Adcom's venner?

el_mariachi

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Er vi flere som nyter musik med Adcomutstyr eller er jeg i ensom majestet?
Synes at særlig effekttrinnene gir svært bra lyd i forhold til prisene som er på brukmarkedet, og hvem kunne ikke tenke seg å eie en GFP-750?

Få høre om deres erfaring med dette merket da.
 

thomand

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Elektron skrev:
Tror du er alene i hele verden :'(
Og det er litt synd, for adcom låter virkelig bra syns jeg. Ihvertfall effektforsterkerne har imponert meg.
 

el_mariachi

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Selv er jeg i ferd med å oppgradere porteføljen med en GFP-750.
 
M

MasterBlaster

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Bruker selv en GFA 6000 som forer senter og bak med godt resultat.
Kjøpte den brukt for 3500.-. En av de beste kjøp jeg har gjort....
 

el_mariachi

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MasterBlaster skrev:
Bruker selv en GFA 6000 som forer senter og bak med godt resultat.
Kjøpte den brukt for 3500.-. En av de beste kjøp jeg har gjort....

Gøy at det er flere som liker utstyret fra Adcom, forholdet pris/ytelse/lydkvalitet er veldig bra.
BTW, GFP-750 er en aktiv/passiv stereopre.
 
M

MasterBlaster

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Pen den pre-ampen. :) Antar at det er den som ble testet i Fidelity for et par år siden.
 

el_mariachi

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MasterBlaster skrev:
Pen den pre-ampen. :) Antar at det er den som ble testet i Fidelity for et par år siden.
Kan det stemme? Vet du hvilket nummer?
 
J

Jurassic

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Gratulerer med ny pre.
Husker den fikk god omtale i Fidelity
 
J

Jurassic

Guest
Har ikke erfaring med Adcom men ut fra det jeg har lest så virker det jo som om de leverer.

Var på jakt etter en Adcom effekt etter at jeg hadde kjøpt nye brukte høyttalere sommeren 05 men det dukket opp en Parasound i passende størrelse og til en ok pris først.

Forøvrig er det befriende med hifi komponenter som ser ut som det de er istedenfor å se ut som et juletre.
 

el_mariachi

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Her er omtalen av Adcom GTP - 750 publisert i Sterephile i 1999. Grunnen til at jeg poster den er i hovedsak at flere har nevnt omtalen denne fikk i Fidelity der de nesten latterliggjorde stereophile's skribenter og deres sammenligning av denne pre'en med dyrere produkter. Stereophile har en del målinger å vise til her. Fidelity får bare synset.


Adcom GFP-750 preamplifier

Wes Phillips, March, 1999


Adcom is one of those companies that's just too consistent for its own good. Year after year, they put out well-engineered, fairly priced gear, while we audiophiles become jaded and almost forget they're there... You want a good-sounding CD player that doesn't cost an arm and a leg? [Yawn.] Well, you could try Adcom. Need a power amplifier with some sock that won't make your tweeters crawl down your ear? There's always Adcom.

To break through our complacency, Adcom would have to produce an outright unlistenable turkey—or a product that raised the bar so high that any audio manufacturer would get a hernia just thinking about raising it again.

Well, brace yourself, Bridget—Adcom's GFP-750 is a solid-state preamplifier/passive line controller that will demolish your expectations.



At least...do no harm (footnote 1)
The GFP-750 looks like an Adcom component. It ain't fancy—just a solid black box with four rotary knobs and a discreet brass rectangle sporting three levers. I do mean solid: This 15-lb preamp has a rugged, no-nonsense feel. Two of the four sturdy knobs control electronic switches that choose the source, and set the outputs to stereo, reverse, or mono. The other two, motor-driven for remote control, adjust volume and balance. The three switches toggle between passive and active output, power on and off, and engage a processor bypass—a handy way to integrate multichannel capabilities.

The rear panel accommodates one pair of balanced XLR outputs and one balanced XLR input pair. It also features four additional RCA inputs, a processor loop on RCAs, two pairs of RCA outputs, and remote sensor and repeater jacks.

The GFP-750 is a Nelson Pass design—essentially a variation on the Pass Labs Aleph P and Pass's DIY project, The Son of the Bride of Zen (footnote 2). The circuit couldn't be simpler. Says Pass, "It's a differential pair—the end. A single gain stage, balanced input, balanced output, no feedback....We took a pair of MOSFETs, and the inputs go to the gates of the MOSFETs. The MOSFET sources are tied together and biased with a current source, with the signal taken off the drains. [The circuit] can run unbalanced on either side, although the performance is best when it's run balanced."

Other than glue logic and the transistors used to drive the relays, the 12 active devices—four gain blocks, each with three devices—are HEXFETs from International Rectifier. The output stage is intended to function as a pure voltage source, making the GFP-750 relatively immune to cable differences or low amplifier impedances. As we've come to expect from Adcom, the preamp sports a honkin' big toroidal transformer, with multiple secondary windings for each channel. A large heatsink on the left-hand side carries the power supply regulator chips.

Both signal and control circuitry is carried on one large double-sided printed circuit board, though these are physically separated. The parts quality is superb throughout, and care has been taken to keep signal paths as short as possible. The input switching relays, for example, are all adjacent to the rear-panel sockets. Did somebody mention the proverbial brick outhouse?

In passive mode, the signal sees only input switching and the attenuator.

