GamuT Di150 LE integrated amplifier

As Stereophile's true cub reporter—sorry, Herb Reichert, you're senior staff!—I work in the domestic fields of the high-end audio landscape. Meanwhile, my fellow Stereophile correspondents trot the globe, attending international audio shows, experiencing all the sweet spots offered by such far-flung locales as Munich, Montreal, and Northamptonshire, UK. Am I complaining? Not! But when an audio show of merit invades New York City, still the capital of the civilized world, you can believe I'm there on opening day, pen and pad in hand. The first rooms on my must-visit list usually include Audio Note UK, DeVore Fidelity, MBL—and, when the gear is warm and the good vibes flowing, as they usually are, Wes Bender Studio NYC.

Consider the typical high-end presentation at an audio show: machines clad in cool-to-the-touch brushed aluminum and other scientifically validated materials, voluptuous women beckoning you into suites hosted by men in suits, and sound and music that may be good, bad, or indifferent.

Wes Bender Studio NYC? Totally different experience. At the 2016 New York Audio Show, Bender provided booze, fun, and high-octane sounds. When I walked into Suite 814 of the Park Lane Hotel, Bender and GamuT's US distributor, Michael Vamos, were partying with the Rolling Stones, Santana's Abraxas (on Mobile Fidelity 45rpm LPs), Blood, Sweat & Tears, and singer Vanessa Fernandez's album of Led Zeppelin covers, When the Levee Breaks. A washtub overflowed with iced Hacker-Pschorr Weisse NaturtrÅb (a naturally cloudy hefeweizen, or yeasted wheat beer). I couldn't hear everything Bender was saying, but clearly audible were "crazy," "damned shame," and "buy the ticket, man!" Vamos, who resembles the 1970s actor Jan-Michael Vincent, pointed at the tub o' beer. In one corner of the suite, AudioStream.com's Michael Lavorgna, the ever-sly Jana Dagdagan (Stereophile's editorial coordinator), and AudioQuest communications VP (and former Stereophile staffer) Stephen Mejias smiled at me like characters from La Dolce Vita. ZZ Top's "Jesus Just Left Chicago" blasted the boogie. The sound of Bender's all-Gamut system—the center of this surreal, volume-pounding scene—was truly fascinating.

Along the room's long wall, GamuT's RS3i stand-mounted speakers ($20,990/pair) were getting their mojo workin' via the company's D3i dual-mono line-stage preamplifier ($8380), D200i dual-mono stereo amplifier ($13,990), and CD3 CD player ($7990), all connected via GamuT Reference interconnects, speaker cables, and power cords. Analog goodness was provided by a Pear Audio Blue Kid Thomas turntable with Cornet 2 tonearm ($7995), Pear Audio Blue Classic phono stage ($1995), Pear Audio external power supply ($1995), and a Transfiguration Proteus cartridge ($5,999). This mighty system provided gusto and glory, music bouncing off the walls with true force, unerring musicality, and heartfelt fun. I wanted more!

But I was on a quest for the absolute integrated amp. I asked Vamos if GamuT offered a high-powered model of such design. They do: the Di150 LE dual-mono integrated amplifier.

Design
GamuT's Di150 LE (for Limited Edition) is a Danish-built, 59.4-lb, aluminum-encased powerhouse that outputs 180Wpc into 8 ohms, 360Wpc into 4 ohms, or an-ear challenging 700Wpc into 2 ohms. The Di150 boasts a frequency response of 10Hz–50kHz, ±0.1dB—none too shabby! At its center is a circuit topology introduced by GamuT's founder and designer, Ole Lund Christensen.

In the early 1980s, GamuT made amplifiers for Denmark's professional recording studios. Forgoing the usual banks of transistors, which he believed only smeared the music, Christensen instead sourced massive negative-positive-negative MOSFET transistors used in industrial welding, using only one or two per rail. Eventually, GamuT sold these N-channel MOSFET amps to high-end devotees across Europe.

