What makes the F7 so special is its inherent textural sweetness and warm tonality. There are many (too many?) solid-state amps out there that manage to sound smooth and refined yet lack the organic character of live music. The F7, on the other hand, managed to sail through reproduction of violin tone with superb upper-register sheen and transient finesse—a rare feat for any solid-state amplifier. Having been raised on tube sound, I find textural warmth to be a most welcome attribute, though the F7 does not approach the effusive warmth of a classic tube amp. If you crave even more warmth, do as I do and hook the F7 up with a tube preamp. This is not a euphonic amplifier. Relative to say, a Marantz 8B, the F7 delivers far more incisive transients while its command of space is competitive with the sort of 3-D spatial presentation tube amps excel in. The total harmonic distortion has been trimmed to 0.05% at 1 watt. But Nelson points to the distortion spectrum at 1 watt and 1kHz, and the 10dB ratio between the second and third harmonic as being contributing factors to the F7’s musicality.
Since just about all pop music is being recorded in a studio and mixed on a multitrack console, sound engineers are given the opportunity to play various games with the final mix, which may include vocal overdubs, canned reverb for individual tracks, pan-potting, eq, flanging, gain riding, and compression. The F7 was able to dig deep into a mix and resolve such trickery without much effort, a tribute to its superb transient control and laser-sharp image focus. The Eximus DP-1 DAC makes it possible to upsample a Red Book 44.1kHz input to 192kHz on the fly. Discerning a sonic change with some amps is not an easy task. That was not the case with the F7 in the chain. It highlighted significant sonic changes, the opening up of the treble range and tightening of image focus being two major ones. There’s no doubt in my mind that this amp is a high-resolution device.
I spent some time pitting the F7 against the F3. While the F3 sounded a bit cleaner, the F7 was better controlled in the bass range and displayed more personality. To confess, the F7’s warmer, slightly lusher textures suited me just fine. I have to disappoint those of you who expected the F7 to go down in flames. Much to my surprise, I ended up preferring it over the F3. Make no mistake about it, the F3 a terrific single-ended amplifier. It’s just that the F7 is the more seductive of the two, just as dynamic, and ultimately a more musical performer. And that’s a remarkable finding for any push-pull amp.
The F7 is easy to embrace musically. Its sound is sufficiently addictive that I’m finding it extremely difficult to evict it from the reference system. For the record, it’s likely to stay put for many weeks to come. If the F5 can be said to offer a “half-nelson” grip on sound quality, it would be accurate to characterize the F7’s performance as nothing less than a “full-nelson.” Simply put: one of the best low-power amps money can buy.
SPECS & PRICING
Output power: 20Wpc into 8 ohms (1% THD at 1kHz); 30Wpc into 4 ohms (2% THD at 1kHz)
Frequency response: –3dB at 100kHz
Total harmonic distortion: 0.05% (1W)
Input impedance: 10k ohms
Input sensitivity: 0.57V (1W); 2.53V (max output)
Damping factor: 100
Class A envelope: 50W peak at 4 ohms
Noise: 100µV unweighted, 20Hz–20kHz
Dimensions: 17" x 5.5" x 15"
Weight: 26 lbs.
RENO HI-FI, INC. (U.S. Distributor)
P.O. Box 20728
Reno, NV 89515
Basszilla Platinum Edition Mk 2 DIY loudspeaker; Kuzma Stabi Reference and Technics SL-10 turntables; Audible Illusions L3A and Brown Audio Labs SP-1B preamps; Experience Music autoformer volume control; MacBook Pro laptop running Amarra V3.03 software, April Music Eximus DP1 DAC; FMS Nexus-2, Wire World, and Kimber KCAG interconnects; Kimber KCAG speaker cable; Monarchy Audio AC-Regenerator; Sound Application power line conditioners