My attempt to compare an Outlaw 7500 and a Parasound A51

[RichB]

Actually, according to the survey of "Amps Sound Differently or Same", it is the prevailing thought that amps sound differently.

More guys voted for "Amps sound differently".

So you are technically in the majority.

Yeah, I knew that but it was a weighted average

- Rich

 

[PENG]

Amen to that

I really was hesitant to post this here because it is not the prevailing thought.

- Rich

Please don't ever hesitate, I am sure I am not the only one who enjoy this thread. I also thought it is the prevailing thought, that more expensive amps do sound better. Almost every, if not all online reviews I read back that up. Show me one amp review by Stereophile, Hifi Choice, Absolute Sound etc., that didn't say something about when the review subject was compared to a more expensive reference unit they previously reviewed, the more expensive one sounded better. They would praised the A21, and then they would tell you how their jaws dropped when they heard the JC monoblocks. At least I can see that you tried hard to be objective. Too bad I just don't believe human can be objective with their eyes open.

 

[PENG]

No, it isn't, and subjective analysis of audio equipment isn't my thing either, unless it is being compared with a known reality, but that doesn't mean that your preference is completely invalid. It was still interesting to read.

Wow, I could have said that myself, that's why I read reviews mainly for the specs, measurements and entertainment.

 

[fmw]

Just as an aside, the reason people believe more expensive amplifiers sound better is because of expectation bias. If they were to engage in a bias controlled listening test with accurate level matching, they would learn how easily their brains have fooled them. Most audiophiles don't want to learn that. They prefer to prefer more expensive gear. It is expectation bias that drives the entire high end audio industry.

 

[AcuDefTechGuy]

Please don't ever hesitate, I am sure I am not the only one who enjoy this thread. I also thought it is the prevailing thought, that more expensive amps do sound better. Almost every, if not all online reviews I read back that up. Show me one amp review by Stereophile, Hifi Choice, Absolute Sound etc., that didn't say something about when the review subject was compared to a more expensive reference unit they previously reviewed, the more expensive one sounded better. They would praised the A21, and then they would tell you how their jaws dropped when they heard the JC monoblocks. At least I can see that you tried hard to be objective. Too bad I just don't believe human can be objective with their eyes open.

The only thing we can say is that we either liked it better or worse. No justification required.

At the end of the day, that's what counts anyway. If something sounds better to us, than keep on doing it.

We will all have different opinions as expected. Just lay it all out in the open.

 

[RichB]

At least I can see that you tried hard to be objective. Too bad I just don't believe human can be objective with their eyes open.

Mee too, so when selecting a significant other, spend some time listening to them with your eyes closed.
It is only through extended listening that you can properly judge which ones are less fatiguing.

- Rich

 

[RichB]

I suppose I could get some EE help and measure the voltage gain of both amps with a 1KZ tone and repeat the test.
If I find the time, I may do that.

I feel certain that doing so will not increase the confidence level of the findings
Still, I would like to know.

- Rich

 

[RichB]

It was mentioned that on another thread that Gene said that even DBT's can be setup to skew to results to the presenter’s product. I have photos of some where the speakers are clearly not full range. It may represent the mainstream but it has little relevance to many systems found here.

For me, this all started when I helped my brother-in-law put together are preamp-less 2-channel system consisting of an Oppo BDP-105 and two Outlaw M2200 mono-block for his B&W CM’s. It sounded much better than the Pioneer SC-25/Oppo BDP-83 that it replaced.</SPAN>
I was impressed so I invited him and another friend over for an HT play date.
The other guy brought his Focal Electra 1008’s over as well.
</SPAN>
First, we listened to the Salons with my Sunfire 7400 and then with the in the M2200’s.
After playing the M2200 for a while without comment, we all had the same reaction. The M2200’s sounded much better; It was not even close, the Sunfire was strident and harsh on some recording. Trust me; this is not where my bias would have led me or anyone else in the room </SPAN>J</SPAN></SPAN>
This fortunate event set me forth on the search for a new amp: Outlaw 7500, ATI2005, and now. the Parasound A51. When I first bought the Outlaw and plugged it into the Panamax power conditioner and it also sounded harsh. Annoyed, I went to bed. </SPAN>

t would be reasonable to assume that either this is a bias problem or this amp is defective. There is nothing I can do about that so I looked for another answer. So, I began to ask: what was different?
Then, it came to me; I had plugged the M2200's directly into the wall.
I plugged the 7500 directly into the wall, and it sounded a whole lot better. Inline, with what I remember coming from the M2200. I chose a Lady Gaga song that goes from unlistenable to just awful when properly amplified </SPAN>L</SPAN></SPAN>

