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Old 07-06-15, 03:58 PM   #1
AC_Hacker
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I use my A/V stuff alot. I really enjoy it because it has brought me a lot of pleasure and also has much educational value (I try to avoid mindless time-suck).

I recently bought what I thought would be a very useful A/V box that would give me HDMI switching (Denon AVR-S500BT). It appeared to have useful features, some of which seemed like they could be valuable in the future (fatal thinking, as it turns out). The box did things I didn't really care about, and didn't do many of the things I really do care about, and consumed WAY TOO MUCH POWER and then it died.

It is presently on it's second warrantee trip to some distant Service Center. It's really racking up the miles, while I grow tired of carrying dead equipment back to the post office. The best I can hope for is that I will finally get a working unit that still doesn't suit my needs.

In contrast to this, I bought a tiny amp for my computer that is cheap, quiet and works just fine.


2 x 15 Watt 4 Ohm Class D Digital Audio Amplifier TA2024 15W Stereo Mini T Amp | eBay

It works wonderfully to amplify sound & music from my PC.

So, I'm thinking about something that would have more flexibility (HDMI switching, multiple inputs, etc.) to use for my main A/V system, that would be very simple, and consume very little power.

I have some efficient speakers, and I have recovered from the 'Home Theater' virus. Stereo is just fine.

Anyone else working along these lines?

Best,

-AC

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Old 07-06-15, 11:14 PM   #2
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When I moved to Kentucky, I was an electronic tech in civilian life, an avionics tech in the navy reserve, and a ham radio operator for fun. I moved here from Colorado. After interviewing around, I took a job at a "pimp my ride" shop mainly due to the sorry wages the local industry was offering. I ended up running the shop for 5 years, securing premium product lines to grow the business and its reputation. I learned more about the consumer electronics industry during that time than I ever wanted to know.

The one unwavering premise that resounds with audio and audiophiles is that everything is subjective. Yes, there is theory to guide you, but what sounds good to one person sounds like crap to the next guy. It just depends on you and your ears.

Toward the end of that gig, Sony came out with the super audio cd. All this bitstream audio and 4k video that you see in the market now was already figured out way back then. The mpeg4 standard had already been designated as the platform that would replace the compact disc audio and DVD video formats.

Within two weeks of each other, our tech and sales staff had classes from Sony, Samsung, and Panasonic that were literally the same as each other. The only difference between all three classes was the product offering sections and the tech tips for troubleshooting said products. All three mandated that "premier" dealers purchase the same hd test equipment, a sencore box. We did.

This major event happened right before the DMCA was enacted. As soon as the manufacturers had the law behind them, two tons of new hd products hit the market. This was before the hdmi standard was agreed upon, so most products used dvi and either toslink or RCA digital audio. Thus began the great divide between the new hd, totally digital experience and the old school, analog signals.

Back then, the cutting edge stuff was class bd and class d in audio. Now, they are way up to class t in amplifier technologies. To me, most of the newer, high efficiency, dsp driven gear all sounds either very sterile or doctored up to not sound lifeless. The only real exception to this is in subwoofer technology. It is actually difficult to color bass notes without getting unwanted harmonics and/or phase distortion that is immediately unpleasant.

As for me, I still like tube amps the best. They just sound like they should, are easy to troubleshoot and repair, and if you want to make them sound exactly how you like, just roll some tubes through the sockets. They are still being manufactured today, and with the mail order internet, you can trade tubes with others to test drive before purchase if you like. Even though technology has advanced and miniaturized everything, speakers and ears have not changed drastically.
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Old 07-06-15, 11:59 PM   #3
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for casual (non critical) listening, Class-D (some calls it class -T) amps are quite alright.

Efficient (85% typical); cool running, decent PSRR, reasonable power output in very small package are it's strong points.

However, for my critical listening, I still found these digital amps missing some micro-information that I need.


When it's time for critical listening, I still rely on my delibrate set up (vinyl spinner, got 2 of them side-by-side, with a spare Linn Sondek in storage; MOS-FET based amp or 2A3 SE tube amps with 12AU7 preamp; etc.)

My speakers (I have several pairs: from bookshelves such as Energy RC-10; to KEF 103.2 (BBC voicing), to JBL 4425 studio monitors, etc.

These speakers can reveal some of the shortcomings of Class-D amps (to date, although technological progress is not getting quite good, coming close to that of conventional Class B transistor amps).

My take on the Class-D amp subject. YMMV.
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Old 07-07-15, 02:27 AM   #4
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Many years ago, I built two super efficient amps:
http://ecorenovator.org/forum/applia...ome-audio.html
http://ecorenovator.org/forum/applia...d-digital.html

But they're both analog input "hybrid digital" amplifiers, not pure digital like the state of the art units. Most of the pure digital amplifiers on the market (e.g. those home theater boxes) largely negate the efficiency advantage with overboard internal processing and many even have poorly designed/cost cut power electronics that are very lossy at idle. (Tip: don't buy a digital amplifier that significantly heats up the output stage just idling. Heat coming off the DSP part is OK, but tends to be a sign of an overkill DSP stage.) But DIYing a pure digital is not the least bit easy and there aren't even very many kits out there.

Ultimately, it's hard to beat headphones from a cost value and energy efficiency point of view. At typical listening volume, headphones run on an average power in the microwatt range. (At that point, everything else dominates power use.)

