The Gilmore Raptor 500D Monoblock Power Amplifiers

by admin on November 10, 2009 · 1 comment

in Amplifiers

by Henry Wilkenson

Individuals who were music lovers before anything else created the high-end or specialty audio industry. The products that they did and still produce were created with music as the main focus. If it were up to the large multi national corporations whose focus is the bottom line, we would be listening to a very different level of gear.

Mark Gilmore, founder of Gilmore Audio can be added to the long list of high end innovators. Mark has been a life long music lover and guitarist. He also went on to become an aerospace, digital and computer engineer. All of these abilities came together when Mark founded his company, Gilmore Audio. The first products created by Gilmore Audio were the very distinctive Model 2 and the smaller Model 3 loudspeakers. Each of these is a four woofer, full ribbon planar dipole design. While I have yet to hear them, I hope to do so soon. Among their other products are the Raven stereo power amp and the six channel Dragonfly amp, both are rated at 250 watts per channel. The Dragonfly is built to order and is delivered within one month. The Blackbird preamplifier is a class “A” balanced differential design with individually buffered inputs. New to the lineup is the soon to be available 400 WPC Puppy stereo power amp with a mono block version to follow. The Puppy is a full class D design with a switching power supply. As you would expect from Mark Gilmore, this will be anything but a “typical” class D design. The early word is that it will be a highly modified proprietary design that will deal with the noise generated by most class D amps. The Mega Raptor is a 1000 watt version of the Raptor. It too is made to order, like the Dragonfly, and is delivered within one month. Finally there are the Raptor 500D monoblocks, the subject of this review.

Background

Recently, there have been a number of class D power amplifiers that have come to market creating quite of bit of industry buzz along the way. From the look of things, that number is growing. While many performance claims have been made for them as a whole, they still remain very controversial. I find it interesting to note that many of the detractors usually comparing them to class A/B amps that cost two to three times or more. While the Raptors are digital amps, they could be described as ‘class “D” with a twist’.

The Raptors measure 12” X 12” X 4” high. While they are fairly compact given their power output, their size makes a much lower demand for precious shelf space than a typical class A/B amp of comparable power. Along the front panel, there is large mute switch and a LED to indicate status. The mute switch does just that, mute the output. There is no on/off switch since the amps are intended to be left on and powered up at all times. Given the efficiency of these amps, the LED consumes more power than the amps do with no input signal. From left to right along the rear panel are the speaker binding post, the balanced input, high or low gain switch , RCA input, fuse holder, power cord socket and voltage setting switch. Each amp sits upon high quality composite feet made by EAR that provide additional chassis dampening.

The chassis is built from 1/2 inch machined T-6061 aircraft aluminum. It should be noted that this is true aircraft grade aluminum. This grade of aluminum is much harder and is more difficult and expensive with which to work. There are sixteen hex nuts around the top plate of the chassis in addition to special internal locking clips that secure the top plate. The unit is sealed making it impervious to dust. The amp must only be opened by a Gilmore Audio technician. In fact, if you open the chassis, not only will you not be able to properly reassemble it, you also will void the warranty

Earlier I said that these amps were class D with a twist. While these amps contain proprietary class D circuitry, it is coupled to an analogue (non-switching) power supply employing a huge and expensive toroidal transformer; hence the 37 pound weight. The circuitry utilizes a highly modified, very high sampling rate ICE digital engine. This is not the same off-the -shelf, engine that is typically used in many other amplifiers. Rather, it is highly modified and unique to the Raptors. The proprietary circuitry, analogue power supply, digital filtering and chassis design all combine to reduce the RFI that would normally be created by these amps to ravishingly low levels. In this regard, these amps can be considered hybrids. This is a solid approach when dealing with high amounts of RFI that class D amps produce. The high rates of RFI created by the switching power supplies of some class D amps, can result in serious sonic consequences if it is picked up by other components and fed back through your system. Finally, according to the manufacturer, the circuit boards are of equally high quality and, are populated with high grade components.

Setup

The hardest part of setting up the Raptors is hefting their 37 Lbs into place. The inputs are clearly marked and well spaced, so making the necessary connections is a breeze. I particularly liked the Cardas speaker binding post. They are very high quality and provide a very large surface area for securely connecting spade lugs. Even the thickest spade lugs are easily accommodated. I understand that the amps currently in production are being outfitted with even better speaker binding post that will provide more uniform pressure on the speaker wires spade lugs and make it virtually impossible to short out the amp by making a bad connection.

I especially liked the high/low gain feature. It is a very useful to be able to tailor the gain to different preamps since some of them can have a very high output. The plain box styling will appeal to some and not to others. Personally, I find their unobtrusive styling to be quite welcome.

The Sound

According to Gilmore, one of the design goals for these amps is that they have no sound of their own. I have heard this claim made for other components, only to find that brightness was being passed off as neutrality and worse, treble extension. In this case, these amps really have no sound of their own; so, how do you describe how they sound? Since it is futile to try to describe “No sound”, the best way to approach this is by describing what these amps do and not do. Their sonic presentation has a total lack of edge or hardness, (Thank You). There is also a lack of any electronic hash or haze with the sound. As far as being warm or cool, these characteristics do not apply to the Gilmores. Any warmth or coolness has to be laid at the feet of other components upstream. In short, these amps are very revealing of associated equipment while they remain as close to “neutral” as I have heard in any amplifier to date.

