I searched but there does not seem to be an extensive comparison of the two from a sonic perspective. Side comments seem to hint that STA540 is more musical, while LM4780 may be better technically, though I don't really know what these assessments mean.
Whether it's the dual supply for LM4780 or the single (I think 18v) supply for STA540, I will be using linear regulated power supplies based on LT1083 (7.5A capacity) -- the one for LM4780 will have two LT1083 while the one for STA540 will have one.
My speakers are 8ohm and very efficient. The STA540 will be wired BLT, so each amp will see 4ohm. The typical gainclone gain setting (fixed in STA540 and 20k/680ohm for 4780) would work perfectly for my speakers.
Any thoughts on any sonic/qualitative differences? I am a strong believer of KISS and like chip amps for their simplicity. Goal is to get as close to colorless sound as possible.
Whether it's the dual supply for LM4780 or the single (I think 18v) supply for STA540, I will be using linear regulated power supplies based on LT1083 (7.5A capacity) -- the one for LM4780 will have two LT1083 while the one for STA540 will have one.
My speakers are 8ohm and very efficient. The STA540 will be wired BLT, so each amp will see 4ohm. The typical gainclone gain setting (fixed in STA540 and 20k/680ohm for 4780) would work perfectly for my speakers.
Any thoughts on any sonic/qualitative differences? I am a strong believer of KISS and like chip amps for their simplicity. Goal is to get as close to colorless sound as possible.
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The National Semiconductors LM chip is a two channel amplifier and the STMicroelectronics STA chip is a quad amplifier.
Read the data sheets to make a decision, try not to allow those that are not technical to colour your decision.
Read the data sheets to make a decision, try not to allow those that are not technical to colour your decision.
The STA can be easily wired to serve as a two-channel amplifier -- see figure 5 in the datasheet for the "dual bridge" configuration -- this setup is in fact good, as it eliminates the output capacitors. From a practical point of view (i.e., implementation), the two amps are similar.
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How about building both? It's not a big undertaking, and you can use the same power supply for both.
Then sit down and compare ;-)
Whatever non-technical preferences people here give, they are all personal and subjective and thus of limited, if any, value to you.
Might as well form your own opinion.
Jan
Then sit down and compare ;-)
Whatever non-technical preferences people here give, they are all personal and subjective and thus of limited, if any, value to you.
Might as well form your own opinion.
Jan
The power supply part would be tricky -- different transformers (dual 23vac for LM, and single 19vac for STA) and different layouts (dual supply vs. single supply), cases (I always put power supplies in a separate case), and heatsinks . I take power supplies very seriously (lol), and unfortunately I do not have the time and resources to do two sets of power supplies.
I am interested in people's subjective views on the two amps, so long as they are well informed.
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My guess is you will be quite happy with both.
STA540 seems like a "high voltage" (max. 22V) version of the TDA7377 car amplifier. It uses very few peripheral components and needs only a single supply voltage. 25-30W max. output in 8 Ohm, enough with your efficient speakers. No doubt a good sound. An easy job with moderate risk.
The LM4780 is quite different in that it belongs to the higher power chip amps, like the LM3886. Need for dual power supply and possibility for somewhat higher output power than the STA540, in particular if you bridge it, but you do not need that power. Fine THD specs. Need for a bigger heatsink than with the STA540. A somewhat bigger job for you in particular due to the dual supply voltages. If you use a Veroboard, terribly many pins to deal with on the LM4780.
STA540 seems like a "high voltage" (max. 22V) version of the TDA7377 car amplifier. It uses very few peripheral components and needs only a single supply voltage. 25-30W max. output in 8 Ohm, enough with your efficient speakers. No doubt a good sound. An easy job with moderate risk.
The LM4780 is quite different in that it belongs to the higher power chip amps, like the LM3886. Need for dual power supply and possibility for somewhat higher output power than the STA540, in particular if you bridge it, but you do not need that power. Fine THD specs. Need for a bigger heatsink than with the STA540. A somewhat bigger job for you in particular due to the dual supply voltages. If you use a Veroboard, terribly many pins to deal with on the LM4780.
Thanks. "No doubt a good sound." -- it would be great if you could elaborate more here.
I did a quick comparison of the two datasheets. STA's crosstalk appears to be materially worse (10-15db) than LM. Any thoughts?
Or, to ask the same question from a different angle, why wasn't STA540 as popular as the LM chips in the DIY community, given that STA540 is easier to implement?
If you want to try, nothing is stopping you from using a +/- 19 VAC PSU and use 2 STA540's (they're cheap) in a bridged-parallel per channel. That way each channel can be powered from each respective rail-to-ground. (mind your polarity!)
Same PSU would work fine for a 3886 or the like.
The STA540's fixed gain is less appealing to me, and from what I remember years ago, the 3886 is a higher performance chip across the board.
Same PSU would work fine for a 3886 or the like.
The STA540's fixed gain is less appealing to me, and from what I remember years ago, the 3886 is a higher performance chip across the board.
Bridged-parallel would be violating my KISS principle, and it's just too much work (real reason)! I use breadboard or P2P for chip amps and power supplies (why I have not tried class D chips).
I agree that technically 3886/4780 are better across the board, but (brief and vague) comments from people who had heard both suggest that the STA is more musical.
I have had 4780 before and found them to be a bit hard sounding. But I was also using hard-to-drive speakers at the time.
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We all have to decide what our value proposition is. 🙂 I'd be looking at TomChr's taming the 3886 thread/write-up and see if his recommendations might help your already-owned parts do better. Otherwise you're quickly getting into optimization that isn't really...
