Axiom Home Page Forums General Discussion Technical Questions B&K Receiver for M80's

Hello all: I've been researching seperates and receivers for M80's for the last several months. What has gained my attention is the B&K AVR 507. This a surround receiver is rated at 185 X7 @ 4ohms; THD 0.09. It has the following abilities: Surround Sound Dolby Digital® • DTS® • DTS ES® • THX EX® • Dolby Pro Logic II & THX Certification Ultra.

This receiver is however from a past generation and is without any HDMI inputs and the latest decoding processes. In reading what one can do to take advantage of the newer processes I believe that by buying a blu ray dvd that has its own processing of the newer technologies I wouldn't be missing much. Also if this player had analogue outputs from the dvd I could easily plug them into the receiver & the sound would be almost as good as with HDMI. In any case I realize that I could buy a Denon or the like just as easily with all I need. But from what I've read this higher end stuff really makes a difference. The newer B&K 705 & 707 costs well into the $3000's. Apparently the 507 cost was similar when it first appeared some 7 years ago. I can pick up a used 507 for about $800. I'd like opinions as to whether or not what I've stated is true, or if you have suggestions for similar performance that would show the M80's at its finest (I don't own the M80's yet). I listen a moderate levels (around 80db) in a 2000 cu ft room and mostly to classical music with a desire to expand to HT. For now I wish to listen without a sub. I hope this is enough info for some responses. Thanks folks....Lee

Lee, it appears that you've been doing some reading in the realm of audio fantasy. Your "show the M80s at its finest" phrase implies that there would be some difficulty in achieving this and that a "high end"(i.e, high priced)receiver would be needed to do the trick. On the contrary, one of the wonders of the current audio scene is the availability of plentiful clean power at modest cost. Properly controlled blind listening tests indicate that amplifiers with flat frequency response from 20Hz-20KHz and with inaudibly low noise and distortion at their designed power output level(again, readily available at moderate cost)allow any speaker to perform at their "finest" within those power levels(certainly at the levels you mention for great classical music). Nothing more is possible from amplification.

For a unit with more up-to-date features, including Audyssey room equalization with Dynamic EQ and Volume, consider the similarly priced Denon and Onkyo models available as factory refurbs or the new models(e.g., Denon 4307, Onkyo 3007)if you're willing to spend a bit more than the $800 figure you mentioned.

Hi Captain,

At least with the B&K you'll be getting a very robust amplifier section with lots of power, more than most AV receivers supply, and it will easily drive the 4-ohm M80s. B&K is among the brands of AV receivers (also including Denon, NAD, H/K, Outlaw Audio) that have never had a problem driving 4-ohm loads.

JohnK's comments notwithstanding, I always applaud buying lots of power output. Some orchestral peaks with a few classical CDs I own are 30 dB louder than the pianissimo sections, and you certainly want a reservoir of watts to handle those cleanly.

B&K gear, like McIntosh stuff, has always been expensive--you should check to make sure they are still in business, for parts availability.

Regards,
Alan

I agree with Alan. I have listened to B&K AVRs on very large and supposedly hard to drive speakers (Wilson Watt Puppy and the BIG Martin Logans) and came away very impressed as they have tons of power and run fine at 4 ohms. While JohnK is surely right about not needing more power than a "cheap" AVR can make, many of us find the real world experience of adding a better power section pays dividends that can't be explained by the math until you turn it up past the 90db range and factor in the kinds of 30db peaks Alan mentions. I would take the B&K amp section over the Denon every time - and I am a big Denon fan and owner. Moving up to a separate amp (i.e.., more robust, more powerful) improved the sound in my system over my Denon AVR 3300. I expect the B&K would do the same.

Also, I am living with a similar geriatric system setup to what you are describing - no HDMI, no Audy, no TrueHD, etc. I planned to buy the Denon 4310 after the projector purchase was done. But after extended listening and watching (over 700 hrs since May 1) the only feature I wish I had was voice delay.

My (all) projector(s) has a bit of a lag that I would love to fix. My point is, I would not buy the refurb or cheap Denon in order to get those features if you can get a B&K amp section. As long as the B&K can be used as a separate amp later (need pre-ins) I would go that route and upgrade the decoder section later. That technology gets cheaper every day, and as you said, and outboard decoder cure much of your concern.

I'd like to offer a compromise: Get a current Denon so you have the bells and whistles, and if you find you need more power, add a couple of monoblocks or a good two channel amp to help relieve the Denon power supply...

Whatintha? That sounds like really good advice! What have you done with Mark!! I demand you release him!

