My attempt to compare an Outlaw 7500 and a Parasound A51

[RichB]

So, I finally got around to do a comparison of my Outlaw 7500 and Parasound A51 amps. The Outlaw 7500 was bought used and recently, I sent it to ATI to get repaired where the transformers, caps, and power switch were replaced. It was tested by ATI so I assume it should be operating up to its specification. The Parasound A51 is a few months old.
</SPAN>
The Setup</SPAN>
I used an unprocessed path for music with all processing disabled:
J River media center streaming from a PC to the Oppo BDP-105 USB DAC.
The Oppo BDP-105 7.1 analog inputs are feeding the Marantz AV8801 processor.
The AV8801 was set to Pure Direct Mode and connected via XLR's.
Both amps were connected to Revel Salons running in Full mode.
The source material was CD rips using DBPowerAmp.
I have measured my room under these conditions and the response is very good across the entire frequency range with on some small dips here and there.

I used OmniMic V2 to measure SPL of both amps using the Preamps test tones and both amps measures about the same SPL
I picked about 10 tracks and played them at 55 (-35) on the AV8801 using the positive scale. This is a comfortable level that measured average peaks (Fast mode with OmniMic) in the low 80DB range. I did a second run at a high SPL but I did not want to get fatiqued.</SPAN>
Even so, the Outlaw did not seem as loud so I added .5 DB louder.</SPAN>
I picked music that was not necessarily the best recording but ones that can sound good, but if something is off, it is easily heard; Music with female vocals, quiet passages, mixed instruments, and the occasional solo piano.
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The Songs</SPAN>
A Fine Frenzy</SPAN>
What I wouldn’t do (Bomb in a Birdcage)
Electric Twist (Bomb in a Birdcage)
Pinesong (Pines)
Avalanches (Pines)
Whisper (One Cell in the Sea)
</SPAN>
Alison Krauss</SPAN>
Paper Airplane (Paper Airplane)
Lie Awake (Paper Airplane)</SPAN>
Amy Grant</SPAN>
How Can We See That Far (Heart in Motion)

Adele
Cold Shoulder (19)</SPAN>

Anne Bisson</SPAN>
Dragonfly (Blue Mind)
September in Montreal (Blue Mind)</SPAN>

Laura Shay</SPAN>
First to Fall (Bittersweet)</SPAN>

Expectations</SPAN>
I expected these amps to sound very similar. Before the test, I had the impression that the Parasound sounded great but I felt that the Outlaw might have better bass. The Power ratings are similar. The Outlaw puts out a little less into 8 ohms but is actually a bit more powerful into 4 ohms. Nothing very significant though. Neither of these amps was working hard. Given then levels of first test, I expect I was using less than 5 watts peak and about a watt using one of those SPL calculators. As such, I thought I would have a hard time hearing any sound quality differences between the amps.
</SPAN>
Impressions</SPAN>
I am very familiar with each song but for each one I wrote down my impressions of the sound as it occurred: Cellos, bass guitars, drums, vocals, pianos, and overall clarity and dynamics.</SPAN>
Although I wrote notes for each song, in the end the observations were consistent.
After the low level listening, I repeated the songs at with the volume turned up 7DB to 62 (-18). This did not change my observations.
</SPAN>
Drums</SPAN>: The Outlaw and Parasound had very good bass but the Outlaw was less defined and the Parasound had better definition and Toms had better tone and overhang.</SPAN>

Cellos</SPAN>: In songs that had them, were better defined on the Parasound. This is probably do to the high frequency detail.</SPAN>

