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Why are digital amplifiers so wimpy?

post #1 of 172
2/5/07 at 3:48pm
Thread Starter 
I am wondering why the digital amplifiers they use in some of todays receivers seem to be wimpy? I have tried to give these new amplifiers a fair listen, but they seem to sound harsh and wimpy compared to more traditional power amps/receiver amplifiers. I have heard the argument that they are more efficient and do not need to draw alot of power. If speakers still need a certain amount of current to create a certain SPL then how is a digital amplifier going to do the same job of a traditional design?

I am looking to replace my current receiver around the end of the year or the beginning of next year. The problem is that I am on a budget like so many other people, dam budget.

Am I being to picky and not giving digital amps credit or is my current view justified? The last thing I want to deal with is a new receiver that clips because the amp section is wimpy. If someone here can educate me on the real performance differences with the pros and cons. I would greatly appreciate it, thank you.
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post #2 of 172
2/5/07 at 4:27pm
What speakers do you run and what kind of power are you looking for?
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post #3 of 172
2/5/07 at 5:16pm
If receiver power was as beefy as a seperate power amplifiers, then you'd have no
power amp market and companies go belly up.... layoffs, etc... Idiocracy..






/joke
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post #4 of 172
2/5/07 at 5:17pm
What amp are you using?
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post #5 of 172
2/5/07 at 6:14pm
Quote:
Originally Posted by Dave Moritz View Post

I am wondering why the digital amplifiers they use in some of todays receivers seem to be wimpy? I have tried to give these new amplifiers a fair listen, but they seem to sound harsh and wimpy compared to more traditional power amps/receiver amplifiers. I have heard the argument that they are more efficient and do not need to draw alot of power. If speakers still need a certain amount of current to create a certain SPL then how is a digital amplifier going to do the same job of a traditional design?

I am looking to replace my current receiver around the end of the year or the beginning of next year. The problem is that I am on a budget like so many other people, dam budget.

Am I being to picky and not giving digital amps credit or is my current view justified? The last thing I want to deal with is a new receiver that clips because the amp section is wimpy. If someone here can educate me on the real performance differences with the pros and cons. I would greatly appreciate it, thank you.


Digital amps are more efficient, that's why they draw less power for a given output - the digital amp can turn more of the power it draws into output power. For instance, a "traditional" class AB amp may be roughly 50% efficient but a truly digital amp may be roughly 90% efficient.

Efficiency is also the reason they can be smaller and lighter. If more of the input power is converted to output power, then less heat must be dissipated so huge heatsinks are unnecessary. Also, the power transformers aren't as big because they don't need to be oversized nearly as much due to the higher efficiency of the amp stage(s).

I picked up one of the Panasonic XR55 receivers just to see what the hype was all about and I think it's pretty darn good - especially considering its price. There is no doubt in my mind that its ~80wpc @ 8 ohms is every bit as powerful as any other receiver 80wpc @ 8 ohms.

If the conventional and digital amp are competently designed, the watts of one are no different than the watts of the other.
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post #6 of 172
2/5/07 at 8:20pm
Thread Starter 
Currently am using a Yamaha RX-V995 that I bought in 97'. At one point I was powering my front left & right via preout to a Soundcraftsman eq and then out to a Onkyo Intergra intergrated amp. I know not the best way to run a home theater, but the Onkyo was a two channel and was really beefy compared to the Yamaha. When comparing two channel performance heads up. But now I just run the internal power of the reciever to run all my speakers. At one point I had 2 pair of rear speakers, center channel and my Altec A-7's which had 4 - 15" woofers and it never clipped.

My System
Yamaha RX-V995 (5.1 DTS & DD Surround Sound) 100 Watts X 5
Sony DVP-S9000 ES DVD/CD/SACD Player
Denon DVD-2200 DVD/CD/DVD-A/SACD Player
Toshiba HD-A1 DVD/HD-DVD Player
Marantz LV-520 Laserdisc Player
Denon DTR-2000 DAT Recorder
Sony KDF-E50A10 50" LCD HDTV
Panasonic 4 Head VHS Recorder
Monster Power Center
JVC QL-50 Turntable

Main Speaker: Altec Lancing - Voice Of The Theater A-7's (One 15 & H.F. Horn Driver) Power Handling from 1 watt - 300 watts rms. My father used to own these Altecs and he use to run a comercial Yamaha that was 300 watts rms. I witnessed him pegging the needles at 300 watts continuous and the speakers could have most likely handled more.