It isn't always the best science to say that something cannot be.
Sometimes, it is best to say, if it is, then why is that?

For SS amps, these items remain open unanswered:</SPAN>

• Does the first watt matter?
  (This is where I spend the vast majority of my time)</SPAN>
• Does Class-A bias help at low listening levels?
  (the A51, ATI3005 have more and I liked them better than others I have tried)</SPAN>
• Do the input stage components color the sound?
  (Parasound claims they do, are they full of it?)
  </SPAN>
• Are THD+N enough since it includes artifacts within a 250 HZ and does not include other harmonic?
  </SPAN>
• Do traditional measurements truly represent the distortion and performance of amps driving complex waveforms into actual speaker loads?
  </SPAN>

Proving once again, a fool can ask more questions than a wise man can answer.
</SPAN>
I would like to see more exhaustive amplifier testing because it helps the OCD nature of the hobby.
Then, we can say. Thank god, I knew my amp sounds fantastic. Now, there are measurements to prove it.
Finally, I can just sit back and enjoy the show.</SPAN>

- Rich</SPAN>

 

[PENG]

For SS amps, these items remain open unanswered:

• Does the first watt matter?
  (This is where I spend the vast majority of my time)

It does matter to people like you and I who spend lots of time there, but I expect even a mid range AVR will pass the point of diminishing return, i.e. not detectable by human with eyes closed.

See the data here: Miller Audio Research

and tell me if my old AVR-3805 didn't measure as good or almost as good as the Arcam Monblock, the Halo A21, or even the Anthem Statement P2.

• Does Class-A bias help at low listening levels?
  (the A51, ATI3005 have more and I liked them better than others I have tried)

I think it helps, at least psychologically,but I would think many class AB do just that, whether they advertise that or not. Most don't publish idling power consumption so we can't always use that as an indicator.

• Do the input stage components color the sound?
  (Parasound claims they do, are they full of it?)

No idea what they meant, sound like marketing hype to me thought.

• Are THD+N enough since it includes artifacts within a 250 HZ and does not include other harmonic?

According to wikipedia:

Total harmonic distortion

"The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. Lesser THD allows the components in a loudspeaker, amplifier or microphone or other equipment to produce a more accurate reproduction by reducing harmonics added by electronics and audio media. A THD rating < 1% is considered to be in high-fidelity and inaudible to the human ear".

Surely there are many considerations, but at <0.1% that is easily achivable nowadays, those considerations such as the specific orders of the harmonics should quickly become practially irrelevant. I definitely would like to see at least the IMD figures.

• Do traditional measurements truly represent the distortion and performance of amps driving complex waveforms into actual speaker loads?

Most likely not "truly" as such but adequately for sure otherwise other measurements would have been used. No one thinks audio power amps are even high tech let alone rocket science right? All complex waveforms can be 100% represented by sine waves of the fundamental and harmonics (See Fourier series/transform). Even a square wave can be represented in an infinite series of sine waves. Fourier got scientist and engineers covered long time ago in dealing with complex waveforms.

I would like to see more exhaustive amplifier testing because it helps the OCD nature of the hobby.
Then, we can say. Thank god, I knew my amp sounds fantastic. Now, there are measurements to prove it.
Finally, I can just sit back and enjoy the show.

Me too, like you said, nature of the hobby..

 

[RichB]

It does matter to people like you and I who spend lots of time there, but I expect even a mid range AVR will pass the point of diminishing return, i.e. not detectable by human with eyes closed.