Bass Guitar</SPAN>: Again, better defined on the Parasound.</SPAN>

Vocals</SPAN>: All of these were female vocals; many like Ann Bisson and A Fine Frenzy are closely mic’ed with very little reverb. There sibilants sounded right with the Parasound and good but just not as sweet on the Outlaw.
</SPAN>
Pianos</SPAN>: Many songs had pianos some many with individual reverberating keystrokes. The decay of the keys was sounded a little different on these amps. The Parasound had a greater attack and longer decay. Obviously, this is hard to explain. Perhaps, the Parasound has less odd harmonics so I wanted to listen to each note.
</SPAN>
Clarity and Dynamic</SPAN>: Overall the Parasound was noticeably clearer and more dynamic. During the low level testing, there were songs that I wanted to turn up to hear more from the Outlaw so I wanted to turn up the volume. I never felt this way when listening to the Parasound. I even tried giving the Outlaw and extra 2 DB but it did not provide what I was looking for.</SPAN>

What does this mean?</SPAN>
The Outlaw was not new and had been repaired. Even though it was certified by ATI, it is possible that there is something not quite right with it. Perhaps, a new Outlaw 7500 would sound better.</SPAN>
Those who believe that amps working within their limits all sound that same will conclude that this is the case. Amps certainly measure close enough for this to be the case. However, those measurements may not be a good indication of how well an amp drives real speakers like my Salons.</SPAN>

One thing I can conclude is the Parasound A51 is one hell of an amp.
I have had my Revels for 11+ years and I have never heard better sound in my room.
There are definitely more economical choices in amplification; but I cannot imagine that anyone would be disappointed with the A51. If you listen to two amps in your home and they sound the same when drive within their limits that does not mean all amps sound the same with all speakers in all homes. </SPAN></SPAN>
</SPAN>
ET TU ATI</SPAN>
For a while I had an ATI3005 in my system but I had returned it because of transformer hum. When I had it, I felt it was clearer and more dynamic than the Outlaw 7500. I remember having some of the same reaction to familiar music as I do with the Parasound. Still I think that the A51 has a sweeter high-end. If I still had it I would do the comparison.
ATI OEM amps and in speaking with them, they said they manufacture them according to the specifications provided. I believe that is the case. In my time with the ATI3005, it was a tremendously powerful great sounding amp. I wish they were not so industrial looking. It would not take much to improve them.

- Rich


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[fmw]

"What does this mean?"

Most likely, it means you did a sighted evaluation without level matching. Although it could mean that one unit was operating out of spec.

 

[RichB]

"What does this mean?"

Most likely, it means you did a sighted evaluation without level matching. Although it could mean that one unit was operating out of spec.

ATI just repaired it, so that should not be the case.
Do amps age in other ways? I don't know.
I guess that begs the question, do new amps sound different than older ones ?

I attempted to level correct and even gave the Outlaw a .5 boost.
Even at 2 DB more the Outlaw was louder, but I did not feel it was better.

For first-watter's, this was low level listening.
I expect that you need excellent speakers and room to have a good chance of listening to the differences in amps.
I believe I could demonstrate this to any good listener in my home.

- Rich

Edit: Next time I buy speakers, I will close my eyes

 

[PENG]

I hate to tell you you might have gessed right, that I would be one of those who suspect the Outlaw may not have been repaired to its original specs, except that I do not consider myself in the all amp sound the same camp. I just think that the 7500 and the A51 should be comparable to be point one can't tell them apart in a blind test. I have compared 2 Marantz, 1 Adcom, 1 Anthem, 1 Bryston and 1 Denon AVR in my home and have never noticed much difference at the SPL levels I could tolerate. I do find audible difference between my speakers, not huge but easily audible. I will say this again, it is the quality of the recording that matters most, but I also know this one is hard to prove except to say I have quite a few CD that sounds obviously better than some of my SACD and 24/192 HD flac that I paid HD track too much for. Another thing, if I remember right, the Halo amp did not have the best measurements in THD+N at very low levels so that kind of prove when THD gets below a certain point, it may not matter any more whether it is 0.1% or 0.01%. As to higher order harmonics, from measurements I read for quite a few mid to high end amps, that don't seem to be a problem to worry about either.

 

[PENG]

For first-watter's, this was low level listening.
I expect that you need excellent speakers and room to have a good chance of listening to the differences in amps.
I believe I could demonstrate this to any good listener in my home.

