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question on power/amps

Kingshead said:
Thought the same thing but after further research found most thought this a warm amplifier. But maybe if pushed it revealed its one short coming?
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Well, pure speculation on my part as I've not heard it. Looking at it and reading the stereophile review, it seems they put a lot of work into things like the DAC, torrodial power supply and it certainly measures well... It looks like a very nice piece of equipment... That's why I think it might be the Class D... Since everything else seems to be of very good design and nice quality.

But I wonder how far class D has come and whether it can compare to class A or even Class A/B yet.
 
fred soop said:
How old is this class D? It has only been in recent years with modern manufacturing that it has been possible to accurately implement class D.

I have a B&W MM-1 desktop system that is optimized for near field (desktop) listening. Each box has a 3 1/2 inch and a 1 inch, active crossover, and a total of 4 18 watt class D amplifiers. This is one of the best systems (within its limits) that I have heard for high frequencies and soundstaging. The main drawback is that the 3 1/2 inch "woofers" audibly roll off below 140 Hz. So, I built a 4th order 140 Hz low pass filter, installed it in the Harman Kardon Citation 24 power amp with a rear panel bypass switch, and the AR-3As handle the subwoofer job below 140 Hz. At that low a frequency, the fact that the speakers are across the room does not create phase shift problems.
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There are other advantages in such a system, like active crossovers and bi-amping.. Perhaps implementations like that help overcome some of the flaws of class D (I know there are new techniques to mitigate some of the disadvantages of switching amps anyway).

So like all things.. maybe it is just finding the right implementation..
 
Daunia 70 said:
The more wpc and power consumption a integrated amp or power-amp has.. The more headroom,therefore less distortion will occur whilst listening loud on really high/loud musical passages (Pet Shop Boys "Yes" CD album springs to mind).. Effortless power always in reserve is a good thing to have in a power-amp.
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That depends on the amp.

Some amps distort more at low power then at medium or high power.

Some amps distort the same regardless of output power (as long as they are not clipping).

Some amps distort less at low power, compared to higher power.
 
matteos said:
There are other advantages in such a system, like active crossovers and bi-amping.. Perhaps implementations like that help overcome some of the flaws of class D (I know there are new techniques to mitigate some of the disadvantages of switching amps anyway).

So like all things.. maybe it is just finding the right implementation..
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Historically, the problem with class D has been the accuracy of the comparators. Class D signals are produced by comparing the audio signal with a high frequency sawtooth. Anytime the signal is higher than the sawtooth, a "1" is produced, otherwise a "0". The output is a pulse stream where the width of the pulses contains the audio information. This can then be easily amplified using switching mode amplifiers (very efficient), then the high frequency is filtered out to recover the audio itself. Similar problems existed in the early days of CD. The theory existed decades before the technology was capable of doing the job.

Active crossovers and biamping do help overall though there is additional complexity. The improvements/problems are independent of class D implementation.
 
whoaru99 said:
I'm quite familiar with transient requirements, really. That's why I reasonably understand the potential misinformation in the automatic "you need a bigger amp", "more current", etc., etc. type of replies.

As I've said before and will repeat, more power does you good only if you're exhausting what you have. There is essentially zero solid evidence that's the OPs problem.

Based on some calculators I've found to be reasonably close based on my measurements, the OPs system (assuming the speakers can handle it) should be capable of roughly 102.5 dB at 10 ft. So, from there you can back-calculate the average level one could reasonably expect. If you have music that's got roughly 10dB peak to average ratio then an average level of 92.5dB isn't unreasonable (peaks to 102.5dB). If your music has higher peak to average ratio, say 20dB, then you can expect to produce roughly 82.5dB average level (again, peaks to roughly 102.5dB). This is based on the OP's amp (using the 8 ohm 65wpc figure, should actually be a bit more based on Stereophile measurements at 6 ohms) and speakers I placed at 88dB (listed at 89, but are six ohms) so adjusted sensitivity down to normalize).

