I have completed my first LM3886 project and no mistake I am really pleased with it.
Tonight I decided to listen to and test it against my trusty NAD C320 (recently refurbished on account of the usual start up problem and badly degraded main capacitors). In terms of what I can measure the NAD wins or its a draw. The NAD is quieter, but having said that both are almost completely silent so the measured noise is pretty academic. In terms of what I would expect regarding distortion etc. if I had the right gear to measure it down to the levels these produce, well I expect them to be pretty much the same. In terms of sound? Well that's subjective and my ears are old. Both sound very good to me.
So where does that leave it? NAD C320s and even more up market models can be had off eBay for around £50. Most need some work but it is pretty basic stuff for the most part. I am wondering what the real benefits of the Chip Amp are - it certainly doesn't save money against some of the secondhand bargains that can be had (I also have a Cambridge Audio A3i which has been written about a lot on this forum and is quite frankly superb as well). Here is what I have come up with.
1. The fun of DIY and the possibilities for tweaking and improving and learning
2. Reliability? It does seem that most of those all discrete amps of a certain age are rather prone to failing. I also note that some people do go down a deep rabbit hole of replacing components -- especially electrolytics etc.
What else would anyone add?
Tonight I decided to listen to and test it against my trusty NAD C320 (recently refurbished on account of the usual start up problem and badly degraded main capacitors). In terms of what I can measure the NAD wins or its a draw. The NAD is quieter, but having said that both are almost completely silent so the measured noise is pretty academic. In terms of what I would expect regarding distortion etc. if I had the right gear to measure it down to the levels these produce, well I expect them to be pretty much the same. In terms of sound? Well that's subjective and my ears are old. Both sound very good to me.
So where does that leave it? NAD C320s and even more up market models can be had off eBay for around £50. Most need some work but it is pretty basic stuff for the most part. I am wondering what the real benefits of the Chip Amp are - it certainly doesn't save money against some of the secondhand bargains that can be had (I also have a Cambridge Audio A3i which has been written about a lot on this forum and is quite frankly superb as well). Here is what I have come up with.
1. The fun of DIY and the possibilities for tweaking and improving and learning
2. Reliability? It does seem that most of those all discrete amps of a certain age are rather prone to failing. I also note that some people do go down a deep rabbit hole of replacing components -- especially electrolytics etc.
What else would anyone add?
I'd additionally mention efficiency, as these amps usually can be combined with a good SMPS without notably degrading the audio quality.
Thermal tracking, the quiescent current doesn't vary all over the place due to temperature differences between the output transistors and some kind of temperature sensor (for example a VBE multiplier).
Disadvantage: traditionally the PNP transistors are rather poor in cheap bipolar IC processes.
I think the main advantage for DIY is that you can relatively easily make your own amplifier with them.
Disadvantage: traditionally the PNP transistors are rather poor in cheap bipolar IC processes.
I think the main advantage for DIY is that you can relatively easily make your own amplifier with them.
Monolythic chip means very close matching of all the transistors.
Well built they can sound superb, but how skookim is your build.
I have a superb LM3875, LM1875, and a not great 3886. The 1st a well executed first gen diy group buy amp, the 2nd Point-to-Point, the 3rd an inexpebsive preassembled chinese board.
Executuin is critical, pictures of yours?
Also, what speakers are you driving?
dave
Well built they can sound superb, but how skookim is your build.
I have a superb LM3875, LM1875, and a not great 3886. The 1st a well executed first gen diy group buy amp, the 2nd Point-to-Point, the 3rd an inexpebsive preassembled chinese board.
Executuin is critical, pictures of yours?
Also, what speakers are you driving?
dave
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Hi Dave - described and pictured here https://www.diyaudio.com/community/threads/a-first-lm3886-project.386817/#post-7040805. Speakers are B & W stand-mounters. .865S2
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B&Ws are 685 (S2). Transformer is approx 100-120VA. Power supply is putting out +/- 34v unloaded. All sounds very good and measures very well. So its quieter than the A3i for example.
Low VA supply with high voltage driving a niminal 6Ω speaker.
A receipe for current starvation, something no NAD (likely) can be accused of.
dave
A receipe for current starvation, something no NAD (likely) can be accused of.
dave
Cheap Chinese LM3886 amps are to be blunt **** Poor. Most use Fake /badly copied Chips.
Certainly so given the Non availability of Genuine Lm3886 chips I once ordered Chips from a 'Respected' supplier with assurances they were 100% genuine. They weren't .. not even cosmetically similar.. Emails were never replied to. Lesson learned.
