computer audiophile on the cheap Class D amplifiers, can a chip sound as good as a regular amplifier?

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Wrong forum I guess, but... yes, class D amps will give you the highest watt-per-dollar you can find. IME it can be a reasonable option if the rest of the equipment is not particularly great, but only if your power demand is high for some reason. If not  - and you should not if you want good sound on the cheap - class AB amplifiers can be found for just a few bucks more than similar class D amps if you're into doing some DIY. Plug in a linear power supply and you can have a trully killer piece of equipment for the money. 

 

 

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Hi Bob

 

Actually, car audio uses a lot of class D amps, especially for subs, exactly due to their power efficiency. Class D will always deliver the most power for the money, but not necessarily the best sound quality. They have the advantage of being inherently less sensitive to the PS due to their switching nature... so yeah price-wise a good class D would be difficult to beat. Just the class of the amplifier doesn't tell you you much - in theory, class AB is superior to class D and probably is used by the majority of hi-fi amps out there. In practice, it is hard to make "fair" comparisons due to the lack of definition of what is "fair" (comparing same prices, same powers, etc.).

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Ralf - the industry norm for "hi-fi" level components is class A to have for pre-amps and class A/B for amps. I agree with Supperconductor, class D are becoming better. Mosfet amps from 20 years ago were terrible, but the industry has pushed a lot in this field due to the significant price advantages of PWM circuits. 

 

Bob, your quest is certainly commendable. For the last few years since I moved overseas, I've been living off computer speakers at home which cost me less than a box of chocolates. My "hifi" rig has always been my headphone rig and I've been living happily this way. Just now I've decided to build a stereo system. Anyhow, what I wanted to say is that we sometimes tend to overspend on our hobbies, and sometimes we should take a more frugal approach to life. 

 

Vintage equipment may be a good option, however in order to get the best value for the money I would make sure that the particular model I was buying would be a really good quality one and I would have the amp serviced and recapped. Without doing this, I wouldn't really bother due to the risk of bringing a lemon to the living room. 

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27 minutes ago, bigbob said:

 

Well, that's where Sasa, my electronics technician comes in to play. A key to the "Computer Audiophile on the Cheap" is knowing a technician who can make the minor repairs, blow out the dust bunnies, check some voltages and such and "make it better than new"... He said anything that is broke on the older stuff can be fixed, if not improved, because the components used thirty years ago have been improved upon.

 

Fair play! I would personally fancy an old Naim Nait, I may do it for a second system in the future when I need one - not something for now.

 

Jud, I'm sorry but GUTB is right on this one. It is not a matter of "belief" that class D is an inferior approach - that's just the physical truth behind the architecture. There may be shitty class A amp implementations and good class D ones, however "inherently" as he said it is a fact fact of life that a single linear gain is superior to a quantised signal modulator. This could be easily shown mathematically. 

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I see you didn't understand (or didn't care to understand), so I'm not going to argue... 

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55 minutes ago, plissken said:

You do realize that Class a was a solution to the problem of transistor cross over distortion.

 

Lol are you trying to rewrite history? The first audio amplifier were triodes (valves if you never heard of them), which naturally operated in class A. That was invented by the Marconi company at the turn of the xxth century. Class B was invented later as a way to reduce the heat dissipation, however it sucked for audio. Quickly class AB was realised, for which there were two implementations - AB1 and AB2, the difference being essentialy on the way the valves are energised. That was all decades before the transistor was even invented - essentially it doesn't matter whether the amp is transistor or valve based, the block diagram is the similar aside from the valve supply.

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6 hours ago, plissken said:

 

That doesn't absolve it of the fact that Class A is a fully energized push/push and that is so there is no waveform distortion. That's the problem it solved in transistor amps. 

 

Class A/B and D, the other predominate audio amplification classes solve the crossover distortion PLUS efficiency, heat, and weight. 

 

Flyback and derived supplies were in use in the 30's. So what's your point again?

My point was that you implied that class B amps existed before class A, which is not true. 

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6 hours ago, Jud said:

 

Here is some higher mathematics:

 

- Spectral Audio Class A top of the line mono amp: 98dB S/N unweighted 

 

- Mola Mola Kaluga Class D amp: 128dB S/N unweighted 

 

Are you trying to troll me or what? First of all, read again the part where I said there can be bad class A amps and good class Ds. That doesn't change the underlying physics of the amp construction. 

 

Regarding sn ratios, you should know by now (and that's why I can do nothing but think you're trolling me for this obviety) that class D have inherently lower sn ratios than other classes. That's due to the nature of the pwm which doesn't amplify the line noise, unlike the direct gain amps which amplify everything in the path including the line noise. That's one reason linear amps end up being expensive - getting rid of noise demands great attention to detail. 

 

For thd the mechanism is different, in few words the pwm can match the original with less total error because it doesn't have problems with nonlinearity on the gain. However, if you look at derivative of the signal it is terrible compared to a linear amp. You cannot see this direcly, but he fact that the speaker receives the current in little spikes affect their magnets and it is the reason why some shitty class d can sound annoying in good speakers. On the other hand, the nonlinearity in the linear amplifier creates what we call "colour" - the signal may be smooth, however the amplitudes are not anymore he same as of he original signal. This is one of the things that afficcionados are doing when tube rolling (another is the change in the harmonics which also make for poorer measurements).

 

However, in the end Thd only measures the error in the signal and not in the derivative of the signal. Your speakers care about the derivative of the signal and not so much about the signal itself since it is the current variation that creates motion. Also a high sn radio is nice to have, however when it becomes inaudible one could claim it's good enough. So be careful when cherry picking numbers out there which doesn't tell you the whole story.

