The F6 is one of the best sounding amplifiers I have ever heard.

 

The First Watt F6 offers a fantastic option to anyone in the market to drive sensitive speakers in the 90db’s/8ohms territory and even picks a compelling fight with speakers that are moderately difficult to drive. Throwing everything I had in-house at the F6 left me with a new found respect for Nelson Pass. I can easily suggest the F6 as one of the best sounding amplifiers I have ever heard. Keep your wits about you when pairing this amp with the right speakers and you just hit the jackpot! Highly Recommended! 

Nelson Pass Q&A

 

What baseline rules should someone consider when selecting the right speaker for the F6? If they are looking at speaker sensitivity, what would you suggest as a good starting point?

It really depends on how loud you want it.   It will drive 4 ohms to nearly 60 watts at less than 1% distortion.  Being a Class A design with low feedback, the distortion always declines with power, so the greatest precision is at a few watts.

My reference system has Tannoys with a 95 dB sensitivity and I listen at fairly low levels, typically with 100 dB peaks. This can be achieved with a 2 watt/ch amplifier.  The F6 has about 15 times this amount of power, so it can either deliver this level with 83 dB speakers or it can drive the Tannoys to 113 dB peaks.

For most people, probably 90+ dB speakers at 8 ohms is recommended.

Of the First Watt current production amplifiers, do you have a personal favorite and if so, why?

I needed to be creative outside of Pass Labs without creating trouble, and so formed First Watt to explore unusual, even subversive approaches to power amplifiers.  This has annoyed some members of the audio world, making it even more fun.

Consequently the amps tend to be quite different from each other, although they are all low wattage and they are all Class A circuits.

The F1 is a push-pull current source, the F2 a single-ended current source.

The F3 was the first power Jfet amplifier (that I am aware of).

The F4 is a no-voltage gain follower.

The F5 is a two stage push-pull Mosfet/Jfet design with low impedance feedback.

The Aleph J and the J2 are revised versions of the original single-ended Aleph 30, probably the only instances of repetition in this list.

The SIT-1 and SIT-2 are single-stage single-ended SIT (VFET) amplifiers without feedback.  The SIT-1 has a user adjustable “load line” adjustment which allows control of the second harmonic characteristic, the SIT-2 is a stereo version without the knob.

The F6 is single-stage push-pull complementary amplifier that uses an input transformer to drive the power Fets while also processing feedback control.

All of these amplifiers sound different, and each has found a small community of audiophiles who particularly appreciate what they offer.  I enjoy the sonic differences between them.

How could I have favorites?

Do you have a preference when it comes to vinyl or digital?

I love vinyl, but I have digital playing when I work, which is most of the time, simply for the convenience.  I have customers on either side of that fence or merely agnostic, so it is important for me to use both for critical listening.

Relaxing with a nice Cabernet?  Vinyl.

Do you believe a cable or set of cables can make an audible difference in a hi-fi system?

I have experienced it – even measured it, so it is possible.  That said, it is not the subject of my focus.  When cable manufacturers send me samples, I send a thank-you note and put them to work.

When I listened to the F6, one of the things I liked the most was the top end extension, which to my ears sounded very detailed without sounding harsh or bright. Based on the design of the F6, is there a specific component in the design that could be most attributed to this quality?

Interestingly, the response of the F6 is -3dB at 50 Khz, so you are not hearing what we would call wide bandwidth.  What you are probably hearing is the character of a simple single-stage Class A amplifier with a modest amount of feedback.

The design has very little in the way of high order harmonic distortion, and in ordinary listening the second harmonic is a modest 0.03% or so, with a lesser amount of third harmonic, keeping the amplifier in the sweet-sounding category.

What is your first memory of experiencing hi-fidelity?

My parents acquired a “high quality” console in the early 60’s, and my mother had a nice little collection of light classical, show tunes, and pop music from that era.  By the time the Beatles showed up, I was the dominant user of that hardware and eventually graduated to a Garrard turntable and home brew speakers and amplifiers.

If you could only listen to one pair of speakers for the rest of your life, what speakers would that be?

Don’t know.  Right now the constants are the Tannoy 15” HPD coaxials in Jensen Imperials and a pair of SR-1’s with lower efficiency and impedance.

I do keep a variety of other loudspeakers; two pair of JBL’s, Rushmores, some open baffle full ranges.  There’s some work on big horn-loaded systems and compression drivers, but that’s just for kicks…

What amps inspire you or do you like the sounds of? Meaning, are you just looking for ruler flat, aka sterile, or do you believe your amps add character? What character are you seeking?

Enjoying the differences between amplifiers, I try lots of things and listen to them.  Ultra accurate products have their place, and I’ve built my share of them, but they are not as interesting.

The metaphor for amplifiers is bottled water.  When you go to the market, you will find an aisle filled with product.  On the top shelf is the water from glaciers, fizzy mineral water (Pellegrino is my favorite), and not far from that are the sweet offerings.  All of these seem to cost more than gasoline.  Tucked away is the distilled water.  It is not very popular, but at least it costs less than gasoline.

We try to make what our customers really want.  One thing that our customers want is to relax when they listen to their hi-fi.  No fatigue – people listening to our amplifiers should find themselves invited to listen more, going through their record collection until the late hours of the evening.

Listening to hi-fi, I want that illusion of live music, kind of an organic quality, and to relax and feel good.  When experiencing this, I want to tease the secrets out of that amplifier and reproduce them elsewhere.  After 45 years or so, I’ve become pretty good at it.

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