- Rich

I understand your points, but the difference you described seem significant enough that I would think most people should be able to detect. For sublte difference, then yes I agree one does need to have speakers that have the resolution to do the trick. Most people don't have Salon2 yet many think they could hear differences between amps that are designed to be straight wire with gains, back up by lab measurements, even at low listening levels. At least you have the "excellent" speakers and have taken the time to try and equalize everything for a fair comparison, just that it is still a sighted test. I would think that, when you are comparing amps such as the 7500 and A51, you need an unsighted test to find the truth and yes preferably both are new or tested to factory specs.

 

[fmw]

ATI just repaired it, so that should not be the case.
Do amps age in other ways? I don't know.

Neither do I. Did they provide some sort of report on the amps performance after the repair?

I guess that begs the question, do new amps sound different than older ones ?

For the most part, no. But that is a very broad answer to a very broad question. Many tube amps sound different from solid state amps, for instance, because of audible harmonic distortion.

I attempted to level correct and even gave the Outlaw a .5 boost.
Even at 2 DB more the Outlaw was louder, but I did not feel it was better.

Level matching is generally done with a voltmeter across a pair of speaker terminals. We want a variation of less than .01 volt. You didn't level match adequately with your ears.

For first-watter's, this was low level listening.
I expect that you need excellent speakers and room to have a good chance of listening to the differences in amps.
I believe I could demonstrate this to any good listener in my home.

And I could demonstrate the opposite with a properly conducted bias controlled test.

- Rich

Edit: Next time I buy speakers, I will close my eyes

Not necessary. Speakers all sound different from one another. That is something you should expect and you will encounter.

 

[RichB]

I hate to tell you you might have gessed right, that I would be one of those who suspect the Outlaw may not have been repaired to its original specs, except that I do not consider myself in the all amp sound the same camp. I just think that the 7500 and the A51 should be comparable to be point one can't tell them apart in a blind test. I have compared 2 Marantz, 1 Adcom, 1 Anthem, 1 Bryston and 1 Denon AVR in my home and have never noticed much difference at the SPL levels I could tolerate. I do find audible difference between my speakers, not huge but easily audible. I will say this again, it is the quality of the recording that matters most, but I also know this one is hard to prove except to say I have quite a few CD that sounds obviously better than some of my SACD and 24/192 HD flac that I paid HD track too much for. Another thing, if I remember right, the Halo amp did not have the best measurements in THD+N at very low levels so that kind of prove when THD gets below a certain point, it may not matter any more whether it is 0.1% or 0.01%. As to higher order harmonics, from measurements I read for quite a few mid to high end amps, that don't seem to be a problem to worry about either.

I agree the Outlaw may not be up to the performance of a new unit.
It does sound good and without a comparison, I may not have picked it as a candidate for improvement.

I know the Parasound is not squeaky clean at low power levels from the measurements on HomeTheaterMag. We do not know is the composition of that, noise floor, odd high frequency harmonics, etc.
The Parasound does have very clean measurements when operating in class-a mode.
Here is review of the Parasound that has extensive measurements in the PDF which I have attached:

Review: Parasound P3 Preamplifier & Halo A21 Power Amplifier | Hi-Fi

Measurement PDF: http://www.avhub.com.au/images/stories/pdf/ParasoundP3&HaloA21HFMar08.pdf

They included a simulated speaker load test and there are minor dips in the frequency response. The author also states that many amps do not perform this well un this load test. I do not think that amp measurements tell the whole story.

The ATI2005 was also a great sounding amp. When I had many occasions when I was surprised at how good the sound was with ATI3005.

- Rich

 

[RichB]

Neither do I. Did they provide some sort of report on the amps performance after the repair?

Nope. I tooK some prodding to get this information out of Outlaw.

Level matching is generally done with a voltmeter across a pair of speaker terminals. We want a variation of less than .01 volt. You didn't level match adequately with your ears.

I used the OmniMic V2 to level match. If I try it again, I will see if I can figure out this method. Any particular frequency?

And I could demonstrate the opposite with a properly conducted bias controlled test.

