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hector.murray
02-14-2005, 07:26 PM
I was treated today to a demonstration of a 1200 Watt class D amplifier. Having been involved in electronics for over 30 years, it took me a minute to remember my classes of operation, class A - signal output for 360 degrees of input cycle, class AB signal output of more than 180 degrees and less than 270, class B signal output for 180 degrees of input cycle, class C, less than 180 degrees of output and my memory failed me ( and I later remembered why) for class D. I later remembered that it was because the output is terrible ( or was) with regard to fidelity.
The demonstration I listened to showed me that the fidelity was anything but terrible.
I put my skepticism in my pocket and listened. The sound I heard was not distorted. I confess I was not familiar with the program material used for the demonstration, but the trumpets sounded like trumpets, the drums sounded, well like drums should.
Afterward, I touched the amp case. Tentatively at first, expecting heat, but found that the amp was merely warm, and they had been driven rather hard feeding a pair of 15" subwoofers and a pair of 3 way speakers besides.
When I returned home I did a search on the net for class D amps and found that there have been some significant advances in this area.
I'm sure by now you're asking "what's your question ?". My question is simply:
Has anyone here played with any class D amps in the last 2 years and what was your experiance?

GordonW
02-14-2005, 09:08 PM
They're not class-D (digital clocked-sample-and-PWM, usually), technically, but I have heard the new PS Audio DCA-series amps and preamps, which are "gain-cell" design... pulse-width-modulated but NOT hard-clocked (variable pulse widths, but not limited to specific pulse "cycle times"). Boy, have I been IMPRESSED. Best sounding solid-state preamp I've heard, personally... and that includes Mark Levinsons, Aragon, and a number of brands. Actually beats the pants off of many TUBE preamps!

And the amps... incredible sonics, with unbelievably low power demands. We've got them at work, with the PS Audio PowerPlant (AC waveform 're-generator'- not only does it effectively FILTER the AC power from noise, it can GENERATE 'custom' waveforms to more efficiently feed power supply transformers, diode bridges and such in amp power supplies)... the PowerPlant, among other functions, has an AC watt-meter, that shows total power demand. With the preamp AND amp on the meter, we literally had the ROOM RATTLING on a pair of Tannoy TD12s (about 93 dB sensitivity), and the TOTAL POWER DRAW of the amp/preamp combo was LESS THAN 70 WATTS, average!!! :jawdrop:

It's nice to see some really clean-sheet designs such as these being done... someone willing to throw away all the "assumed limitations" of design, and start building from scratch. Many times this procedure doesn't work, but in a case like this where it DOES... BOY, do you get SERIOUS advances in what is possible, to do...

Regards,
Gordon.

hector.murray
02-15-2005, 05:47 AM
These amps really gave me pause to think. I'm going back for a second listen in a couple weeks. I want to confirm what my ears heard and reconfirm the price, which I believe is $600 Canadian (don't quote me on this yet - I really do need to reconfirm). The amp itself fit inside a computer server 1U type rack case, if you're familiar with those, about an inch and a quarter thick, 18" wide and 20"deep (approx). I held one of these amps on the fingertips of one hand. The only thing that put me off about the amp was the Power supply, and I confess, this is an old personal bias, that being the switch mode power supply in the unit. I'm an old copper and iron man. give me a 30 pound transformer and some monster filter caps and I'm in heaven (not to mention having t'shot a few blown switch mode power supplies) but hey it works.

Charley Rummel
02-15-2005, 05:25 PM
I recently came on board with a company which manufactures portable sound systems, as Manager of New Product Development. Out of respect to the forum, I will try my best not to make this read like a sales pitch for my new company.

We have a unit which is similar in size of an L100, has a powered 2-way speaker system, built-in 3 channel mixer, tape and cd, as well as an available selection of additional accessories we can offer. It is powered by two rechargeable industrial batteries that develop 12 volts DC. The power amp is a true class D 100 watt (peak) design. At this time we are developing more powerful models to be released soon.

The class D design is remarkably energy efficient allowing hours of use from a single battery charge. The circuit also runs very cool; no massive heat sinks needed as in class A, AB or B type circuitry. Furthermore, we're getting good fidelity from our amp design.

Regards,
Charley

hector.murray
02-15-2005, 06:44 PM
I appreciate your comments. Anyone else with an encounter with a class D?

evans224
02-15-2005, 10:40 PM
Panasonic (that's right, no misprint) makes a pure class d HT reciever that is getting raves. The model is SA-XA70, is a 6.1 with 100 WPC. It has the new HTMI cable that carries the digital signal from a like-equipped Panasonic DVD/CD player. It's supposed to be incredible when listening to DVD-A. 6.1 channels of sound that supposedly put stereo to shame. I've been trying to find it, and finally located it at Fry's Electronics. It's priced at $499. And it is very easily bi-amped- no expensive active crossovers etc. The DVD/CD player is $300. I'm going to listen to it tomorrow, and will let you know what I hear. Check out vintage asylum.com and search for SA-XA70. Guys are going crazy over these things.