The music is presented with a very high degree of clarity yet, there is a total lack of brightness. This is something that I hear all too often with much of the gear that I have come across of late. I believe that this is in large part due to their very low noise floor. While the music comes from a dark background, it is not the anechoic black hole sound that to me is very unnatural sounding. This is testament to the careful design of the power supply. It is difficult and quite expensive to achieve a quiet power supply using a toroidal transformer. One of the by products of these transformers is noise unless they are very well made (expensive). The old ear to the tweeter test revealed a very low level of hiss that turned out to be tube noise from the pre-amp rather than any noise from the amplifiers.

Really good recordings have a presence and vibrancy that went un-noticed previously. Two that stood out were “A Night in Copenhagen”, by the Charles Lloyd Quartet, Blue Note [ST85104]. This is a live, not necessarily audiophile pressing, that was well none-the -less, well recorded. I noticed that the low level hall cues that give a sense of the space the musicians are performing in were more prominent but still sounded quite natural .

Another recording in the same vane is “Friday Night at the Blackhawk, vol. 1” by Miles Davis, [Columbia Cl 1669]. This is an original six-eye original pressing. These amps allow the presence and vibrancy of this recording to flow out of the speakers as I have never heard before from my system. I readily understand why original pressings are so often highly prized.

Treble extension is quite good. Where it exists in the recording, cymbals have bigness, shimmer and decay that create an illusion that is much closer to the real thing. The high degree of resolution allows the tumbrel differences between different cymbals as well as triangles to be heard much more clearly than with my Bel-Canto amps.

The mid-range tends to be a touch on the dark side. This characterization is usually taken to be a negative criticism. That is not in any way my intention here. To be clear, this “darkness” is in comparison to other gear that I find to be somewhat bright in this area. The Raptors present instrumental timbres with a fullness and richness that to my ears mimic real instruments. I have to admit that this is much to my liking. Pianos sounded weightier with less emphasis on the initial transient but more on the body of the notes. Keith Jarrett’s “Up For It”, [ECM 860B0000406-021] is a good example. Here again, the shimmer and decay of the notes were very good. The emphasis is on the body of the notes as opposed to razor sharp transients. It is not as if this was an artifact that is added on rather, it’s just that these amps allow these qualities to come through the speakers unimpeded.

The mid to upper bass is handled quite well. It is tuneful and well detailed. The lower bass is another area that I was impressed with. These amps can go deep but they also do so with weight and authority. Large orchestral pieces are no problem for the Raptors. Aaron Copland’s “Fanfare for the Common Man”, from his Third Symphony, [Reference Recording RR-93CD] is a case in point. This piece was reproduced with the appropriate size, dynamics and tumbrel weightiness that make for a realistic presentation.

Conclusion

The reason that this review took so long to write is that these amps compelled the kind of listening that had me revisiting much of my record collection. Because the way these amps performed, far more time was spent listening rather than trying to isolate, describe and write about the usual sonic checklist of audiophile attributes or artifacts. Mark Gilmore has combined a unique class “D” circuit design with a very high quality analogue power supply and, it works exceptionally well in this case. The design focused on only those elements that resulted in an audible improvement; Hence, the lack of fancy graphics and other unnecessary add-ons. The result is a musical presentation that I can best describe as whole cloth analogue as opposed to the spot lighted digital sound that is so common today. I find them highly engaging and they make listening most pleasurable over the long term.Mark Gilmore and Glacier Audio are so confident in their products that they come with a very liberal one month in home auditioning period before making the final purchase. I don’t think that you will run into this deal very often. In addition, should you convince a friend to purchase a pair of Raptors, you will receive a $500.00 finder’s fee, ($250.00 for a Raven.) Once you spend some time with the Raptors, you will understand why they have the confidence to make these kinds of offers.

The Gilmore Raptor amplifiers may not be as well known as a number of other entries in their class at present; I believe this will soon change. Never the less, considering their excellent build quality and performance, they are being offered at what I judge to be a reasonable price. Keep in mind that the price would be much higher if you had to purchase them through a dealer. If you are in the market for a pair of amps in this price range, do not overlook the Raptor monoblocks. These amps are true winners.

Associated Components

Analog Source: VPI HW-19 IV MK 4 turntable Rega RB 700 tonearm Benz Ruby3 cartridge
Digital Sources: Sony 777 ES CD player (Modified)
Amplification: VAC LE Pre Amp Bel Canto EVo 200.2 power amps bridged mono NuForce Ref 9SE power amps
Loudspeakers: Dynaudio 3.3
Cabling: Wasatch Ultama Speaker Cables Acoustic Zen and Von Gaylord Audio Chinchillia Interconnects and Speaker Wire
Accessories P.S. Audio Power Plant P-300 Mapleshade Triple point Coupling Devices DH Labs Isolation devices

Specifications

Class D Monoblock power amplifiers
Output Power: RMS power 250 watts @ 8 ohms, 500 watts @ 4ohms
Frequency Response: -3db @ 60 kHz, 8ohms -3db @ 4Hz, 8 ohms +/- 0.3 db, 20 - 20 kHz
Output Impedance: 50 mil-ohms @1kHz
Output Stage Efficiency: 93% or greater up to full rated power
Gain: 27 db in high gain position nominal 20 db in low gain position nominal
Harmonic Distortion: THD +N Less than .1% up to full rated power, 4 and 8 ohms.
Measurements: 12” X 12” x 4” Weight: 37 lbs each

Manufactured by Gilmore Raptor Glacier

P.O. Box 7668, Kalispell, Montana 59904

Price

MSRP $5,000 per pair 3 year non transferable limited warranty on parts and labor

E-mail:mark@gilmoreaudio.com

Gilmore Audio website

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