Fair enough,
Both chips have THD values of around 0.02-0.03%. Will that leave us a basis for concluding which sounds best? - probably not. Only A<>B test using the same speakers, with superb recording of a type of music we know may allow us to come to a conclusion on which chip we (individually) prefer. Other persons, other speakers and a different kind of music may leave different conclusions.
At present I am building an STA540 amplifier into an old car-amp housing (original electronics hopeless and TDA2005 based) as a general purpose amplifier. I know the STA540 sound should be good and the specs are good. I do not even have the LM4780 chip so I cannot do an A<>B test.
I am not competent to give you a reply on the comparison of sound quality between the two.
Lacking basis for a qualified subjective opinion, we have to cling to facts. The STA540 is limited in power to 25-30W in 8 Ohm and a bit more in 4 Ohm (current limitation). For young people today life starts at 100W - for the mid-aged at 50W. The STA540 has never had the power potential to be considered a serious candidate for audiophile equipment.
STA540's little sister seems to be TDA7377. They have pretty much the same specs but TDA7377 can only handle up to 18V operational. TDA7377 is designed for CAR USE! Can you imagine an audiophile admitting to friends that his audio-gear include parts intended for cars?
TI has been clever and included the LM4780 in the "Overture" series with other chips like the notorious LM3886. An unambiguous smell of class for those who cannot hear the difference.
Two very different imaginary starting points.
There are those who give a toss about anything but sound quality. Output power, physical presentation and any kind of filters are disregarded or directly banned. They use Lowther drivers and strange looking horn designs from Sweden. Or, vacuum tube gear with a divine sound but a THD that is not worth mentioning. Most are not like that - we like the aesthetics of the gear and a potential sound level that exceeds the disturbing sounds from spouses and kids. Such that we can shown the gear to the neighbor without shame.
I believe you should make an STA540 amplifier of high quality. If you just make an LM4780 amplifier you will be one among many going for the trivial choice. You need little power with your efficient loudspeakers and with your sprouting revolt against traditional thinking you may cross the boarder into rational sanity. An STA540 is sufficient and it may sound at least as good as an LM4780 amplifier though the effort is considerably less.
Only through seeking new ways we develop.
I will finish my STA540 amplifier and rethink the purpose into the audiophile domain. Then, at least there will be two weirdo's in this world.
Both chips have THD values of around 0.02-0.03%. Will that leave us a basis for concluding which sounds best? - probably not. Only A<>B test using the same speakers, with superb recording of a type of music we know may allow us to come to a conclusion on which chip we (individually) prefer. Other persons, other speakers and a different kind of music may leave different conclusions.
At present I am building an STA540 amplifier into an old car-amp housing (original electronics hopeless and TDA2005 based) as a general purpose amplifier. I know the STA540 sound should be good and the specs are good. I do not even have the LM4780 chip so I cannot do an A<>B test.
I am not competent to give you a reply on the comparison of sound quality between the two.
Lacking basis for a qualified subjective opinion, we have to cling to facts. The STA540 is limited in power to 25-30W in 8 Ohm and a bit more in 4 Ohm (current limitation). For young people today life starts at 100W - for the mid-aged at 50W. The STA540 has never had the power potential to be considered a serious candidate for audiophile equipment.
STA540's little sister seems to be TDA7377. They have pretty much the same specs but TDA7377 can only handle up to 18V operational. TDA7377 is designed for CAR USE! Can you imagine an audiophile admitting to friends that his audio-gear include parts intended for cars?
TI has been clever and included the LM4780 in the "Overture" series with other chips like the notorious LM3886. An unambiguous smell of class for those who cannot hear the difference.
Two very different imaginary starting points.
There are those who give a toss about anything but sound quality. Output power, physical presentation and any kind of filters are disregarded or directly banned. They use Lowther drivers and strange looking horn designs from Sweden. Or, vacuum tube gear with a divine sound but a THD that is not worth mentioning. Most are not like that - we like the aesthetics of the gear and a potential sound level that exceeds the disturbing sounds from spouses and kids. Such that we can shown the gear to the neighbor without shame.
I believe you should make an STA540 amplifier of high quality. If you just make an LM4780 amplifier you will be one among many going for the trivial choice. You need little power with your efficient loudspeakers and with your sprouting revolt against traditional thinking you may cross the boarder into rational sanity. An STA540 is sufficient and it may sound at least as good as an LM4780 amplifier though the effort is considerably less.
Only through seeking new ways we develop.
I will finish my STA540 amplifier and rethink the purpose into the audiophile domain. Then, at least there will be two weirdo's in this world.
Good write-up! You inadvertently (or perhaps intentionally) touched upon a few points that resonate with me. I am building a pair of full-range, single-driver, crossover-less speakers using, wait for it, 2.5 gallon glass jars (i.e., acoustic suspension that is actually airtight) to cover 100hz and up (I have a pair of subwoofers and a stereo amp with DSP for the bass). And I do want to "revolt" against the LM-based gainclone crowd by using the STA. But since time and resources are always limited, I do need to make sure that STA540 is the worthy candidate for my endeavor.
If my single-driver speakers do not work out well, I may end up with compression drivers behind strange looking horns to cover 500hz and up -- I am tired of conventions!!!
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Taming the LM3886 Chip Amplifier
He compiled the series of posts on the same topic into a (very nice) website. It's useful information regardless the final chip you choose.
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