Perhaps. If such a thing truly exists. What about the pressure-bias. You know, nervousness and fear that you be proven a fool </SPAN>
It may also be speaker dependent and not to how well an amp drives real speakers.
Suppose a blind participant could hear difference on the Titus 8’s. Does that prove to someone driving Gold Ear speakers
</SPAN>

- Rich</SPAN>

 

[PENG]

I agree the Outlaw may not be up to the performance of a new unit.
It does sound good and without a comparison, I may not have picked it as a candidate for improvement.

I know the Parasound is not squeaky clean at low power levels from the measurements on HomeTheaterMag. We do not know is the composition of that, noise floor, odd high frequency harmonics, etc.
The Parasound does have very clean measurements when operating in class-a mode.
Here is review of the Parasound that has extensive measurements in the PDF which I have attached:

Review: Parasound P3 Preamplifier & Halo A21 Power Amplifier | Hi-Fi

Measurement PDF: http://www.avhub.com.au/images/stories/pdf/ParasoundP3&HaloA21HFMar08.pdf

They included a simulated speaker load test and there are minor dips in the frequency response. The author also states that many amps do not perform this well un this load test. I do not think that amp measurements tell the whole story.

The ATI2005 was also a great sounding amp. When I had many occasions when I was surprised at how good the sound was with ATI3005.

- Rich

I actually wanted to buy that amp, but being in Canada I ended up with Bryston and Anthem. I also realize the A51 is high biased class A/AB so at low level the harmonic contents are likely the sweeter types. All I am saying is that the theoretical difference/better than the 7500 should be subtle and may not be all that obvious had it not been a sighted test but given the choice I would definitely take the Halo. Similarly, given the choice between the 7500 and the XPA-5, my choice would be more than obvious, though theoretically and in a blind test I may not be able to pick out the Outlaw.

It is also highly possible that my ability of discerning sq differences limits me to those between source media, speakers, room acoustics, but not between mid, mid high to high end amps. Then again, I have not compared any Outlaw amp to Halo amp, you have, so it actually is easy for me to believe your assessment. The only problem is, I have been thinking of acquiring a H300, now I have to also consider the A21, your fault.

 

[RichB]

It is also highly possible that my ability of discerning sq differences limits me to those between source media, speakers, room acoustics, but not between mid, mid high to high end amps. Then again, I have not compared any Outlaw amp to Halo amp, you have, so it actually is easy for me to believe your assessment. The only problem is, I have been thinking of acquiring a H300, now I have to also consider the A21, your fault.

Sorry about that.
I have had the Salons for 12 years and they have never sounded better.
The BDP-105 analog outs, Marantz AV8801, and A51 are all contributing.
I am listening to some of my older CD's again.
I am not sure if it is the A51 alone, but I find the system sounding sweet and clean.

J River and the BDP-105 DAC have made it so convenient to listen to music I need to keep ripping and possibly find new music somewhere.

I agree about HD Tracks, some of the stuff I bought was not better than the CD.

- Rich

 

[Cos]

Now I am really tempted to upgrade my A52 to the A51, my dealer said he would give me 100% of my money back towards a trade in, so I am tempted. Only problem is that I only paid $1300 for the A52 and then would have to get the A21. Not even sure if the extra power is necessary and the overall spec's are very similar between the two.

My test was in no way scientific when I switched out my Anthem to the Halo when I was troubleshooting my 80.3. The bass to me seemed to be exactly as you described in comparison. Then again, I never had good luck with my Anthem Amp.

I will be moving in 6-8 months as I am taking over my parents old house. I already have estimates on my man cave and those amps would make a great addition to the 4K Sony Projector I plan to install

 

[RichB]

Now I am really tempted to upgrade my A52 to the A51, my dealer said he would give me 100% of my money back towards a trade in, so I am tempted. Only problem is that I only paid $1300 for the A52 and then would have to get the A21. Not even sure if the extra power is necessary and the overall spec's are very similar between the two.

My test was in no way scientific when I switched out my Anthem to the Halo when I was troubleshooting my 80.3. The bass to me seemed to be exactly as you described in comparison. Then again, I never had good luck with my Anthem Amp.

