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Old 23rd October 2011, 11:41 AM   #21
Electrons are yellow and more is better!
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A practical difference is the MUTE pin on the LM3886, very nice feature at startup.
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Old 23rd October 2011, 11:42 AM   #22
frank1 is offline frank1  United Kingdom
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^ actually that's common knowledge
Source please?
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Old 23rd October 2011, 11:46 AM   #23
AndrewT is offline AndrewT  Scotland
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Source please?
That's the polite way of asking.
I am afraid to admit, I would be less diplomatic.
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Old 23rd October 2011, 12:04 PM   #24
Electrons are yellow and more is better!
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I'll guess this phenomena is not so important here. frank, if the transistor works near it's Vce max then the distortion will increase and this is noticable in a VAS stage in particular when you have large voltage swings.

The LM3886 is a newer design so I'll guess it's improved compared to the LM3875
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Old 27th October 2011, 09:40 AM   #25
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That's the polite way of asking.
I am afraid to admit, I would be less diplomatic.
HELLO?

BANDWIDTH? BGP?

Have we all forgotten everything about transistors?

Let's forget about facts and science for a moment since that seems fleeting, and just do the old school, try-it-and-decide-for-yourself-test.
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Old 28th October 2011, 07:17 AM   #26
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For a different approach, meaningful data might include head to head measurements of real life running samples, tested at the same location, with the same equipment, on the same day and with the same methods. Otherwise, bunk.

If you want to prove speed, it could be possible to rig them both as RF amplifiers and see which one hoots to the highest frequency while also amping a reasonable quality signal. The fastest one will operate at the highest frequency with the signal still useful.

As far as operational speed as an audio amplifier, both amplifiers top out at gain 45 (48 is much poorer quality signal) when run on typical voltages, which are different. If, both amplifiers are run at the same voltage as typical for LM1875, one of them is considerably more useful for music playback. Since in this comparison, LM1875 operated further above potential and more efficiently, it would win this useless contest that didn't employ LM3886 typically. In fact, the spike system blocked validity of this, and most, comparisons. Removing that noise to achieve a hi-fi class amplifier requires Howland Current Pump (myref) or Nesting/Composite or the spurious noise cancellations of Parallel Amplifier (PA150). This is merely a financial matter. LM1875 does hi-fi cheaper and easier due to a major difference in ideal support circuit. This thread is almost like an earlier thread that talked about the quality of small op-amps with no mention of optimized support circuits for them. That still doesn't work.
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Old 29th October 2011, 09:17 AM   #27
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^ While I agree to some extent about "signal still useful", that isn't quite the whole story.

You can have a bandwidth above what is required for a signal, that (just barely) gets sufficient levels in the right time span to discriminate them digitally (or audibly) but the resolution is still poor. Rather than just falling withing the time window of a certain frequency, it still matters how close the response comes to the target.

For example, we'd never even consider a (hypothetical) transistor with a bandwidth of only 20KHz to reproduce a 20KHz signal.
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Old 1st November 2011, 11:19 AM   #28
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Okay, your scenario is possible, but we'll have to cheat.
To exploit the LM1875's speed towards a power output gain, you'd use decreased current at the feedback in addition to decreased negative feedback, a combination that's unwise for the slower LM3886. This cheater (colloquially "turbo") design for LM1875 still doesn't give it enough of a boost to out-power the LM3886.

If you ask LM1875 to make quiet quieter and loud louder, average power output doesn't increase. You did stay within safe operating area and did successfully make higher charge, slightly more efficiency, and too much gain. You made it hyperactive.

Really great for music, absolutely awful for movies.
They already whisper. Use LM3886 for movies.
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Old 1st November 2011, 12:20 PM   #29
AndrewT is offline AndrewT  Scotland
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would it help if I understood what is being posted?

Is there a willing translator in the house?
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Old 1st November 2011, 05:26 PM   #30
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Right! Comparisons between these two chips make no sense unless for specific speakers:

Bookshelf speakers that have no need of 65w?
Class A headphone amp?
A 4 ohm MTM with $5 worth of LM1875 (parallel chips) versus $6.50 worth of LM3886 (solo chip)?
Uber efficiency speakers that have no need of 65W?
Mid and Treble drive for bi-amp?

No matter how weird the comparisons may get, it still comes down to a matter of speakers.
Like apples versus oranges, its not useful as a baseball.

Last edited by danielwritesbac; 1st November 2011 at 05:30 PM.
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