Product Review - Adcom GFP-750 Two-Channel Stereo Preamplifier - November, 2000
Adcom GFP-750 Stereo Preamplifier
Modes: Active and Passive
MFR: 5 Hz - 85 kHz Ī 0.5 dB
Input Impedance: 47 kOhms Unbalanced, 94 kOhms Balanced
Output: 1 Volt
SNR: 102 dB A Weighted
Size: 3 1/2" H x 17" W x 11" D
Weight: 15 pounds
MSRP: $1,250 USA
- Adcom; http://www.adcom.com
The GFP-750 stereo preamplifier is part of Adcomís high performance separate components series, which, according to their website, are conceived under the companyís philosophy to provide exceptional performance for the money. As we all know, a company may put whatever fancy claims to their product they want, but we, as the customers, will only care if the performance of the product justifies the companyís claims. With a claim comes an expectation, and a company of Adcom's stature knows better than to make a claim that is unsubstantiated. So, does the GFP-750 really live up to the companyís claim of high performance at a great price? Read on.
Features and Build Quality
The GFP-750 is more stylish than some other units in their line. A touch of gold on the simple front panel of this black colored box gives an elegant impression to the unit. Two of the four rotary knobs function as electronic switches to select the source and to set the outputs to stereo, reverse-stereo, or mono. The other two are motor-driven and are used for adjusting volume and balance. The golden rectangular plate in the middle of its front panel sports three toggle-switches that are used to power on or off the unit, change the preamp mode to passive or active, and engage or disengage the processor loop. The connections on the back are spaced nicely and gold plated. Overall, it is a very well-built preamp, feels very rugged, and gives a solid impression. It is also quite heavy for a stereo preamp (15 lbs).
The GFP-750 can accommodate up to four line level input sources, labeled on the panel as CD, Tape, Aux1, and Aux2. It also provides an alternative set of balanced XLR inputs for the CD source. Two pairs of unbalanced RCA outputs, plus a tape output for monitoring, as well as one balanced XLR output set, are provided. The provision of two pairs of unbalanced main outputs is very handy, e.g., for bi-amping. The preamp does not have a phono section, so it may not be a vinyl loverís cup of tea.
The GFP-750 can operate in active or passive mode. According to the productís brochure, in the passive mode, the audio signal input to the preamp only sees the input switching and volume attenuator before it is sent out to the output, a minimalist approach that will definitely be applauded by a purist audiophile. The minimalist approach is also applied to the design of its active circuitry, which is provided in case one needs to drive a difficult load with this preamp. There is no treble or bass control, again meeting the purist ideals. The balance control only works when the preamp is in active mode. The active or passive mode can be selected by using one of the toggle switches. A red LED above the switch lights up when the preamp is in passive mode, and is off otherwise. I found this a little bit against intuition initially. I would have thought that when the light is on, the unit would be in active mode. But, oh well, so much for intuition. I have been able to teach my brain to adjust to Adcomís convention now.
Another nice feature of the GFP-750 is the processor loop. This loop is engaged by switching the processor toggle and can be accessed with the remote control. When this loop is activated, all the preamp functions are bypassed, allowing the connected surround sound processor to take over the control. Obviously, you would be sending only the front left/right processor channels through the 750. I very much applaud this feature, and I think every company out there should consider adding it to their stereo preamp line. It allows easy integration of music and home theater into one system. We have had many questions from readers as to how to use both their stereo preamp and their surround sound processors in one system. Now you may argue that one can eliminate stereo preamp with a one-box surround processor/preamp, since the stereo mode is always provided in such a device. While this may be a good enough solution for many, it may not satisfy a purist audiophile. One has to climb up high on the price ladder to get a satisfying stereo performance out of a home theater preamp. Or, suppose you wanted to use a Class A triode stereo preamp and a solid state processor together? Anyway . . .
The supplied remote control is slim and quite simple. It can access most of the GFP-750 functions, except the active-passive and the stereo-reverse-mono switching. It can also be used to adjust the balance. As much as I enjoy the convenience of adjusting balance from the comfort of my seat, I would rather have the luxury of not having to re-adjust the balance again after it is set right. In other words, I prefer not to have the balance control button on the remote control, because one can easily press it accidentally and mess up the properly calibrated balance. Fortunately, this is not an issue if the preamp is used only in the passive mode. Muting is also provided on the remote control, but not on the front panel. Therefore, muting can only be done by using the remote.
