New York Audio Laboratories Futterman OTL-1 power amplifier

Few people in the high end know the difference between glorious excess and wretched folly as well as Harvey Rosenberg (footnote 1). Harvey's audio equipment always strives towards the glorious folly of providing the most romantic sound possible with modern technology. This may explain why his relatively small company, New York Audio Laboratories, can build an amplifier like the Futterman OTL-1, which costs a glorious $12,000 a stereo pair and actively competes for the title of best amplifier in the world.

At the same time, Harvey's prose always strives towards the most wretched excess possible with a modern word processor. In fact, one might almost suspect that Harvey deliberately writes prose designed to make people run out and listen to music on his equipment—if only to forget what they have just read in his advertising literature.

Fortunately, I am only an humble equipment reviewer and not a literary critic. I can take advantage of the positive side of Harvey's character; his OTL-1 stereo power amplifier is so good that it even makes me forget his prose.

The Technology
The Futterman OTL-1 is NYAL's attempt to build the best tube amplifier in the world (footnote 2). Its designer has attempted to minimize the problems an output transformerless design encounters in coping with low impedance loads. The Futterman OTL-1 can provide 150W into a 16 ohm load, 65W into an 8 ohm load, and 35W into a 4 ohm load; it's effectively current-limited into loads below 16 ohms, but this is nevertheless an extraordinary amount of power for an OTL amplifier. Its ability to deliver the clarity of a transformerless amplifier into an unusually wide range of loads is enhanced by an extraordinarily large, regulated B+ power supply.

A regulated B+ power supply is unusual in any tube amplifier—the D-250, for example uses regulated supplies for the low-level stages and for the output screen grids but not the output plate supply—but is probably unique in an OTL design. It must be able to handle both very high voltages and very high currents at the same time, dissipating up to 5000 watts. The OTL-1 supply is designed to provide 100% regulation from 2Hz-100kHz at full-power output.

The end result of all this power output capability and regulation is physically and acoustically impressive. The amplifier weights 250 lb and comes in four heavy rack-mountable 17.5" by 18" chassis. It is styled using the kind of rugged industrial or laboratory quality meters, switch knobs, and heavy metal construction that was common in hand-built military test gear used during the 1950s ("Dr. Zharkov, we're going to crash!" "Don't worry, Flash, I know.").

The inside of each chassis is strictly 1980s, though, filled with all the latest in active and passive components, and clean circuit boards and wiring layout; the construction standards are superb. Quite frankly, the kind of construction you find inside a Futterman OTL-1 makes the internal wiring of a product like the Jadis embarrassing. The Futterman exemplifies how high-end equipment should be built (footnote 3).

The NYAL Futterman OTL-1 measures up to its performance specifications, at least to the limited extent I can make such tests. It has an extremely fast rise time and an excellent squarewave response for a tube amplifier, and provides wide bandwidth up to full power. The signal/noise ratio is excellent, although I can't test much below 80dB.

I should also state that the Futterman OTL-1 amplifier proved exceptionally reliable. It came perfectly set up from the factory, worked right out of the box, and required almost no adjustment after very extended listening—which included use of a wide range of cables and speakers, and such reviewer mistakes as popping the odd interconnect out while the unit was playing. The OTL-1 is not a "hothouse" unit; you can have real fun with it and not worry about ongoing tube problems, shock, constant readjustment, etc.

The Sound
The OTL-1 is probably the best amp available for the tube fanatic seeking the maximum possible emotional impact from recorded music. This does not mean that the OTL-1 is colored in any normal sense of the term. As I have already said, it measures very flat, and harmonic and intermodulation distortion are both exceptionally low for a tube amp. It reveals at least as much detail into compatible loads as any amplifier I have ever heard, and is so natural and convincing in overall sound characteristics that only a small handful of designs—the best Krells, the Conrad Johnson Premier Five, the Audio Research D-250 II Servo—are its rivals.

Nevertheless, use of the term "romantic" is the only fair way to express this design's unique character. In fact, the Futterman OTL-1 qualifies for all the best buzz words used by reviewers in characterizing the romantic tube sound: "sweet," "warm," "transparent," "dynamic," and "musical" (in the best sense of the term).

This shows up on a wide range of music; brass has bite without bitterness; unlike many amplifiers that have high transparency, male and female solo voice have their full body and impact; strings retain their natural hardness without added hardness or loss of information; orchestral music has both natural power and convincing detail, even in soft passages; solo instruments never seem to be floating in limbo right next to the microphone to the extent common with most competing amplifiers.

