My Impressions: Sierra-2's + Separate power amp

[Mag_Neato]

Ok, here goes....

I have been powering my Sierra-2's since upgrading them from the NrT's over a year ago with my trusty Marantz SR6003 AV Receiver. This is a wonderful sounding AVR for music. Rated at 100 watts X 7, it has a fairly beefy power supply and pushes the Sierra's louder than I can stand for extended periods with pretty good dynamic capability. I usually have them crossed at 60Hz to my 12" Rythmik. I have been toying with the idea of adding dedicated amplification to see if there was hidden potential to be unleashed. The cost of a new amp with enough of a power advantage, in my mind, to truly make it worth it, has been prohibitive. I finally found a used Adcom GFA-5500 which fell within, or rather, at the outer limits of my budget. A local hi end AV shop took it in trade and were about to put a classified out there to sell it, but gave me first dibs. I grabbed it.

Now, the predominant opinion on the forums is that power is power when operating at similar output levels and that you won't be able to hear a difference. In a general sense, and for non-critical listening, I will mostly agree. What I found with material I regularly listen to is this: (1) Yes, you can absolutely play louder with 2X the horsepower. (2) While playing loudly the amp maintains an iron grip control of the drivers and does not get "soft", harsh nor let the bass get sloppy. The Sierra-2's sound absolutely incredible with the added power and reserve capacitance on hand. Wow! (3) Even when played at the same average SPL there is increased dynamic swing and punch, and overall more detailed fleshing out of bits and pieces of the material being played. It throws things out there, imaging around the room that are not quite as present with the Marantz driving them. The amp has distortion alert LEDS for each channel when levels approach 1%. They never blinked even when my average SPL hit 96dbs. This was in Pure Direct mode, no sub, and the speakers never sounded strained or lost composure in any way I could detect.

So, I will be keeping the Adcom in the system as long as it will keep working!

[FirstReflect]

Cool!

Congrats on your purchase, and thanks for sharing your experience here.

Are you currently using just the pair of Sierra-2? Obviously, the GFA-5500 being a 2-channel amp, you are powering just a pair of Sierra-2 with that amp, but I was curious if you were previously powering more than two speakers with your Marantz. In my experience, it has certainly been more noticeable that a separate amp is making an audible difference as the number of speakers I am powering with any given amp has increased. For example, when powering just a pair of Sierra Horizon RAAL speakers, my Onkyo TX-NR5010 honestly delivered the lowest noise floor I have ever had in my theater, and given the small size and close seating distance of my current setup, it had the same level of dynamics and maximum output (that my ears could stand, not that the speakers or amps could deliver) as any of my other, separate amps. But once I was powering 5 speakers with the TX-NR5010's internal amps, the noise floor rose ever so slightly. When I tried powering 9 speakers all from the TX-NR5010 (which is the maximum number of speakers that the TX-NR5010 can drive on its own), the noise floor rose substantially, and the dynamics and headroom were noticeably decreased.

Where I think you and I will agree is in saying that the improvement you've heard by using a separate amplifier, while nice and perhaps even "worthwhile" for audio enthusiasts like ourselves, is still rather subtle in the grand scheme of things. That is why I tend to recommend that a separate amplifier be one of the last upgrades made to most sound systems.

I like to work "big to small". I like to recommend that people spend their money where it will make the largest audible difference first, and then upgrade other parts of their system as funds allow. So, for example, if someone has $1500 to spend, and they are currently using a mid-level AV Receiver and some inexpensive, entry-level speakers, I would much sooner have that person use the $1500 for a new pair of speakers, or perhaps a new pair of speakers AND a subwoofer vs. having them spend all $1500 on a separate 2-channel amp. Powering $1000/pair speakers with a $500 subwoofer is going to make a huge audible difference in replacing the inexpensive, entry-level speakers. But powering the same inexpensive, entry-level speakers with a $1500 2-channel amp isn't going to make much of a difference at all!

So that's how I look at the situation with separate amps. I tend to find they make the most difference on the extremes - they can deliver a lower noise floor, and they can deliver louder, cleaner dynamics and headroom. Those can be worthwhile upgrades to audio enthusiasts, but they aren't top priorities, in my book. Once you have excellent speakers, at least a pair of optimally positioned subwoofers, and a feature-rich AV Receiver or Pre-Pro that can deliver excellent decoding, bass management, and equalization, THEN I would consider recommending a great separate amp. But I would not prioritize the amp over any of those other items. Big to small ;)

But as you've nicely pointed out here, if you've already purchased all of those other items, an excellent separate amp can be another nice improvement to your system. I'm a nut job for a silent noise floor myself, so I certainly appreciate my ATI amp just for that, if nothing else :D

- Rob H.

[Mag_Neato]

I only ever used the Marantz for 2 channel. To appreciate the benefits of a dedicated amp you need to know your system intimately before adding one to truly process the gains.