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First Watt F8 Stereo Power Amplifier

first watt f8

By my count the F8 represents the sixteenth First Watt power amp authored by the undeniably prolific Nelson Pass. Each unit has been a unique creation said to be “best” in some particular way, though they all happen to look similar because they use the same basic chassis and power transformer. The F8 represents a variation on the popular J2. Its origins go back to 2015, when Nelson had the notion to create a design similar to the J2, based on the SemiSouth Silicon-Carbide R100 power JFET, but using an alternative front-end gain stage. The prototype, says Nelson, was a clear improvement, but because of the J2’s popularity the decision was made to wait. After some additional work over the past six years, that alternative design was finally released as the F8. It is a stereo single-ended Class A amplifier with only two gain-stage devices per channel, a single Toshiba 2SJ74 JFET input, and the SiC R100 power JFET output. Both of these transistors are no longer in production, but available in limited quantities from the First Watt new-old-stock “vault.”      

Circuit-wise, the F8 is quite similar to the J2 amplifier with a virtually identical output stage. However, only one front-end transistor is used instead of six, and it is operated as a current-feedback amplifier as opposed to the J2’s voltage-feedback design. One consequence is reduced gain (only 15dB), but according to Nelson, a simpler front end is more consistent with the single-ended approach to amplifier design and pays off in a purer second-harmonic character, less distortion with lower negative feedback, greater bandwidth, and a higher damping factor. Specifically, comparing the published specs for the J2 and F8, it’s clear that the F8’s damping factor and high-frequency response are twice as good, and that its THD is 0.02% versus the J2’s 0.03%. Unlike the J2, the F8 does not have a balanced input. It also incorporates AC output-coupling in the form of two large electrolytics (10,000µF each) in parallel, bypassed by one polypropylene cap, to eliminate any DC at the output. The resultant bass roll-off frequency is 1Hz. 

Power output is similar, as well. Keep in mind that this is a low-power amplifier, 25Wpc into an 8-ohm load and half that into a 4-ohm load. As such it needs to be carefully matched with a compatible speaker. An 8-ohm speaker with a minimum sensitivity of 90dB would be ideal. The Fleetwood DeVille that I grew quite fond of this past year (and reviewed in Issue 309) was used for all the listening tests. It certainly meets the requirements and offers a sensitivity of 94dB, to boot. The F8’s power dissipation is 170 watts to produce an output of 25Wpc, which means quite a bit of waste heat. Be sure to allow plenty of ventilation around the chassis. Even so, it runs fairly hot to the touch after about an hour of being powered up.

first watt f8 rear

So what does it sound like? Well, it turned out to be the sonic equivalent of Reyka, an Icelandic vodka that has been said to taste dangerously close to fresh water. The F8 started off much like a tabula rasa, a clean slate, distinguished by the absence of inherent sonic colorations. It didn’t sound bright or warm, but consistently took on the flavor of whatever front end I threw at it. That’s not to say that it didn’t have its own sonic imprint. To my way of thinking, what it did right was a logical consequence of a confluence of three factors: simple single-ended circuit topology, wide bandwidth, and an excellent damping factor. 

The resultant airy treble, tonal purity, and superb transient speed were instantly endearing. So was its startling soundstage transparency. It shouldn’t come as a surprise when I tell you that my favorite matching preamp was of the vacuum-tube variety. The F8 allowed tube virtues such as a deep and layered soundstage to shine through, while maintaining an authoritative midbass. Tympani strikes were staggering; drum kits were persuasively resolved with satisfying kick-drum crunch; and brush work was delicate. It was like having your cake and eating it, too. The upper bass and lower midrange weren’t shabby, either. On my favorite performance of the Dvorˇák Cello Concerto in B Minor, with Jacqueline du Pré and the Chicago Symphony Orchestra conducted by Daniel Barenboim [EMI CDC-7476142], the loving collaboration of soloist and orchestra shone with emotional intensity and uncommon clarity. 

When it came to macrodynamics, 99% of the time I didn’t feel that I was missing anything. On a rare occasion, on highly dynamic material, there was a hint of compression. But most of the time the F8 didn’t sound at all like a low-power amp. It managed to project plenty of authority through the power range of the orchestra. Coupled with its robust boogie factor, it was able to extract the music’s dramatic content with total conviction.

