What the heck? It's less than lunch!

Founder of XSA-Labs
Joined 2012
Paid Member
Mark,
Can this amp run on 19 volts? Favorite amps? The TPA3118D2 is now my main amp for listening to my favorite CD's. It's bigger brother, the 3116 may replace it once I finish the build and compare sound. There is something in how clean and detailed it sounds with terrific bass that is very easy for it to do with no effort. The soundstage is also very open. The noise is very low and the efficiency can't be beat. I run it without a heatsink quite loudly. I let it run continuously for 3 days to burn in and so far no problems. It has not auto shutdown yet. Can't recommend it enough.
 
The reason I stress that efficiency is 4 times worse than a comparable class D amp is that many of such amps are sold for the 12V portable market. And here it will have a huge impact on battery life is it's one or the other type. So the $6 amp here could very fast end up costing much more than a $20 class D amp because you need a 4 times larger battery to get the same run time..
Sorry but your Math is wrong.:(

Example:
let's compare a 20W class AB amplifier , say, 70% efficient meaning 30% waste with a 20W Class D amplifier, say, 92.5% efficient meaning 7.5% waste.
Made up numbers but reasonable and chosen to match your "4:1" ratio.
(Which, by the way, was also made up :) )

You are *actually* comparing "waste" and calling this "efficiency".
It must be so, because it's the only way to reach a 4:1 ratio .

What will each 20W amp pull from the Battery?

In a very simplified calculation:

20W Class AB - 70% efficient - 30% loss = 20/0.7=28.6W

20W Class D - 92.5% efficient - 7.5% loss = 20/.925=21.6W

The Class D one wil indeed rune more time from the same battery.
How much more?= 28.6/21.6=1.325=32.5% more time.

Interesting, useful, it may give you, say, 10 hours music instead of 7 or 8 hours ... but no way 4 times more run time.

Sorry for writing this, but it's a very common misconception in Class D amp users.

Remember that besides "loss" (which respectively amounts to 8.6 and 1.6W) , you *still* have to provide those 20W to the speaker.

And the battery couldn't care less, an Ampere is an Ampere , no matter what it was used for.
 
NATTERING NABOBS OF NEGATIVISM

Oh, you naysayers.

You, who said this wouldn't be any good because it's $6, or because it's from China, or the myriad other reasons.......you nattering nabobs of negativism...you audio snobs who think only $10,000 amps and preamps can sound "good"...

;-)


(I couldn't resist. The only thing good Spiro Agnew ever gave us!)

WELL...........A proper power supply came in today, and the little Lunch Amp is sounding great. By "proper" I mean a 12VDC, 2 amp computer type power supply. Not expensive. I think it was about $10, delivered.

I tried all sorts of other power supplies while waiting, waiting...not so patiently. But none of those had the proper amperage ratings and the little $6 amp hummed in protest. But when the 2 amp power supply was introduced...no more protests at all. Just music.

The $6 Lunch Amp as I'll call it is dynamic, amazingly detailed, and dead quiet at idle! Saxes sound like saxes, and drums are quick. I'll try some voices later.

But right now I'm happy listening to a very good jazz CD I'll recommend to you jazz lovers. Curtis Counce: "You Get More Bounce With Curtis Counce". The cover alone is worth the price of the CD! Check it out.

I'm very happy with this amp. Now I'll make an enclosure for it!

Later guys,
Mark
 

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So....does this mean you will be building a "lunch-box" for your amp?
I'm glad your happy with the sounds your machine is making. This thread reminds me of the "sounds good" vs. "measures good" debate that has been festering within our community........some of us will measure, calculate, theorize till the "numbers" say it's good......some use their ears to declare what "sounds good"........Ying & Yang I guess....build yourself a beautiful, artistic enclosure, something to be proud of.......& enjoy!

_____________________________________________________Rick.....
 
So....does this mean you will be building a "lunch-box" for your amp?
I'm glad your happy with the sounds your machine is making. This thread reminds me of the "sounds good" vs. "measures good" debate that has been festering within our community........some of us will measure, calculate, theorize till the "numbers" say it's good......some use their ears to declare what "sounds good"........Ying & Yang I guess....build yourself a beautiful, artistic enclosure, something to be proud of.......& enjoy!

