First Watt Amps - Nelson Pass

[mark1101]

So as not to hijack another thread concerning tubes vs. ss I started this.

Does anyone own or have heard any of the First Watt amp designs and what can you say about the performance characteristics?

Cask (Chris).......which one do you have? Why that one? Comments on any of the others?

There are so many different designs........it's almost like the guy is "Joking" with electronics. He is such a genius.

If I was looking for a simple ss audiophile amp for a 2 Ch system I would buy one in a minute to try.........if I knew which one. Just reading about them all, I can only imagine how nice they must sound.

Anyhow.........go ahead about all things First Watt.

[Chris A]

Does anyone own or have heard any of the First Watt amp designs and what can you say about the performance characteristics?Cask (Chris).......which one do you have? Why that one? Comments on any of the others?

Mark,

This is actually an interesting subject. I went with the recommendation of the Reno Hi Fi guy that sells them (over the phone, with a free trial period) after I described my application, i.e., TAD compression drivers. I wanted an F5, but as you might have noticed, they aren't for sale anymore, and there were only 100 units made, total. I still want an F5 to hear but I probably won't want to buy it for my application. I'm more than a little happy with what I've got.

If you look across the amplifier specification table (http://www.firstwatt.com/prod.html) you will see some VERY interesting combinations of performance measures. When you read Pass's articles, then it becomes a little clearer what he is trying to achieve. First, note that he listens almost exclusively to full-range open baffle drivers, such as Lowther and Fostex, etc. So his power needs are low. Second, he is trying to retain "micro-detail" in his amplifier designs. Third, he has chosen to use non-tube technology--so that he isn't plowing old ground. Fourth, he likes tube sound, such as SETs.

So, to answer part of your question, I own an F3 to drive my TADs: it is a single-stage JFET design (one amplifier stage) with low distortion, low noise, and is rated at 15 W/channel. Better than that, the distortion curves for low-power operation are posted, and they're very low noise figures. The design uses feedback--the only downside that I see. I'm also looking at the J2 - but the price is high. The M2 looks to be too noisy for TADs, but I'm interested in hearing one, nevertheless, since it doesn't use feedback.

The F4 is a current follower - you could use it to drive speakers off the main outputs of another power amplifier. The rationale for this amplifier is a little esoteric for me. The SIT amplifiers are brand new and use very new-to-market devices. But you can see that they're mostly for the SET folks - their noise figures are high as well as their distortion figures (probably all second harmonic). Since I am sensitive to amplifiers with high second harmonic and listen to a lot of string music (orchestras, solo string instruments), I'm not that interested in his SIT designs. You need to know that the SIT devices in those amplifiers cost Pass almost as much as the amplifier sales price (yikes!), so he is basically giving them away.

The rest of his amplifier designs aren't available anymore.

Cool? Confusing?

Chris

[mark1101]

I'm still not sure I understand what he is trying to accomplish with all these different designs. I amy be a little thick here, but the understanding is more of "which one is right for me"?

What types of preamps are best suited for some fo these if you don't mind going into that.

Honestly, I had never considered using a First Watt in my active system as you are. I would have a huge power imbalance. I would lean toward a Klipsch speaker with a high end passive network, a tube preamp, and a high end DAC to accept all my sources. Simple all the way.

[Chris A]

I'm still not sure I understand what he is trying to accomplish with all these different designs. I may be a little thick here, but the understanding is more of "which one is right for me"?

I believe that he describes each amplifier design approach in detail with each respective users manual. The F3 is a evolutionary design based on his "Zen" amplifier designs, etc. It's actually an interesting yellow-brick road to follow.You can also read the 6 moons audio site for reviews, although I think that the guy that reviews them is a little "affected" with audiophilia.

What types of preamps are best suited for some fo these if you don't mind going into that.

I think that the input impedances of the amps are also listed in the table, but note that if you're worried about a tube preamp driving one, I'd simply email or ask the Reno Hi Fi guy, or you could even email Pass himself. I use SS preamp (actually an AVR) and have no problem, of course. I think that some of his amp designs have switchable input impedance...(well, at least one design does that I read about).

I would have a huge power imbalance.

Humm, maybe I'm missing something here: I've run 110 dB in-room, no problem.