Yes, the HDMI switching (and integrated bass management) makes operating the system much easier. Sure, you CAN find other methods, but you just have to press many more buttons. All the damn time. You can usually find excellent stereo power amps for sale used, and there is very little risk since there are no moving parts.

So, yeah, I agree with Mark. Again.

I have his head pinned under a mortiser while I, instead, give advice!

We need pictures!

Don't dull the bit!!

I'm pressed for time this week...this is all you get. Yes, my mortiser is freakin' huge...I'll go with that.

The bit gets dull just being around me....

Well done! Thank you!!

It is going to take a hell of a larger bit to drill into that rock.

Kids, do not try this at home.



(He's not wearing safety goggles)

I'm not sure what a mortiser is or does, but it looks dangerous! Plus I love the brand name: Steel City. Could be a new action movie title. Should I start working on a cheesy screenplay?

Alan

Apparently it is for removing wax build-up in the ears.

Excellent! Those special drops don't work at all. Must try it.

It's not a screenplay, but I have an idea for a remake of a popular movie.

Now THAT's good! AND funny!

In an "Arnie" voice,

::PRE-Pay-Ah to be MAH-tissed, GAHLY BOY::

Arnie's from Gorgia?

Charles, note that Alan spoke of 30dB over a pianissimo passage, not over average level. Many of the classical CDs which I own have a range on the order of 50dB from the quietest pianissimo to the loudest peaks, which again, are handled well by typical receivers in the 100-150 watt area.

I think Zimm's comments describe the thoughts I had relative to showing M80's at their finest. I have a very good and critical ear and am sensitive to high transients and detailed mid-range inner voices and just about everything else. My understanding about equipment on the order of B&K is that these details would be produced to a better degree and with a reserve of power that at higher levels would be as clear and natural (or neutral) sounding as at lower levels. Mark's suggestion is one I've considered but for now I haven't the room to add mono blocks. I could however live with Outlaw's preamp and amp combination, but I think the B&K for some reason is still my preference. I am open to other suggestions. As a rule I am a thorough researcher on any products I buy. Next to a house and a car, this is going to be a big item purchase for me and my technical knowledge is residual carryover from the 90's! I've learned a great deal from this forum and all of your comments have been instructive. I've stayed with the thought of buying Axioms...read all about the angst regarding upgrading so I think the M80's or maybe 60's would do the trick for me. The main reason I am leaning toward the 80's is for its bass reproduction and apparently better defined highs (that is my conclusion from my reading). In any case thanks for taking the time to respond...Lee

I thought it was low level street transients who are sensitive to inner voices......

That, and womens clothing.

CRAP. Lee just unintentionally threw me under the bus...before backing up and then speeding away. Now JohnK is going to say those of us with golden ears should definitely buy the more expensive gear...as he snickers!

There is a gap of agreement on the issue of power needs, but my research (um, well that is a strong word) indicates those with loud (95db and up) comfort levels need stronger amps to keep those 15 and 30 and 50 db spikes well controlled. John accurately notes hearing damage can (does) occur at those volumes after some period of time. But if I don't turn it up, I can't hear over that constant buzz in my ears!

But my enjoyment of music has, since childhood, been tied to feeling music not purely hearing it. I love the feel of guitar strings being plucked, or drums thumping in my gut - the way I feel at a live performance, even with soft Jazz. I don't get that at 75db in my system. It is all a matter of taste - I mean preference, not that John has no taste. As Alan said, "JohnK's comments notwithstanding, I always applaud buying lots of power output." There must be some reason for that - well besides Axiom making a 1,000 beast of an amp.

(Was that long enough for everyone to forget the golden ear inference???? )

Mark!!

You and your mortiser are needed at Charles' house

I tried to use my biscuit joiner, but made an awful mess.

I get that.

I've always had the same feeling. And I've mentioned here before that when I had a very powerful NAD amp in the past, if offered a feeling of "live" that I never got with a receiver. I had thought of it as better transients or attack.

I don't like being attacked by transients.

Freak.

Could be worse....a transcientologist.

Well there doesn't seem to be consensus here. Having read this forum for several months I am not surprised. But I am nowhere closer to a decision on the receiver. Let's go another direction. Since M60's are another possibility, what are your opinions with respect to its performance vis-a-vis the M80's at moderate levels (around 85db) for listening to classical music? I suppose I would miss some of the lower bass. Again I am not interested in a sub...yet.

I am using the AVR507 to power an epic 80 7.1 system and have been very happy with it. No problems driving all those speakers for movies. Did have it shut off with thermal shutdown once when my dad decided he wanted to listen to music in the garage, which is on the other side of the house...

