SKU: 24315073204

Adcom GFA-555ms Stereo Power Amplifier

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Description

Adcom GFA-555ms Stereo Power AmplifierAdcom GFA 555ms Stereo Power Amplifier at Vinyl Sound Toronto Canada The Adcom GFA 555ms is a high current stereo power amplifier built on one of audio's most respected amplifier legacies, redesigned for greater control, lower noise, and a more transparent presentation. Designed for those who demand both authority and composure in a two channel system, the GFA 555ms drives a broad range of loudspeakers, including those with very low impedances and

Adcom GFA-555ms Stereo Power Amplifier at Vinyl Sound Toronto Canada

The Adcom GFA-555ms is a high-current stereo power amplifier built on one of audio's most respected amplifier legacies, redesigned for greater control, lower noise, and a more transparent presentation. Designed for those who demand both authority and composure in a two-channel system, the GFA-555ms drives a broad range of loudspeakers, including those with very low impedances and highly reactive loads, at sustained high-power levels without compression or loss of detail. Available at Vinyl Sound in Toronto, Canada.

Power Output and High-Current Design

The GFA-555ms delivers 125 watts per channel into 8 ohms and 200 watts per channel into 4 ohms, with bridged mono operation providing 400 watts into 8 ohms for high-power single-zone or subwoofer applications. Its high-current circuit topology allows the amplifier to maintain consistent output voltage and current delivery even as speaker impedance drops or the phase angle between voltage and current becomes highly reactive, a requirement for driving electrostatic, planar magnetic, and low-efficiency dynamic loudspeakers to their full potential.

Low Distortion and Circuit Design

Special attention was paid during the GFA-555ms's development to ensuring that distortion remains extremely low under all load conditions, particularly when driving reactive loads in which the phase angles of voltage and current diverge substantially. The result is a wide dynamic range with excellent grip and headroom at all listening levels, with bass that is powerful yet controlled, a midrange that is open and dimensional, and high frequencies that extend cleanly without harshness. Both unbalanced RCA and balanced XLR inputs are provided, and dual voltage compatibility at 120VAC and 230VAC allows worldwide use.

Key Features

  • 125W per channel into 8 ohms / 200W per channel into 4 ohms — high-current output for any speaker load
  • Bridgeable to 400W mono into 8 ohms — for high-power single-zone or subwoofer applications
  • High-current design for demanding, low-impedance, and reactive speaker loads
  • Ultra-low distortion circuitry for greater transparency, resolution, and detail retrieval
  • Balanced XLR and unbalanced RCA inputs for compatibility with any preamplifier
  • Wide dynamic range with excellent grip and headroom at all listening levels
  • Dual voltage compatible — 120VAC and 230VAC / 50-60Hz for worldwide use
  • Damping factor greater than 400 across 20Hz to 20kHz for precise loudspeaker control

Technical Specifications

Specification Value
Output Power — 8 Ohms (Stereo) 125W per channel
Output Power — 4 Ohms (Stereo) 200W per channel
Bridged Mono Power — 8 Ohms 400W
Frequency Response 10Hz to 20kHz, +0 / -0.25dB (1W into 8 ohms)
Power Bandwidth (-3dB) 10Hz to 100kHz
Input Impedance 100,000 ohms
Input Sensitivity 1.38V rms (125W into 8 ohms) / 123mV rms (1W into 8 ohms)
Damping Factor Greater than 400 (20Hz to 20kHz)
Inputs Balanced XLR; Unbalanced RCA
Power Supply 120VAC and 230VAC / 50-60Hz
Power Consumption — Quiescent 48VA
Power Consumption — 125W into 8 ohms 420VA
Power Consumption — 200W into 4 ohms 730VA
Power Consumption — 400W bridged 800VA
Maximum Dimensions (H x W x D) 6" x 17" x 12.5" (152 x 432 x 318 mm)
Weight 28.6 lbs. (13 kg)
Shipping Weight 33 lbs. (15 kg)

Frequently Asked Questions

What is the Adcom GFA-555ms?

The Adcom GFA-555ms is a stereo power amplifier rated at 125 watts per channel into 8 ohms and 200 watts per channel into 4 ohms, with bridged mono operation providing 400 watts into 8 ohms. It accepts both balanced XLR and unbalanced RCA inputs and is designed to drive a broad range of loudspeakers, including those with very low impedances and highly reactive loads. It is available at Vinyl Sound in Toronto, Canada.

What is the correct power output of the Adcom GFA-555ms?

The Adcom GFA-555ms is rated at 125 watts per channel into 8 ohms and 200 watts per channel into 4 ohms in stereo operation. In bridged mono mode, the amplifier delivers 400 watts into 8 ohms. These figures are confirmed by Adcom's official technical documentation and power consumption data: the amplifier draws 420VA at 125W into 8 ohms, 730VA at 200W into 4 ohms, and 800VA in bridged 400W mode.

Can the Adcom GFA-555ms be bridged to mono?