Life is short, the art long . . .
You'd think that designing a preamplifier would be simplicity itself, especially in these days of line-level sources. But the truth is, getting rid of a preamp's electronic fingerprint hasn't proven that easy—do a bypass test and the difference can be astounding. Preamps, even well-regarded ones, seem to compress dynamic range, muffle low-level details, and generally throw one of those much-talked-about veils over the sound. Some digital sources, like Wadia's processors and players and a handful of others, allow you to jettison your preamp, at least as a volume control, but you're plumb out of luck if you need to switch between multiple analog and digital sources.

The GFP-750 must be a disciple of Hippocrates, because it does about as little to a system's sound as any preamplifier I've heard—at any price. There is a slight—extremely slight—softening of details when it's used as an active preamplifier, but many audio cables have more sonic impact than the '750. So do most other preamps, for that matter. If you need to drive a long run of cable, or if you have a difficult amplifier impedance, I wouldn't hesitate to use the GFP-750's active circuitry.

In comparisons with the $1495 Audio Research LS8 (reviewed elsewhere in this issue by Martin Colloms), the active GFP-750 sounded considerably more open and extended. On discs with deep bass, such as Robert Rich's Seven Veils (Hearts of Space 11086-2), the Adcom quite simply captured the power and heft of the synth-produced bottom end in a way that the Audio Research did not. Without the direct comparison, I would probably have been quite happy with the LS8's bass response, but the Adcom had a lot more impact down under.

Nor did the LS8 reproduce the harmonic overtone structure of the recorders on the Flanders Recorder Quartet's Armonia di Flauti (CD, Opus 111 OPS 30-201) with the harsh and extremely extended—extremely alive—effervescence of the GFP-750. That harshness, which almost clangs, is what gives this fantastic-sounding CD its sparkle, but it was subdued by the LS8.

Again—while I clearly heard the Adcom as having superior overtone presentation in a direct comparison with the Audio Research, I did not find the ARC particularly closed-down on its own. It is not as transparent as the best preamps I've heard—which the Adcom is—but it is by no means among the most colored either. It's enjoyable, if not exemplary. The Adcom is both.

Actually, the preamplifier that most reminded me of the GFP-750 was the Mark Levinson No.380S, which costs $6495. The two had similarly open, grainless characters. In direct comparisons I had an extremely difficult time discerning differences between them—and that was a sighted comparison! Blindfold me and ask me to identify which one was playing and I'd probably have to flip a coin.

Unless the Adcom was in passive mode, when it was the sonic equivalent of nothing at all. What's it sound like? After many hours of listening, I'd have to say, "What did what sound like?" The GFP-750 is the preamp for the audiophile who hates preamps.

But if I had to describe the sound of no preamp, I'd say open, open, open. Open as in huge soundstage, uncompressed, naked—nary a veil in sight.

Not everybody prefers their sound so unembellished. I'm not sure I always do—sometimes a little euphony can be very appealing. That's okay. There's a lot to be said for liking something simply because it's pretty... But if you want to hear what the signal really sounds like, then the Adcom is the preamp for you.

Experiment treacherous, judgment difficult
But sometimes, judgment is simple. Adcom's GFP-750 is a remarkable preamplifier. It's well-built and elegantly designed—on the inside, where it counts. I've gone just gaga over it, not simply because it performs well for the money, but because it begs comparison with the best preamplifiers I've ever heard. Period. No matter how much you've budgeted for a stereo preamplifier, listen to the GFP-750 first. If you end up choosing something else, then you'll know that your choice is very good indeed.

Sidebar 1: Specifications

Description: Solid-state, remote-control preamplifier switchable to passive attenuator/switcher. Rated main output level: 1V. Frequency response: 5Hz-85kHz, ±0.5dB. S/N ratio: >102dB, A-weighted. Input sensitivity: 183mV balanced, 365mV unbalanced. Input impedance: 94k ohms balanced, 47k ohms unbalanced. Output impedance: 1200 ohms balanced, 600 ohms unbalanced.
Dimensions: 17" W by 4.25" H by 12" D. Weight: 15 lbs.
Serial number of unit reviewed: P751DB 01896.
Price: $1250. Approximate number of dealers: 400.
Manufacturer: Adcom, 10 Timber Lane, Marlboro, NJ 07746. Tel: (732) 683-2356. Fax: (732) 683-2358. Web: www.adcom.com .


Sidebar 2: Associated Equipment

LP playback: Linn LP12 Lingo/Cirkus/Ekos/Arkiv.
CD playback: Audio Research CD2/DAC3, Linn CD12 Sondek, Sonic Frontiers Iris 3 transport/DAC 3.
DVD player: Denon DVD-3000.
Preamplification: Linn Linto phono section, Audio Research LS8, Conrad-Johnson ART preamplifier, Mark Levinson No.380S.
Power amplifiers: Accuphase m2000, Audio Research VT200, Cary 805C, Mark Levinson No.332.
Loudspeakers: Alón Circe, B&W Silver Signature.
Cables: AudioQuest Lapis, Madrigal CZ-Gel 1, Siltech SQ-80B G3.
Accessories: API Power Wedge Ultra, Cinemedia PowerPro 20 Professional Series AC Line Balancer, OSAR equipment and amplifier racks.
Room Treatment: ASC Tube Traps, Studio Traps, Bass Traps; RPG Abffusors; eumorphous feline.—Wes Phillips


Sidebar 3: Measurements

I agree with Wes Phillips about the sheer quality of the Adcom GFP-750's construction. One thing that had me confused was that the passive option is selected when the red LED above the switch is illuminated. For some reason, I assumed that the light being on meant that the active stage was engaged. Serves me right for not reading the manual!

