digital amp specs (1 Viewer)

[Wayde_R]

Hello

I'm looking around at specs on various amps and am finding some interesting features on some JVC offerings. These new generation of digital amp/receivers by JVC and Kenwood (I've only looked at specs from both) show some weird specs I'm not used to seeing on conventional amps.

What worries me is this...(from a JVC RX-D401S)

"110 watts per channel, 6 ohms at 1kHz, with 0.8% THD"

#1/ at 1kHz ?!? That's just one freq, not a range. I'm used to seeing 20Hz-20kHz. Is this just a way of saying that it can't do 110 watts with any more than one freq at a time?

#2/ The other concern is this 6ohm thing. I thought the accepted standard outlined by the Federal Trade Commission said that home amps were to be spec'ed at 8ohms? Are we slipping backwards here? Are 6ohm home speakers making a comeback? Are there special digital speakers you must use for a digital amp that are 6ohm.

I'm a bit confused.

Thanks for any explanation.

Wayde

 

[Arthur S]

Yeah, they are using the loosest possible guidelines to show the most power. You forgot to mention 0.80 percent THD. That is about 10 times what you would want.

If that receiver were rated at 8 ohms, from 20-20, at 0.08 percent distortion, the power rating would likely be closer to 45 watts per channel.

 

[John Garcia]

All speakers are analog.

What Arthur said. They're just fluffing the specs so it appears to have a lot of power, because if they quoted it's real output of something like 40wpc, most unknowledgeable consumers would not even give it a second look because it doesn't have 100wpc. Digital amps tend to have higher distortion also, though that doesn't necessarily mean they don't sound good, it's just that they are showing you a measurement that makes the power #s look good to the average consumer.

Check out the Panny XR55.

 

[Wayde_R]

Thanks for the recommendation John, and the insight Arthur, I knew I could count on this forum to dispell.

Actually I suspected exactly what you said Arthur but didn't want to jump out with it because I wasn't sure. If I saw those specs on a standard amp, that I know, I would have screamed foul.

Thanks for the Rec on the Panny John, I'll definitely check that one out.

 

[Kevin C Brown]

The Panasonic is similarly rated:

Note that it's "stereo mode" too and not all channels driven. For whatever reason, most of these digitally powered receivers are underpowered. I have seen reviews of the Panasonic XR-70 or something, and some new JVC at Sound and Vision, and both were not recommended to be used with 4 ohm speakers. With the right speakers, yeah you're OK, but forget about low impedance or low sensitivity speakers.

 

[FeisalK]

Sound and Vision Mag did lab tests on a couple of Panasonic XR amps you can download the PDFs

XR25 - review / lab results
XR70 - review / lab results

 

[eddieZEN]

I don't know about the JVC digitals, but the Panasonic sa-xr55 is most definitely NOT underpowered by any stretch of the imagination---in fact it easily outpowered my NAD separates which are very conservatively rated at 100wpc at 8 ohms.

Bear in mind that most budget analog amps (Denon, Marantz, and especially HK being the exceptions) tend to have inflated RMS numbers.

As for the distortion specs, remember that most humans can barely hear 10% distortion, so the difference between .8% and .08% is completely meaningless in real world performance.

 

[Kevin C Brown]

The xr55 *is* underpowered. It is rated into 6 ohms, not the industry accepted 8 ohms, so it *seems* on paper as if it is more powerful than it is, and it is *not* rated into 4 ohms at all.

The problem is that most "8 ohm" speakers are actually not 8 ohms across the entire frequency spectrum. An 8 ohm speaker *can* dip down into the 4 ohm range or lower at certain freqs. Add to that the fact that the Panasonics *do* have trouble delivering enough power to low sensitivity speakers too.

Don't take my word for it either. Many people have commented on these problems over on AVS and Audioholics. Yes, there is a "fundamentalist sect" at AVS that hold that these receivers are the greatest thing since sliced bread, but some of us who have actually listened to these things into difficult to drive loads, know that they have limitations their analog counterparts do not.

To be honest, that *is* why they are priced as cheaply as they are. For the money, they are a good deal. But make darn sure the speakers you have them hooked up to are appropriate for their output.

 

[eddieZEN]

> The xr55 *is* underpowered. It is rated into 6 ohms, not the industry accepted 8 ohms, so it *seems* on paper as if it is more powerful than it is, and it is *not* rated into 4 ohms at all.

