What the heck? It's less than lunch! - Page 6 - diyAudio
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 Chip Amps Amplifiers based on integrated circuits

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diyAudio Member

Join Date: Jun 2005
Location: Copenhagen, Denmark
Quote:
 Originally Posted by JMFahey 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.

Last edited by Saturnus; 2nd April 2013 at 02:07 AM.

diyAudio Member

Join Date: Feb 2005
Location: Davis, California
Quote:
 Originally Posted by Mark2727 Hi there! 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
can someone compare the sound of this to t-amp?
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Good sound from Davis, CA

diyAudio Member

Join Date: Mar 2009
Quote:
 Originally Posted by sofaspud 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

diyAudio Member

Join Date: Mar 2009

Quote:
 Originally Posted by radiosmuck 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

 2nd April 2013, 10:07 PM #55 diyAudio Member     Join Date: Oct 2012 Location: Metro DC area 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.
 2nd April 2013, 10:38 PM #56 diyAudio Member     Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence. 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.....
diyAudio Member

Join Date: May 2011
Location: Danbury, CT
Quote:
 Originally Posted by Mark2727 Saturnus, Everyone, I'd be interested in knowing your particular favorite class D or chip amp --- regardless of cost. Mark
Here's my favorite class D modules. One of the better sellers I've dealt with for over 2 years now. More than \$6 though.

Edit: Here are some pics of the amp I built using these LJM modules.

Rick
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redjr

Last edited by redjr; 4th April 2013 at 02:16 AM.

 4th April 2013, 02:26 AM #58 diyAudio Member     Join Date: Oct 2012 Location: Metro DC area 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?
diyAudio Member

Join Date: May 2011
Location: Danbury, CT
Quote:
 Originally Posted by xrk971 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
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redjr

diyAudio Member

Join Date: Jul 2012
Location: Montreal
Quote:
 Originally Posted by xrk971 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
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.

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