Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap • Hacker News Board

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#211

Post by chadcmulligan » Thu, Nov 01, 2018, 1:53 PM UTC

utopcell wrote: post #208

S_A_P wrote: post #123

Audiophilia is a study in contradiction. The ask is a flat "uncolored" accurate sound. The gear that sells for ridiculous prices is usually tube gear with limited bandwidth and makes ~15 watts at 5-10% (admittedly usually even order harmonic) thd. Hardly uncolored. That said, and Ive mentioned this before on HN. My (now late) uncle had a bunch of audiophile friends in Dallas. He hung around folks who had spent upward…

What did he listen to ?

The cannons from the 1812 overture, over and over again. Did you hear that? Did you hear that? wasn't that awesome? Hang on I'll play it again, let me just adjust this setting first....

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#212

Post by beat » Thu, Nov 01, 2018, 2:02 PM UTC

Modern class D amps are terrific, but it's annoying to see THD brought up as a measure of audio quality. THD is terrible measurement - its value is not that it's relevant (except to demonstrate things aren't actually broken), but rather that it's easy to measure.

An amplifier's ability to reproduce a 1khz sine wave into a resistive load tells us nothing about how it behaves in the face of 8-10 octaves of frequency range and the real dynamic range and harmonic complexity of actual musical content, when hooked up to the absurdly complex and nonmusical behavior of real speakers. The 5% THD of single-ended tube amps that people who've never heard one tell us proves how "inaccurate" they are is inaudible, but the grimy, dull sound of cheap amps that have excellent THD specs is plain to hear.

It's frustrating, in part because this stuff is, so far, mostly impossible to measure. It's hard to get a sense of how an amplifier will sound from specs.

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#213

Post by beat » Thu, Nov 01, 2018, 2:17 PM UTC

setquk wrote: post #163

S_A_P wrote: post #123

Audiophilia is a study in contradiction. The ask is a flat "uncolored" accurate sound. The gear that sells for ridiculous prices is usually tube gear with limited bandwidth and makes ~15 watts at 5-10% (admittedly usually even order harmonic) thd. Hardly uncolored. That said, and Ive mentioned this before on HN. My (now late) uncle had a bunch of audiophile friends in Dallas. He hung around folks who had spent upward…

I’ve heard such things. Two points to note: 1. Decent monitor headphones or speakers sound the same. That’s under $500. Even some Sennheiser HD25’s are literally up there. 2. The equipment used to record such music cost less and was lower quality. Adding $500k doesn’t add anything because there isn’t anything there. Then again I have no problem with people who spend $500k on audio kit. That’s up to them. If it makes…

The original directional cables, sans mythology, are a real thing. Grounding for cable shielding matters a lot, and is plainly audible in many circumstances. "Directional" cables only ground the shield at one end, preventing ground loops and interference from grounding both ends. This is electronics 101.

An interesting aside on cables... I play electric guitar a lot, which is far more sensitive to cables than hi-fi gear, because guitar pickups are high impedance, low output devices - enough that capacitance can have audio-frequency passive filtering, and grounding is a huge problem. With passive pickups, I can easily hear differences in various cables I own. But some of my guitars have active electronics onboard (EMG pickups or other preamps), and produce a low-impedance signal. I can't hear the difference with those guitars.

When it gets down to it, I use the cables that are most reliable and comfortable to handle. Sound quality doesn't even enter into it, whether or not it's audible.

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#214

Post by setquk » Thu, Nov 01, 2018, 2:18 PM UTC

TheOtherHobbes wrote: post #205

setquk wrote: post #163

Earlier quoted context omitted.

I’ve heard such things. Two points to note: 1. Decent monitor headphones or speakers sound the same. That’s under $500. Even some Sennheiser HD25’s are literally up there. 2. The equipment used to record such music cost less and was lower quality. Adding $500k doesn’t add anything because there isn’t anything there. Then again I have no problem with people who spend $500k on audio kit. That’s up to them. If it makes…

Not actually true about recording equipment. Top end mixing desks cost > $1m. Top end engineers and producers usually have at least $100k of outboard processing on hand - everything from mic preamps to vintage compressors. Top end mastering studios will work with similar budgets. Add exotic guitars, vintage synthesizers, and other esoterica, and the total hardware budget for a mainstream commercial hit album is comfo…

Yes but the point is the signal path in those probably less than $100 end to end. Instruments excepted.

A decent audio grade opamp is $2 for example.

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#215

Post by beat » Thu, Nov 01, 2018, 2:21 PM UTC

Tsiklon wrote: post #194

mmaunder wrote: post #154

Google audiophile headphones. Then go to sweetwater and search for studio headphones. If the price of source gear is a quarter of the price of gear attempting to reproduce source, something is broken.

I like to look on high end headphones as I would any other luxury item - I'm willing to pay for nice materials of a higher quality or a better experience, if the item is right. That could perhaps explain some of the price - plus I think we're at the point where many of the headphone companies have discovered that there is an ultra-high end market for some of these products. You can see this in the prices of many top…

Some people understand the law of diminishing returns, but have the resources to not care. If a $2000 pair of headphones is no more real financial pain for you than a $200 pair, and they're better despite diminishing returns, then why not get them?

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#216

Post by pps43 » Thu, Nov 01, 2018, 2:27 PM UTC

AnthonBerg wrote: post #167

scblock wrote: post #135

Earlier quoted context omitted.