Guess that all depends on your definition of "underpowered." Despite its 100wpc at 6 ohms rating which I agree is odd, Sound and Vision tested the xr70 to 88wpc at clipping with all channels driven.

In comparsion, the Denon 3801 which costs several times more, claims 105wpc and was tested to actually deliver 92wpc at clipping with all channels driven:

http://www.geocities.com/Area51/Holl...vsac.htm?20055

That does not sound terribly "underpowered" to me, unless you are comparing the Panny to say a high end Hafler amp that puts out over 250wpc.

Now granted I would probably not run a pair of massive, power-sucking floorstanders with them but then again I would not use a low- to mid-priced analog receiver on such speakers either.

I have however read of people running 4 ohm Magnepans with these Pannies without any problems.

So a more accurate statement is that *higher-end* analog receivers will probably be more suitable for demanding loads. A midfi analog like a Pioneer 1014 or Yamaha 657 however is *not* any better powered merely by virtue of being analog.

 

[MikeNg]

By contrast, HK has these specs published for their DPR 2005 -

Stereo Mode
Continuous Average Power (FTC) per Channel 120 Watts per channel, 20Hz – 20kHz, @

 

[FeisalK]

Mike, what sort of problems are u having with the DPR2005?

 

[eddieZEN]

Mike, the subtle hiss that you report with your HK2005 is a common complaint I've heard about HK's analog receivers and NAD's AVRs on many different audio forums. This is the first I've ever heard this about the 2005 though.

It would be worth your while to purchase the Panny for a side by side comparison, and return it if it proves clearly inferior. I have heard both positive and negative consumer experiences of the HK2005, it seems to be getting more mixed reviews than the Panny despite its 3x higher pricetag and far more respected HK origins.

Personally I have never heard anything resembling a hiss or noise or distortion on my Panny, whether at 50db or 95db listening levels.

 

[MikeNg]

Thanks Eddie. I've actually experienced the 'subtle hiss' from other HK analog AVR's, specifically on the AVR8000. Man that was a nice unit, but I had to get rid of it. What I'm getting on the 2005 is a hiss that's at about the level of -40dB, so not that subtle but it does not vary.

I did a little more research and stumbled on a reference to the 2005 and an inability to handle 4 ohm loads. My center is just that. So I'm going to swap out the speaker and see what it does.

At 3X the price, I'd probably go back to my AVR 7300 or go separates. Just not sold on the d-amps yet.

 

[eddieZEN]

Mike,

you may want to read this thread:

http://www.avsforum.com/avs-vb/show...t=591368&page=3

read posts #53, 56, and 57 are owners of a Denon 5800, HK7000, HK7200, and Denon 3802.

 

[MikeNg]

:frowning:

Link did not resolve...

 

[FeisalK]

here

 

[MikeNg]

Post 53: He believes that most of the distortion is out of hearing range, but the speaker may be able to reproduce it. Huh? I understand the concept of digital path receivers and the theory that it should yield a better result than multiple analog conversions in traditional amps, but unlike he, I'm just not hearing the gains. I wonder what speakers HE'S listening to. I'm running RBH 661-SER's in the LCR positions.

Post 56: He says it sounded good, and was no longer happy with the HK. That's fine, but that just tells me that it's DIFFERENT. I already know that. It may be different to his liking, not necessarily cleaner or even more accurate.

Post 57: Okay, but this really doesn't tell me much about the Panny, only that he liked it better.

If I had lesser speakers up front I'd probably be more inclined to just give it a try. Heck, I might do that anyway to see what the Panny can do. Might be a sleeper like the Oppo DVD player. I just wish posters like these would also say WHY they liked one over the other in greater detail.

Thanks for the information. Maybe I'll try one out.

 

[eddieZEN]

I think it's worth a try, $15 return shipping to Amazon.com is peanuts IMO. Would love to read a detailed review from you on it esp. comparing against the HK2005, plus those RBH speakers look very interesting.

 

[MikeNg]

I've decided to get an RMA from HK to fix the 2005. Once it gets back, I'll get a hold of the 7300 AND the Panny and see if I can pull off some sort of comparison between the three.

At the very least, I can post my impressions, how's that?

Oh, and those RBH's are really something else.

So sweet...

 

[eddieZEN]

a 3-way shootout between the HK2005, HK7300, and the Panny?

whoo-ee, I can't wait to read the results of that!