A Good Lm3886 Amp, as in competently designed and Built ..IN.. the first world
Will handily outperform an NAD.
If yours doesn't ... then You have your answer.
Certainly so given the Non availability of Genuine Lm3886 chips I once ordered Chips from a 'Respected' supplier with assurances they were 100% genuine. They weren't .. not even cosmetically similar.. Emails were never replied to. Lesson learned.
A Good Lm3886 Amp, as in competently designed and Built ..IN.. the first world
Will handily outperform an NAD.
If yours doesn't ... then You have your answer.
Chip amps are usually simpler to build due to less components.
However layout is important and feedback path should be as short as possible or some instability might occur.
I got caught out with a chip amp.
I built one up and it wouldnt work.
A good visual inspection spotted the front legs of chip amp were touching back leg pcb pads in places.
So replaced it but raised chip amp slightly off the pcb and it worked fine.
However layout is important and feedback path should be as short as possible or some instability might occur.
I got caught out with a chip amp.
I built one up and it wouldnt work.
A good visual inspection spotted the front legs of chip amp were touching back leg pcb pads in places.
So replaced it but raised chip amp slightly off the pcb and it worked fine.
@planet10 So I guess that is the impedance curve from my speakers? FWIW I cannot tell any difference between my Chip Amp (LM3886) and the NAD when driving these speakers. At various times doing an A -> B listen I think maybe the Chip Amp is slightly smoother in the treble ... But I conjecture that is just confirmation bias and don't think I would pick it up in a blind test. I listen at very modest volumes and don't have particularly 'bass rich' music taste. So perhaps if I was using them to pump out a lot of heavy bass in the 40-80hz region it is then that the inadequacies of the power transformer would appear. Or maybe I need better ears!Low VA supply with high voltage driving a niminal 6Ω speaker.
A receipe for current starvation, something no NAD (likely) can be accused of.
dave
From a DIY perspective the chip amps offer one very nice feature: No bias adjustment. This means even relative beginners can put together an amp without too much fuzz. It simplifies debugging. And in the right hands (and especially with some error correction) they can really shine.
They're also small, low cost, highly reliable, and usually easy to find in stock. Or at least they were before the world melted down from COVID.
Tom
They're also small, low cost, highly reliable, and usually easy to find in stock. Or at least they were before the world melted down from COVID.
Tom
@tomchr - yes the more I read about this and use my creation the more I appreciate the benefits. The simplicity. The lack of components to fail or deteriorate (thinking of the dozens of electrolytic capacitors on the main board of the NAD C320!), the tweakability, the built in protection etc. etc. My next iteration when funds permit will be to have a stab at one of your Modulus models. I need to get my head around the theory of error correction vs. feedback correction (just curious really). I just fancy building something 'state of the art'. In the meantime I am perfecting my small signal chip amp (aka a preamplifier).
Implementation and execution is everything...
- mains wiring (inside an amp), power supply, capacitors used, wiring length & type of wire used, local power rails' decoupling, signal routing, grounding....
- the case used (some ring like church bells), choice of feet (sound isolation... or sound coupling; sound in this context =vibrations)
- comparison based on same test conditions: same power cable, same power outlet, same interconnect cables
Which, of course, suggests an experiment: Use the same chassis, feet, power supply, I/O connectors, mains wiring, wire length, type of wire, and capacitors -- but swap out the amp channel cards. (case 1) is 100% discrete channel cards; (case 2) is chipamp channel cards. Is there any difference between the two? IMPLEMENTATION AND EXECUTION IS EVERYTHING so we expect no difference at all. But what is actually observed?
One benefit of chip amp is, when it fails, you won't have to fix it. Throw it away.
I have a NAD C320 which blew a fusable resistor when a small bypass capacitor shorted in the 18v supply. I fixed it. This amp has a dense schematic with a large number of discretes. Now I also have a NAD 3045 class D. The metal NAD logo gets finger burning hot from the internal Hypex module. It is glued together with a tarry substance .. not intended to be repaired.
https://unbarthefoo.blogspot.com/p/add-power-on-led-to-nad-d-3045.html
I have a NAD C320 which blew a fusable resistor when a small bypass capacitor shorted in the 18v supply. I fixed it. This amp has a dense schematic with a large number of discretes. Now I also have a NAD 3045 class D. The metal NAD logo gets finger burning hot from the internal Hypex module. It is glued together with a tarry substance .. not intended to be repaired.
https://unbarthefoo.blogspot.com/p/add-power-on-led-to-nad-d-3045.html