Will more power hurt? Only if the OP uses it to exceed his speakers (or his lease) capacity. Will it help? Based on what we know at best it's maybe, maybe not.
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Zero solid evidence but a reasonable assumption imo. Especially with that higher peak to average you mention. I would not consider 88db efficient. Add to that potential impedance swings and it's no wonder he's yearning for more. There is however only so much you can expect from a bookshelf speaker by itself.
 
uplander said:
Here's a supporting example from my experience. Listening to ADS 1290s with 140 WPC B&W sounded good. Inserting a 200 WPC Acurus completely woke up the ADS, with much tighter, better controlled and deeper-sounding bass. Music selected was acoustic jazz, and it made the string bass sound much more real. Rarely do I listen at more than 75-80 DB, so I really doubt the B&W was running out of juice.

The difference was likely due to more available current, and I could probably be as happy or happier with a 100 WPC amp with a huge power supply. And those are expensive.

The point being, an amp can make a very notable difference, but based on more than just their wattage rating, regardless of whether or not it's being pushed to clipping.
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I'm not saying your totally wrong but you are making an assumption based on anecdotal evidence. Given the fact that 1290s do 90dB at 1W/1M it was probably more likely the amps were voiced differently and you preferred one over the other.
 
barkerd said:
Disagree : you are always using it :

there was a test done in the 80's where they positioned a loudspeaker system and a snare drum behind a screen ...... they needed 600 watts before the listeners could not distinguish between either source on single snare hits ........... for the probable 1/10 000th of a second that that power was needed ....... it was still distinguishable when not present
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Would be interesting to see a source for this. Is it possible it was done by a company that manufactured high powered amps?:scratch2:
 
Bugler said:
Actually it's torque that pushes you back in the seat more so than HP
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Yes, that's true. Exactly my point. HP is only important when used in conjunction with a system that can use it and needs it. Relatively efficient speakers don't benefit from power they're never using.
 
donberry said:
Very simply, I am sure you have seen those graphs on speakers showing their impedance curves. Very simply if the line on the graph is on the negative side (down) it is a capacitive load, positive side is a resistive load. A capacitive load is harder to drive then a resistive load............
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Many thanks for taking the time for such a detailed explanation. That's what makes this place so great.

I've never heard the term "capacitive phase angle," and that helps me visualize it. I kind of grasp the concept, and I've seen the graphs without really understanding what I was looking at. Now I need to do some research to try to really understand what a capacitive load is vs. a resistive load.

This great, learning about concepts that I've kind of, sort of grasped, but were always extremely hazy. Thanks again.
 
kahlfin1k said:
I'm not saying your totally wrong but you are making an assumption based on anecdotal evidence. Given the fact that 1290s do 90dB at 1W/1M it was probably more likely the amps were voiced differently and you preferred one over the other.
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Agreed, I did make an assumption based on anecdotal evidence. And agreed, the amps are voiced differently. The B&W is a touch "sweeter" in the top end. But I don't hear nearly as dramatic of difference in the bass when I compare the amps playing my Snells or Tannoys.

It seems this would support donberry's conclusion that there's something in the ADS that is more difficult to drive specifically in the low end. Whether that's "capacitive phase angle" as he theorized, or that the ADS present a different load due to being sealed vs ported, or something else, I'm not sure.

I think this is an example of what makes better synergy between some pieces of equipment. Fascinating stuff.
 
uplander said:
Agreed, I did make an assumption based on anecdotal evidence. And agreed, the amps are voiced differently. The B&W is a touch "sweeter" in the top end. But I don't hear nearly as dramatic of difference in the bass when I compare the amps playing my Snells or Tannoys.

It seems this would support donberry's conclusion that there's something in the ADS that is more difficult to drive specifically in the low end. Whether that's "capacitive phase angle" as he theorized, or that the ADS present a different load due to being sealed vs ported, or something else, I'm not sure.

I think this is an example of what makes better synergy between some pieces of equipment. Fascinating stuff.
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I've actually experienced a similar thing with some L810s. A much more extreme example though. Went from a 65WPC AU-517 to a 3 WPC SET but in my case the highs and dynamics weren't there. The L810's are 93 0r 94 dB but really don't like low powered tubes. I switched to Hereseys at about the same efficiency and the dynamics and highs were there in spades. I have a suspicion a lot of it comes down to damping factor. Obviously there's a balance of the voicing of the speakers and amps. The sansui was bright and the ADS dark and the opposite with the Klipsch and tubes.
 