See the data here: Miller Audio Research

and tell me if my old AVR-3805 didn't measure as good or almost as good as the Arcam Monblock, the Halo A21, or even the Anthem Statement P2.

You may be better than I at reading these but aren't some of those harmonics only 40 DB down?
There appears to be a fair amount of ringing that does not deminish at higher frequencies.

Here is the

I think it helps, at least psychologically,but I would think many class AB do just that, whether they advertise that or not. Most don't publish idling power consumption so we can't always use that as an indicator.

You can use them if you measured them like me
In the HomeTheaterHifi review of the A31, check of the 19 and 20 khz test at 2 volts and 5 volts.
You can see much less ringing. Some amps have more harmonics than others.
The IM numbers look better with higher signals because they are computed as a percentage of a higher volume.
For low volume listeners, these harmonics are a larger proportion.
The A51 is extremely clean at low levels.
There are many that are as clean or better so I guess the question is when can it be heard?
No one can argue that differences are measured between amps with simulated loads.
I doubt it gets better with a real load. But, that depends on the speaker.

No idea what they meant, sound like marketing hype to me thought.

Maybe, but since i do not think all amps sound the same. Maybe not.

According to wikipedia:

Total harmonic distortion

"The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. Lesser THD allows the components in a loudspeaker, amplifier or microphone or other equipment to produce a more accurate reproduction by reducing harmonics added by electronics and audio media. A THD rating < 1% is considered to be in high-fidelity and inaudible to the human ear".

Surely there are many considerations, but at <0.1% that is easily achivable nowadays, those considerations such as the specific orders of the harmonics should quickly become practially irrelevant. I definitely would like to see at least the IMD figures.

This HomeTheaterHifi review of the Lexicon RX-7 (looks a alot like the Outlaw 7900) there were harmonics not included in the IM measurements:

And at 20 volts, IMD was actually less, at 0.014%. If you look at the peaks around the 2 kHz fundamental, they are higher than the ones in the 5 volts graph. The reason the distortion number is less is because the fundamental is higher in relation to the distortion peaks than in the 5 volts test. Note also that there are more IM peaks around the 4 kHz, 6 kHz, 8 kHz regions (multiples of 2 kHz) than in the 5 volt test, but IM measurements only take into account the peaks at ± 250 Hz around the fundamental (2 kHz), so this is why showing the actual graph is important, rather than just giving a number.

Most likely not "truly" as such but adequately for sure otherwise other measurements would have been used. No one thinks audio power amps are even high tech let alone rocket science right? All complex waveforms can be 100% represented by sine waves of the fundamental and harmonics (See Fourier series/transform). Even a square wave can be represented in an infinite series of sine waves. Fourier got scientist and engineers covered long time ago in dealing with complex waveforms.

Nope, but some measure better than others.
I am interested in the actual performance driving speaker which measurements help in the determination.
Sound waves can be represented sure. Does that have a bearing on a particular amps performance in the wild?

If in fact amps sound different, there is a reason and that would have to do with how they drive speakers.
The Review of the A21 has the test result PDF showing a change in performance with a similated load.
The A21 does not deviate much but the reviewer stated that he has measured other amps the do.
Of course, we may not see that behavior in well designed SS amps. It would be nice to measure it.

- Rich

 

[RichB]

Here is the review of the XPR-1 on HomeTheaterHifi that measure it driving the Carver ribbon speaker.
Here is the Audioholic review of the XPR-1 which is also very good but their THD+N numbers hover around .002 as opposed to the HTHFI measurements which climb to .05.
Not that that .05 is bad but it is over 10x of the simulated load.

- Rich

 

[PENG]

You may be better than I at reading these but aren't some of those harmonics only 40 DB down?
There appears to be a fair amount of ringing that does not deminish at higher frequencies.