_____________________________________________________Rick.....



Hi there!

Ha. This amp would "swim" in a lunch box! I'll probably build something on the order of what I did for my Jerry's Electronics amp. But smaller. See below.

Yep, I've always been amazed on forums how guys will model stuff to death rather than just try it: speakers, amps, preamps, what have you. Uh... "Just Do It".

This thing is a total no brainer. It does most certainly need a 2 amp power supply though. It squealed like a girl when I hooked those salvaged ones that were rated in the millivolts up to it.

Incidentally, in my quest for a salvaged DC power supply I noticed WILDLY varying voltage outputs from what is stated on the thing. I had one rated at 9VDC that measured double, and a 12VDC that measured only 2VDC. Considering this wild variation in DC volts, it's no wonder so many cordless telephones fail, or even computers.

So, word to the wise for anyone trying any DC power pack: measure it with the DC setting of your volt-ohm meter before you plug it in.

-Mark
 

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Oh, you naysayers.

You, who said this wouldn't be any good because it's $6, or because it's from China, or the myriad other reasons.......you nattering nabobs of negativism...you audio snobs who think only $10,000 amps and preamps can sound "good"...

;-)


(I couldn't resist. The only thing good Spiro Agnew ever gave us!)

WELL...........A proper power supply came in today, and the little Lunch Amp is sounding great. By "proper" I mean a 12VDC, 2 amp computer type power supply. Not expensive. I think it was about $10, delivered.

I tried all sorts of other power supplies while waiting, waiting...not so patiently. But none of those had the proper amperage ratings and the little $6 amp hummed in protest. But when the 2 amp power supply was introduced...no more protests at all. Just music.

The $6 Lunch Amp as I'll call it is dynamic, amazingly detailed, and dead quiet at idle! Saxes sound like saxes, and drums are quick. I'll try some voices later.

But right now I'm happy listening to a very good jazz CD I'll recommend to you jazz lovers. Curtis Counce: "You Get More Bounce With Curtis Counce". The cover alone is worth the price of the CD! Check it out.

I'm very happy with this amp. Now I'll make an enclosure for it!

Later guys,
Mark
Isn't it exciting to get a small package delivered that cost almost nothing and then there is the fun of connecting it up to various speakers and being amazed.
Buying little amps is rather addictive
 
Yep, I've always been amazed on forums how guys will model stuff to death rather than just try it: speakers, amps, preamps, what have you. Uh... "Just Do It".
So, word to the wise for anyone trying any DC power pack: measure it with the DC setting of your volt-ohm meter before you plug it in.
Knowing when it is appropriate and when it isn't. Good advice and worth pointing out.

What kind of speakers do you have hooked up to your $6 Lunch Amp?
I may get a couple for some low-budget active two-ways.
Re: your power supply quest
Was that a combination of new and salvaged, linear and switched-mode supplies? I've never noticed such wide discrepancies, but then I wasn't really looking for that either.
I thought I had that Counce disc, but no. I do have a bunch of his sideman work (w/ Clifford Brown, Shorty Rogers, Chet Baker & Art Pepper, etc.) A great too-short-career bassist.
 
well if 'good enough' was good enough, and looking at the real behavior of the amp offbounds, we could just take a couple of datasheets for the simplest opamps and build those forever more and this forum would field nothing but questions of how to hook up the power... looks like your 'poweramp' chassis cost many times more than the amp, for me thats strange priorities, but hey.. enjoy!
 
Sorry but your Math is wrong.:(

It's your math that is wrong. And the basic knowledge behind it.

A class AB amplifier is typically 20% efficient at 10% RMS output where it's supposed to be measured. That means 80% waste.

A class D amplifier is typically 80% efficient at the same 10% of RMS output. That's 20% waste.

So it's 4 times more efficient.

So if the we take a stereo amp of both types on a 12V battery and playing into 4 ohms speakers at maximum volume before clipping.

The class AB amp will then use: ((((12^2/4)*0.8)/0.2)/9) = 16W
And the class D amp will use: ((((12^2/4)*0.8)/0.8)/9) = 4W

So it uses 4 times as much power under load as well.