Not enough heatsinking in one little box to really sustain those kind of levels for any long period of time but i dont think there's any reciever that could. The quality of this reciever is pretty much head and shoulders above anything "new" you can get for that price. That was the case when we got it a few years ago for some $1800 bucks or something

Hi Captain,

Did we get any idea of your room dimensions (length, width, height) and how loud you like to listen? My own living room is about 2200 cu. ft (19 x 13 x 9 ft) and when I listen to classical or opera, I sometimes like orchestral peaks to hit 96 dB to 100 dB SPL (C weighting) where I'm sitting. The latter can be between 9 ft and 12 feet back. I have M80s as well as M22s, either pair of which I can run with an EP500 subwoofer.

The M80s on their own have wonderfully deep bass that goes deeper and there's greater output than the M60s. I'd call the bass from the M60s "very good". I would not say the M80s are more detailed than the M60s, however the 80s are a bit smoother through the midrange than the 60s.

Actually, the M22s have a little more detail than the M80s but we are talking nuances here--the difference is only audible with immediate A/B comparisons, which my system has. Conversely, the M22s can sound a little harder on a poor recording than the M80s; e.g. a recording that has exaggerated or EQ'd mids and treble.

You don't "need" the B&K's power output unless your room is much larger than mine and you listen at levels louder than those quoted above. Some of my Axiom colleagues listen to rock at what I call "deafening" levels--well over 100 dB SPL, in which case you do want very large amplifiers.

Regards,
Alan

Distance is certainly a key factor that is often overlooked when recommending 'receiver only'.
Our main floor listening position is about 14' from the speakers and on occasion, if one is listening to music while in the kitchen, over 22' away, sufficient power is a necessary requirement that cannot be fulfilled by a receiver.

My own testing of the M22/M60/M80s had the M22s most detailed/less bass, the M60 did it all very well and the M80s more detailed/open sounding with the best bass. They do it all very well at all volume levels. I found the M60s to sound very similar to the M80s at the SPL you are asking about Captain. The M80s have better detail at lower volume levels.

Thanks to all. My listening area is about 2000 cu ft with a ceiling that goes from 8' and slope upward to about 14'. The speakers will be aligned across the wall with the ceiling that slopes. Not ideal but the only placement that is logical. I listen at moderate levels about 80 to 85 db, sit about 10' from the speakers. I do have an older sub from "Speakerlab" that goes down to about 25Hz and is driven by a separate external amp. Just as an aside I found a pair of M80v2's for $800 (without shipping) online. they are in Beech but I prefer Boston Cherry. That has been one of the hold-ups for me in fully considering it as well as the need to acquire a receiver. I do however have an early 1990's Denon receiver @ 55watts per channel. Would that work for the M80's?

Sure, Lee; it'll work to the extent that a peak doesn't exceed the capability of the Denon(presumably a bit over 55 watts). The M80s would use about 1 watt for an 86dB level at about 10', so a brief peak on the order of 103-104dB would be accommodated.

If it is an early '90s Denon you can't assume the 55 watts can be reached before clipping occurs. To beat the gravetop of this old horse: My 105 rated AVR 3300 starts to clip at 84 watts. It is a 2001 model.

Just saying, if based on what John lays out you think you will often run over the mid-80s db then keep the effect of clipping in mind when you judge the sound of the M80s.

Naw, Charles; no Denon, including your 3300, clips at a number below its power rating unless it's defective. At the rated number all receivers have distortion below audibility and are nowhere near clipping.

Hey, can someone pass the popcorn?

I used up all my popcorn reserves last month, sorry.

I see your "Naw" and raise you one HT Labs Measurement from Home Theater Magazine, November 1999. Maybe they don't mean clipping, I don't know. But it explains (to me) why my experience with more clean power has not jived with your knowledge of the controlling equations. I could have misunderstood it, no doubt about that.

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From Wikipedia (I know, great source):


So, if the receiver hit maximum power at 78.6 watts, how did they 'push' an extra 57 watts through it to get to 135 watts? Admittedly, my knowledge of electronics is shaky, so I'm open to a reasonable explanation of how this could happen.

Also, I'd say that .016% distortion is pretty damn low. I wonder what they mean by clipping.

A clipped waveform is by definition distorted. So before the amp starts clipping in the least there's a 0.016% THD. The while the clipping may not be hugely detrimental at 135 Watts, it has increased the distortion level to 1%.