Once I got that out of the way, I started to measure the GFP-750. The mute control gave a full mute to silence; the unity gain setting of the volume control in active mode was at the 2:00 position; and the preamp was noninverting from the unbalanced outputs and from the balanced XLR jacks (pin 2 is wired as hot). (Throughout this section, "unbalanced" means an unbalanced source into the GFP-750's Aux 1 jacks and an unbalanced output from its RCA jacks; "balanced" means a balanced source into the balanced CD input XLRs and a balanced output from the XLR jacks.)

The maximum gain in active mode was 8.33dB unbalanced and 14.33dB balanced. In passive mode with the volume control set at its maximum, the output dropped from unity gain by a negligible 0.145dB. The input impedance was 21.1k ohms in active unbalanced mode, this dropping to a low 1945 ohms in unbalanced passive mode. Both figures are lower than specified, but this should not be a problem unless the source used has a high source impedance, such as some tube CD players.

The output impedance in active mode was a little higher than specified, at 970 ohms unbalanced, 1920 ohms balanced. This should present no problems. In passive mode, the output impedance will depend on the setting of the volume control. I checked at three positions: with the control wide open, the calculated impedance was 14 ohms, presumably due to the Audio Precision's 25-ohm source impedance being shunted by the potentiometer resistance; with the control at 10:00, the output impedance rose to 168.75 ohms; and at the 2:00 position it was 512 ohms. None of these figures will give rise to problems unless the Adcom is used with very long lengths of highly capacitive cable.

The frequency response in passive mode was, as expected, ruler-flat. In active mode (fig.1), a small but negligible rolloff can be seen above and below the audio band. A note on the excellent channel balance seen in this graph: It appears that any imbalance in the volume-control tracking and the gain of the active stages has been optimized for the balanced CD inputs. Repeating the measurement for the unbalanced Aux 1 input in active mode gave the response shown in fig.2: there is now a 0.4dB channel difference at the 2:00 volume-control setting used for this measurement. This is trivial, and was easily corrected by setting the balance control to 11:45, but it did puzzle me at first.


Fig.1 Adcom GFP-750, frequency response into 100k ohms, balanced active mode, with volume control set to 2:00 (0.5dB/vertical div.).


Fig.2 Adcom GFP-750, frequency response into 100k ohms, unbalanced passive mode, with volume control set to 2:00 (0.5dB/vertical div.).


The channel separation was fine, though the crosstalk in balanced active mode (fig.3, top traces) was a little higher than in unbalanced mode (bottom traces). Above 2kHz, both graphs showed a rise in crosstalk due to capacitive coupling between the channels, but this was still less than -60dB below 16kHz.





Fig.3 Adcom GFP-750, Crosstalk (from top to bottom): L-R, R-L, balanced mode; L-R, R-L, unbalanced mode (10dB/vertical div.).


Distortion (fig.4) was very low in both active modes, if a little higher in unbalanced mode and at high frequencies. Despite (or because of?) its minimal circuitry, the GFP-750 is very linear. Fig.5 shows the spectrum of the balanced output driving 50Hz at 1V into a 600 ohm load. This is a punishingly low load for a preamplifier to drive; even so, the distortion harmonics are negligible in level, other than the third at almost -100dB, which is still extremely low. In unbalanced mode, AC-supply harmonics at 180Hz and 300Hz made their presence known, but were still well down (below -80dB) in absolute level.



Fig.4 Adcom GFP-750, THD+noise vs frequency at 1V into 100k ohms, unbalanced mode (top at 1kHz), balanced mode (bottom).



Fig.5 Adcom GFP-750, spectrum of 50Hz sinewave, DC-1kHz, at 1V into 600 ohms, balanced active mode (linear frequency scale).



Finally, fig.6 shows the GFP-750's percentage of distortion+noise in both balanced and unbalanced modes, plotted against output voltage into loads of 100k ohms and 600 ohms. At a 1% THD+N figure, the maximum output voltage in balanced mode was 26.5V (100k ohms) and 6.5V (600 ohms); in unbalanced mode, it was 13.3V (100k ohms) and 5.0V (600 ohms). All voltages are well above the level required to drive any known power amplifier well into clipping. Note that the shapes of these traces imply that the preamplifier offers its lowest level of distortion and noise at around 2V, the maximum voltage likely with a real-world power amplifier.






Fig.6 Adcom GFP-750, distortion (%) vs output voltage into (from right to left): balanced mode into 100k ohms, unbalanced mode into 100k ohms, balanced mode into 600 ohms, unbalanced mode into 600 ohms.


This fine set of measurements indicates good engineering.—John Atkinson


Footnote: 1 All headers by Hippocrates.

Footnote 2: See www.passlabs.com for more information on these products. While there, you can also access patent 5,376,899, which covers the GFP-750's circuit.
 
M

MasterBlaster

Guest
Gratulerer med ny pre-amp el_mariachi! ;)
Hører du forskjell på passive/active drift?

mvh

MasterBlaster
 

el_mariachi

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MasterBlaster skrev:
Gratulerer med ny pre-amp el_mariachi! ;)
Hører du forskjell på passive/active drift?

mvh

MasterBlaster
Takker.
Hører forskjell, noen plater låter bedre i passive mode, men de fleste låter best i aktiv mode.
 

sODDoff

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Har i mange år sverget til amerikansk kraft til mine B&W 603, ADCOM GFA 2535 er 4 kanals kraftverk, yter 4 ganger 60 i 8ohm, og er moro å bruke i ett bi-ampet oppsett. 15 kg med vellyd i mine ører...
 