Michael Vamos led me deeper down the rabbit hole of N-channel MOSFET design: "Many amps use up to 48 transistors per channel, which creates a lot of sonic and signal compromises," Vamos claimed. "Whenever you use more than one transistor, they're never matched exactly, and they will sound different. When you listen, especially in the midrange, you will get a phase issue. The transistors aren't reproducing exactly the same in order to get all the power; they're slightly different. That will muddy the signal. But if only one transistor is reproducing the sound, then it will only reproduce the signal.

417gamut.bac.jpg

"The GamuT MOSFET is ten times the volume of the biggest hi-fi transistor," he continued. "And they're both NPNs, which eliminates the difference of having a positive and a negative transistor. Each NPN is technically and sonically the same. That eliminates crossover distortion." (footnote 1)

Benno Meldgaard, GamuT's chief of design, wrote in an e-mail that "GamuT's single MOSFET is class-A/B design, biased to 14 watts class-A. This is to run the transistors at an optimum temperature that results in the best sound. GamuT also includes NPN bipolar transistors capable of putting out 25 watts of power which drive the huge [N-channel] MOSFET output transistors. And the two [500VA] toroidal transformers contribute greatly to the solid sound quality. [In] the GamuT design, both the negative and the positive rail have . . . MOSFETs that sound exactly [the] same, which results in a shorter pathway, with less components in the pathway, which gives a very low distortion of even-order harmonics."

Description and Setup
What couldn't be easily driven was my body as, one stairstep at a time, I upended and turned over—and over and over—the Di150's large wooden crate, until I reached my seventh-floor Manhattan crib. Said crate rolled into said crib, I then had trouble releasing the secret panel that would reveal precisely how to uncrate the Di150 LE. After much cursing and sweating on my part, the amplifier sprouted from its sarcophagus of roughhewn wood.

I removed the eight stainless-steel screws that affix the Di150 LE's heavy top plate to its enclosure and peered into its inner workings. Dominating the interior are two massive, Danish-made Noratel toroidal transformers, positioned next to four oversized RIFA capacitors. A handful of smaller Vishay capacitors populate two horizontal circuit boards. The long control rod of an Alps potentiometer ("a special low-resistance version, creating 10dB better signal-to-noise ratio," per Vamos) visually halves the amp's interior. Unusual for any amplifier, no Zobel network is used on the Di150's speaker outputs to keep the amp stable.

417gamut.2.jpg

Substantial but svelte, heavy-duty but manageable, the Di150 LE slid, with effort, into my Salamander rack, looking quite out of place below my green Shindo Laboratory preamp and power amp. GamuT recommends 100 hours of break-in, which I accomplished via Apple iTunes Shuffle. Thereafter, I left the Di150 powered on 24/7.

The Di150 LE may be a hulking machine, but I believe it would find its place in any décor. Its silver faceplate is offset by a black case—both formal and flashy—and dominated by a large volume-control knob at the center of its display. Flanking the display are two columns of four silver pushbuttons each: on the left, Balance 1, Balance 2, CD, and Dim; on the right, Tuner, Tape, HTH, and Mute. (A tiny toggle switch on the amplifier's rear panel enables HTH—presumably for Home Theater—mode, in which the Di150's preamplifier section is bypassed so that the user can insert a processor—or, according to Vamos, another preamp, the Di150 then functioning as only a power amp.) These controls, including Volume, are duplicated on a remote-control handset (included). Though rather cheap-looking, the remote handled all functions without a hitch—and unlike some fancier remotes, its batteries never fell out.



Footnote 1: A quasi-complementary output stage doesn't intrinsically eliminate crossover distortion, which requires the correct application of output-stage bias current. But the fact that the two N-channel transistors are by definition perfectly matched does, I believe, confer better open-loop linearity.–John Atkinson
COMPANY INFO
GamuT Audio
US distributor: GamuT Inc. (Audio Skies)
Los Angeles, CA
(888) 252-2499
ARTICLE CONTENTS

COMMENTS
mrkaic's picture

You get MUCH better performance from the Benchmark ABH2 for a quarter of the price of this thing. In my opinion, this GamuT amplifier is worth between $370 and $415.