Chris

[The Dude]

Well, this answers some of the questions I asked in that ss vs tube thread. Mark I hope you don't mind me watching your decision unfold.

[mark1101]

There is no decision. I have read almost every word on the First Watt website 3-4 times over the last year or so. I think they are some of the very best low powered amps on the planet and will probably serve up every micro detail available yet be smooth about it.

I'm just not in the market for such a product at the moment.

I'm surprised there haven't been more takers from this site but I understand due to the pricing.

[RRFL]

There is no decision. I have read almost every word on the First Watt website 3-4 times over the last year or so. I think they are some of the very best low powered amps on the planet and will probably serve up every micro detail available yet be smooth about it.

I'm just not in the market for such a product at the moment.

I'm surprised there haven't been more takers from this site but I understand due to the pricing.

I can make do without a car and slam the budget hard on everything else, that is how I justify the pricing on a sliding scale of what is most important in my life.

I think I also went down the same path your thinking about and this is where I ended up.

I also read almost every word on the First Watt countless times.

Then read I seemed to be re-reading everything else about his concepts. His passion inspired me.

My understanding of all this lead me down this path.

Initially I found myself drawn to get a pair of the XA30.5 to drive my Jubilee. These are the only Stereo Class A and considering everything I think they are a bargain. You get that attention to detail of the first watt. While they are 30w/channel they leave class A @ 60w/c and slip into class AB to more than 150w/c before getting to their rated distortion. They have a proper power supply.

I settled on a pair of the X350.5 as they are the biggest stereo amps @ 350w/channel AB. They are single ended class A for the first watt area then become push pull class A leaving class A at 40w/c slipping into class AB. They have only 2 gain stages and the feed back is minimal local. With one channel driving the LF and the other driving the HF, I considered that the very significant power supplies would provide ample power for whatever I could ever want to drive the LF with 400w as the HF from the same amp would only require 50w, yet the design made the detail available in the first watt. The X350.5 has good bass slam when driving difficult speakers when compared to other designs.

I'm using the Ashly NE8800 as a balanced preamp so I can process the direct output of the OPPO BDP 105 as 5.1 without anything else in the signal path. Old School Minimalist thinking here.

I will use my old Yamaha C2A preamp direct into the Ashly inputs 7 & 8 for everything else.

I hope this gives you some more food for thought.

[Don Richard]

So, to answer part of your question, I own an F3 to drive my TADs: it is a single-stage JFET design (one amplifier stage) with low distortion, low noise, and is rated at 15 W/channel. Better than that, the distortion curves for low-power operation are posted, and they're very low noise figures. The design uses feedback--the only downside that I see. I'm also looking at the J2 - but the price is high. The M2 looks to be too noisy for TADs, but I'm interested in hearing one, nevertheless, since it doesn't use feedback.

The F4 is a current follower - you could use it to drive speakers off the main outputs of another power amplifier. The rationale for this amplifier is a little esoteric for me. The SIT amplifiers are brand new and use very new-to-market devices. But you can see that they're mostly for the SET folks - their noise figures are high as well as their distortion figures (probably all second harmonic). Since I am sensitive to amplifiers with high second harmonic and listen to a lot of string music (orchestras, solo string instruments), I'm not that interested in his SIT designs. You need to know that the SIT devices in those amplifiers cost Pass almost as much as the amplifier sales price (yikes!), so he is basically giving them away.

I've been looking at the Firstwatt amps and am not sure if the F3 will work well for my application - driving the HF horns on my triamped Khorns. I am using a CD horn with a driver that has an 8 ohm nominal impedance. The F3's output Z might be high for that driver, but the F4's is much lower plus no NFB. My crossover should have no problem outputting enough voltage to push the F4 to full output.

I need to check the Z curve for my driver to see if the Z in the frequency range that I am running is higher than the nominal rating. If not the F4 could be in my future. Otherwise the F4 is available new for the same $$ as the F3 with a 6 week delivery. Thoughts?

[mark1101]

Red Rocket.........so how does it sound? It seems well thought out and makes sense to me.

Don.........my thoughts are..........Why a First Watt on the tweeter of a Khorn? You said HF horns on a tri-amped Khorn. What are you using on the MF and LF for amps?

