjustment among the 3886s in a x3 board. Without resorting to DC servo, I may DC isolate all the inputs of the inputs and fine tune the AC gain by multi-turn trim pot of each 3886.

Well a high-quality input film cap may cost more than the DC servo.

pacificblue 15th August 2011 06:36 AM

How much cheaper than one LME498xx and a few transistors are four LM3886 and a bigger heatsink?

And what is it that four parallel LM3886 can drive in the permitted operating voltage range that three in parallel cannot?

AndrewT 15th August 2011 09:34 AM

less current clipping/limiting for improved SQ.


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