Low distortion and noise Accurate reproduction of signal

Will not be forgiving of poor recordings

Setup: I use three 505's to power the L/C/R speakers in my home theater. The speakers are Dunlavy SC-1 A/V monitors. The speakers are biwired using MIT wire. The amps are plugged into a Van Evers Unlimiter which is plugged into a dedicated 20 amp breaker. I leave the amps power up as per the 505 manual. Sound: Without any signal there is virtually no noise emitted from the tweeters. I have to remove the grill and put my ear right next to the tweeter to hear anything at all! During extended lisitening sessions to acoustic recordings this lack of noise makes for a very pleasant experience. These amps seem to effortlessly reproduce even the most difficult passages without distortion or smearing. Only after turning up the volume well above reference level do things start to get a edgy and harsh sounding. It should be noted, however, that this has happened to every amp I have ever auditioned/listened to with the possible exception of the R.E. Designs. Plus, lisitening to sounds this loud is not good for your most important listening component, your ears. The 505's are very accurate. They will not "repair" a bad recording. What you put in is what you will get out. Thus, if you are looking for something forgiving I would look elsewhere. Reliability: I can't speak for the previous owners, but I use these amps every day for both music and home theater and I have had no issues whatsoever. The amps are heavy, well constructed and appear to use high quality parts throughout. If well ventilated, as they are in my setup, they run cool even after several hours of listening at reference levels. Price: My value rating reflects the price I paid in the used market. Even at full retail, however, I think you would have a hard time finding a similarly powered monoblock amp that sounds and performs as well as this one at that price.

Sound, Build, Appearance

None as I'm aware, but at the price they may seem too small for "big expensive amps"

I purchased these amps used in the UK. For the amount I paid they are a great value. At retail price I think they still offer great performance and satisfaction.

The build quality is excellent and the performance is incredible. They never seem to run out of power. The combination of my Meridian system: 502 Pre, 505 Amps, and 506.24 CD has opened up world of high resolution and sheer sonic pleasure that I hadn't yet experienced.

These amps, compared to the Rega Mira that it replaced, seemed to make the music sound clearer, bigger, and better. So much so that I replaced my original Celestion A1 + Rega Storm III arrangement and went with a pair of Celestion A3's by themselves. Even though I loved the REL, I like the A3's powered by the 505's alone better than the A1 + REL combination. (Also, I had to sell the REL to finance the A3's) To this end I now believe that a full range speaker gives greater listening pleasure than a smaller monitor speaker augmented by a subwoofer. Just sounds more "right"

The 505's are very nice. A couple pieces of equipment that can satisfy. Well built, good looking, simple to use.

At retail they seem to be a pretty good deal. Bought used they are fantastic.

I purchased my 505's along with a 502 pre-amp and run them in a balanced configuration. I NEVER thought that a preamp and amplifier could make such a difference. Much better than I could have anticipated.

Special Note: I've noticed that Meridian (along with Linn and Naim) tend to keep models going for many years making improvements to the original design as time goes on. To me this adds to the value of a purchase from these companies. Meridian has been making the "500 Series" for about 6 years now, with steady improvements as the years go by, but since the basic components tend to stick around this doesn't "devalue" your equipment as time goes on. Plus, you don't feel compelled to run out and buy the "newest" thing. Most of the high end English companies respect your investment in their products and attempt to make low cost upgrades available to existing owners. To me the 500 series seems to be a purchase I can live with for a very long time, and there's satisfaction in that too. Have fun!

Similar Products Used:

Quad 707

The Meridian 505 Power Amplifier
Apology.

I hate to be such a protagonist for Meridian products, but the truth is that I like them, and I have decided that they offer a good enough value for the money that I have parted with a little over $8,000 in Meridian's general direction .. via my dealer, of course. The MSRP of the 505 is $US1400, and given the low demand and the recent vintage, they are pretty much special order items according to dealers I have talked to. For example, I am still dealing with Magnolia Hi-Fi in Seattle (where I lived between 1985 and 1991) because the local Meridian dealer near my home doesn't carry anything except the digital home theater, and the two CD players. When I asked in California about buying Meridian power amps, the response was "Did you know we carry Classe?" My feeling is: "Did you know I sweat easily, and that I pay PG&E handsomely for my electric service?" So, I called Seattle one more time.

What is a 505?

