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Adcom GFA-555

Stereo Power Amplifier

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Adcom GFA-555

Description

The Adcom GFA-555 represents the most advanced thinking in audio amplifier design. At 200 watts per channel, it offers exceptional value and superior performance at a reasonable price.

Specifications

  • Power output: 200 watts per channel into 8Ω (stereo), 600W into 8Ω (mono)

    Frequency response: 10Hz to 20kHz

    Total harmonic distortion: 0.09%

    Damping factor: 800

    Gain: 27 dB

    Input sensitivity: 1.75V

    Signal to noise ratio: 110dB

    Semiconductors: 42 x transistors, 2 x zener diodes, 13 x diodes, 2 x IC, 2 x diode bridges

    Dimensions: 185 x 432 x 310mm

    Weight: 16kg

  • Power output: 200 watts per channel into 8Ω (stereo), 600W into 8Ω (mono)

    Frequency response: 10Hz to 20kHz

    Total harmonic distortion: 0.04%

    Damping factor: 800

    Gain: 27 dB

    Input sensitivity: 1.75V

    Signal to noise ratio: 110dB

    Semiconductors: 42 x transistors, 2 x zener diodes, 13 x diodes, 2 x IC, 2 x diode bridges

    Dimensions: 185 x 432 x 310mm

    Weight: 16kg

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Reviews

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rating
Reviewed Apr 11th, 2017 by wdpayne

Great sound, ridiculously powerful.

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Reviewed Sep 27th, 2016 by guest

While some profess to the 555's reliability, I have found that certain flaws in design can cause failures.
Namely that the driver transistors are pushed to their limits, and not on heatsinks, eventually causing failures.
This situation seems to be mostly in the 555's that do not have cooling fans installed.

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Reviewed Sep 22nd, 2016 by APAPAS

The Adcom GFA-555 represents the most advanced thinking in audio amplifier design. At 200 watts per channel, it offers exceptional value with serious HI-FI sound.

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Reviewed Jan 04th, 2015 by firthoffifth2523

Bought this gem new in late 85 right here in n.j An early one with square rack handles. this has been one of the finest sounding, most reliable purchases i have made in audio, still working fine never any issues!

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Reviewed Jan 02nd, 2015 by saniewski

Picked this amp for 200 dollars, dirty but after clean up it is perfect, driving a set of Polk SDA's with it, other amps clip when trying to drive the 3 ohm load.

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Reviewed Aug 26th, 2014 by JohnnyTelecaster

I have a never used GFA-555 in the box, only removed to inspect it and see if it powered up -- it did. I don't know whether I should sell it or use it. I am in limbo. But I'm also in no hurry either way.

This Nelson Pass design broke ground when it came out, getting rave reviews and providing tank-like reliability at a decent price. That these are much in demand after so much time is strong testament to their value and durability.

I auditioned one of these long before I owned one. They were used as a standard power source in a HiFi store, where they easily pushed Dalquists, a range of ADS speakers and Bose 901s. The sound was always great switching to and from any of the speakers. So my high rating is based upon actual listening back in the day, despite the fact mine is in its box and never been used.

I also have a GFA-545 II and a GFA-585, both that I truly love to run my Infinity Quantum 3 and Quantum 2 speakers, respectively, and Adcom preamps. They do the job rather well and match nicely. The Proton D1200/P100 I use on another Quantum 3 pair is a bit better than the 545 II, but not by much.

This is a 1960s-1970s American muscle car among amplifiers. Yes, there are purists and discriminating people of means who want a Ferrari or Lamborghini for an amplifier -- who wouldn't? They will pay a high premium for their choices. But mere mortals like me - who don't print money in their basement - find Adcom, NAD, Proton to be quite good stuff for their costs.

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Reviewed Jun 19th, 2014 by Route 66

I've been using mine for over 25 years with no problems at all. I shorted it out once by touching two speaker wires together while they were connected to the amp. I thought I'd have to pay through the nose to get it repaired, but all I had to do was pop the top off and replace one of the internal fuses.

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Reviewed Apr 16th, 2014 by dbear44

Had one when they first came out and recently picked up another for a backup amp. A real powerhouse for the money. Simple, reliable circuit. Sounds tight and dynamic but not very fleshed out. Can get a little hard sounding but to get better you'll probably have to spend more. Don't expect it to replace your reference amp but for less demanding apps. it fills the bill.

Beware-if the clipping lights come on you probably just blew your tweeters!

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Reviewed Mar 21st, 2014 by calvinbigbucks

All analog and performs better than amps costing much more than you will beleive...A lease breaker4 sure

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Reviewed Jul 31st, 2013 by Jazzyguy

In 30 years I have had no trouble at all.I blew a transistor but it was my own fault.I have a pair of them Bridged and they are on most of the time.

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Reviewed Jul 30th, 2013 by Andre GIMENEZ

Powerfull, smooth, perfect with a sweet price !

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Reviewed Jul 13th, 2013 by Mikey210

A no-nonsense unit which has pushed a reasonably good signal at acceptable current into a pair of big electrostatic speakers (Acoustat2+2).

 

Comments

re: GFA-555

sweet piece for pennies

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