That's 4 times less battery life. In fact, it's even less as current draw is higher which makes the actual capacity of the battery lower but then we'd also have to know the type and size of the battery used.

I am sorry for correcting your ignorance but that is what many misunderstand with class D amps. And amps in general. Music signals average 11% of RMS output. Or to be more precise -12dB under peak. That is the mastering standard. And therefore amp efficiency at RMS means nothing. It's the efficiency at 10% of RMS that is important and that's where the class D is vastly more efficient than a class AB amp.
 
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Knowing when it is appropriate and when it isn't. Good advice and worth pointing out.

What kind of speakers do you have hooked up to your $6 Lunch Amp?
I may get a couple for some low-budget active two-ways.
Re: your power supply quest
Was that a combination of new and salvaged, linear and switched-mode supplies? I've never noticed such wide discrepancies, but then I wasn't really looking for that either.
I thought I had that Counce disc, but no. I do have a bunch of his sideman work (w/ Clifford Brown, Shorty Rogers, Chet Baker & Art Pepper, etc.) A great too-short-career bassist.


Hi Sofaspud,

I run Klipsch La Scalas with ALK crossovers. I picked them up reasonably cheap, and repaired the cabinets, and painted them black.

Yeah, the power supplies I tired while waiting for a 2 amp one were old wall wart telephone types, and also one like you'd typically use on your computer. It was a big eye-opener to see how much they varied in DC volts.

I like all those jazz men too. Chet Baker more the playing than his singing though!

Mark
 
Addictive indeed

Isn't it exciting to get a small package delivered that cost almost nothing and then there is the fun of connecting it up to various speakers and being amazed.
Buying little amps is rather addictive


Boy, you ain't kidding. Since Christmas I've messed with this $6 amp, the Jerry's Electronics Amp, and a Sure Electronics TK-2050 (I found a used one.) All really nice. The last two were under $25 without the power supplies. So, still not bad.

I really think in the past few years these types of amps have taken giant leaps sonically from the original HLLY and Topping amps I also own. They're good, but these are really good and much cheaper than what I paid 4 or so years ago.

Mark
 
Mark..........Well no wonder your lunch amp sounds so good!!! A pair of LaScalas?? Flea power rules!!!!
I also get wild variations of voltage readings from "wall warts" My guess is the so-called DC ratings printed/embossed on wall warts is RMS.......the devices seem to be rectified but not filtered....capped. So depending on the varied ability of your DVOM to cope with the line frequency.......the readings will be all over the map. This is where a scope would come in very handy.

________________________________________________________Rick.....
 
Those look nice - similar to all the UcD designs going on in the other threads - self oscillating I think and two power MOSFETS give it a lot of current drive. Do they sound good?
I had it hooked up to 2 DefTech Studio Monitors 350 and I thought the sound was sweet indeed. Not as silky smooth as my Pioneer SC-05 in my HT, but then again, that uses my 'mostest' favorite class D amp modules the B&O ICEPower. They, IMO are simple the best. But, alas it's not DIY either! :)

The 350's have side baffles that added some bass reinforcement and of course the mids and highs were clear and concise. I was also using the new Doug Self 2012 pre that I finished up earlier in the year. That gave me a bit more control over the tweaking the sound. And of course, that pre sounds out of this world to me - regardless of the amp I have it hooked to! The LJM modules are very popular as there are a few dedicated threads about them also. Well made with good components. I'm extremely happy with them. And the price is very reasonable.

Rick
 
I get the same rush when assembling an amp from mere parts that cost under $15 to get the TPA3118D2 dead bug that plays wonderfully loud clean music.
Jeez, I had no idea of what you had achieved until I took delivery of my ready made tpa3123 board. Was this just a one off challenge or do you intend to build other tpa31xx amps?
The dead bug looks more like a cancerous growth, I mean that in a nice way:p
I'm appreciating the sound of this amp, perhaps more than the ta2020 whch I have several of. I cannot see there being any difference in sound quality between the tpa31xx amps?
I just need to chase down some faceplate lamps before putting my old McIntosh ss amp on Craigslist, I'm a d-amp convert.