The 505 is too new for it to be listed in Meridian's web site, at least the last time I checked. I have serial numbers 137 and 22. The 505 is housed in the same box as the 556, which means it is about the same size as one of the 500 series components with heat sinks attached to each side. This also means that they won't fit into one of those neat racks that you might own if you are attached to the Meridian/ Linn/ Naim size of components. In an almost information free manual (how much is there to say about a piece of equipment whose only feature is a power switch that is inaccessible?), Meridian states that the 505 is a mono power amp with the same gain as the 551 power stage, the 555, the 556, and the 557. It is listed at 160/270 watts across a 8/4 ohm load. I have verified the gain with a Fluke multimeter, but the wattage is hardly verifiable with my current equipment. The 505 has two pairs of widely separated, oversize binding posts so that all you folks who keep the wire companies in business can feel unencumbered. Single ended and balanced inputs are provided, along with shorting plugs for the single ended inputs with the balanced inputs are in use. The fittings are first rate. The only thing on the front panel is a single green LED; an unblinking eye with no purpose except to acknowledge that the power is connected. As with all Meridian components, the power switch is on the rear panel, and the units are designed to be left powered on.

My philosophy of amplifiers ...

Despite the tendency of many people on the road to hop up their cars by installing wider tires, more muscular engines, or snazzy paint, a car is a system that is usually designed to work pretty well as sold. My philosophy of amplifiers is similar: look for balance. An amplifier has at least four choke points: (1) the amount of current that can be cranked through the gates of the output transistors without melting them, (2) the voltage of the power supply rails, (3) the instantaneous discharge capability/effective series resistance of the power supply for the short term needs, and (4) the size of the power transformer, because a constant drain that is greater than the transformer's ability to keep the power supply fully charged will cause the amplifier to suffer.

The Mark Levinson and Krell design philosophy is great, but the truth is that even with my KEF Reference 3's rather demanding load, I'm never going to use all the features into which they put their R&D money. I have always had a bit of fear of higher power amplifiers. Many of the large power amplifiers that are available have significant drawbacks. They can all be expensive. They tend to be more complex devices; i.e., they have more parts. They can be chowers-of-power, which in turn translates into warm rooms. They can have high background noise levels. They can have mechanical hum because of the power transformer's surging as the filter caps are recharged in synch with the AC frequency. They can also be living room hogs, and there is just no way that exposed heat sinks are ever going to be attractive.

Under the hood ...

I can never resist the temptation to open up stuff, and the 505 was far too tempting to leave alone. There is a neat, heavy, 800VA toroidial power transformer in the middle rear of the amp, and a single circuit board with three transistors on each end toward the front. One might question Meridian's decision to put the transistors near each other on the end of the long heat sinks on each side, but keep in mind that you depend on the ability of aluminum to transmit heat several times each day in other devices you own, from engine blocks to pots and pans. I measured the rail voltage at about ±60V (assuming I measured in the correct spot), and each amplifier has two 10,000 microFarad capacitors providing the bulk of the rather modest energy storage. There are few legitimate measurements I have the equipment at home to make, but I can say that the DC offset on one unit was a mere 1.2 mV, and the other unit had no measurable DC offset. The background noise level was low enough that only with the grilles off the fairly sensitive KEF Reference 3s, and my ear right next to the tweeter could I hear any noise at all. The noise profile sounds free of power supply hum - just a soft hiss. There are three 2SA1302 Toshiba transistors on one side, and their matching 2SC3281 partners on the other side. These are the same transistors used in the 551 (one pair per channel), so it is no wonder that Meridian can claim that all their amplifiers "sound" alike.

So I look at it this way: The power transformer will limit the amplifier to 800VA (roughly speaking, 800W) of output. 60V is the maximum output swing that you might find across a nearly infinite resistance, and 20,000 microFarads of capacitance is not a huge amount, but considering the amplifier has some kind of variable bias circuit, that amount is probably quite sufficient for any ordinary operation. Considering also that the transformer is large, the amplifier has ability to "refill" the capacitors nearly. I like to look at the ratio of transformer size to 8 ohm wattage as a kind of "quality factor" for power amplifiers. In this case the ratio is 5:1 (800:160) which means that the transformer is not going to get hot when the amplifier is under any except test bench conditions.

Remind me again, what am I doing with the 505?

Our listening room is 22x18 with a vaulted ceiling .. average height 10 feet. The speakers sit about ten feet apart, about a foot out from the short wall with a large aperture fire place between them. The room is carpeted and bare walls are blocked by seating furniture and cases for books and compact discs irregularly placed around the periphery.

The 505 pair is either complementing or replacing (depending on how you look at it) the power amplifier section of the Meridian 551 integrated amplifier that was actually our first piece of Meridian gear a few years ago. The 551 was used as a preamp only, along with borrowed 541 and 502 preamps that we have been considering purchasing. A new-ish 506 is being used as the CD player. While the 505 and 551 provide a useful biamp combination, I am using only the 505 full range. There are two reasons for this. The 505 is a better amplifier than the 551, and this is no surprise. The other reason is something of a surprise, and worth commenting on here for the purpose of helping the readers avoid similar situations.