The bass varies considerably with different loads, although the OTL-1 provides by far the most natural measured and apparent deep bass of any OTL design to date. With the right load, it is exceptionally fast and dynamic, without losing control. The Quad ESL-63 or Vandersteen owner is going to love this amplifier, as will owners of speakers which have fairly flat impedance characteristics greater than 4 ohms, especially if they are electrostatics and don't require biamping.

The lower midrange is strong and vibrant, with the punch and emphasis of the older concert and opera halls. The OTL-1 does not correct the evils of close miking so prevalent in the last couple of decades, but it certainly gets the best out of modern recordings. Its midrange provides the kind of conviction sadly missing in most modern power amplifiers precisely because it is transparent and dynamic, without attenuating the lower midrange. The OTL-1 is superior in this respect to any transistor amplifier I have heard, rivaling in this respect the Conrad Johnson Premier Five. It provides a flatter transition into the highs and bass than I've heard from the Jadis, and reveals what I regard as the one real weakness in the Audio Research D-250 II Servo: a slight recession of lower midrange power and dynamics.

While the highs are not quite up to the very best Audio Research designs, they are slightly superior to those of the Conrad Johnson Premier Five, and far superior to the rolled-off highs of the Jadis designs. Nevertheless, the highs will not sound "flat" by the standards of most of the competition, because the OTL-1 provides the lower midrange and upper bass power and dynamics missing in virtually every amplifier. One has the feeling of natural treble attenuation that one gets from sitting in rows G-M of a good hall.

Everything you need to enjoy the music is there, but this is a balance chosen for someone who wants to get all the emotional impact of the music on most recordings, not every little bit of music available at the violinist's armpit. If you want the purity of OTL designs and a more forward and slightly "flatter" sound, look to the Counterpoint SA-4. The SA-4 does not have quite the bass extension, power, or dynamics of NYAL's OTL-1, but it is still a truly superb amplifier and a good benchmark if you want to find out what OTL designs can offer.

The OTL-1's soundstage is open, wide, airy, and live, with natural imaging, good centerfill, and excellent stability. It is, however, a bit load-dependent. This is particularly true of depth, which can range from good to superb, depending on the speaker. The competition is also load-sensitive in terms of soundstage performance, but the OTL-1 is a little more load-sensitive than most. I advise consultation with your dealer, and close attention to cables and speaker placement, to get the best soundstage performance out of this unit. This is one case where careful listening and a little effort can pull you from the doldrums of the merely excellent to scale the heights of the superb.

In fact, the one reservation I have about this design is the fact that it requires even more careful demonstration and set-up, and even more attention to speaker and cable compatibility, than the few top-quality products with which it competes. I never found a cone speaker, an electrostatic, or Magneplanar design that the OTL-1 would not drive, but "drive" simply isn't good enough with an amplifier this good. You can't substitute a Ferrari for a Rolls.

Accordingly, if you are one of the few audiophiles who goes beyond literary voyeurism to deliberately buy the ultimate system, I'd suggest you both spend a lot of time talking to your dealer and to the folks at New York Audio Laboratories. The New York Audio Labs OTL-1 is a serious candidate for such a system, and this is the highest praise I can give. It is a very difficult unit to have to return, and extraordinarily easy to fall in love with.

Footnote 1: Harvey Rosenberg passed away in 2001.—Ed.

Footnote 2: I exempt the Moscode Black Hole Power amplifier, which sells for $267,000, and which is part of the Harvey Rosenberg "Wretched Excess Signature" series. The Black Hole is evidently New York Audio Laboratories' top-of-the-line amplifier, but has strictly limited distribution. I have listened extensively to the specifications of this design. While it is a bit pricey, no other amplifier I know of has quite the same styling or sound character. In this case the image is the sound! It is a unit you must hear for yourself, and I can assure you that any top audio dealer will instantly drop anything he is doing to spend hours auditioning this unit for you. For example, simply whispering "Harvey Rosenberg's Black Hole" in Mike Kaye's ear will produce fawning obeisance. One modification, however, is vital: a water tower is also needed on the left channel to balance the liquidity of the sound on the right.

Footnote 3: The OTL-1 comes, quite seriously, with a lifetime electrical and mechanical warranty. NYAL states (not so seriously) that this covers nuclear attack, and that the warranty can be extended into your next lifetime for $50. (Readers may feel free to protest to Consumer Reports.)

New York Audio Laboratories
Company no longer in existence (2018)

Anton's picture

Thanks for the trip down memory lane.