Vedlegg

el_mariachi

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Omtale av Adcom GFP-750 i hometheaterhifi.com

Product Review - Adcom GFP-750 Two-Channel Stereo Preamplifier - November, 2000

Introduction

The GFP-750 stereo preamplifier is part of Adcom’s high performance separate components series, which, according to their website, are conceived under the company’s 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 company’s 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 company’s 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 lover’s cup of tea.

The GFP-750 can operate in active or passive mode. According to the product’s 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 Adcom’s 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.

Performance

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 Krall’s 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 Klugh’s guitar strings from the album "Sudden Burst of Energy" was very life-like. So was the piano sound from Jim Brickman’s "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 Koz’s 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.

Conclusions

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 you’d be hard-pressed to find a better all around preamp even at higher price points. So, the company’s claim of high performance of a great value is substantiated indeed. Adcom’s 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.

Associated Equipment

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 -
 

el_mariachi

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Omtale av Adcom GFP-750 i POSITIVE FEEDBACK

Revisiting an old Friend - the Adcom GFP 750
by Robert H. Levi




Through a fortuitous set of circumstances, I moved my Adcom GFP 750 preamp out of storage and into my SET system. I generally don't review gear in this price range, but wonders never cease. Designed by none other than Nelson Pass just for Adcom, and marketed as the company's top preamp for the past ten years, this solid-state unit was great ten years ago at $1450. It is even more splendid in 2006 at $1495.

With its fully balanced design and huge power supply, this ultra-flexible line stage truly delivers. Designed for maximum definition and suave, sophisticated tonality, the 750 is the best entry-level high-end solid-state preamp available today. Though it can be used as a passive unit, don't. The active stage is where the action is. To reach even greater sonic heights, use the balanced connections (though the single-ended connections are quite fine, I assure you). I used the 750 with a Cary 300B SET amp and JM Labs' 806S Cobalt Monitors wired with Harmonic Technology Magic speaker cables. I used Harmonic Technology Cyberlight interconnects between the 750 and the Cary amp to maximize the 750's performance, and the ultra-high-value Harmonic Technology Pro Silway III interconnects between the components and the 750. The HT Fantasy power cord provided current to the preamp.

I don't care if the GFP 750 was designed ten years ago. It will shock and amaze you. You can discern Nelson Pass's touch from the first note. You won't believe the drive, definition, and linearity of this baby. Modern cables bring out the unit's accuracy, smoothness, and all-around dynamics. It could compete with much more expensive preamps from ARC and Levinson in 1995, and its 2006 performance has improved. It's that good. The Adcom 750 is the under-$2000 choice for solid-state preamps, while the E.A.R. 834L is the vacuum tube choice. Both were designed by engineering masters—Nelson Pass and Tim de Paravicini—and both have stood the test of time.

The Adcom GFP 750 sings elegantly and powerfully, with imaging as solid as the rock of Gibraltar. The entire musical range is beautifully integrated, and definition and imaging are outstanding. The sound is slightly crisp, but not disturbingly so. The 750 sounds very smooth, with lovely musical nuances and textural cues. It is oh-so-dynamic and powerful, with very little grain and ultra-low distortion. This preamp sounds like it should cost $3000. Like other great solid-state pieces, it has excellent deep bass, with power and definition. It also has lots of air and stage depth. Leave it on for at least 72 hours before critical listening, especially if it hasn't been used for a while, and don't ever turn it off.

The Adcom GFP 750 is perfect for the high-end newbie looking for sound quality and flexibility at a great price. The 750 has many features, and a very well-designed remote. For the audiophile who wants a solid-state preamp with tons of performance without paying a ton of money, the Adcom GFP 750 should be your first choice.


 

el_mariachi

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Omtale av Adcom GFP-750 Preamplifier i stereotimes

ADCOM GFP-750 Preamplifier

Martin Appel
2 August 1999



Specifications

Output Level (Rated) 1.0V
THD + N @ Rated Output (20 Hz to 20kHz)
Balanced, <0.025%
Unbalanced, <0.095%
THD + N (1 kHz)
Balanced, <0.015%
Unbalanced, <0.017%
Output Impedance:
Balanced, <1200 ohms
Unbalanced, <600 ohms
Input Impedance:
Balanced, 94k ohms
Unbalanced, 47k ohms
Frequency Response: 20 Hz to 20 kHz, +0/-.25dB
IM Distortion (@ Rated Output):
CCIF from 4kHz to 20kHz (Balanced) <0.009%
CCIF from 4kHz to 20kHz (Unbalanced) <0.035%

SMPTE (Balanced) <0.05%
SMPTE (Unbalanced) <0.05%
Signal to Noise Ratio (Ref. To 1V)
"A" Weighted (Balanced) >102 dB
"A" Weighted (Unbalanced) >102 dB
Input Sensitivity (@ Rated Output)
Balanced 183mV
Unbalanced 365mV
Power Consumption: 30 VA
Chassis Dimensions: 3.5" × 17" × 11" (H × W × D)
Weight: 15 lbs.
Price: $1250

Manufacturer: Adcom
10 Timber lane
Marlboro, NJ 07746
Tel: 732/683-2356
Fax: 732/683-2358
Web: www.adcom.com





Preamplifiers
What do they do, what shouldn’t they do and why do we need them?

"It must amplify the smallest of musical signals and depending upon the complexity of its switching circuitry, direct the signal without altering it in any way to the power amplifier--ideally, the proverbial straight wire with gain."

Most people who develop an interest in audio grow from a one box mass market receiver into a system of separates usually containing a stereo preamp, power amp, and various source components.