My situation is that I am pretty much done with my active MCM-3 Grand system.+ 684 subs. Other than to upgrade my DAC any more money spent on amps or such would probably be a minimal at best incremental improvement. I have all McIntosh. The system is a monstrosity and trounces everything else in my house, and just about every system I hear outside my house. My wife tells me the same thing. So I think it's done. It's good enough for me.

In order to continue in the hobby other than buying more music, I'm looking to go a hair smaller to upgrade my summer outdoor stuff and go to passive networks and either 2 or 3 way with something like a First Watt to drive the whole thing. I have a spare pair of 402s, 500Hz. (for dual K33) ALK ESNs all auricapped...........I just need drivers, and bass cabinets. I have my eyes on both.

I do need to liquidate some equipment to make room. Basically, I need to sell all my lascalas or I'm out of room.

[Chris A]

...not sure if the F3 will work well for my application - driving the HF horns on my triamped Khorns. I am using a CD horn with a driver that has an 8 ohm nominal impedance. The F3's output Z might be high for that driver, but the F4's is much lower plus no NFB. My crossover should have no problem outputting enough voltage to push the F4 to full output.

I need to check the Z curve for my driver to see if the Z in the frequency range that I am running is higher than the nominal rating. If not the F4 could be in my future. Otherwise the F4 is available new for the same $$ as the F3 with a 6 week delivery. Thoughts?

Watch out for the F4's lack of gain - if you have enough preamp gain range, then perhaps.

Roger that on the output impedance of the F3 - 1 ohm, while low enough for my TAD drivers, is a bit high for the the bass bin and the tweeter on the stock Khorn crossover (see figure excised from the Richard Heyser Khorn article: http://forums.klipsch.com/forums/storage/6/1223350/KHorn%20impedance%20curves%20Heyser.pdf)

Also note that the F4s that I've seen have been on sale over the past year or two ostensibly because it is such an esoteric product that the marketplace apparently hasn't grappled with its appearance yet. This is especially true of pre-owned units, which I would have no qualms about since Pass himself does the maintenance/refresh on his products. My F3 was bought off AudiogoN for significantly less than list.

I must have a psychological barrier about paying more than about $2K for any piece of electronics gear: that's a personal hangup only. If you've got the budget for Pass Labs products (versus First Watt products), then by all means...you certainly won't be disappointed by performance.

Chris

[Don Richard]

The new price for the F3 and F4 is the same, $2195 from Reno Hifi. There are used F3s available from Reno that are cheaper but I don't think that one will work well with my HF driver. Reno has a good return policy which would ease my concerns regarding purchasing any equipment I haven't heard.

[mark1101]

There are used/refurbished/demo F3s from Reno in the $1600 range on Audiogon and one on Ebay for $1495.

[Cornman]

Dang Mark, you spilled the beans, I had my name on that one on E-Pay. ..[8-)]

Just kidding Mark,[]

Cornman

[The Dude]

After taking some time toaday and looking around I did see some of the Firstwatt stuff around for under 2k. It must be more of the Passlab stuff that goes for 10 grand. When you guys say hf horn are you talking just the K77 or the k402 or after market.

[Cornman]

K 402, which is covering bothh mid's & trbl in the 2 way Jub's.

[consistent]

Hi Guys

I have his J2 amp and an Aleph 30. Had so many amps over the years...ended up with First Watt (Pass Amps) cause there was no other amp that I beleived mated with the Khorn so well. The J2 is sheer marvel to grab detail, match the 'pace' that a Khorn can provide, the J2 provides a realistic sound stage and even better (3D) when you have a great CD player, the amp doesn't get in the way of the music!. Forget what you think you know about SS amps until you hear the J2

Cheers

[The Dude]

I am on the mailing list for the amp camp mono block diy kits to come in over at diyaudio.com

I figure for a less then $200.00 I can start with that and if my build is a success I will give the f4 or f5 clone kit a try. But like I said I am on the mailing list to be notified when the kit comes in.

[Cornman]

Ok, this thread has given me First Watt fever. I have ordered a refurbished F3, should be here this Friday. We shall see how it compares on the K402's.