Center Channel: Klipsch RC-64 (power handling 200W RMS)

Rear Speakers: Klipsch RB-81 (power handling 150W RMS) I have 1 extra pair for a 7.1 setup.

SVS Subwoofer

Future Upgrades:

Blu-ray Player w/ HDMI 1.3 - Currently saving for this player, might buy a Sony, Pioneer or Panasonic?

Reciever w/ HDMI 1.3, DTS Master Audio, Dolby True HD, assignable component inputs, assignable digital inputs and assignable HDMI.

Sony SXRD VPL-VW50 1080p HD Projector w/ Stewart Firehawk 120" screen


For some reason the Sony receivers sound lacking and seem to have almost no headroom to the amplifier section. The STR-DA7100 IMHO was very blan and lacking in dynamics and lacked transparency. I also was not to crazy about the problems with there scaler ether. I am looking to spend $1500 min to a max of $2500 and thats pushing it, dam bills.

The amplifier section has to put out at least 100 watt per channel as I like to turn it up. So the amplifier has to be able to be able to reinforce every frequency at high volumes with as little distortion as possible. And hopefully that brand will have DTS Master Audio and Dolby True HD by the time I am ready to buy.
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post #7 of 172
2/5/07 at 8:33pm
Can we assume that you mean a Class-D amp? It's really no more "digital" than any other amp and that terminology is not correct. A Class-D amp is, as noted by others, typically more than twice as efficient as a Class-AB amp. With your listed equipment, you really don't need as much power as you seem to think. 2-watts into those speakers would be deafening. A good digital amp like the Rotel-1077 would be a lovely addition that would power your system to any level without even breaking a sweat.
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post #8 of 172
2/5/07 at 9:18pm
Thread Starter 
I am guessing that Sony's S-Master Pro digital amplifier is actually a Class D amp? I am not sure why words like digital drive are used for these amplifiers then. I wish I had the cash then I would just buy some McIntosh power amps and be done with it.

Choosing a receiver has never been such a pain as it has been with these newer receivers. It should all be worth once I have that new receiver sitting in my HT.

This is why I am asking people here so I have a better understanding of what the so called digital amplifiers are. I imprecate everyones help in giving me input on this subject so I can make a more informed decision when buying a new receiver.

I almost forgot to mention that beyond the need for playing back standard lossy surround tracks. It will need to deliver and reproduce lossless DTS-Master Audio and Dolby True HD audio as well. And it do have some SACD and DVD-A music I listen to as well.
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post #9 of 172
2/6/07 at 4:54am
Please read the following on Amplifier Classifications:

Amplifier Classifications

It explains better than I.....
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post #10 of 172
2/6/07 at 8:08am
Unless you are having problems paying your electric bill I would not worry too much about amplifier efficiency. I would look for an amp that is capable of remaining stable into low impedances and when large dynamic peaks are needed. Unfortunately you won't find either in most mass market receivers. I would invest in a good multichannel or stereo amp that will stand you in good stead for years to come and just use a receiver or low price AVP for a pre/pro. My recommendation for a great 7 channel amp is the Sherwood Newcastle A-965, which can be had at a discount under $1k if you shop around. Or buy a used amp at Audiogon or Videogon for even less.
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post #11 of 172
2/6/07 at 8:28am
Thread Starter 
Thanks for the link Desmo888 there was alot of information there and I hope to use it to help buy my next receiver. Class A seems to be the best in regards to audio performance but waste power. Class D does not wast power and claims to have great dynamic range but suffers in the clarity area.

I am still trying to figure out how an amp that looks like a cheap under performer can have great dynamic range. For example the Sony STR-DA7100ES/B uses a small single capacitor and so it ends up with poor dynamic headroom. Not sure why small capacitors where used but IMHO its a mistake. When I saw the picture of the insides of the Sony I wanted to laugh. It looks like a cheap no name brand with the basic low quality parts.

Right now I am saving up for a Blu-ray player and I hope to have one no later than October. At the point where I have saved up the money for the Blu-ray player I will start saving for the receiver so I have plenty of time to get educated on the new designs. And try to end up with the best product my money can buy.