Preamplifiers provide a control center for your system, switching between the various sources and stepping up their lower output voltages to levels that are able to drive most power amplifiers to full rated output and beyond. Each piece in the chain from the source component to the speaker influences what you finally hear. The preamplifier has a very difficult and vital job. It must amplify the smallest of musical signals and depending upon the complexity of its switching circuitry, direct the signal without altering it in any way to the power amplifier--ideally, the proverbial straight wire with gain. For the most part this is impossible. Even preamplifiers in the price range of three to four, or even ten times the price of this review unit, can not fully achieve this.

The Adcom name is one familiar to most people in the high end audio world because many of us on real world budgets started out with Adcom equipment. It was relatively inexpensive, solidly built with good sonic attributes and the door through which we entered into the high end.

Fortunately, my system is comprised of the Uther 3.0 DAC by Camelot which has its own volume and balance controls and two sets of outputs. My power amp, the David Berning ZH 270 OTL has two sets of single-ended inputs, switchable on the front face of the amplifier with an A/B switch. Input A was fed directly by Camelot DAC and input B was connected from the DAC to the Adcom 750 preamplifier and then to the power amp. System conduit consisted of Harmonic Technology Truth-Link interconnects, Pro-11 power cords, and Pro-9 Bi-wire speaker cables. For my evaluation, only the unbalanced RCA inputs and outputs of the GFP-750 were used.

Other associated gear included a Sony DVP 7000 DVD player as the transport; the speakers were TMS Adiabat 8.5’s and Phantom 5.2’s. Vibrapods and Black Diamond Racing Cones were used as well.

"With any new piece of equipment, the GFP-750 included, I set aside a period of about two weeks playing the unit five to six hours a day, using a variety of sources, to burn it in. No critical listening was done but a positive impression was surfacing."

Before starting the review process I want to mention a few facts about this fine product and then we will see how close the Adcom GFP-750 comes to that straight wire with gain, or in other words, to no preamplifier.

The GFP-750 operates in two modes, passive or active. In the passive mode, a toggle switch is thrown which activates a red LED on the face plate. The signal only sees the four gang volume control which is really nothing more than a line level controller. The passive mode greatly reduces the chance for signal alteration by eliminating active circuitry from the signal path. Since any distortion introduced by the preamplifier will be magnified by the power amplifier, maintaining the purity of the signal is critical.

In the active mode, only one active gain stage is used and it’s class A at that. It offers five unbalanced RCA-type inputs, and one set of balanced XLR inputs with true differential balanced circuitry. There are two pairs of RCA outputs plus a tape output, as well as one balanced XLR output.

Adcom has built a unit with a hefty power supply and short signal paths, with high quality HEXFETs used in the active gain stage. A HEXFET is a type of MOSFET manufactured by International Rectifier. For you tweakers, there92s a detachable power cord. An external processor loop is provided for connection to an external surround sound processor, bypassing the volume control when activated. In keeping with contemporary styling trends, the remote control has a rather slight profile. One can adjust the volume and balance, and select inputs as well as mute. It does not allow you to change from stereo to mono, or stereo reverse, or from the active to the passive mode, which can all be done via the front panel controls. As you can see, this is a feature-laden unit.

With any new piece of equipment, the GFP-750 included, I set aside a period of about two weeks playing the unit five to six hours a day, using a variety of sources, to burn it in. No critical listening was done but a positive impression was surfacing.

Listening impressions

My first evaluation would be to compare the preamp in its bypass mode against a direct feed from my digital source. The Berning OTL power amp is a tube unit with amazing abilities (see my previous review, May 1999). When switching in the preamp I did not expect what I heard. The soundstaging and timbre of instruments as well as voices were extremely--and I do mean extremely--close. The preamp did not introduce any coloration or artifacts altering one’s appreciation of the music. All the clarity was there but something was missing (which is not always bad).

At various listening sessions, my son Marc, a trained musician for both trombone and guitar, (not an audiophile) would join me and add his input. One CD we listened to was Keith Jarrett’s At The Blue Note: Saturday, June 4, 1994, First Set (ECM1577 78118-21577-2). The trio was beautifully recorded and it became evident that what was missing was the air and extension in the high frequency range, which manifested itself on Jack DeJonette’s delicate and varied cymbal work. To paraphrase Marc, it was as if the decay of the cymbals was cut short. In the bypass mode, this was slight but noticeable and to a lesser degree with Keith Jarrett’s piano. The bass resolution, timbre, and resonance of Gary Peacock’s bass playing were right there with no apparent differences in achieving the full body of the instrument.

Through the Adcom, the dynamics of the piano and the full body of the instrument almost matched the direct feed, but that slight loss of full note decay or ambience was just barely noticeable. And I do mean barely. I feel this is still quite an achievement and more an act of omission than addition of coloration or artificiality. Consider also the fact that an additional set of interconnects and connectors are in the chain. This in itself will cause some losses to the sonic protrait.

" …the comparisons were made comparing the Adcom against no preamp. I dare any preamp to fully pass that test without exhibiting some deficiencies."

In the active mode, the sound in general is still very high caliber, but some of the very slight problems evinced in the bypass mode grew more noticeable. The sound took on a slightly darker character, which might work better with other harder-edged electronics that have strident high frequency reproduction problems.

Playing Chesky’s The Ultimate Demonstration Disc (Chesky UD95), these qualities once again manifested themselves. Rebecca Pidgeon’s voice on her rendition of "Spanish Harlem" was beautifully presented through the Adcom and was eminently enjoyable. But when I switched to the direct feed, it became apparent that a small amount of air was missing and through the active mode, a slight softening occurred accompanied by a further loss of decay. Even with these slight differences, the sound was always extremely listenable and musical.