From Wikipedia on Clipping:
"Clipping is a form of waveform distortion that occurs when an amplifier is overdriven, which happens through attempts to increase the voltage or current beyond its maximum power capability. Driving an amplifier into clipping causes it to put out power in excess of its published ratings, which are customarily done with a "clean" sine wave signal just at the onset of clipping."

Right, it can keep pouring more fuel on the fire, it just gets more and more distorted as more of the signals peak is chopped off - i.e., there is more area in the clipped segment of the signal cone. My Denon gets harsh on certain frequencies when driven hard. My separate amp does not, because it is not clipping the signal at the same db as the Denon was.

Maybe my Denon and the HT Mag test unit came from the same defective lot? Then again, I don't think I even had it at the time of this press release.

And here is another example i found; again, I could be mis-reading this but it looks to me like this modern amp can't meet its rated output without clipping the signal:
S&V TestYamaha RX-V863 A/V receiver
Rated: • 7 x 105 watts
Test Report
(continued)
By Daniel Kumin
September 2008
DOLBY DIGITAL PERFORMANCE
All data were obtained from various test DVDs using 16-bit dithered test signals, which set limits on measured distorting and noise performance. Reference input level is -20 dBFS, and reference output is 1 watt into 8 ohms. Volume setting for reference level was -3. All level trims at zero, except for subwoofer-related tests, all speakers were set to "large," subwoofer on. All are worst-case figures where applicable.

Output at clipping (1 kHz into 8/4 ohms)
1 channel driven: 77/111* W (18.9/20.5 dBW)
5 channels driven (8 ohms): 45 W (16.5 dBW)
6 channels driven (8 ohms): 41 W (16.1 dBW)
Distortion at 1 watt (THD+N, 1 kHz)
8/4 ohms: 0.05/0.05%
Noise level (A-wtd): -71.8 dB
Excess noise (with sine tone)
16-bit (EN16): 0.6 dB
Frequency response: 20 Hz to 20 kHz +0, -0.1 dB
* Speaker-impedance setup software-switch at "8-ohm" position. With switch set to "6-ohm," output was limited to about 35 watts (15.4 dBW) in all tests.

MULTICHANNEL PERFORMANCE, ANALOG INPUT
Reference input and output level is 200 mV; volume setting for reference output level was -3.5 dB.

Distortion (THD+N, 1 kHz, 8 ohms): 0.03%
Noise level (A-wtd.): -85.3
Frequency response: <10 Hz to 138 kHz +0, -3 dB

STEREO PERFORMANCE, DIGITAL INPUT
Reference level is -20 dBFS; all level trims at zero. Volume setting for reference level was -3.5.

Output at clipping (1 kHz, 8/4 ohms, both channels driven): 66/97 W* (18.2/19.9 dBW)*
Distortion at reference level: 0.04%
Linearity error (at -90 dBFS): 1.5 dB
Noise level (A-wtd): -76.4 dB
with 96-kHz/24-bit signals: -80.5 dB
Excess noise (with/without sine tone)
16-bit (EN16): 0.35/0.5 dB
quasi-20-bit (EN20): 12.5/10.1 dB
Noise modulation: 3.3 dB
Frequency response: 20 Hz to 20 kHz +0, -0.2 dB
with 96-kHz/24-bit signals: 20 Hz to 43 kHz +0 -3 dB
*Speaker-impedance setup software-switch at "8-ohm" position. With switch set to "6-ohm," output was limited to about 35 watts (15.4 dBW) in all tests.

How can these all be wrong? Here is a "•100 watts x 7 (per channel, 8 ohms, 1% THD)"" Sony clipping at about 75:
Sony STR-DG910 A/V Receiver [2007]
STEREO PERFORMANCE, DIGITAL INPUT

Reference level is -20 dBFS; all level trims at zero. Volume setting for reference level was 60.

Output at clipping (1 kHz, 8/4 ohms, both channels driven): 75/109 watts (18.8/20.4 dBW)Distortion at reference level: 0.05%
Linearity error (at -90 dBFS): 1 dB
Noise level (A-weighted): -74.5 dB
with 96-kHz/24-bit signals: -78.8 dB
Excess noise (with/without sine tone)
16-bit (EN16): 0.25/0.35 dB
quasi-20-bit (EN20): 14.7/14.8 dB
Noise modulation: 0.6 dB
Frequency response: 20 Hz to 20 kHz +0, -0.1 dB
with 96-kHz/24-bit signals: 20 Hz to 43 kHz +0, -0.5 dB

The ghost of the horse asked me to move on...