Amplifier designers most certainly are. Class D has significant energy efficiency advantages, and significant sonic challenges. It’s taking an analog waveform, whether decoded by a DAC or starting as pure analog, and chopping it into a series of pulses (pulse width modulation). The amp is switching transistors on and off very quickly, rather than using them as a variable linear gain stage. It’s not the same as PCM en…

The thing is that transistors’ behvior is more linear and controlled when fully on or off rather than when used as continuously variable. Class-D can and does sound _amazing_ if built with good theoretical understanding. Check out Hypex amps designed by Dutch engineer Bruno Putzeys on strong control theoretical foundations.

Actually the opposite is true. Transistors are approximately linear in half-open state, as in Class A, and non-linear at the extremes (when either fully open or fully closed).

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#217

Post by beat » Thu, Nov 01, 2018, 2:33 PM UTC

rectang wrote: post #134

AceJohnny2 wrote: post #3

Earlier quoted context omitted.

Tangentially, the placebo effect is everywhere. If it can affect tasting (wine) and hearing (audiophile gear), I'm surprised not to have noticed its affect in discussing photography. Will "computational photography" (as touted in the latest iPhones) that alters photos based on criterion of perceived quality end up bringing these kind of inane discussions there too? Edit: Never mind, I didn't factor in all the argumen…

I made my living as a mastering engineer for two years... To do good work in mixing and mastering, it's important to study the human perceptual mechanism and its propensity for illusion, and it's also important to understand masking effects and how to amplify certain components long enough to tweak them before dialing them back to recede into the gestalt. It's also important to understand that in sound reproduction t…

I feel your pain. I produce and mix records - at an amateur level, but enough to get quite good at it. It makes me want to toss all this "objective", "measurable" bullshit from the skeptics right out the window - the subjective experience is all that matters. But it also makes me want to toss the audiophile voodoo out the same window. "Accurate" reproduction? I just want to show them how records are mixed.

My pet example is that I put high-pass filters (12db slope) at 250-300hz on almost everything that isn't a drum or a bass instrument. I'm slaughtering the bottom two octaves of guitars! And if you solo a guitar track, you can hear it. But in the context of a mix, all those bottom two octaves do is make mud and confusion, distracting from the clarity that the kick and bass (guitar || synth) needs. And I need that clarity, because I'm not mixing for $500,000 audiophile systems. I'm mixing for car stereos, boom boxes, Alexas, cheap earbuds, and worse.

So all that matters for me with audiophile systems - and I love audiophile systems - is that they sound good. That doesn't mean they sound accurate.

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#218

Post by beat » Thu, Nov 01, 2018, 2:38 PM UTC

taejo wrote: post #43

AceJohnny2 wrote: post #3

Earlier quoted context omitted.

Tangentially, the placebo effect is everywhere. If it can affect tasting (wine) and hearing (audiophile gear), I'm surprised not to have noticed its affect in discussing photography. Will "computational photography" (as touted in the latest iPhones) that alters photos based on criterion of perceived quality end up bringing these kind of inane discussions there too? Edit: Never mind, I didn't factor in all the argumen…

While there are endless debates about manipulation , when it comes to actual capturing of images, the photographic community (in my experience) has a healthy dose of "the best camera is the one you're carrying" and "a great photographer can take great photographs with any camera but even a great camera won't help a lousy photographer take great photographs" to go with its love of gear (who can help but love gear?)

Camera nerds are the worst. They're worse than audiophiles, if that's possible. Good photography requires nothing more than a bit of reason and observable standard practice, applied to aesthetics. You don't have to look hard to find someone with a $5000 camera/lens combo who doesn't know what the Rule of Thirds is or how to apply it.

Last weekend, I was in DC, and snapping pictures of the Washington Monument on my phone. My sister was shocked at how good they were. It's not hard, really.

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#219

Post by pps43 » Thu, Nov 01, 2018, 2:41 PM UTC

mrob wrote: post #75

MrTonyD wrote: post #56

I'm probably the only one with this opinion...but I sure miss the old days of tube amps that weren't able to be highly accurate. They would roll-off the on the high end, distort a bit all over, and gave a very warm and relaxing feel to the albums I played obsessively. Now I've owned high-end tube and solid-state gear, and the music hasn't sounded good for decades. Combine that with the very limited bits provided by C…

>Combine that with the very limited bits provided by CDs, preventing any possibility of good playback 16 bits gives you 96dB SNR (and subjectively more with dithering), which is plenty at non-deafening listening volumes. It's more than even the highest quality vinyl ever had. High bit depth is mostly useful so you've got some headroom during editing.

16 bits give you 96 dB SNR only if your signal is one-bit. In a quiet room with decent headphones set to comfortable level I can easily hear one-bit flips in otherwise silent WAV file.

Not a problem for popular music that's consistently loud, but a real problem for classical music with wide dynamic range.

Re: Build Your Own Professional-Grade Audio Amp on the Sort-Of Cheap

#220

Post by lb1lf » Thu, Nov 01, 2018, 2:51 PM UTC

chadcmulligan wrote: post #211

utopcell wrote: post #208

Earlier quoted context omitted.

What did he listen to ?

The cannons from the 1812 overture, over and over again. Did you hear that? Did you hear that? wasn't that awesome? Hang on I'll play it again, let me just adjust this setting first....

In fairness, though, the 1812 ouverture IS a pretty impressive piece to listen to, if it is properly recorded and reproduced.

While my setup is somewhat (cough) less impressive/over-the-top than the one referenced above, there's no denying listening to a proper 1812 is a physical experience.

I'm partial to Kunzel's recording with the Cincinnati Pops - those cannons are LOUD. (Better be careful not setting the volume too high or you're likely to find yourself a couple of woofers short afterwards.)