After all, the above comparisons were made comparing the Adcom against no preamp. I dare any preamp to fully pass that test without exhibiting some deficiencies.

In order to be fair, I wanted to compare the Adcom to another preamp with a worthy reputation. I had on hand an Audible Illusions Modulus 3, a well-respected tube preamplifier. I placed the AI 3 in the system. The AI 3 is a value-laden preamp costing about $1000 more than the Adcom, but it includes a phono section. The RCA Living Stereo CD, Stokowski: Rhapsodies (RCA 09026-61503-2) was very instructive in portraying the strengths and weaknesses of each preamplifier. Both gave beautiful performances, but the air and warmth of tubes were clearly evident through the AI 3, with the addition of a little euphony. The Adcom’s bass reproduction again proved to be the superior of the two, a little quicker, cleaner, and more accurate.

That air and decay proved to be a notch more there through the AI 3 but images were a little better focused with the Adcom. Both units provided an enjoyable listening experience with different strengths and weaknesses. The Adcom, having a remote control, something the AI 3 doesn’t have, as well as a single stereo volume control, made life a lot easier than making adjustments through dual mono volume controls of the AI 3.

Phono—No-Go

When discussing my upcoming review with Mark Rooyakers of Adcom, I inquired whether or not Adcom intended to make a phono section, either internal or external, to go along with their preamplifier. Sadly, the answer was no.

I hope they reconsider. Admittedly, the company has made a business decision to focus on home theater as well as digital sources and didn’t see fit to include vinyl as a profitable area. A pity. If their design skill was directed towards a phono section at a price point comparable with their fine preamplifier, it would be a can’t miss opportunity. Vinyl, as we all know, is making a comeback and even with a small market, in this writer’s humble opinion profitability could still be realized.

"How many of us spend time listening to the real thing? I mean acoustic instruments without thousands of watts of amplification. As a reviewer, my reference will and should always be live music…"

My Bottom Line

All in all I must give the Adcom high marks. After all, the idea of paying an exorbitant amount to hear nothing except a volume control is not Adcom’s way. For those of you out there wanting a preamp with a solid footing in the high end, the Adcom GFP-750 gives it to you and still leaves you enough cash to spend on those other necessities of life--like hearing live music.

The Adcom in general showed itself to be a much more than entry level performer, with super bass control and reproduction that was detailed, with excellent imaging and smoothness. At the same time, a good sense of pace and rhythm was evident. The spatial presentation was 3-dimensional and far from the flat, hard, 2-dimensional one that some earlier Adcom offerings produced. Adcom should feel quite good about itself on two fronts: one, for producing a winner at this price level comparable to other preamps at two to three times its price, and two, for making the decision to employ the design skills of Nelson Pass.

I’ve often wondered when I read other reviewer’s work as to what they use as a reference. Often times, in discussions with colleagues, we go on and on talking about this piece of equipment or that speaker with incredible midrange, using all sorts of audiophile lingo to describe what we’ve heard. How many of us spend time listening to the real thing? I mean acoustic instruments without thousands of watts of amplification. As a reviewer, my reference will and should always be live music, not someone’s idea of the ultimate system with all sorts of audiophile values. Keep listening.
 

el_mariachi

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Adcom GFP-750 Line Stage Preamp Redux Stereotimes

Frank J. Alles

2 February 2000



"Suffice it to say that the Adcom throws an expansive 3-dimensional soundstage that is very precise in locating instruments and performers."


Martin Appel originally reviewed the ADCOM GFP-750 line stage preamp here at The Stereo Times in August 1999.

Meanwhile, my own review of the GFP-750 was published in Vol. 5, No. 6 of The Audiophile Voice magazine. This article will serve as an adjunct to both of those reviews. It contains additional information about my listening experience, concerning the use of sound-enhancing audiophile feet and a budget home-brew tweak that will tend to raise some eyebrows…

I will forego the usual description of the unit’s features and its circuit topology. That information can be found in Martin Appel’s review (see above).

Reading through the published specs I was happy to see that the "A" weighted signal to noise ratio was extremely low, greater than 102 dB down, which is about as quiet as it gets in a consumer audio preamp. My highly efficient InnerSound Eros speakers signified their thanks by the lack of audible hiss emanating from the electrostatic elements. The S/N and distortion figures are a bit lower for the balanced circuitry than for the unbalanced, indicating that the unit’s performance is optimized for balanced operation. This was more obvious in looking at the graphs that accompanied my test sample than from the published specs. Both THD and IM distortions are very low in either case.

The output impedance is less than 1200 ohms at the balanced outputs and less than 600 ohms at the unbalanced outputs. This is sufficiently low to ensure negligible high-frequency roll off with long cable runs driving most modern amps. However if you’re using primarily the passive mode, it’s best to keep the interconnects as short as possible.

Set-Up

To put the GFP-750 through its paces I used it in two different systems. I tried both the passive and active modes of operation and I used the unbalanced as well as the balanced inputs and outputs.

My source components were the same for either system. I used the Townshend Audio Mk III Rock turntable with a modified Rega RB-300 tonearm and a Transfiguration low-output MC cartridge. This fed a custom AHT/P phono stage, which I connected, to the "Tuner" input on the Adcom. My digital source was the Parasound C/BD-2000 transport coupled to a Parasound D/AC-2000 processor via a Harmonic Technology digital cable. In this system, the GFP-750 was substituted for an AHT tube line stage using two 5692 tubes. The amplifiers were the Monarchy SM-70s, used as monoblocks to feed the electrostatic panels of my InnerSound Eros speakers. The InnerSound bass amp drove the woofer sections. I used this configuration off and on in conjunction with a Paradigm Reference Servo-15 subwoofer.