Dcode's picture

Don't say it's too expensive. Just be honest. Say you can't afford it. It makes more sense.

mrkaic's picture

Dear Sir, what makes you so certain that I cannot afford it? Have you used some techniques worthy of Sherlock Holmes to deduce my credit worthiness? :))

Or are you just trying to deflect the attention from the undisputed fact that many much cheaper NAD amplifiers will perform just as well as the Gamut?

Dcode's picture

It's true though, isn't it?

vilasound's picture

You may be right If you want to purchase an amplifier for measurements only. If you know of an amplifier that plays music like the GamuT please (PLEASE!!) tell me which one costs only 400$!!! I want at least 2 of them.

mrkaic's picture

Buy a NAD 3020D. Seriously.

If you need any further advice, feel free to ask. :))

vilasound's picture

I own an HIFI shop. I have had a NAD D3020 on demo, and many other amps. If you are joking about the NAD D3020 being comparable with the GamuT then great. I'm with ya. If you are being serious though than it is actually impossible to continue any further discussion. I'm sorry, I don't even know where to begin.

mrkaic's picture

...is a blind test. Do you have the courage/energy to compare both amps in a blind test? Only if you can tell them apart, can you make claims about the Gamut being better.

mrkaic's picture

I am happy to hear that you own a HiFi store. It must be good to be in business for yourself.

You are also in an ideal position to compare both amps, measure them thoroughly and pronounce the winner.

Tansparency = low THD. And the superb timing of the Gamut (due to a single MOSFET per phase) is something that is quite easy to check with an oscilloscope. I am happy that you have made such measurable claims.

I am also quite certain that your store has a lot of electronic equipment to measure both amplifiers. You can easily prove your claims by doing and publishing some measurements.

vilasound's picture

1) Doing a blind test between the NAD D3020 and any GamuT would be like testing a Renault Clio vs a BMW M6. Would you HAVE to be blind to believe in the diferences? Wouldn't they be too damn obvious? I'm not even exagerating in the comparison for the sake of argument.

2) I don't like to discuss measurements because they do not actually tell you anything about how the equipment actually plays. HOWEVER, you keep telling everyone how the Gamut is comparable to a NAD in measurements when it is not the case at all. The Gamut can output 300W at 4ohm with 0.006% THD. The D3020 will go as far a puny 40W with 0.009% THD. They are worlds apart (there are plenty more data to discuss but the point is made).
Are you on some sort of mission against Gamut or just trolling around?
If you actually only need 1W then yeah, the Gamut isn't for you. In that case I would recommend you look into tube single ended amplifiers with lots of THD that sound great.

mrkaic's picture

...so the extra power of the Gamut is not very important. If you don't want to blow your ears out or if you don't have a very big listening room, you are using about 1 Watt of power anyway. (And if you want 300W, you can get cheaper and equally good amplifiers as the Gamut.)

I am not on mission against Gamut or anyone else. But as a trained physicist, I am horrified by the anti-science bias, prevalent in the audio community. And I am not alone, the world has awakened and has unmasked audiophiles with gusto: https://rationalwiki.org/wiki/Audio_woo

vilasound's picture

If you really think that you can compare amplifiers at 1W spec then you are even more out of your depth than you can possibly imagine.
I strongly advise you to forget measurements for a bit, get off your seat and go and have a listen to audio gear. It's that easy. Sure, bring along a blindfold if you doubt yourself that much. No one will stop you from doing blindfolded tests. The fact of the matter is that you lack a tremendous amount of empirical knowledge about these things, that is very clear once you claim a NAD D3020 is comparable to a GamuT Di150.
Don't worry about me! I have a PhD with published peer-reviewed articles. I know a thing or two about science vs mambo-jambo. You are reading too much into graphs that have no demonstrated correlation with psicho-accoustic pleasure. A true scientist questions, experiments and, while being skeptic, should keep an open mind and consider all possible explantions for the observations of his experiments. You are merely extrapolating knowledge you don't master.
This has been fun but it's enough. I will stop arguing with you and instead listen to music in very expensive unmeasured gear that makes me feel like I have just been teleported to a live private concert.
Nothing against the NAD D3020, I have sold a few - it is a decent bit of kit for the money, but it will never convey that feeling of being there. Unfortunately.