Upgrade Plan
1. Blu-ray Player
2. Receiver

At that point I might just take a brake and concentrate on building my Blu-ray library for awhile and see what my next upgrade needs to be?

thanks for your input dsmith901 and while I have not cared for Sherwood in the past. I might just keep the A-965 in mind as it might do the job? I will be looking into other power amps in the $1k to $2k range and see what the best one is for the money. It really sucks being on a tight budget and it narrows down ones choices. But I agree that adding an external amplifier would be greatly beneficial to the performance of my home theater. There is alot of good product out there and it is not always easy to pick just one particular model over the rest.
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post #12 of 172
2/6/07 at 8:59am
Quote:
Originally Posted by Dave Moritz View Post

I am wondering why the digital amplifiers they use in some of todays receivers seem to be wimpy? I have tried to give these new amplifiers a fair listen, but they seem to sound harsh and wimpy compared to more traditional power amps/receiver amplifiers. I have heard the argument that they are more efficient and do not need to draw alot of power. If speakers still need a certain amount of current to create a certain SPL then how is a digital amplifier going to do the same job of a traditional design?

I am looking to replace my current receiver around the end of the year or the beginning of next year. The problem is that I am on a budget like so many other people, dam budget.

Am I being to picky and not giving digital amps credit or is my current view justified? The last thing I want to deal with is a new receiver that clips because the amp section is wimpy. If someone here can educate me on the real performance differences with the pros and cons. I would greatly appreciate it, thank you.

There aren't that many receiver with class D, or digital amps in them as far as I know. JVC makes one and it got good reviews in The Perfect Vision. As far as class D amps being wimpy, why are the most common uses in powered subs then? Also, for some really good class D amps check out Rotel.
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post #13 of 172
2/6/07 at 9:36am
Thread Starter 
The only class D I have heard so far actually is the Sony and I was not impressed. I also talked to some sales people about the Panasonic and they did not have much good to say about it.

I am still trying to look into how Class D can get dynamic range with small capacitors and small transformers. To me it still seems like a cheap way of making an amp but thats why I am asking questions and doing some reading. And as far as subwoofers go they also operate in a very narrow frequency band compared to a full range amp. And I also believe that distortion is not as important in reproducing low frequency's that would explain the use of Class D the way I see it.

http://www.audioholics.com/productre...ES_inside1.jpg
Take a look at that amp inside the Sony STR-DA7100 and tell me that does not look like a cheap toy. They are calling it there S-Master Pro digital amplifier and for some reason a few years ago at CES. I could swear they said it was a class D amplifier but I could be wrong.

I think I might have found the power amp that I will use with my next receiver. I will have to go audition it first and then decide if I will actually spend the cash on it.

The Adcom GFA-7607 cost under $1700

- 125 watts x 7 channels into 8 ohms
- Power rig circuit topology
- Gold Plated 5 way binding posts
- Huge torriodial transformers
- Power bandwidth 10 Hz -100kHz
- 12 volt trigger on circuit
- Dimensions 5 x 17 x 14 inches
- Unit weight: 48 lbs.

http://www.adcom.com/data/compare/Mu...Power_Amps.pdf
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post #14 of 172
2/6/07 at 10:13am
Quote:
Originally Posted by Dave Moritz View Post

I am still trying to look into how Class D can get dynamic range with small capacitors and small transformers.

Class D refers to the power amplification stage, and it requires no transformers. Perhaps you're confusing the power supply with the power amp section?
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post #15 of 172
2/6/07 at 11:03am
Quote:
Originally Posted by soundlovr View Post

Can we assume that you mean a Class-D amp? It's really no more "digital" than any other amp and that terminology is not correct.

it depends on how you define "digital".

most of the class D amps are PWM amps where the output stage can be either on or off. In that sense, those amps are "digital".
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post #16 of 172
2/6/07 at 11:05am
Quote:
Originally Posted by Dave Moritz View Post

I am still trying to figure out how an amp that looks like a cheap under performer can have great dynamic range.

you don't need to pile on gold to achieve "great dynamic range".
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post #17 of 172
2/6/07 at 11:11am
Quote:
Originally Posted by Dave Moritz View Post

I also talked to some sales people about the Panasonic and they did not have much good to say about it.

Of course not. If you bought a Panny digital receiver off the internet for $250, they couldn't sell you their $2500 receiver or pre/pro and then go home to eat filet mignon.
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post #18 of 172
2/6/07 at 11:12am
I have owned the panasonic (xr55) and I can honestly say that I don't understand why people rave about it.

good but not superb sound.
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post #19 of 172
2/6/07 at 11:15am
Quote:
Originally Posted by tlf9999 View Post

I have owned the panasonic (xr55) and I can honestly say that I don't understand why people rave about it.

good but not superb sound.


Sure, not many people say it's the ultimate, but certainly many agree its sonic performance is well beyond its pricepoint.

Anyway, my point was not to make this a Panasonic digital receiver thread, merely to use it as an example in the discussion.
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post #20 of 172
2/6/07 at 11:25am
Thread Starter 
Quote:


Anyway, my point was not to make this a Panasonic digital receiver thread, merely to use it as an example in the discussion.