Right out of the box, the performance of the Adcom GFP-750 was excellent, and it got better after some break-in. In my system, the effect of break-in was the slight broadening of the soundstage. For this review, only the unbalanced inputs and outputs were used.
The difference in the sonic performance between the active and passive mode is audible, but both modes are very transparent. This is a quality that is hard to come by at this price point. In my system, the active mode adds a little bit of sparkle to the sound. I could imagine that this may actually be preferred in some systems to get a livelier presentation. On music that emphasizes vocal, I feel that this characteristic makes the vocal sound a tad unnatural. For example, Diana Krallís voice in her album "When I Look in Your Eyes" became slightly edgy in the active mode compared to the passive mode. The soundstage presentation in the active mode is also a little bit forward than the passive mode. This is minor, however, and it does not reduce the depth of the soundstage. I also noticed a slightly better bass definition and extension in the passive mode than in the active mode. All in all, I feel that the passive mode is more natural sounding in my system, and so I prefer using it over the active mode. Again, the difference is subtle, and I could be happy with either mode. Most of my comments below come from my listening impression of the passive mode.
Vocal comes out liquid, open, and natural through the GFP-750. There is no hint of excessive sibilance, except when it is in the recording. In fact, vocal reproduction is one of the strong points of this preamp. I remember when I listened to the Chiro C802 AV preamp that I used to own, which by the way has a highly regarded stereo mode, I got the impression that the sound was very open, but the vocal seemed to be a bit thin. With the GFP-750, the vocal is full bodied. When I listen with my eyes closed, this preamp can make me believe that the singer is actually in the same room.
Musical instruments also sound very natural through the GFP-750. The decay of the Earl Klughís guitar strings from the album "Sudden Burst of Energy" was very life-like. So was the piano sound from Jim Brickmanís "Destiny" album. This preamp did not hide the boxy resonance sound coming from the piano, which made it sound so real. The sound of Dave Kozís saxophone in his album "The Dance" was also reproduced with a high degree of realism.
Another GFP-750 strong point is its capability to paint a very focused image. Because of this wonderful characteristic, the sense of separation among the instruments playing is vividly presented. At one point, I compared the Adcom GFP-750 with a more expensive Krell KAV-250p preamp. Although the Krell by itself was a very nice preamp, comparing it with the Adcom exposed some of its weaknesses. The most noticeable one was that the image produced by the KAV-250p was not as focused as the one produced by the Adcom.
The GFP-750 is very neutral and revealing. It gives you whatever there is in the recording without adding anything to it. If you want your electronics to do some alteration the sound, this may not be the preamp for you. But, if accuracy is what you are after, then the GFP-750 is among the best at it, in my opinion.
I also tried connecting my surround processor, a B&K Reference 20, to the processor loop, and I was really impressed. I did not notice any degradation of the processor sonic performance going through this loop. Also, no loudness re-calibration was needed, as the volume level of the main left-right speakers was not changed by the processor loop.
As you can tell by now, I really like the GFP-750 performance. It never disappointed me in any aspect. Its performance rivals and sometimes betters some preamps with much heftier price tags that I have tried. Definitely, it is one of the best stereo preamps in terms of price to performance ratio.
I think Adcom hits the right note with the GFP-750. It is a very well-built preamp with exquisite all around performance. At its price point, I do not think that you can come up with something better. It may not be a cost-no-object design, but youíd be hard-pressed to find a better all around preamp even at higher price points. So, the companyís claim of high performance of a great value is substantiated indeed. Adcomís thoughtfulness to provide the GFP-750 with a feature for easy integration with a home theater system makes it very versatile as well. This is a must audition for someone who is in the market for a stereo preamp or who wishes to improve the stereo performance of his/her all-in-one home theater-music system.
CD playback: Yamaha CDC-755 (used as transport), MSB Link DAC
DVD player: Toshiba SD2109
Preamplification: B&K Reference 20, Krell KAV250p
Power amplifier: ATI AT1505
Loudspeakers: NHT 2.9
Cables: MIT Terminator 2 speaker cables, MIT Terminator 4 interconnects
Accessories: Parasound SCAMP, Monster Power surge suppressor
- Tiauw Go -
© Copyright 2000 Secrets of Home Theater & High Fidelity
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