The original thread is here
One year out I am still thrilled with my investment in the X600.5s, which were installed on 4/10/13. The amp's sound significantly improved during the first 8 days of use, then reached a performance plateau, then after a month of being on 24/7, there was a further increase in image weight and bass weight. No further improvements or changes were observed until vibration abatement was applied in October of 2013 and no improvements or changes were observed thereafter. The amps have been left on continuously since installation and have only been turned off for very brief periods of time when switching components or cables during equipment measurements or trials.
Pass Labs introduced a ".8" series of amps in January of 2014 that has higher class A output. In the case of the X600.8, it offers 100 watts of class A operation compared to the X600.5's 80 watts of class A operation. The X600.8 costs 18% more than the X600.5. Since I am still on a "honeymoon" with the X600.5s, it will be a while before I consider upgrading.
Those of you who are not Pass amplifier owners may want to skip this section since "meter movement" is somewhat of an inside joke. The meter movement of a Pass Labs power amplifier indicates the state of bias current at a particular time. When the needle is stationary, the amplifier is operating in pure class A mode. When the needle moves, it indicates class AB operation.
I only see my meters move under two conditions: (1) Heavy bass content during at normal listening levels. (2) Heavy bass content during higher than normal listening levels. Here are two example videos. The videos were taken with the following equipment and were posted to YouTube straight out of the camera with no video or audio post processing:
Camera: Nikon D800 (Set at ISO 2200, 30 fps, f/3.5, 1080p)
Lens: Nikon Nikkor AF-S f/2.8 24-70mm Zoom
Microphone: Nikon ME-1 Stereo Microphone (70-16,000 Hz FR) mounted on a tripod.
The music in the first video is "Isunova Pi" by E. S. Posthumous ("Cartographer" CD). The needle moved during the heaviest bass notes, most notably during the first 20 seconds. The average sound pressure level was 90 dB-C. The XP-30 preamp volume was set at 64.
Video 1. Meter movement at normal listening levels.
The music in the second video is "Your Love Is My Love" by Whitney Houston ("Whitney's Greatest Hits" CD). The needle moved constantly during the driving bass beats. The sound level was turned up to 72 to get an average sound pressure level of 104 dB-C. This resulted in easily noticeable meter movement (and the need to wear ear plugs). At normal listening levels the meter barely moved during the bass beats.
Video 2. Meter movement at high listening levels.
I was surprised the audio came out as well as it did considering the D800's relatively "noisy" audio circuits (which are optimized for voice) and the limited frequency response of the "cheap" ME-1 microphone.
Increased Electricity Usage
As previously mentioned, I prefer to keep my power amps on continuously. The X600.5s draw 25% more current and consume 25% more power at idle than my previous power amps, Parasound Halo JC 1s. Table 1 shows the differences in idle current draw and idle power consumption between the two amplifiers.
Table 1. Parasound Halo JC 1 and Pass Laboratories X600.5 Idle Power Consumption
Table 2 shows my electricity bills before and after (in red) the X600.5s were in stalled on 4/10/13. The June 2013 bill, which covered the period from April 23, 2013 to May 22, 2013 was the first full month of X600.5 use.
Table 2. Electricity Bills Before And After X600.5 Installation
At $0.09 per kilowatt hour, the JC 1s cost $41.60 per month to run continuously. The X600.5s cost $55.66 per month to run continuously, which was an increase of 33.8% ($14.06) over the JC 1s...and it was/is worth it! All the amounts in red in table 2 would be $14.06 less if I still had the JC 1s.
Audio System Upgrades After The X600.5s
I've done a tweak hear or there during the preceding 12 months. Nothing major, just some further efforts in electrical and mechanical noise abatement. It's nice to be able to sit and listen without thinking about a bucket list of audio projects.
1. Black Hole 5 vibration damping material for SDA SRS 1.2TL loudspeakers. (4/26/13)
2. Dynamat Xtreme vibration damping material for XP-30 and XP-25 preamps and X600.5 power amps. (10/11/13)
3. Dynamat Xtreme vibration damping material for Cary CD 306 PV SACD/CD player. (10/12/13)
4. PS Audio AC 12 power cords for preamplifiers and source components. (11/09/13)
5. AudioQuest Perfect Surface Silver jumpers for SDA SRS 1.2TL loudspeakers. (4/09/14)