When I was using pretty inefficient speakers, doubling up on power made a large difference in the sound quality, even when I wasn't giving the system much of a push. There was no change in the brand or model of amp, I just bought another of the same kind that I already had, ran them as monoblocks. Using more efficient speakers that can't possibly use the power available (wattage limited), I still run two monoblocks; I ran just one amp for a bit, but hooked the other amp back up because the systems sounds better to me this way. In my experience, buy as much quality power as you can afford, you'll never regret it, and you may really need it down the road.

whoaru99 said:
When ever I read someone having bookshelf-type speakers and expressing concern about problems at higher volumes, first thing that crosses my mind isn't the power/power amp. It may be a great speaker, but it's still a small speaker, perhaps the expectations are too high for its capability in that situation.
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In OP's case, I'll bet this is the problem. While there are some mighty fine small speakers out there, in the end it gets back to no replacement for displacement -- if OP likes his speakers that much, he should likely just get a sub.
 
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Phase angle can go either way, capacitive or inductive.

Here's a excerpt regarding phase angle from a Stereophile article about measuring speakers. I've made bold some points I think are key.

Perhaps most important, you can predict from its impedance plot how hard the loudspeaker is for an amplifier to drive. Because a loudspeaker's impedance is reactive, the current will lag or lead the signal voltage by the phase angle [25]. In the worst case—when the phase angle is 90 degrees—the amplifier is required to source the maximum current at the same time as the signal voltage approaches zero. Simply to specify a loudspeaker as having an 8 ohm nominal impedance, therefore, can be misleading. Depending on the phase angle of the impedance, which will be different at every frequency, the loudspeaker could look to the amplifier as having a much lower impedance. However, as the late Peter Baxandall pointed out in an Audio Engineering Society presentation in 1987 [26], the maximum phase angle never occurs when the impedance has its lowest amplitude. As both are two-dimensional projections of a three-dimensional phenomenon, they're mathematically related.

There has been much conjecture on this subject for the past 20 years in audiophile circles. Eric Benjamin of Dolby examined the matter in detail in 1992 [27]. (The "References" section of his paper is comprehensive.) In particular, he looked at the theoretical power dissipation in an amplifier's class-B output stage, which will depend on the speaker impedance magnitude and phase angle. While he found that the maximum current drawn by a loudspeaker almost never exceeds that predicted by the minimum impedance value, the calculated dissipation in the amplifier output devices was between 120% and 270% of that predicted, depending on the impedance and the drive signal.

It appears, therefore, that amplifier output stages need to be overspecified from slightly to considerably, depending on the loudspeakers they are required to drive. That most amplifiers don't appear to be significantly stressed is due to the fact that, as E. Brad Meyer has pointed out [28], at typical listening levels in a typical room with typical loudspeakers, a consumer amplifier is never required to deliver more than a few watts.
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Complete article is here: http://www.stereophile.com/features/99/index.html

The part about phase angle is toward the end.

My take on the parts in bold (relative to the paragraphs):

1. The two (phase angle and impedance) don't stack up against you (or, perhaps more importantly, against the amplifier).
2. Talking about the speaker's impedance and the amplifier power (current and voltage) as if it were strictly resistance generally works. And, despite a bad phase angle, a "high current" amplifier isn't necessarily going to drive the speaker better, but a high current amp tends to be more robust so it may survive the mission longer in such cases.
3. The whole phase angle point doesn't seem to be as big a deal as it's sometimes made out to be. It doesn't materially affect most people/most situations.
 
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uplander - here is some info on impedance and phase angle HERE
Should have just pointed you there in the 1st place :yes:

I read a better description once but can't remember where, but this should do it for you.
As I mentioned, the only reason I researched it because I tend to gravitate towards low efficiency speakers and reading a review on Stereophile about my SL3's they talked about the -47 phase angle......so thought while I didn't need to become an expert, thought it was a good idea to become familiar with it.
Once I did, I understood the importance of it
 
donberry said:
uplander - here is some info on impedance and phase angle HERE
Should have just pointed you there in the 1st place :yes:
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Funny, I ran across that article last night after I decided I've some learnin' to do. Now I need to go and study exactly what is capacitance, and what is inductance, etc. In other words, I want to understand the building blocks better, more than just a glossed over fuzzy picture. Electrical theory 101, here I come....

Thanks again for taking the time.
 
I researched it pretty good but that was a while ago and now I just remember the big picture parts. I really don't concern myself with it too much anymore as I started "collecting" nothing but higher power/mostly higher current amps.
 
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