In my alternate reference system, the Adcom fed a Sonogy Black Knight amplifier, connected to Eminent Technology LFT-8a speakers. Custom made Walsh-type tweeters were switched in and out with the ETs, so that I could better gauge the Adcom’s high frequency performance.

The Sound

"To the far right and left at the outside edges of the speakers, the harmonious strings of the Pop Arts String Quartet came to life with noteworthy precision. Chris Spedding’s bouzoukia, a long-necked mandolin-like instrument, added its own unique flavor to the sound."

My initial impression of the GFP-750 was that it was a touch bright throughout the treble spectrum. However after a few weeks of break-in, this slight brightness seemed to diminish. Later, when I switched from the WireWorld Equinox III interconnects to Kimber Kable Hero balanced interconnects, the high frequencies abated a bit more to the point where, if anything, the treble spectrum became just slightly reticent (comparatively). This had the effect of showcasing the beauty of the Adcom’s grainless midrange reproduction, while retaining slightly soft detailed and focused highs. Hmmm.

I can recall playing the late Harry Nilsson’s "Remember," (Warner Sunset/Atlantic 83153-2) from the You’ve Got Mail soundtrack album. At that time I was using the Eminent Technology speakers. Harry’s vocal was locked into center stage, a few feet behind the speakers, perfectly focused--I mean rock-solid, without the slightest tendency to wander. To the far right and left at the outside edges of the speakers, the harmonious strings of the Pop Arts String Quartet came to life with noteworthy precision. Chris Spedding’s bouzoukia, a long-necked mandolin-like instrument, added its own unique flavor to the sound.

In fact, a couple of days later, I had a non-audiophile friend over to listen and I played him the same cut. After listening attentively for a short time, he turned to me with a puzzled look on his face and asked where the other (surround) speakers were! I explained that there were none and he looked at me like I was pulling his leg. Suffice it to say that the Adcom throws an expansive 3-dimensional soundstage that is very precise in locating instruments and performers.

Moving the unit to my primary reference system with the InnerSound Eros speakers afforded me an opportunity to play with a suspension system for the Adcom. Originally I set the unit atop a Townshend Seismic Sink which was sitting on my concrete floor. My impression of the sound was quite favorable.

In looking back through my notes I see a recurrent theme. The sound was superbly focused. Lyric comprehension and inner detailing (especially true in balanced) were among the best I had experienced in the system. It appeared that the passive mode of the Adcom held a slight performance edge over its active stage. The soundstage dimensions were very close, but I thought that the bass went a little deeper and that the sound was even more focused and transparent--though not by much.

The only thing I could point to as being slightly off the mark was that the presentation was just a bit dry--devoid of the harmonic lushness that tubes can impart, perhaps related to a slightly recessive lower midrange region. This was true of both passive and active configurations.

The Way It Sits

Just when I was musing something along the lines of: "Excepting the slight dryness, this preamp would be mighty-fine," an idea struck. On a hunch, based on a demonstration I had witnessed during a recent meeting of the NJ Audio Society, I took a common 12.5" × 1.75" butyl bicycle inner tube, pumped just enough air in it for it to take its shape and support the weight of the preamp, and then inserted it between the unit’s chassis and the Seismic Sink. I also put a Shakti Stone on the cover over the power transformer and that seemed to help a bit too--but not nearly as much as the bike tube.

This seemed to allow the active circuitry of the GFP-750 to more closely match its passive prowess. The bass seemed to delve deeper with more impact and this added a bit more space to the soundstage, but more importantly, the piece sounded somehow sweeter and more harmonically engaging--more ah, tube-like.

Going to FOURPLAY’s album of the same title (Warner Bros. 9-26656-2) I was surprised at how dynamic and lifelike the instruments sounded. Playing track 9, "October Morning," the kick drum almost blew me out of my seat toward the finale where the band’s really kickin’ it. I swear I got the same kind of a rush I get when I hear a live band. It was that dynamic and forceful.

My vinyl sounded great too. Playing L’Histoire du Soldat, from Igor Stravinsky Conducts 1961 (Columbia MS 6272), I was very taken with the natural timbre of the violins and the brass. The interplay of the instruments from their respective positions in the soundstage was somehow more involving than I could recall from my past listening sessions. I think that this was due to a combination of factors, such as an improved sense of dynamics, a lower noise floor, low distortion and timbral accuracy.

I also tried using a set of Black Diamond Racing’s Mk4 Pyramid Cones under the preamp, which resulted in a more extended and detailed top end and tighter, but less ample mid-bass reproduction.

On George Gershwin’s Rhapsody in Blue, from Dayful Of Song (Delos DE 3216), the nimble finger stabs of Andrew Litton on the grand piano were clearer, with less homogenization than before. One could easily hear the sharp initial attack of the hammer hitting string, which was impressive in itself, but combined with the full glorious decay of the notes it proved to be very involving. Going to An American in Paris, from the same CD, the cymbals on the left channel were very distinct and airy and reached way back to the rear of the soundstage. This was clearly the best I had ever heard them sound. I was definitely hearing many of the subtle nuances of this recording that I had not detected previously. BDR Mk3 cones were tried as well, but this resulted in a sonic portrait that was more vague (or less precise) and for that reason I preferred the Mk4 cones with this particular piece of gear.