The Reference 3 has terminals on the back that would lead you to believe that biamping them would be an OK thing to do. However, with only the low frequency units "connected" to the 505, the sound of music coming from the other drivers can still be heard at a reduced level. Since each driver is in a separate enclosure, this isn't attributable to anything except leakage in the crossover. This would leave me to believe that the terminals present a bit of a kludge, and that the speakers weren't really designed to be used in a biamp configuration. Now, no matter how you feel about the electrical, aesthetic, or financial merits of biwiring, the 505's are close enough to the speaker that the run from the amplifier to the speaker is pretty short .. less than a meter. Inside the amp, you will find about half a meter of 14ga Van den Hull wire from the output devices to the binding posts, so that is what I went with the rest of the way to the speaker. It seems to be fine. Really. I don't want to make it sound like my whole point in getting mono amplifiers was to save money on wire, but I think you will be just fine with a short run of something copper.

But how do they sound?

The 505 is a competent amplifier with little sonic signature of its own. My wife and I have reached this conclusion after three months of ownership. Believing that it is probably best to compare a piece of equipment with both its direct competitors and something quite different from it, I set about my test. The KEF Reference 3 is sensitive enough that even in my fairly large room 10V -- across a pure 4 ohm resistance this would be 25W -- is seldom called for. (The 505 has some kind of plateau biasing based on my measurements of its power consumption, and so it didn't get noticeably warm except during a few records with sustained organ pedal. As I mentioned above, the amplifiers are designed to be powered on at all times, so I didn't even bother evaluating warm-up effects.)

Compared with a little Naim NAIT2 that we keep around for a backup system, the 505s offer a bottom end that is quite a bit more effortless, although I would characterize the NAIT2 as somewhat darker, and bass heavy overall. As a little guy, it just can't move the five drivers in each KEF around nearly as well as the 505. The 505's inherent lack of background noise makes for a startling presentation of well recorded material. The music emerges from the silence in an eerie way. On the other hand, the lack of any hum or hiss tends to be rather unforgiving of source material that has hiss of its own.

Over the years of the CD revolution, I have come to believe that stochastic resonance is the most likely culprit in distinguishing what we hear in our electronics. My theory (somewhat supported by research) is that each noise signature interacts with the signal being processed. The interaction of the signal with the noise floor makes some noise components stand out far above their nominal level which one might presume was below audibility. In quite a few amplifiers I notice a fuzzy, high frequency buzzing that is apparently modulated by the signal, and produces a fuzz that is most obvious during transients of all kinds, and music where a quiet high frequency signal is present with a sustained lower frequency sound. My torture test for evaluating amplifiers has been any of the Leslie Howard, Hyperion, Liszt series. Particularly on issues that feature many of Liszt's more introspective pieces, such as Canticle of the Sun, we get to hear Howard's powerful left hand near the bottom end of his Steinway while his right hand delicately plays the theme four or five octaves higher. The Meridian 505/KEF 3 system reproduces this type of music as "fuzz-free" as do my Sennheiser 600 headphones hooked up to their amplifier. Several other large power amplifiers I have listened to have noticeable background noise. It is truly wonderful. This background noise seems to jump forward and surround high notes of the piano in a way that sounds a bit like the character of a bad FM broadcast (of course, not that dramatic).

My wife and I have driven Hi-Fi stores nuts with the BIS recording of the original version of the Sibelius 5th Symphony, BIS CD-800. The image is wonderful, and while the sound is not bad with the NAIT2, the image collapses quickly as instruments are added to the sound. The 505s, never breathing hard at all, take it all in stride. The sound is glorious. Perhaps the most amazing thing about the 505 is that it doesn't do anything at all to the sound.

I should note that the variable bias isn't an instantaneous thing, and it definitely does not cause the amplifier to run anywhere near class A. The circuit is mentioned in the manual, so I set up my current meter in the line feeding both power amps. I have all our other equipment hooked up to one AC, and the power amps are alone on another line. Measuring the current feeding both power amps gave me a bit better resolution on a linear scale 0-10 amp meter. Running at background radio levels, the 505s draw about 0.4 amps each. The slowly responding meter could have been a component in what I observed as it removed any instantaneous measurements of power draw. What I did see was that the steady state power consumption moved the needle steadily with the average power consumption, and that during music containing loud passages, the amplifiers were drawing something like 1.0 amps each. This isn't a lot of steady state power consumption, but it is more than you might expect to find in an amplifier with a fixed low bias.

My ears can't tolerate the SPL that would be involved with clipping the amplifiers, so about all I can say about behavior at the sub-physical-pain level is that there is no sign of compression or the other markers of amplifier strain. There is no good reason that this $2800 pair of mono amplifiers will not work with a speaker of your choice. Fundamentally, the 505 is a neutral amplifier. There is one drawback: at $2800/pair, you may not feel like you have spent enough money. In that case, I suggest a trip to Tower for some new music.