I actually got back into HD audio (as in really into it instead of just casual interest as I did for many years) a few weeks ago due to a story involving a new best friend with an audio boosting "magic power" that appears to defy current understanding of science. Long story short, I accidentally discovered that any analog audio cable she solders together (or even any cable that is assembled within a few feet of her) becomes a "magic" cable that boosts the sound quality of well encoded MP3s and FLACs. Nothing happens with digital cables as they just carry data. Power cables don't have any effect unless there's a flaw that unintentionally makes them part of the signal path, in which case you have bigger problems. (She and I earned the nickname "audio Mythbusters" because of the testing we did to try to better understand the mysterious power, only to end up with more questions than answers.)
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Old 07-07-15, 07:28 AM   #5
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This subject is fascinating. I still have my Thorens turntable, tube pre-amps/amps and speakers I built in the 70's (new tweeters, but the rest is still perfect).

The direct to disk method of recording, if you have not heard them, are jaw dropping - even for non audiophile types.

But ALL that heat with 12AU7s or 12AX7s! Talk about inefficient!

Had a great talk with a similar audiophile friend who is an audiologist and professor where I used to teach. He feels that many of us, who grew up on AM radio, still have some RIAA equilization "mind set". He thinks our ears "learned" from AM radio. There is good data from so called "primitive peoples" that he is correct.

I also find the MOSFET amplified signals, to be "sterile". I hear this if I use analog or digital inputs. I wish I truly understood what the hot tubes add (or don't add).

And yes, headphones are the most efficient way to listen. Had a GREAT paid of wireless Sonys that would work throughout the house, but my son's damn dog chewed them up. The new replacements don't sound nearly as good and I just can't stand listening to them.

Physioacoustics is a wonderful world of electronics, inner ear transduction and brain processing. Our ears have used the latter two for many hundreds of thousands of years and we still don't understand much of how the brain processes audio. The more I learn, the more questions are out there.

For simple casual listening, an efficient class D may well be the least bad.


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Old 07-07-15, 11:49 PM   #6
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Thank you for sharing thoughts on the said subject.

Class-D (or T if you like) is gradually gaining popularity, in areas such as car stereos, etc. for it is an area where nobody seem to care about microdynamics, low-level micro sonic details, etc.

There are strengths in Class D amps though, and that is the soundstage is quite stable when loud; with proper staging and good speakers, the soundstage can literally penetrate the wall a couple of feet or more, thus giving you the illusion that you are there. Depth is a problem, however, for the lack of microdynamics and some details that typically required to construct the so-called "ambience" that certain amps are good for.

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Old 07-08-15, 02:42 AM   #7
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Modern digital amplifiers can be very good. That's especially true of HVIC based units like the two I built. HVICs have the MOSFETs and MOSFET drivers (and in some, even more like the Delta Sigma stages) on one piece of silicon, meaning the least possible parasitics and the capability for very high carrier frequencies. But all too many units sold for home theater use use the older IPMs (MOSFETs and driver are separate pieces of silicon in one package) or even through hole discrete MOSFETs.
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Old 07-08-15, 09:01 AM   #8
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My favorite acronyms in this realm are the mash and bash amps, originally invented by panasanyo. They are super efficient as far as power consumption is concerned. Sound quality is decent as well. The inside joke was that the metal heads and g unit pimps could bash their heads until they mash their brains and the amps would survive.
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Old 07-08-15, 11:35 AM   #9
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This discussion, but it has veered so far off the original question that it seems to be answering a completely different question all together.

Let me start again...

I don't want to create new technology.

I don't want to roll my own, if there is available equipment to do what I want.

I just want to co-ordinate my media boxes and enjoy various forms of audio and video (I almost never watch TV... too polluted, too stupid), without having a room heater.

I do not want a big-watt solution, even of it reproduces the subtle essences of music.

I am not interested in tubes. I grew up with tubes, that was enough for me.

I know that 10 or 20 watts is more than I require.

I do not want a stack of equipment that sucks down 100 watts, just waiting to see if if I'm going to push the 'on button'.

I like the HDMI idea because it reduces the cord count. My TV has 3 HDMI connectors that work OK, but I don't want to have the TV sucking down power just so that I can listen to my FM tuner.

I included the picture of the tiny amp to give you an idea of something that could do the amplification.

Perhaps the ideal would be just getting a pre-amp unit. I have a dandy tuner already. I also have some legacy stuff that I occasionally need to use, to retrieve fragments from, in order to convert to digital for editing.

The current A/V amp catastrophe that I mentioned before, has only one RCA input (R & L). It has bluetooth, I work with bluetooth just fine, but if I just want to find a 10 second segment from an old cassette or VCR, I don't want to find a bluetooth transmitter dongle, go through the 'pairing dance' too.

I have a very nice surround sound video switcher with no amp (but no HDMI), and it sucks down 30 watts just sitting still... but it does have gold-plated connectors.

In my desperation, I have even thought of finding an A/V box with HDMI switching and analog inputs, and performing a surgical amplifier-removal on it, because I know that the huge transformer alone is going to drink up power, but the complexity of developing a power supply to replace the amplifier's transformer that formerly powered the logic, was too overwhelming... I am already whelmed enough... I don't need any more whelming.

Maybe I am at the forefront of a general realization that we have been sold a load of power-sucking goods, that have very marginal returns, regarding the quality of our lives.

So, to clarify, I know all I need to know about amplifier theory.

Right now, switching seems to be the biggest obstacle.

BTW, I have a nice Hafler 220 for sale.

Best,

-AC
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Old 07-08-15, 09:25 PM   #10
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There are cheap HDMI switches available along with reasonably cheap VGA and component to HDMI converters.

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