Steve Gonzales
02-16-2005, 02:50 AM
One of the good things about these amps is they are typically better than 85% efficient. That is why there is very little heat sink area needed. In my home theater set-up, I use a *^%$&$ subwoofer that has a 1500 watt class D amp and a 12" driver with a P-P Xmax of 4"! Holy cow! The thing barely gets warm even after a high DB demonstation of Saving Private Ryan or some of the choice chapters of Lord of the Rings. I am glad to hear that the technology is to the point that it can be used in full range applications. I did audition the Class D offerings from Sony for home theater use and found them to sound rather dry, not my cup of tea as far as HiFi 2CH for music is concerned, but in all fairness, I don't believe that Sony geared these HT amps for that purpose. There seems to be more to class A or A-B amps that give you that realistic traslation and soundstage that probably has more to do with their topology than a pure comparison between mere specifications on paper would imply. Regards, Steve G

duaneage
02-16-2005, 04:33 PM
You can thank the car stereo market for some of the advances in Class D technology since they had to work with less power. I have heard Class D sub amps and they are truly remarkable. I was under the impression that class D was suitable for low frequency work with high voltage power demands and not good for upper range. Maybe they have advanced tha art. i hope so, class d is more affordable technology speaking than traditional methods.

johnaec
02-16-2005, 05:26 PM
12" driver with a P-P Xmax of 4"!What, pray tell, is that?? RE? Does it still have any fidelity at those extremes, (or even half that)?

John

jblnut
02-16-2005, 06:09 PM
Panasonic (that's right, no misprint) makes a pure class d HT reciever that is getting raves. The model is SA-XA70, is a 6.1 with 100 WPC. It has the new HTMI cable that carries the digital signal from a like-equipped Panasonic DVD/CD player. It's supposed to be incredible when listening to DVD-A. 6.1 channels of sound that supposedly put stereo to shame. I've been trying to find it, and finally located it at Fry's Electronics. It's priced at $499. And it is very easily bi-amped- no expensive active crossovers etc. The DVD/CD player is $300. I'm going to listen to it tomorrow, and will let you know what I hear. Check out vintage asylum.com and search for SA-XA70. Guys are going crazy over these things.

HK also has a separate line of Class-D AV receivers. I've seen a bunch on ebay very cheap and I've been tempted.
I believe it's the "DPR" line.

jblnut

bob newton
02-16-2005, 07:13 PM
class A - signal output for 360 degrees of input cycle, class AB signal output of more than 180 degrees and less than 270, class B signal output for 180 degrees of input cycle, class C, less than 180 degrees of output and my memory failed me ( and I later remembered why) for class D. I later remembered that it was because the output is terrible ( or was) with regard to fidelity.



Man!, You guys blow my mind, havn't a clu what the devel you are talking about!:hate-pc:


BTW , My amp is a class XYZ, Bet I got you on that one! I lie

hector.murray
02-16-2005, 07:54 PM
Lots of input. Thanks Guys!
Bob, it's ok, we know that there are some here who are technologically challanged. Stick around, and you may end up talking the talk if not walking the walk....
I know I'm learning more everyday! This place is like school, and when I go to Montreal and visit the (name withheld) audio shop, its' like college cram!

bob newton
02-17-2005, 04:08 AM
Well, I am not totally lost. I understand class A and AB like as in push pull :applaud:

But I guess thats old tube stuff. This is a great web site,you don't need to tell me that. I am keenly aware! And Hooked.:eek:

evans224
02-17-2005, 10:18 PM
The 18 year olds working at Fry's wouldn't allow me to check out the Panasonic, they had to ask their boss who was not around. I told them that they have a hot commodity on their hands and needed to hook it up. They didn't have the DVD/CD player-model is S95- but promised me that if I came back next week, I could at least talk to someone in charge so I could listen to it. I'll keep you informed.

Baron030
02-21-2005, 08:00 PM
Well, I can't say that I have had any experience with Class-D ampllifiers. But, for several year now, I have been using a Class-I amplifier. It is also know as BCA (Balanced Current Amplifier). And most commonly know as a Crown K1. It is capable of putting out 350 watts per channel into my old D130s. Needless to say I have not tried to push the gain to full power. The result would be a pair burned voice coils. But, I can say that it has made my old 030 system. sound a lot better. So, I would recommend a crown K- series to anyone who wants a lot of bang for buck.

bob newton
02-21-2005, 08:10 PM
350 watts per channel

You got a killer sexy beast there! I think it would murder my JBL L-100's

:p