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.The Setup
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.
Even so, the Outlaw did not seem as loud so I added .5 DB louder.
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.The Songs:A Fine Frenzy
What I wouldn’t do (Bomb in a Birdcage)
Electric Twist (Bomb in a Birdcage)
Whisper (One Cell in the Sea)Alison Krauss
Paper Airplane (Paper Airplane)
Lie Awake (Paper Airplane)
How Can We See That Far (Heart in Motion)Adele
Cold Shoulder (19)Anne Bisson
Dragonfly (Blue Mind)
September in Montreal (Blue Mind)Laura Shay
First to Fall (Bittersweet)Expectations
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.Impressions
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.
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.
What does this mean?
- Drums: 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.
- Cellos: In songs that had them, were better defined on the Parasound. This is probably do to the high frequency detail.
- Bass Guitar: Again, better defined on the Parasound.
- Vocals: 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.
- Pianos: 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.
- Clarity and Dynamics: 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.
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.
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.
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. ET TU ATI
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.