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8 hours ago, jabbr said:

https://diyaudiostore.com/collections/kits/products/amp-camp-amp-kit?variant=21206375620

 

 

 

Hi Jabbr, I was just going to post a similar idea. Bob's original question seemed to imply that "chip" amps need to be class D, however this is not true! The same chips that you see in amps in the market can also be had in DIY form. I've seen this amp camp before, however it is quite a little project to be completed (and you'll need a good soldering iron). 

 

Audiophonics in France has a ton of class A and AB amp boards based on different circuits. I crave building one of these sometimes. Just one example, they have a 2x68 W based on the LM3886TF (which is a very fine chip for DIY btw) for 29 euros (with european VAT - even less if you're outside EU), an oversized linear regulated PS for 45 (optional but well worth it), a 30 VA transformer for 18, a softstart board for ~10 euros (also optional), about the same for an oversized heatsink, say 5-10 euros for the connectors plus 6 euros for a hifi metal cookie box and - voilà! You've got a pretty decent amp for about 100 euros (as low as 50 for the basic stuff!) *and* cookies to enjoy the music *and* no soldering required! How good is that? 

 

http://www.audiophonics.fr/en/amplifier-boards/lj-gc-lm3886tf-stereo-amplifier-class-ab-2x68w--p-9965.html

 

 

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Silly Goose is just trolling and giberishing here, as he did on the Dynaudio thread. Ignore him and he'll go away.

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On 15/04/2017 at 7:10 PM, Jud said:

 

Your understanding is inadequate.

 

*All* amp topologies have inherent advantages and disadvantages.  The design problem with each is of course to maximize the advantages and minimize the disadvantages within whatever specific constraints exist on the project.  jabbr understands this well, as do most other people following the thread: Note he said making a really good SPMS involves more than a simple circuit, not that it is impossible.  And when you do make a really good one, that stuff about switching noise artifacts becomes nonsense.  You won't hear switching noise or any other artifacts 128dB down.

 

It's also a fact that people hear differently.  At the price levels BigBob is talking about, careful choices about what to look for and buy and what things do and do not bother you must be made. That's what is so interesting about his journey - to understand his particular exploration of the *many* ways, not just one, we can hear music that moves us.

 

Hi Jud, you may be correct but the fact that the theorethical S/N ratio is 128 dB does not mean that the switching noise is -128 dB. The switching noise is very high frequency (not audible) and is filtered at the output. The circuit noise is typically minimised by a feedback loop in this kind of amp. What GUTB means is probably distortion cause by the switching inaccuracies which is unavoidable for a pwm circuit due to jitter and other effects. 

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4 hours ago, Jud said:

 

I am happy to see measurements of these inaccuracies or their effects.  What particular types of common (or even uncommon) distortion measurements would you expect to be affected by these inaccuracies?

 

Good luck with that. Digital domain systems work in the z plane and are not trully analysable in the frequency domain (s plane) afaik. In other words, you cannot "see" the difference between  waves created by a digital and an analog amp with an oscilloscope or a low frequency digital analyser. You need a high frequency digital analyser (and believe in the AD approximation which works quite well).

 

I've found some good readings on Maxim Integrated's website, you may want to check there - they have a good library of articles on the subject. 

 

By the way, DSD works in a similar way - it is a digital representation of an analogue system, and it also cannot be analysed directly in time or frequency domains but mostly by approximations (it is a lot simpler when converting from DSD to PCM which is easily analysable in the frequency domain).

 

If you're handy with Laplace transforms I could try to explain all this in more details, it's not very easy for me to put in simple words from the phone.

 

Cheers

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2 hours ago, rikard said:

I had an idea about a neutral powerful amp, with any possible warmth or colouring coming from a LampizatOr DAC only (balanced with volume control). I would say the experiment was very successful and I'm very happy with the result. I do not hear any of the shortcomings one normally thinks about with class D, as lifeless, boring, too perfect etc. I think class D has come a long way, and I'm pretty sure this is only the beginning as well. Just look at the Aavik U-300, which was recently praised as best integrated of the year (not cheap though).

 

Hi, I apologise in advance for getting way out of topic here, but which Lampi model did you get and does it have ss or tube regulator? I'm very curious about how does it sound in a very transparent system since I'm gonna give it a try myself.

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Jud, Jabbr, those are excellent questions! I haven't got much time to think about right now, but I'll try to enjoy some pcm streams in the meantime 

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On the signals. When you convert a digital into an analog signal (assume the conversion is perfect), you'll be left with a serrated modulation since the conversion has a certain resolution. If you want to measure this signal, you'll need a much higher resolution (rule of thumb is one order of magnitude greater). With a standard oscilloscope (say 16 bits / 100 kHz), one will not be able to see the quantization errors (eg. jitter) created by the amp which has a carrier frequency of the same order. This way, a cheapo amp will measure good and a good quality amp will measure... just equally good. You'll need some better measurement tools in order to get meaningful information. 

 

I think the same idea applies to PWM in class D, PCM and DSD. However, the output stage has quite an impact in minimising these quantisation errors in a DAC. Also note that the DSD frequencies and resolutions are much higher which also minimises these problems. However, a simple class D amp will not have an additional stage at the output, therefore afecting the sound. I'm sure that the good amps mentioned here take good care of this in their design!

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8 hours ago, rikard said:

 

Golden Atlantic, tube rectifier, balanced, volume control. It's difficult to describe how it sounds in words, but as I already said I'm very happy with the combination and don't really miss anything. I honestly think any Lampi model would be a good match.

 

Next week I'll hopefully get a passive preamp from Music First to try and see if it makes any difference. Not that I feel that I need it, but I'm curious to try it...

 

Thanks. I don't bother about the tube rectifiers, balanced circuitry and so forth. However, I like the idea of a clean path on the DA output. Can't wait to have one in my hands to see how it sounds!