I spoke to DJ Casser, president of Black Diamond Racing to glean some insight as to what was happening. In his opinion, air-bladder suspensions have the effect of rolling off high frequencies and boosting the mid-bass/lower midrange area. My observations would generally support his views, but in my estimation, the alleged high frequency roll-off was more subtle than severe. Casser also feels that some degree of dynamic compression and blurring occurs and I did detect a slight loss in clarity in the midrange and upper frequencies, and perhaps a smidgen of compression there as well. But in the lower frequencies, I felt that the extra mid-bass plump offered by the bike tube suspension might be preferred, by some listeners, to the tighter and more controlled yet leaner sounding presentation offered by the BDR Mk4 cones. This would be especially true if one’s speakers are also bright sounding, because the air-bladder approach tames the high frequency spectrum a bit—in concert with the fuller mid-bass reproduction.

But...

Although I don’t have many nits to pick with the Adcom’s sound, I can find something to criticize about some of its control features. For openers, my InnerSound speakers are very efficient and the Monarchy SM-70 amplifiers have unusually high input sensitivity. What happened, is that turning the GFP-750’s volume control to the 8 o’clock position (practically off) resulted in moderately LOUD listening levels in my room. The passive (no-gain) mode worked a little better--I could get past the 9 o’clock point with that. In most (less sensitive) systems, higher volume settings should be the norm.

Also, I found the unit’s remote to require a bit of practice, dexterity and patience. The rotary volume knob is motor-driven and it doesn’t start turning the moment you press the button, nor does it stop rotating the moment you release it. For me this resulted in a series of up and down adjustments to hit the volume level I was aiming for. As I recall, the Krell KAV-250p with its electronic volume control and sequential LED readout had a greater range of adjustment toward the lower volume settings and was easier to operate with its remote.

Additionally, you can not see the setting of the volume or balance knobs from across the room. There is no mark or indicator light that can be seen from distances of more than a few feet. My solution to that was to cut two small strips of Peter Belt’s ‘phile-foil and stick one to the face of each knob to show the location of the indicator groove. This worked well and who knows, the mystic rainbow foils may have improved the sound a bit as Belt claims.

Further, you have to flip a switch on the face of the preamp to switch between the passive and active circuitry. Since the position of the switch is indicated by a LED on the front panel, it would have been nice to have that capability on the remote control as well.

The Final Analysis…

The renowned design skills of Nelson Pass combined with Adcom’s no-nonsense approach have produced an affordable winner. Despite my nit picking on the ergonomic shortfalls of the GFP-750 I must admit that this is a very exceptional preamplifier. It is solidly built, includes infrared remote control and both passive and active operating modes, not to mention balanced and unbalanced circuitry. For the low price of only $1250, one would expect a preamp offering all these features to be sonically compromised in some way. I’m happy to report that this is NOT the case.

A slightly recessive lower midrange was my only real complaint; and no, it is not as lush sounding as some tube preamps. In my view, experimenting with the bike-tube suspension and the BDR cones helped an already great sounding product to perform even better.

Another point that I should make regarding the use of audiophile feet and suspensions under preamps is that my findings are not particular to the Adcom unit. In fact, I have observed similar sonic improvements to a few other preamplifiers in my audio system, regardless of whether they were solid-state or tube devices. In other words, my comments shouldn’t be construed as being indicative of any design flaw(s) in the Adcom preamp—rather, they should be looked upon as an endorsement for the effectiveness of different feet and suspension systems.

I am quite confident in asserting that the GFP-750 is an outstanding piece of audio gear. If you’re in the market for a line stage preamplifier and you’re thinking, "Perhaps a nice Mark Levinson, or maybe a new Krell..." do yourself a favor and couple the Adcom name to that train of thought.
 
K

krille_krokodille

Guest
Hyggelig å se at flere liker Adcom. Jeg har alltid undret meg over at Rotel har oppnådd den statusen de har, mens Adcom mer eller mindre har blitt oversett med unntak av en sporadisk omtale her og der.

Tilgjengeligheten er vel også en forklaring på hvorfor det ikke selger mer. Når jeg skulle ha meg mulitkanalsanlegg for et par år siden var Adcom et av merkene jeg var seriøst interessert i å sjekke ut med en del pre/power løsning, men kunne ikke finne noen som førte varene i Oslo eller omegn. Endte opp med en integrert fra McIntosh isteden, noe som iogforseg er helt greit, men syns det var litt døvt den gangen at jeg ikke engang fikk sjansen til å sjekke det ut. Tror Adcom kunne vært en ok match med Klipsch. 8)
 

rock

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Eier en GFA 5500 jeg også og er godt fornøyd.

Ett ørlite brum fra trafo kan høres rett ved amp, men høres ikke i lytteposisjon.

Faktisk kunne jeg tenkt meg en til for biamping av tungdrevne høytalere.
 

AndreasKarm

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Hei. Bumper denne tråden litt jeg. Har selv fått meg en ADCOM 5400 effektforsterker, og er fonøyd med denne. Litt egen støy i form av susing i høytalerene. Ikke helt sikker på hva som gjør dette enda.
 

Norlenning

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Hei,vurdere sterkt å handle det Adcom-settet som ligger på Finn. Har egentlig ikke bruk for preampen; GFP-345 men selges kun samlet med GFA-555. Settet har vært til service,loddet over,skiftet noen deler i utgangstrinn++ Er justert DC-offsett og bias også.Dette er gjort hos JFS Sound System,har sett kvitteringa,fikk den på mail.Så et par spørsmål,hvordan spiller så dette,noe å satse på? Hvor varm blir effekten? Dette er jo en Nelson Pass-konstruksjon så den spiller vel bra den dag i dag,eller? mvh Filip
 
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