- Rich

Actually I did not see any 40 dB down at the lower output levels, did you look at the distortions at 1W? I did see something around 40 dB down but that's at 188W output. The Denon is only rated for 120W. There isn't any review for the A31 and A51 on that site but the A21's 1W and below THD isn't the best when compared to other amps reviewed. I am sure the A21 is an excellent amp I am just saying the only measurements I saw at that site did not show lower distortions at low output levels or less offensive harmonic frequencies. I also think whatever the differences wouldn't matter in the real world because all these talks about lower or higher are in relative terms only. In absolute term they are too low to be worry about, sorry for repeating, you can't hear them if you can't see them.

 

[PENG]

You can use them if you measured them like me

Most people don't have the necessary measuring instrument that's why I referred to published specs. I do measure mine with my Fluke multimeter and Hioki clamp on current meter. How do you do yours?

In the HomeTheaterHifi review of the A31, check of the 19 and 20 khz test at 2 volts and 5 volts.
You can see much less ringing. Some amps have more harmonics than others.
The IM numbers look better with higher signals because they are computed as a percentage of a higher volume.
For low volume listeners, these harmonics are a larger proportion.
The A51 is extremely clean at low levels.
There are many that are as clean or better so I guess the question is when can it be heard?
No one can argue that differences are measured between amps with simulated loads.
I doubt it gets better with a real load. But, that depends on the speaker.

Thanks for the link, I read those. Here's one for a Bryston, not too shabby either and a speaker load was used. I have compared it with the A31 in great detail yet but the distortions seem lower in general.

Bryston 3B SST2 Stereo 150 Watt per Channel Power Amplifier - Secrets of Home Theater and High Fidelity

Maybe, but since i do not think all amps sound the same. Maybe not.

Neither do I, except that I think at some point the difference are not detectable but imaginable by most human. Say that point is when we compare the A21 to a 4B SST2 or one of those ATI amp that you have had briefly, if they sound difference it shouldn't be hard to prove it with a single DBT.

Nope, but some measure better than others.
I am interested in the actual performance driving speaker which measurements help in the determination.
Sound waves can be represented sure. Does that have a bearing on a particular amps performance in the wild?

It does, without Fourier analysis we wouldn't have today's telecommunication technologies. It provides the basis for engineering design, research and development, demystify myths about assumed difficulties in dealing with non-sinuisoidal waveforms. I am talking in generic terms but I think we both are.

If in fact amps sound different, there is a reason and that would have to do with how they drive speakers.
The Review of the A21 has the test result PDF showing a change in performance with a similated load.
The A21 does not deviate much but the reviewer stated that he has measured other amps the do.
Of course, we may not see that behavior in well designed SS amps. It would be nice to measure it.

No doubt, but we do need to consider the point of detectability by human. And don't forget speakers do have much higher level of distortions, even excellent speakers such as the Salon 2 are not immune to that.

 

[RichB]

Most people don't have the necessary measuring instrument that's why I referred to published specs. I do measure mine with my Fluke multimeter and Hioki clamp on current meter. How do you do yours?

Thanks for the link, I read those. Here's one for a Bryston, not too shabby either and a speaker load was used. I have compared it with the A31 in great detail yet but the distortions seem lower in general.

Bryston 3B SST2 Stereo 150 Watt per Channel Power Amplifier - Secrets of Home Theater and High Fidelity

Bryston are well reviewed. I have never heard them and they are too pricey for me.
I like these measurements with actual load.
If someone wants to bring a 3B over, I am happy to have a listen and bloviate </SPAN>
Amps are in a world of demishing returns. But each users system/room creates a different threshold.
Great amps remove an obstacle. I am sure there are better amps than the A51.
Hell, I am not sure it sounds any better than the ATI3005, I am confident about the 7500 in my house.
I am not confident about other 7500's.

Neither do I, except that I think at some point the difference are not detectable but imaginable by most human. Say that point is when we compare the A21 to a 4B SST2 or one of those ATI amp that you have had briefly, if they sound difference it shouldn't be hard to prove it with a single DBT.