vilasound's picture

If you refuse to go listen to audio gear, or have really bad earing, I would recommend you read some Nelson Pass articles. Yes, he sells amplifiers but he is highly regarded in the DYI community even amoung the naysayers; and he has been around forever.
His website (http://www.firstwatt.com) has plenty of articles about amplification theory (in his view) and maybe you can start with http://www.firstwatt.com/pdf/art_se_classa.pdf

mrkaic's picture

Don't get me wrong, I don't refuse to listen. But when I listen, I don't want to be swayed by placebo factors. [As regards placebo, you may wish to read Dr. Sean Olive --http://seanolive.blogspot.com --- a guy who has done more audio research than 99.99% of audiophiles and audio experts.] BTW, I have a decent hearing for my age. If one day my path leads me by your HiFi store, I will be delighted to audition some gear.

I have read some of Nelson Pass articles. Let me tell you, why I am not exactly impressed with him -- he talks a lot, but shows few equations pertinent to his circuits. When I want to understand a circuit, I model it in SPICE (or LTSPICE) and get a clear picture of its workings. Professional electrical engineers do the same. Set up the the equations and solve them. Without quantitative analysis we can talk for days about our impressions -- kind of what you and I have been doing. :)

You are a very intelligent man and this has been fun. Thank you for a nice and cultured exchange.

Best wishes,

MM

vilasound's picture

Placebos produce an effect, that has been well established long ago, and must be ruled out whenever possible. My moto though is that if you need to rule it out and do blindfolded testing to be sure then the difference is not that big and you should just pick the cheapest.
The other thing most people don't know about the placebo effect is that most of the time people are biased AGAINST 'believing'. That is prevalent in a hifi shop. People with limited budgets who WANT to believe that the cheapest option is more than enough for their needs and then find out they 'need' to spend more.
And I can't count how many times I have had professional electrical, computing, mechanical, electronic engineers absolutely dismiss upgrading powercords or USB cables UNTIL they listen. The powercord especially is the easiest to demonstrate and to this day no one has ever said they couldn't hear a difference. A fantastic thing happens once these professionals experience the upgrade: they come up with possible theories to explain the phenomon. I have learned a lot from these people just moments after they absolutely denied any chance of a powercord making a difference.
And yes, plenty of audiophiles dismiss certain equipment and certain brands because they are not pricey enough or have a certain prestige, but to them and to the skeptics, the solution should always be listening (blindfolded if you have to).

OK. Fair enough about Nelson Pass. With that level of expertise you do need more info.

mrkaic's picture

By all means, wish you much enjoyment of your gear and music.

Before you go, one final question. Congrats on your PhD and peer-reviewed articles. What is your area of research?

vilasound's picture

That was long ago. I am full time hifi. I have a degree in biochemistry (with lots of physics, physical chemisty and even a 6-month module on basic electronics - crazy). The articles during my PhD and onwards were in the field pathology/chronic infections (herpesviruses and mycobacteria).

darcman's picture

Trolls are everywhere, why even bother with a stupid comment you just embarrass yourself. If you looking in this price range, the Gamut Di150LE should be on every ones short list....looks great!!!

mrkaic's picture

A lot of mediocre (and sometimes even substandard) audio equipment these days is terribly overpriced. It takes a suspension of critical thinking (i.e. subjectivism) to justify purchases of such stuff.

Sad, but true.

darcman's picture

The comment was still stupid. The price of the Gamut is right in line with the top offerings from others. It would be nice if it was $5k cheaper but it isn't. If they were able to sell it for $415 they would put EVERYONE out of business...True Story LOL

mrkaic's picture

...is the price of this stuff and comments that defend such outrageous prices by claiming that this is a "top offering". By what measure is this top level?