I agree as the topic is geared towards digital/class D amplification.
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post #21 of 172
2/6/07 at 11:35am
Quote:
Originally Posted by Bob Lee (QSC) View Post

Class D refers to the power amplification stage, and it requires no transformers. Perhaps you're confusing the power supply with the power amp section?

I think he means in the power stage. The Panny XR-55 has a 160 watt power rating, thats how much its allowed to draw from the plug. That means the power supply is probably rated at < 150 watts after you factor in the energy that the power supply itself uses. Theres a pretty small transformer for something thats rated at 7x100 watts output. AB amps typically have power transformers rated at around the power output rating, ie AB amp that does 7x100 watts usually has ~700 watt power supply. Once you factor in the greater efficiency, its still a small power supply.
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post #22 of 172
2/6/07 at 11:37am
Quote:
Originally Posted by Dave Moritz View Post

I agree as the topic is geared towards digital/class D amplification.

To which the example of the Panasonic fits well - except it has a few more goodies inside like a tuner, etc.

It is a fully digital from input to output when fed with a digital signal - there are no DACs inside, the whole thing is essentially a DAC of sorts.

Back to the topic at hand...
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post #23 of 172
2/6/07 at 11:43am
Quote:
Originally Posted by pulse333 View Post

I think he means in the power stage. The Panny XR-55 has a 160 watt power rating, thats how much its allowed to draw from the plug. That means the power supply is probably rated at < 150 watts after you factor in the energy that the power supply itself uses. Theres a pretty small transformer for something thats rated at 7x100 watts output. AB amps typically have power transformers rated at around the power output rating, ie AB amp that does 7x100 watts usually has ~700 watt power supply. Once you factor in the greater efficiency, its still a small power supply.

This is BS. The back panel rating SELDOM is the maximum input draw.

This thing has been MEASURED to put out ~80 x 7 @ 8 ohms - impossible if the input was only 135 watts (which is what it says on the back of mine).

Again, lets not make this a XR55 thread, but lets also not spread disinformation about it. Yes, I have one, and no it's not my only system nor is it my main system.
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post #24 of 172
2/6/07 at 11:54am
Because you're using the wrong ones.

http://www.diycable.com/main/default.php
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post #25 of 172
2/6/07 at 12:08pm
Quote:
Originally Posted by whoaru99 View Post

This is BS. The back panel rating SELDOM is the maximum input draw.

AFAIK it is a FTC requirement for manufacturers to list the maximum power consumption on the device.
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post #26 of 172
2/6/07 at 12:12pm
Quote:
Originally Posted by pulse333 View Post

Theres a pretty small transformer for something thats rated at 7x100 watts output.

it is a swps so you cannot compare its transformer size with that of a conventional power supply.
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post #27 of 172
2/6/07 at 12:17pm
BTW, Class D is not necessarily digital, and it usually isn't.
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post #28 of 172
2/6/07 at 12:20pm
Quote:
Originally Posted by Bob Lee (QSC) View Post

BTW, Class D is not necessarily digital, and it usually isn't.

it depends on how you define "digital". but more often than not, a class d amp is digital.
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post #29 of 172
2/6/07 at 2:44pm
Quote:
Originally Posted by tlf9999 View Post

it depends on how you define "digital". but more often than not, a class d amp is digital.

Only by your definition that would include all two-state circuitry, which you have argued many times but have probably won few converts. The vast majority of class D amps use analog modulation and switching transistors but are not digital. In order to qualify for a "digital" label, most engineers would probably insist that the amp use some kind of discrete, numerical process (i.e., actually digital) for modulation.
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post #30 of 172
2/6/07 at 3:21pm
Quote:
Originally Posted by pulse333 View Post

AFAIK it is a FTC requirement for manufacturers to list the maximum power consumption on the device.

I'm pretty sure it's not a universal requirement.

There is a UL document that covers this sort of thing, but I'm not paying $200 or what ever it is to download it.

As another example, my Yamaha M-80 amps are FTC rated both channels driven 250wpc continuous @ 8 ohms 20Hz-20kHz. Yet, the back panel rating is listed as only 600 watts input. That would be electrically impossible for conventional Class AB amps - to draw only 600 watts to put out 500...

Even more interesting is the service manual that indicates the listed input power consumption varies by region of sales market - yet the amp has the same basic output power specification.

USA model = 600w
Canada model = 1100w/1300va
Europe/Australia model = 1700w
All other models = 850w

Go figure???
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