I would be willing to chip in to get Art or Herb a fresh example of this amp and see how it holds up vs. the current crop.

What a classic piece of kit!

Herb Reichert's picture

All the way through reading this report I kept saying to myself, damnit I should have leaned a little harder on Harvey and bought one of these beautiful monsters. Harvey was my friend, but he would not cut me a deal I could afford. I did however buy an old Futterman H3aaa but it was kind of a mess. I always wanted an OTL-1 and a Levinson ML-2. I was thinking this afternoon how cool it would be to do a followup on the ML2 comparing it to the latest Pass Labs stuff. Ahhhh I feel a Dream coming on.

Ortofan's picture

... Harman-Kardon Citation II?

If you ever do that follow-up comparison of the ML-2 and a Pass Labs amp, try to include the Accuphase A-250.

Herb Reichert's picture

is one of the finest amplifiers I have used
I have owned a few IIs (including one I was told was modified by Mike Moffit)
it had best output transformers which were only surpassed by Acrosound's UL-II trannys


Anton's picture

....would be reading about you hearing one!


rwwear's picture

The Fourier amps were a continuation of the Futterman design although they had their problems.

Bogolu Haranath's picture

I would not hold my breath :-) ...........

Bogolu Haranath's picture

Promises, promises, promises :-) ..............

tonykaz's picture

Headphone people like our Tyll & Steve G will boast about the OTL Bottlehead Crack. I claim that the Schiit OTL Valhalla is superb.

Loudspeakers don't get built with high enough impedence for OTL Amps so we don't have anyone offering the darn things,

do we ?

Tony in Michigan

Bogolu Haranath's picture

If someone builds it, they will come :-) ............

Bogolu Haranath's picture

May be the loudspeakers get built with low impedance, because they can draw more watts from solid-state amps? ..........

"Watts are cheap" ........... Jim Theil :-) ..............

eskisi's picture

OTL amps can work wonderfully. I have a 2 X 30W Atma-sphere and the sound it produces in combination with a pair of 16 ohm Sterling LA3/5As is remarkable and addictive.

But with an electrostat? OTLs are a compromise of sorts...the design is forcing a low voltage and — relatively — low impedance output from high impedance / high voltage devices by consuming a ton of power: it really wants to see a transformer. An ESL is a reciprocal compromise — it has very high impedance and requires high voltage and it uses a transformer, its and all non-OTL tube amps’ Achilles heel. So the far preferable way to drive an electrostat is with a “normal” tube amp driving it without a tranformer. Like Acoustat did in the 70s and which I do with a Berning tube amp driving Martin-Logans.

Roger A Modjeski's picture

I met with Julius Futterman while he was still building OTL amps himself. I saw his power transformer winder and potting setup. He liked to make his own because the transformer had to be very low impedance to provide the current needed for 6-8 output tubes.

The key design feature of the Futterman and its clones is very low output impedance which is achieved with gobs of feedback which is properly applied and sounds great. I recommend Futtermans early papers which can be found on the internet.

He gave me a copy of an impedance chart he had run on the KLH-9 ESL. He noted it was high and never below 12 ohms or so. Not at all like modern ESLs that dip to an ohm. Even the ESL 57 gets down there at 18Khz.

As one who has designed Futterman type OTLs (the Counterpoint SA-4 and my own) these are not the mate for modern ESLs where the impedance falls to an ohm or so. The famous marraige of the OTL and ESL is particular to the KLH-9 and Futterman OTL.. ONLY.

Beveridge and Acoustat had the right idea in making a Direct Drive amplifier at high voltage and reasonable current. The Beveridge Model 2 and 2SW amps put out 1,500 VA (like watts in this application). The Acoustat amp was not quite as good on current, construction or reliability. It used the wrong output tube.

Since few amplifiers can put out 1,500 VA nor can many step up transformers easily pass it, the DD amp is the way to go. I have made several that put out 2,000 VA for use with the Acoustats, ESL 57 and ESL 63.

One other comment on OTL. Sadly the Atmasphere amps do not drive ESLs or any speaker with varying impedance well as they have very high output impedance (low damping). So lets be careful when considering how OTLs behave with ESLs and in general.

Bogolu Haranath's picture

Nice to hear from you Mr. Modjeski ....... Any comments about OTLs driving electrostatic and/or planar magnetic headphones? :-) .............

John Atkinson's picture
We published a characteristic letter from Harvey Rosenberg in 1999:

John Atkinson
Editor, Stereophile