I also believe that it takes time and ears become easily fatiqued.
Start a thread on how a DBT test should be done and you will not reach consensus.
I am not sure how long I will hang onto the 7500. I have no need for it.
If I do this again, I will measure the voltage and use a speaker switch. Perhaps even blind (someone else switching).
Something tells me, that those who believe decent amps sound the same will not reconsider no matter what I report

It does, without Fourier analysis we wouldn't have today's telecommunication technologies. It provides the basis for engineering design, research and development, demystify myths about assumed difficulties in dealing with non-sinuisoidal waveforms. I am talking in generic terms but I think we both are.

Sure. I am not anti math. I am very fond of DSP's and my phone

No doubt, but we do need to consider the point of detectability by human. And do forget speakers do have much higher level of distortions, even excellent speakers such as the Salon 2 are not immune to that.

Yes but what point does that prove. If most folks have speakers with high distortion and rooms with issues doesn't that make amp differences harder to differentiate.
So if there is a breakdown the setup, then blindness of the judges is irrelevant

- Rich

 

[PENG]

Something tells me, that those who believe decent amps sound the same will not reconsider no matter what I report

I will be converted if there are credible reports that people can identify the "decent" amps in a DBT session. If participants need to take the time to do it, like days, that's fine for me. To me it is not about sounding the same or not, it is about whether we can tell them apart just by listening to our favorite music.

Yes but what point does that prove. If most folks have speakers with high distortion and rooms with issues doesn't that make amp differences harder to differentiate.
So if there is a breakdown the setup, then blindness of the judges is irrelevant

That's what I am thinking too. As long as the amps have low distortions (say less than 0.05%), enough power, high enough damping factor and low enough output impedance, ability to drive low impedance and large phase angle speakers, the sound signature will be mostly determined by the speakers and the sound signature of the amps will be overshadowed.

 

[canelli]

Thanks for taking the time to post your impressions between the two amplifiers.

I am partial to the A51 when compared to the sound of Denon, Pioneer Elite, and Crown XLS. I got the A51 new at a greatly reduced price which I suspect has a big influence on my opinion. Even with a great discount, there are times that I wonder what if I had spent less on an amplifier and more on speakers and/or subs.

As I am getting ready to move to a new house, I disassembled my setup today. An 80 pound amplifier with aluminum fins that leave scratches isn't a ton of fun to move around. Next week, I am dragging it up stairs to its new home. I already asked the wife to buy some extra Advil for my back. I had quite a few moments today thinking about lack of weight for the XLS.

 

[fmw]

Here is the review of the XPR-1 on HomeTheaterHifi that measure it driving the Carver ribbon speaker.
Here is the Audioholic review of the XPR-1 which is also very good but their THD+N numbers hover around .002 as opposed to the HTHFI measurements which climb to .05.
Not that that .05 is bad but it is over 10x of the simulated load.

- Rich

But even 20 times would be well below the threshold of audibility. Everything is measurable. Not everything is audible.

 

[RichB]

But even 20 times would be well below the threshold of audibility. Everything is measurable. Not everything is audible.

True, but not everything is measured and the XPR-1 is an exceptional amp.
Not all ams start that low or end that high.

However:

• some amps produce more harmonics than others.
• IM numbers include only +/-250 HZ, there are more (odd) harmonics that are included in those numbers.
• some amps produce substantially more harmonics with complex wave forms than they do with simple tones. Even two tone tests have shown this.
• some amps are not as linear when driving actual loads as others.
• amps produce different sound than others.

Examining some frequency sweeps and power measurements may not show the above.

Even though amps produce different sound, it may not be detectable by humans.
Even when it could be, many systems and rooms would mask it.

-Rich

 

[fmw]

I'm not criticizing the amp. I'm sure it's excellent.

 

[Irvrobinson]

But even 20 times would be well below the threshold of audibility. Everything is measurable. Not everything is audible.

Time for remedial math, gentlemen. 0.05% is 25 times higher than .002%. Twice 0.05%, which fmv implies is inaudible, is 0.1%, and that's an interesting question, and not so clear-cut as he is implying. 0.1% distortion is equal to -60db. If you are listening at 90db that means the distortion will be at 30db. That's relatively quiet, but if the source was cancelled out 30db of distortion would be audible. So the real question in the scenario is, does 30db of distortion in 90db of music affect perception?