Yes. The GFA-555ms is bridgeable to mono operation, delivering 400 watts into 8 ohms in this configuration. Bridged mono operation is useful for driving a single high-power loudspeaker, powering a subwoofer, or building a biamplified system using two GFA-555ms units. Refer to the user manual for correct bridging connection procedure and input level matching.

Does the Adcom GFA-555ms accept balanced inputs?

Yes. The GFA-555ms accepts both balanced XLR and unbalanced RCA inputs, making it compatible with any preamplifier regardless of output configuration. Balanced connection is recommended in installations where cable runs are long or where the preamplifier provides lower noise through its balanced output stage.

Can the Adcom GFA-555ms drive low-impedance or reactive speakers?

Yes. The GFA-555ms was specifically designed to drive loudspeakers with very low impedances and highly reactive loads, where the phase angle between voltage and current is substantially different. Its high-current output stage maintains consistent output voltage and control even as impedance drops toward 4 ohms, making it suitable for electrostatic, planar magnetic, and other demanding speaker designs that require both high current and low distortion at reactive loads.

Can I turn the Adcom GFA-555ms off daily?

Yes. The GFA-555ms can be powered off and on at any frequency without harm to the amplifier. There is no mandatory warm-up period required before use, and daily power cycling is fully supported. For long-term listening sessions, allowing the amplifier to reach operating temperature before critical listening is recommended, as with most high-current amplifiers.

Where can I buy the Adcom GFA-555ms in Canada?

The Adcom GFA-555ms is available at Vinyl Sound, an authorized Adcom dealer in Toronto, Canada. Browse the full power amplifier collection at Vinyl Sound or contact our team for system matching guidance and in-store listening appointments.

Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
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Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
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SKU: 24315073204