Not to fear, there are a few of us on the forum that feel the same as you, especially after I experienced such a difference in sound from my 3808 compared to the 3808/A1400 combo. You can never have too much power, even if you only use a little of it once in awhile

Charles, thanks for showing those test numbers, because the use of the term "clipping" there makes no sense at all. Actual clipping would be evidenced by distortion at least 100 times that 0.016% figure. The test numbers confirm the excellence of your 3300 and indicate that audibly clean output on the order of 140 watts was delivered.

Although the use of "clipping" in that commentary is, again, incomprehensible, I do know the context in which S&V uses the term. It is the point at which THD reaches 0.3%. This is still rather strange usage of the term(inaudibly low distortion would be a more accurate descriptive term at that point), but not nearly to the same extent. Actual clipping shown by flattening of the top of the waveform doesn't occur at any specific THD level, but certainly in all cases would be greatly in excess of 1.0%.

I disagree on semantics, but agree on principle.

Clipping by definition is when the peaks of the output waveform don't follow the input. The farther it is pushed the more that is clipped. At some point it become audible, and after that visible on a scope as a flatten (DC) line. It is silly when reviewing an amp to say it has reached maximum usable power when if fails to track the peak by a microvolt, as you said that's completely inaudible. But by the time you can see it on a scope, your tweets are on their way out.

So yeah, the amp was "clipping", but not in the audible sense, and far from the olfactory sense.

OK, so as soon as there is any distortion, we technically have clipping?? Like say at .001% THD + N I know this is a somewhat exagerated point, but since we can measure to this resolution...

At any rate, from what I have read, waveform distortion does not become audible until somewhere around 1% on normal program material, or .5% with pink noise (Toole I think).

How are the Maximum power ratings on a receiver determined? I presume there is an FCC spec.

No, there are many types of distortion. Any time the output signal doesn't completely follow the input it is said to be distorted. It's pretty much impossible to build an analog circuit with active components which does not distort the signal in someway as it passes through. Based on that, as you can see, sheering off the tops of peaks is definitely distortion.

There are two classifications of harmonic distortion. Even-order and odd-order. Clipping causes odd-order harmonics, which sound harsh. But tube amplifiers primarily have even-order, which is almost pleasing to the ear, it causes the sound to seem "warm" or "fat". One can have 5% even-order distortion and still think things sound great.

As John said, the usual way one measures an amp is to drive it until the clipping is contributing 0.3% to the THD. At that point the amp is giving all its truly usable power. Though there are still different measurements here. Some use a 1k sine wave, others broadband (20 to 20k) noise, sometimes one channel driven, sometimes all. The FTC says (not the FCC, the Federal Trade Commission came in to stop the deceptive advertising), all channels driven with broadband noise.

Maybe I'm being pedantic, but thats not what John said at all, thats what the magazine article implied.

What John wrote was:


So, is there an accepted 'industry standard', or is this one of those audiophile things that is endlessly debated?

By the way Zimm. I am not implying that you are flogging a dead horse, just asking questions about something I do not quite understand.

No Fred, as Chris noted, there's distortion always present apart from actual clipping, which causes much higher THD numbers than "regular" distortion. As I mentioned above, actual clipping(not the rather strange usage of the term which some audio publications adopt)isn't related to a specific distortion number, but rather, occurs when the top of the waveform is flattened("clipped"), as viewed on an oscilloscope. Distortion at this point would be well above 1.0%, not the 0.3% or even 1.0% figure termed "clipping" by some publications.

Yes, blind tests have indicated that on music distortion isn't audible until it passes a threshold in the area of 1%. The more complex the music, the higher the threshold of audibility.

Maximum power ratings for all amplifiers for home use sold in the U.S.(and in practical effect, Canada as well)are governed by Federal Trade Commission regulations found in Title 16, Part 432 . Basically, following a warm-up period, the amplifier must be driven at the full rated power for at least 5 continuous minutes, with the bandwidth and maximum distortion specified. Note that the number of channels to be driven simultaneously isn't specifically set, although the FTC interpretation has been to require at least two. The vast majority of receivers are rated with two channels driven, which is a more realistic measure in real-world home use than an all-channels driven measure adopted by some manufacturers, but which doesn't reflect a realistic scenario outside of the testing lab, with all channels simultaneously operating at full power for 5 minutes continuously.

The irony relating to published official power ratings is that this is the only area in audio which is governed by relatively strict regulations and where we can be confident of getting what's claimed, yet it's an area where many suspect "exaggeration" "inflation", etc. , which no manufacturer would risk. Some of those voicing such suspicions are also the same individuals who have no problem with believing in magical sound properties in various items, even pieces of wire, despite the lack of solid evidence.