You can get an amplifier that will have comparable measured characteristics for a fraction of the price of this one -- NAD amplifiers come to mind. Is NAD top level too?

johnnythunder's picture

Look, I can't tell you what you can and can't afford as far as listening. I love reading reviews of the most expensive and the best valued components in an attempt to understand the myriad of possibilities available to me as a listening experience. I read car magazines for their reviews of Bentleys and Teslas even though I drive a 1999 car with over 200k miles on it. Ditto with cooking and wine publications. I don't get angry that a certain Barolo costs over $100 and don't demand a blind comparison with lesser expensive wines. If one wants to go through life ANGRY that certain products are beyond their reach and shitting on the joy of others go for it. I think you're missing the point that these magazines are here to NOT be Consumer Reports. They exist to tantalize and offer some sort of aspirational guide to what is out there. Yes our hobby is more expensive than it used to be but I get enjoyment from my 10k system that has been assembled over the years from reading about equipment that the reviewer has illuminated as having appeal to me. One description of a midrange as "thin" or a "hyper detailed tweeter" will send me scurrying to the warmth of my Luxman amp and Jean Marie Reynaud speakers. But I don't get angry that others like that sound. So enjoy your NAD. There's nothing wrong with it. But don't demean the GAMUT because its a luxury product.

mrkaic's picture

Dear Sir:

First, let's get one thing out of the way quickly -- I am not angry at or envious of people who buy overpriced amplifiers. I do pity them though, because I see many of them as deniers of engineering and scientific facts. Instead of buying their overpriced trinkets, "audiophiles" could more usefully spend their money on a few courses in electrical engineering to help them actually understand their cherished hobby.

Second, judged by your frequent use of capital letters, you just might be the angry one. :)

Finally, your conclusion that I have a NAD is wrong. But I might remedy that, they make fantastic products.

johnnythunder's picture

Your term "overpriced trinkets" immediately establishes your pejorative tone with regard to expensive audio components or tweaks or whatever. Your statement/opinion, "In my opinion, this GamuT amplifier is worth between $370 and $415." is pretty ludicrous. I don't pity deniers of engineering and scientific facts when it comes to certain aspects of audio engineering. This isn't global warming. I read for years in Consumer Reports that all CD players sounded the same. I don't "buy" the claims of many tweaks but is it false advertising? Maybe. I really don't care. People can spend money on what they want to. I'm a little disappointed that a well written review of a well manufactured product is tossed away by an insipid argument and it's an argument that has a "rain on my parade" tone. I would enjoy whatever lower priced component you have and allow any future purchasers of Gamut products to enjoy their purchases based on Ken's review.

mrkaic's picture

I have little patience for science deniers. While audio is not global warming, the underlying mechanism of denial is quite similar.

RaimondAudio's picture

Sorry...you can comment about the technical stuff, but you can not comment about the price. Why ? Because we are not in a comunist economy. We are in a free economy. That it is the most important thing. Do not like the price ? Ok, do not buy it, but please, do not atack the free economy.

What about 2%-THD of the tubes amps ? What we will do with them ? What it is the right prices for them ? 10$ ?

mrkaic's picture

Are you trying to censor me? I am allowed to comment on anything I want.

I am glad you talk about free markets. In a competitive market the price is equal to the marginal cost. What is the marginal cost of this amplifier? 2 mosfets for $2 each, a few other BJTs for $10 combined, a few wires, worth less than $1, some capacitors, generously priced at $50, and the enclosure for $40. Am I missing any parts? Maybe a few diodes to bias the transistors. Add some solder, equipment depreciation, and a few hours labor for assembly and the sum is still less than my suggested price of $375. But let's say that with shipping and handling you can get to $375. If they sell if for $415, they will make 10% profit, which is pretty decent for an amplifier with not exactly ground breaking measured performance.

RaimondAudio's picture

:-) Noo. I do not want and I can not censored you. I just spoken about free markets. The profit could be any percent: 1%, 10%, 10.000%. That is tha life in a free markets. Best regards.

Dcode's picture

You obviously have not gone into business for yourself and looked at all the costs involved in owning and operating a company and what real overhead is. Workman's comp, insurances, marketing, legal--let alone what it takes to test and bring a product to market. Testing, re-testing, trail, error, sourcing parts, training staff, fielding lawsuits from freeloading employees looking for a quick buck, getting staff to actually work and care, quality checks on outside parts provided... If you went to a factory and sat down with the owner of a HiFi company and saw how many hours it takes and total devotion with no guarantee of retirement or financial security, you'd shut right up and go back to your cubicle and put your headset back on.

mrkaic's picture

I actually did go into business and co-owned two companies that made decent profits, thank you very much.