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4.6 ★★★★★
Based on 15 reviews
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TeeB
Houston, US
★★★★★ 4
Baking soda never works out well
Flavor Name: 1. Sensitive Mint, Size: 4 Ounce (Pack of 1)
I don't know why I decided to chance it but it didn't take long for my teeth to start aching. I realized baking soda might be the cause of my toothache issues when I switched between a few and realized the baking soda ones were accompanied by aching. I think I went with this because it claims to be for sensitivity and I thought the nhap would help whatever the baking soda affected but not the case. If you have tooth ache, consider it might actually be the toothpaste and don't just go looking for "sensitive" labels. This might work in combination with other toothpaste. I.e. not multiple times a day but once a day and a different one for other brushing. I've noticed not being as able to tell when it's been a while since I brushed. This was the main change so it might be effective at cleaning. The tube is metal and hard to press but the paste consistency is less firm than others so it works out. It didn't take much to get the paste out. It gives a light foam. The taste is not sweet. It's tolerable but borders on bad.
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Reviewed in the United States on May 16, 2026
P
Verified Purchase
Pamela K.
Cuba, US
★★★★★ 5
Mr. Hancock Intrigues Once Again!
Format: Paperback
Mr. Hancock is a fabulous writer/author that I have had the pleasure of reading for many years now! Be it his non-fiction books or like this book, historical-based fiction, he always leaves you thinking and contemplating life and where we come from and how we fit in on this planet and in the this universe! This book had me right from the very first paragraph, I knew it wouldn't take me long to finish it, which it didn't...of course, leaving me hungry for the next book in this trilogy! I have always been intrigued and fascinated with the paranormal and was pleasantly surprised to find it fitting in perfectly and so naturally in this tale. What I would like to thank Mr. Hancock for is his ability to describe scenes, people, actions, interactions, rituals, etc. in such clear, concise and extreme detail using many rarely-used (anymore in this day and age) adjectives making every page come alive for me! I was so enthralled with his writing in this book that I felt like I was watching a movie...very vivid! I almost felt as if I was in that world and that time while reading this fabulous book! I was relating part of the book to my husband one day and actually started out a sentence by saying to him..."she told me", my gosh...I caught myself in mid-sentence...what was I saying?!?! That's how captivating this book and the story was to me...I WAS there! Thank you once again Mr. Hancock for all you do and all your studies...you are always thought-provoking in all you bring to us...your readers, listeners and followers! Your work and travels are much appreciated and certainly needed for the awakening of mankind...please don't quit sharing with us anytime soon!
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Reviewed in the United States on December 30, 2013
Z
Verified Purchase
Zen
Port Orchard, US
★★★★★ 5
Gripping & Enthralling
Format: Kindle
Get this book, and jump on the thrill ride. Savage war dogs in full plate armor, human sacrifice on an industrial scale, cannons firing grapeshot point blank into charging hordes of unsuspecting warriors, intense duels within the Spanish and Native groups... this book is graphic and hard to put down. Just be aware that as pt. 1 of a trilogy, it WILL leave you hanging, and wanting more. I suppose that is just the nature of the beast... and we must patiently await pt. 2. Far more historical than a fantasy, but more fantastic than a history... this novel falls almost perfectly into that middle ground, sweet spot. It is extremely well researched, with few liberties taken, so you really feel like you are observing things that could very well have transpired. However, it goes beyond a flat, boring recreation of the extant journals and histories of the conquest of New Spain, and introduces vivid characters, visions, dreams, and witchcraft to bring the tale to life. Historians might appreciate the graphic and accurate depictions of battles and intrigue, and fantasy buffs might dig the subplots involving mushroom visions, metaphysical "gods," and a young witch in Tenochtitlan (being stuff that couldn't be derived from source material and must come from the prolific mind of Mr. Hancock). Some might prefer these things stay separate and "never the twain shall meet," but there are books enough for purists out there. What Graham Hancock has done is present a page-turning story which fully draws the reader into a world which is a fairly good estimation of that world that existed when Cortez & his worldview met the Mexica & the Maya... and supplanted theirs. Given that most everyone on Earth already knows this story--and how it ends--it was IMHO a very wise decision for the author to add drama and tension by fleshing this out into a "fictional" novel. I would say the breakdown is 1/3rd non-fiction, 1/3rd logical extrapolations from what we know, and 1/3rd pure fantasy. I honestly can't say which part I prefer. Just do yourself a favor and read this.
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Reviewed in the United States on March 6, 2014
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Verified Purchase
Gsorme
Lexington, US
★★★★★ 4
Very impressive
Format: Paperback
I approached this one with caution and came away impressed, glad to have read it, and looking forward to the sequel. It's a fascinating and occasionally breathtaking novel. Hancock has a knack for writing compelling fiction. It's funny: often when people write reviews of his non-fiction books they'll say they read like good thrillers. This one is compelling as fiction but also had enough historical detail to keep me interested beyond the plot and to make me think about the Spanish conquest of Mexico in a different light. I was very grateful for the endnote by Hancock giving an overview of the types of "fictional" elements he introduced into the book (such as combining a couple of historical events into a single event in order to keep the appropriate pace for a novel) because this clarified things and allowed me to come away from the book with a deeper overall understanding of that period in history--which Hancock really does bring alive. Granted, this is Hancock's take on it--even non-fiction historical books have an author's "take" on events--but it seems to be a very well-informed take. Mixed in are supernatural elements and hints of the non-orthodox elements of history that Hancock is known for investigating in his non-fiction. For me, the blend was good. It's not a perfect novel. For example, the style of switching perspective from character to character from short chapter to short chapter was a bit jarring at first; I found it unnecessary and it ended up taking me out of the narrative for a few short moments. (Perhaps this was done to "hit the ground running" and introduce the large cast of characters and plot threads quickly; still, for me it was too much at first.) However, this stylistic approach shifts as the book goes on; the sequences become longer and occasionally blend together. Ultimately this worked, especially given the large cast and numerous plots the book juggles. If it hadn't worked, I would've put the book down; as it was, I did end up turning pages (on my Kindle) rather quickly and not getting bored. There is an immense amount of blood and gore. Very graphic. I won't pass judgment on it. It did give a pretty visceral impression of the whole human sacrifice element of the Mexica and other peoples, and of what battle was probably like at the time. Character-wise the book is diverse and interesting. There are a few semi-saccharine moments and lightly-drawn characters, but in general all are developed to help drive the story forward and to offer possible insights into their historical counterparts. Ultimately I guess we could call this a "sprawling epic," one that wraps up the first part of its story at the end but leaves a huge section to be developed in the next installment. I hope we don't have to wait too long. As I said at the beginning of this review, I didn't really know what to expect from this book but it really was quite fluid, exciting, surprising, and enlightening. Very impressive.
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Reviewed in the United States on August 3, 2013
J
Verified Purchase
Jason M.
Chelsea, US
★★★★★ 5
Graham Hancock has woven a compelling tale of historical fiction that does not feel like history or fiction
Format: Kindle
This has been a relentless and compelling read from page one and comes from one of the most innovative thinkers of our time. Graham Hancock has woven a compelling tale of historical fiction that does not feel like history or fiction. Its characters are real and relatable for their humanity, their virtues, their vices, and their corruption. I especially enjoy his characterization of Montezuma and Cortes, two iconic characters from the pages of history who become living, breathing, understandable humans for the readers. The supernatural elements of the story are undeniably present, but they are handled in a way that blends into the tapestry of the story rather than as silly plot devices. Also, those same supernatural elements help throw into sharper relief the unimaginable brutality and horror of which both of these great civilizations on a collision course were capable. The violence is brutal and horrific, no doubt, but for me the gentleness and humanity of the author in describing it softens its impact. Also, even though the book ventures into some very dark, cruel times in human history, the goodness and humanity of many of the characters prevents the story from becoming a tale of despair or hopelessness. I am a fan of Graham Hancock's non-fiction work, and this book firmly cements him as a fiction author I will be revisiting. Superb!
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Reviewed in the United States on April 28, 2015

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