Thanks Cask,

Cornman

[Rbgcc13]

New here, but thought I'd throw my 2 cents into the pot. I have been a tube guy for over 45 years, although never owned a SET, used a buddy''s for a short while but never coughed up the cash. Ran pentiods on my amps that I owned in both single ended, OTLs and P/P. Last owned tube amp, I ran EL34's in "triode" configuiration, per Sid Smith's instructions for my former Marantz 5 monos. I love tubes, they give the sound a certain thickness, body that 99% of solid state doesn't/can't do. That being said, got sick of maintainance on my tube gear and always needing to bais the amps and having the tubes age at different speeds, and they do. I first was running the amps, marantz 5s, through a custom passive crossover to account for the two 15s showing a 8 ohm load while my mid/high driver was 16 ohms. With the Marantz 5s a very nice sonic picture, good spread and decent front to back with individual players/instruments shown. Bought a First Watt F5 to compare to my quasi triode marantzs and what a difference. First note was a bleaching effect, no more chocalote - warm glow a bass/lower register emphasis that was a signiture of the 5s. What I came to realize is that the marantzs were just colorful and the F5s were not, if they do have a sonic fault it is they're lean maybe, not thin, but not quite meaty enough perhaps. Now I had highs and lows with great attack and good decay, attack is similar to the effect of plucking hard a LP/Jr into a VoxAC30 and then compare that to hit the Jr hard thru a Fender Silver Deluxe Reverb, the Vox has REAL SNAP vs the DR. Same thing here, the quickness of the F5 is amazing when compared to the Marantzs, not even the same league - quick as greased lightening as they use to say. The next big thing I was not really aware of is the noise floor of an amp, that threshold where the amp at idle is generating hiss or noise and how low or soft it is in relation to the music. Horns might actually make this effect worse. This is a key component, in my opinion, for low level detailing and the ability to listen at lower, ear saving, volumes/late night too. The F5 was just a revalation, I heard stuff in my records and music files that I never knew existed, example would be the sound of a snare brush being slid across the drum head, a very soft "swish" that somehow appeared from nowhere on an Alison Kraus (sp??) album. Little stuff the artist or producer purposely put in there that none of us get to hear unless you're using high effieicncy speakers and amps with a very low noise floor, maybe quad57 will get it, not so sure though. I now use 2 stereo amps, both F5, 1 amp per speaker and use Channel D software for playback with includes a very nice digital domain EXO built-in. I also, like may of you, use CD mid/high horns (MR94-288Gs) and the software allows very fine level adjustments over the entire fequency range to EQ the CD horn flat power falling fequency response issue. I find the images of the players and instruments to be be much more developed and phsyical, like Reba - she stands in front separated from the band members, of course this is a built up song by a producer for layering and such, but very telling and on recorded live albums same thing voices from the audiance are shown as such while the musians are depicted and placed very nicely across and front to back - they have form as such. I highly reccomened the FW gear and for thoise who biamp/triamp might look at the F1J/F2J amps more current based and when driving the speaker/driver directly might prove better or maybe not, worth a try.

BTW the whole article on corner horn imaging is incredible and really makes the case - clear and simple. I came from years of monitor speakers, like IMFs, went to Quad57 (stacked and singles) in 1971 then to Beveridge Model II around 1984/5, then about 10 years ago, I swapped a 57 Reissue Strat and a 71 Fender Silver Face DR for a pair of cloned Altec 820s to add to my collection, also have Atec 755As. Took about 2 years of screwing around having the speakers away from the walls like we are led to believe is correct and finally put them in-place as designed along the long wall in the corners, what a wake up call, wasted 2 years of tune time. What do they say "I'm a beleiver" now. The 820s are now bass only and I use a sled on top for the mid/high horn so I can align the centers of the voice coils.

Thanks

Bob

[Chris A]

BTW the whole article on corner horn imaging is incredible and really makes the case - clear and simple.

Thanks Bob - I can tell that we're going to get along famously... [Y] Welcome!

The 820s are now bass-only, and I use a sled on top for the mid/high horn--so I can align the centers of the voice coils.

This is a good way to do it that's simple and effective. I've found that time alignment of ~1/5th to 1/10th of a wavelength at crossover wavelengths is what causes the speakers to go in and out of focus...no better explanation than that, I've found... djk (Dennis) is the guy that first used that explanation, to my knowledge.

Chris