So what you're saying, if I understand it, John, is that what we see as the RMS rating is governed by the FTC. So if an amp is rated at 100 WPC, .08% THD, those figures MUST be correct per the FTC--HOWEVER, that would seem to be somewhat arbitrary, because the same receiver might be able to do 120WPC, at, say, 1.2%THD (assuming it doesn't shut down), and likewise might do 80WPC at .007% THD.

Yes, the FTC Amplifier Rule is more about truth in labeling than a standardized testing methodology.

Reading the actual rule. It seems that he "warm up" is done with a sinusoidal signal of 1 kHz, at 1/8 the rated power for an hour. Then the 5 minute test starts. Because I've always seen the test listed as 20 to 20k Hz, I assumed that was the requirement, but the only requirement is that the test signal be across the band for which the amplifier is rated.

The reason many read the rule as all channels driven is because of these phrases, "...measured with all associated channels fully driven to rated per channel power...", and, "...only those channels dedicated to the same audio frequency spectrum should be considered associated channels that need be fully driven simultaneously to rated per channel power." The second part meaning you don't have the drive the sub at the same time. But a manufacturer could say that the surround and center are not dedicated to the same audio frequency.

Since I resemble that remark I'll respond for all the popcorn fans: I love irony, but really don’t see it in your example. I'm reading test reports from an AV magazine where someone was put in charge of running test in their "lab". They routinely show amps clipping the signal - to some extent - before the rated power. As Chris mentions, perhaps that is because the FTC does not require it to be run 20 to 20, I don't know?

But it seems consistent to believe the better components and better designs lead to better sound. And thus, that a $329 dollar 105 wpc amp is not telling the truth, or the whole story perhaps, about the fidelity of their amps as compared to 105 wpc McIntosh.

And don't be so naive as to think all companies comply with the FTC rule just because it is there. I have spent my entire career litigating antitrust claims (the FTC's primary charge) and I can assure you companies often calculate that violation of the law is much more profitable than compliance, because enforcement is weak, and fines are a small fraction of the profits earned. I presume that is even more true in this area since the FTC is not known for its strong hand in the areas of wpc.

Finally, I'll note that a search for irony is not fruitless. I find it very ironic that some here demand that emotional responses and perception are worthless as compared to science and math. Yet, when presented with lab tests that do not conform to their view, they cite the well accepted theory of poppy-cock and biased journalism. Pretty hard to test those.

I don't know who is right, but frankly I find it less likely that every HT magazine could slander the likes of Denon, Sony, Yamaha, etc., etc., etc., year after year with crazy test results claiming they are violating a federal law, than the likely hood that there might not be as much uniformity in products across the price scale as some assume.

Now where is the damn popcorn!

I'll get you some, would you like it hot buttered?

That would be good. I'll need a distraction for the scientific ass-whipping I just begged for.

I can say that I have found there to be a difference in my experiences with variuos brands, some have better power and sound quality than others, ie, the Sony $400 avr I purchased had a stated output of 100W/ch yet it did not produce the same sound, ie. bass was next to non-existent, compared to the Denon I had purchased because it had better features. Both were 2004 products and the Denon was my venerable 1804, a midline avr. The lack of bass from the Sony I attributed to a weak amp section, whether that be from a lack of capacitors or weak P/S or both I don't know. The Sony might have been able to maintain the power to satisfy the FTC rating to achieve it's 100W rating but it certainly couldn't keep up to the Denon.

Well, I think part of the problem is that that 100WPC rating is shown in a vacuum. If THD is part of that rating, well... one has to take that into account when you mention the rating.

In any case, sorry Charles, it's kind of silly to complain about distortion of .016% and say that the receiver isn't delivering at 84W.


Also: John, with that post, he's got you there.

I appreciated my Pioneer's manual. It shows Watts, channels, Ohms, %THD, and bandwidth (20 to 20k). That's what you really need to know to make a proper judgment. It even says "FTC" at the end of the line.

To be clear, I'm not saying I can hear the distortion at .016%. My point is that my Denon is harsh on high frequencies spikes, and my separate amp is not. Assuming those spikes are hitting when 100 or more watts are being pushed (or 100+ db), then that % climbs above .016 (seed the red 45 degree line on the chart above).