It would be nice if you could focus on the amplifier, not on what I can or cannot afford or if I was ever in business for myself.

It seems that you enjoy going personal and that misses the point of this forum.

Dcode's picture

Made (past tense) good profits. Reminds me of The Fox and the Grapes--one of the Aesop's fables. The story concerns a fox that tries to eat grapes from a vine but cannot reach them. Rather than admit defeat, he states they are undesirable (or too expensive).

The "too expensive" or "no better than something less expensive" cry in the comments of an audio blog is so played out.

vilasound's picture

Unfortunately, the mosfets alone cost, I believe, 50-100$ each. Hopefully, Gamut gets a better deal for them as each Di150 carries 4 of them.
I can't remember the exact model of the Mosfets they use but they are similar to this: http://eu.mouser.com/ProductDetail/GeneSiC-Semiconductor/GA100JT17-227/?... which are listed here at >100$/each

mrkaic's picture

...you have not provided the exact model info and the exact purchase cost.

Not that it would matter. If Gamut uses uses super-duper MOSFETs (designed for welding) to build an amplifier with standard performance (come on, almost 0.03% THD at 1W into 4 Ohms -- measured in this review -- is the same as the NAD 3020D), then they are wasting money. Their amp should still sell for less than $400.

Just out of curiosity -- do you have a background in electric engineering or physics?

vilasound's picture

I will try to find the exact model (I promise) but you can still check many that are similar and are all much more expensive than what you are quoting.
Yes, they are super-duper and industrial but they are there for a simple reason: GamuT uses only 1 mosfet per phase in order to preserve the transparency and timing, you know... Less is more. And for that you need a super duper mosfet that can deliver 180-250W and deal with 50-100A alone.
If you want an amp that 'measures well' (whatever that means) you can build an amp with class D modules or with lots of transistors per channel. It will have power and low THD etc but it might sound like crap.

I do.

mrkaic's picture

Your unwillingness to focus on the amplifier and to keep slinging personal insults is also played out. I am now convinced you have little to no understanding of audio.

dissily mordentroge's picture

Too often I've read angry discussions of the kind above. What is it about audiophiles (audiophools?) that appears to make so many outraged at the enjoyment of others and why are these differences so often expressed in a vitriolic manner with all the maturity of a six year old? An unanswerable question I suggest short of abducting a large sample of such persons from an audio show, isolating them from their toys and subjecting them to several years of psychoanalysis and blind listening tests.
There are so many unanswerable questions in this context. Take for instance the question of why results of clinical hearing tests given audio reviewers aren't published along with their reviews.
My take on the Gamut V Cost controversy? OK maybe it's not worth sum total of research,production, advertising and material costs involved but why get angry if you imagine purchasers are either too deaf or too rich to make what you think is a rational purchase? Maybe we're back at that other hoary old question " Do we really know if laboratory test results tell us everything we need to know to characterise how a component is heard by EVERY listener?
Which leads me back to that other elephant in the room. Can we ever be sure any audio reviewer/audiophile will hear the same piece of equipment the way we do?

mkwglyg's picture

After reading this review, I must admit I'm aghast! Shocked!
It says the Gamut Di150 sounded flat using a standard power cord but suddenly becomes fantastic when using that isotek power cord. Wow! Seriously? Wow!
Does the isotek powercord possess some special superpowers that can raise the dead?
C'mon! if a 10grand equipment cannot even sound right using a standard power cord, something is seriously wrong with it, no cable however magical is going to save it, period.
However, if what the reviewer said is true, then i must get that isotek powercord for all my equipment, cd players, preamp, amps, everything! But surely not the Gamut Di150 which i am highly suspicious of judging from this review.

Get that isotek power cord!

Note: After doing a search on user opinions on the isotek cable, some claimed that its a waste of money. Now I'm totally lost.

vilasound's picture

News flash! EVERY amplifier sounds flat with a standard power cord.
The GamuT sounds much better with the Isotek but you have no idea how much better it sounds with even better powercords.
The reality is that all amplifiers are muffled by poor power cords. Best and easiest upgrade there is out there.

X