After a few days, it dawned on me that I was missing out on my customary dose of textural liquidity. I was curious to find out what would happen if I closed the frequency-response window by trading some of the F8’s bandwidth for a potentially heftier dose of midrange liquidity. Thus, I decided to introduce the First Watt SIT-3 into the evaluation. Its frequency response is already down 3dB at 50kHz, while the F8 is extended to 200kHz. That’s because the SIT-3 uses zero global feedback and also incorporates an autoformer input stage, which makes it behave much more like a classic single-ended triode amp than the F8. 

A confrontation with the SIT-3 was inevitable. I’ve been vocal about the fact that the SIT-3 has consistently blurred the line between solid-state and tube amplification by facilitating an attractively organic midrange. And while no one would mistake it for a tube amp, its presentation is somewhat liquid, warm, and grain-free—welcome traits that enhance long-term listenability. In fact, I had previously embraced the SIT-3 as my favorite First Watt stereo amp, so I had a vested interest in the outcome of this mano a mano shootout.

So how did the F8 fare? As expected, when it came to the midrange, the F8 wasn’t as rich or liquid sounding. But as compensation it offered more detail, more open treble, crisper bass, and an increased sense of clarity. I should add that both amps take a while to get going, and sound their best when the chassis gets pretty hot to the touch. While the SIT-3 captured a slice of tube amplification gestalt, the F8 managed to sound more neutral and ultimately more accurate. 

Its full capabilities were on display on Mark Levinson’s The Legend of La Fenice restoration project, in which tapes of select performances, originally recorded by the house system at the Venice opera house, were rescued from archived storage and caringly remastered. The sound quality on this CD set is variable, partly due to the fixed nature of the microphones, but most of the performances are just delightful. And the F8 revealed all of it—the good and the bad—in an incisive way I had not previously experienced. I should add that the better the recording, the better the F8 sounded. When fed DSD128 discs it bloomed with sumptuous textures and brilliant tonal colors. 

Ladies and gentlemen, please raise your seats to their full upright position and take note: The F8 has joined the SIT-3 on the winner’s podium. These two amps offer differing but equally valid perspectives on sound reproduction. As far as current production goes, they are the two brightest stars within the First Watt family. The F8 is a reference tool in the finest sense of the words, exceptionally revealing of what comes before it in the playback chain. Its directness of expression enhances the illusion of being there, and is a function of its phenomenal clarity and transparency. These attributes should give it wide audiophile appeal. I’m so glad that Nelson Pass took the time to finalize the F8—I think we can all agree that it is a worthy successor to the J2.

Specs & Pricing

Output power (8 ohms): 25 watts @ 1% THD, 1kHz
Output power (4 ohms): 13 watts @ 1% THD, 1kHz
Frequency response:  -0.5dB (10Hz–200kHz)
Total harmonic distortion: 0.02% @ 1 watt, 8 ohms
Gain: 15dB
Input sensitivity (max output): 2.7V
Input impedance: 100k ohms
Damping factor: 38 relative to 8 ohms
Noise: <100µV unweighted, 20Hz–20kHz
Power consumption: 170 watts
Weight: 24 lbs.
Dimensions: 17″ x 5.5″ x 15″
Price: $4000

FIRST WATT
firstwatt.com

Associated Equipment
Loudspeaker: Fleetwood Sound Company DeVille
Phono front end: Revox B795 turntable; TPAD 1000 phono stage; Sound Tradition MC-10 step-up transformer
Digital front end: Denafrips terminator & ANK 2.1 Signature DACs, Audirvana 3.5 software, Alldaq ADQ-USB 3.0 isolator, audiolab 6000CDT transport, ifi SPDIF iPurifier2
Preamplifiers: PrimaLuna EVO 400, Supratek Chardonnay, Blue Circle Audio BC21.1, Manley Labs Jumbo Shrimp, Experience Music AVC, Ed Schilling’s The Truth
Cables: Mogami and Kimber KCAG interconnects; Analysis Plus Oval 12, FMS Blue, & Take Five Audio Cryo treated Mogami 3103 speaker cable
Accessories: Sound Application CF-X & TT-7 power line conditioners

Tags: POWER AMPLIFIER SOLID-STATE

Dick Olsher

By Dick Olsher

Although educated as a nuclear engineer at the University of Florida, I spent most of my career, 30 years to be exact, employed as a radiation physicist at the Los Alamos National Laboratory, from which I retired in 2008.

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