At 108 wpc you get 0.1%, at 135 watts you have 1% distortion. [Not really, because my PSBs are 4ohm, so it is more like 174 wpc at 1%.] At 50 hz, 1% is imperceptible. [See Alan's article.] But at 12,000 hz, from what I have read (which is preschool compared to JohnK's reading) you can hear such inaccuracies - and they are annoying and cause listening fatigue in my brain. See, "The LED begins to become visible at 0.1% distortion, and reaches fairly full brightness at 1-10% distortion, which is clearly audible." QSC Technical FAQs; see also, "In general, the more complex the sound, the less audible the clipping. Light clipping of transients will in fact increase the apparent high-frequency content and give the sound a little more edge." Peavey Support - Clipping Revisited.

With my new amp, which does not come close to clipping at 135 watts or 175 watts, I don't hear those harsh peaks anymore. Or, I should say, I hear the peak now, not the distortion of the peak being clipped.

But, if I switch to 5ch stereo, I can hear the harshness on the center channel - although much less often or pronounced. I assumed that is because there is more power to go around before clipping when ch 1 and ch2 are not being handled by the Denon.

Or, maybe it is all the same no matter what you buy. If so, I still needed to trick my brain to find more enjoyment, and I did. (But now I know I tricked myself, so...crap, I bet I can hear the harshness again. Damn. Time for new speakers.)

OK, it seems that at best the magazine in question used the term clipping completely out of context and that is what I originally questioned.


Yes, but better measured performance is not always audible (eg: .01% vs .001%).

It seems that companies like Denon often exceed their rated specs, so that supports your argument about better components/design. I suspect that manufacturers like Krell are the same.

So, when you are buying a 105wpc Denon, you are getting at least 105wpc, but if you are buying a 105wpc Yamaha, you are getting barely or not quite 105wpc.

All that said, I am looking forward to the day when I can point to a sub in the corner of my room and casually mention its being driven by a pro amp in bridged mono mode delivering 2400 watts. If I can afford a big 21" monster driver, even better!

No, no, no. When you get that 21" monster sub, I want to see you run it with a 10 watt amp, not a 2400 watt amp. That's like Ralph Nader retiring to his non-biodegradable plastic house, with gas burning everything, situated on top of a coal factory.

Don't sell out damn it, too many are counting on you to resist upgraditis!

That's funny.

I refuse to be a slave to "science" or to allow it to impede my joy or invalidate my experience.

Holding Science as sacred implies to me intrinsically that we have already discovered everything that we ever will. And I just don't buy that.

So, despite all evidence to the contrary, I'm going to support Charles' enjoyment of his new amp.

Charles, you're still not getting the point that what those writers termed "clipping" was nowhere near actual clipping.

I'm not selling out, I'm just being fickle.

No, John, you are still not getting the point that I don't believe the major forces in the industry would allow their hand-picked PR mags (as most allege) to publish scientific reports from 1999 to 2009 saying some of their models clip the signal when, in fact, they don't. I think ad dollars would dry up over night.

I guess what you meant to say was I'm still not believing in your opinion. That is true, on this point. I have no problem believing that .016 THD can be caused by a short duration high amplitude frequency being clipped (flattend across the very top) - whether I can hear it or not.

Nor do I have a reason to doubt lab reports that show at near 100 watts my receiver could clip the signal and cause 1% THD. And I certainly have no reason to think almost every publisher in the industry is ignorant of the meaning of the word Clip, but that you have it right. Sorry, I just don't know you that well.

I love a good conspiracy story, but such a leap demands more meat on the bones.

Some clarification please:
My current understanding of clipping in an amplifier is that it is a hard limit related to the maximum amplitude of a signal that can be reproduced. If your amp has a maximum amplitude limit of 10 thats all it can produce. The more you try to push beyond this limit, the longer the signal is in clipping and the longer the signal is in clipping for. The transition from beautiful music to harsh distortion is a rapid one over a range of a few watts.

What the magazine implies is that clipping is a soft distortion of the top of the wave as opposed to a hard limit. Which view is correct?

Don't know. But the way i understand it is this: if 1% of the area inside the cone of frequency (on scope) is clipped off the top, then you have a certain level of distortions compared to the original. Let's call it .001%. But as the cone gets higher or wider more of the area of the cone is above the clipping point. Let's say 10% of the total signal making that freq cone is now clipped off. The resulting distortion is higher because a higher percentage of the original source signal is not being reproduced - i.e., more of the signal is clipped off. So you can easily have clipping causing .0016, then .08, then .1, then 1% as the signal gets louder and the amp must clip more and more of the original information.

But this is at the heart of the matter. If you understand the physics of clipping, you know exactly how it manifests itself.

I wish Tom Cumberland visited these boards.