I will be moving in 6-8 months as I am taking over my parents old house. I already have estimates on my man cave and those amps would make a great addition to the 4K Sony Projector I plan to install

I tried, but I would not call my amp listening as scientific either
However, I believe it was valid.

FYI, There is a silver A51 on Audiogon for $2200. Not too bad.
Parasound used gear seems to sell quickly when reasonably priced.

- Rich

 

[Irvrobinson]

Rich, I wasn't there, so I don't know what you heard, but I see only two possibilities. One, the Outlaw amp is defective. Two, the differences were imagined. Since the amp was certified as meeting specs by ATI, I think it is very unlikely that the Outlaw was defective. Since you were using a Marantz receiver, it is also unlikely that the pre-amp section was in some way affected by the load of the Outlaw more than the Parasound.

I also admit that I don't know what sorts of distortions could be responsible for making drums, cellos, or a bass guitar "better defined" with the Parasound. That's always been my problem with subjective appraisals of electronics; I can't imagine the electrical effects that yield the audible effects.

The Salon1s are a comparatively challenging load, as measured by Stereophile, compared to a typical 3-way speaker, but there's nothing about them that would give either of these robust amps problems.

So I'm not sure what to make of your comparison. As a personal choice for you, my advice would be to stick with the Parasound and be happy, and reality be damned, but I'm not convinced your comparison is telling us anything that we can use.

 

[fmw]

Nope. I tooK some prodding to get this information out of Outlaw.

Then if now have the numbers, then you have your answer.

I used the OmniMic V2 to level match. If I try it again, I will see if I can figure out this method. Any particular frequency?

Most of us just play a 1000 hz tone and match to that.

Perhaps. If such a thing truly exists. What about the pressure-bias. You know, nervousness and fear that you be proven a fool
It may also be speaker dependent and not to how well an amp drives real speakers.
Suppose a blind participant could hear difference on the Titus 8’s. Does that prove to someone driving Gold Ear speakers

I'm not familiar with pressure bias but I can tell you expectation bias is very strong. I don't think this kind of testing is really dependent on speakers. More important is that the listener have no clue about which amp he is evaluating at any given time and that the levels be matched on the money.


- Rich[/QUOTE]

 

[AcuDefTechGuy]

I am not surprised.

Guys who believe amps sound differently will believe just that.

Guys who have never heard a difference in amps will not believe it.

 

[RichB]

So I'm not sure what to make of your comparison. As a personal choice for you, my advice would be to stick with the Parasound and be happy, and reality be damned, but I'm not convinced your comparison is telling us anything that we can use.

I remember some posts about moving from Class-A amps to ATI and found for the first time that the sound was less fatiguing.

Was that you?

- Rich

 

[RichB]

I am not surprised.

Guys who believe amps sound differently will believe just that.

Guys who have never heard a difference in amps will not believe it.

Amen to that

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

- Rich

 

[Irvrobinson]

I remember some posts about moving from Class-A amps to ATI and found for the first time that the sound was less fatiguing.

Was that you?

- Rich

No. I posted that I enjoyed listening to my system more when I moved from a PS Audio 200c to a pair of Krell KMA-100MkII monoblocks in the early 1990s, so much so that I kept the Krells, that I purchased at an estate sale for resale at a profit, and sold the PS Audio. I never could explain why I liked the Krells more, but it was a lot more. I actually didn't want to like the Krells, what with their audible always-on fans and 800w per amp idle power draw. And they were, IMO, ugly. There are aspects of my life, audio reluctantly being one of them, where I give in to irrational biases.

The ATI was fully equal to the twin Levinson 334s I was using years later, so I sold the Levinsons, and for the price I got for just one of them purchased a new AT3005. The ATI also had the advantage of being dead silent through the Salon2 tweeters, while the Levinsons hissed. That sealed their fates.

 

[Irvrobinson]

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

- Rich

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.

 

[AcuDefTechGuy]

Amen to that

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

- Rich

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.