The further pushed into clipping the higher the Watts Root Mean Squared output of an amplifier. Because RMS measures power over time, a sine wave which just kisses the peak will spend less time at full power than a DC signal which is held there.

This hard clipping, when the amp has no more to give, doesn't get any louder because DC holds the cone still. The harsh change in movement into and out of the clip is what causes the audible harmonic distortion.

At the very first signs of clipping, the 0.016% point in this example, there's still some additional amplitude to be had (especially with non-test tones) because of the way the capacitors and transform can handle instantaneous demands vs. continual.

OK, you kinda lost me. Who am I kidding, you completely lost me.

So, at 70 some odd watts the receiver was just barely clipping, but you could still apply another 30 watts before reaching the hard clipping limit?

"Hard clipping" was probably a poor word choice, but it's hard to come up with a way to say it. Maybe some examples.

It's possible to come up with a test tone which is demanding enough of power to keep the caps from building up a full charge, and the current flow has saturated the transformer's core. At this point the peaks of the output waveform start clipping. This is all the power that can be moving through the amp to the speaker at any instance in time. Turning the volume up higher will result in a higher power RMS reading, but the instantaneous power reading will be no higher. It is just the amp is spending more time at its peak output. Instead of just the absolute peaks being clipped some of the lower portions of the signal have gone to DC too.

The other example is a passage which is nearly silent, the caps have a good charge built up, the transformer is far from saturation. Then a shot rings out. This spike in the output can exceed the the level of that continuous bombardment mentioned above.

Most content is more like the second example. A few small peaks with most of the signal not being very demanding. So you may not have a huge power reserve, but you can exceed the levels of what one gets with a test signal. As you turn up the volume further where the amplifier is reaching its limits for this content, the loss of a few little peaks is hardly noticeable. As that happens the lower portions are still getting louder and taking more power to reproduce. It's not until more of the signal is clipped that you think things are starting to sound harsh, and (hopefully) back off a little.

I still don't know if I'm doing a good job describing this. Maybe if you think of sound as being made of lots of little instances, but the power readings are taken with that averaged over time. The more time spent at higher output levels the higher the Watts RMS reading. So if even the tiny peaks are clipping because the amp can't exceed the current flow at that instant in time, it doesn't mean that more power can't be applied to bring more parts of the signal up in level.

Ah, ok. The article Zimm pointed out is a continuous output test and this was the only instance I was thinking about. It is in this instance that I thought that clipping becomes 'hard' so that you can't get clipping at .o16%THD. Is this correct?

I understand what happens with program material and that often you only get clipping of very small parts of the signal.

All reported power measurements are going to be Watts RMS. That's cuts down on the false claims where an amp can hit 100 Watts for a microsecond, but can only deliver 15 Watts RMS.

If you have a signal which is supposed to go: 0.98, 0.99, 1.00, 0.99, 0.98, but instead it goes: 0.98, 0.99, 0.99, 0.99, 0.98. That's clipped, and would create something like 0.016% THD.

Forget I said hard. Tubes tend to compress the signal at first rather than clip, so people call that soft clipping.

OK, the question still stands. If that happens at 70 some odd watts, can you still increase power to 105 watts with distortion staying at or below 1%?

A 60% increase in power leading to 100 times the distortion. That doesn't sound far fetched when the amplifier is reaching its limit.

You ask that question as if as increase from 0.01 to 1.00 is something small. That's two orders of magnitude.

Charles, you appear to be growing personally irritated(including "resembling" a remark I've made several times here in the past and which wasn't in any way directed at you)over a relatively simple point of audio technology which certainly isn't some mere personal opinion. Again, actual clipping isn't defined by a distortion percentage, but rather by the flattening of the top of the waveform, as viewed on the oscilloscope. The percentage of distortion associated with actual clipping varies, but is always far above the percentages those writers applied the term to. A brief analysis of distortion percentages(several percent)with clipping in this book may help illustrate the point.

Manufacturers are generally delighted with the test results that appear in some audio publications because they nearly always confirm the power specs which they published(e.g., the test of your 3300)and often add some flowery subjective language praising their product. The use of non-standard terminology for any topic, such as clipping, doesn't change this, and calling a dog a cat doesn't mean that it'll start to meow(just as calling audibly clean performance "clipping" doesn't make it sound bad).

It goes back to my original understand of when clipping of a waveform starts. My original understanding was that from the beginning of clipping to nasty distorted transducer blowing (but not hard ) clipping happened over a much narrower power range.

I still find it hard to accept that, under continuous power a signal can start clipping in the 70w range and remain inaudible through a 60% power increase, but I think I am the one flogging the dead horse now.