Do I really not need more than 1 watt?!?
- Thread starter MKG
- Start date
I LOVE my F5. I'm getting ready to break it into monoblocks. I've got the second chassis just a few feet from me and I've got the Mouser order together.
Picking a First Watt amp to build is something that deserves some thought. The big questions are "What kind of sound do you want?" and "What do your speakers need?".
I picked the F5 for several reasons. First, my Focal reach down to 2.8 ohm so an amp that "doesn't burp" looking at a 2 ohm load was a plus. Second, it's the lowest distortion FW amp there is. Third, it's got a lot of flexibility. It can be easily scaled up in size and power, and it's tone/distortion can be messed with. I've messed with that second "feature" a lot over the years and learned what distortion actually sounds like and that's been an adventure. Sonically, it's a muscular amp that has plenty of punch and slam, but it glosses over nothing. Cymbal decays go on forever. Echoes trail off into infinity. It's incredibly dynamic, fast, and dimensional, but doesn't overlook the fine details. It's no problem to pick out the ring of a rack tom or splash of a cymbal at the back of the kit from a layered wall of processed, distorted guitars and bass.
The F6 is a different kind of amp. It's weird... It derives all of its gain from a transformer and it defines the sound of the amp. It's got much narrower bandwidth than the F5 (nobody NEEDS 1MHz bandwidth anyways), and it's got a tubey sort of distortion character you can mess with a little by fitting it with different transformers. Not much you can do to get more power out of it. The M2 is another option that can be built out a lot of different ways. The M2X kit comes with a bunch of front ends that do different things. If you want the ultimate in Pass DIY flexibility you should look at the BA (Burning Amp). It comes 3 flavors. The BA1 and 2 use a differential input stage and drive either a single ended or complimentary output stage. The BA3 uses a complimentary input stage that is basically a small F5 without feedback to drive a complimentary output stage like what's in the F5.
I haven't heard any of those other ones, but I can make some good guesses about what I've read and what I've learned playing with my F5. Some people think I'm a little nuts for my build of the F5. The LSJ74 JFET is only rated for 25V and I'm putting 32V on it. 1.4A is kinda pushing it on bias which is why I'm splitting it, to get more cooling. It's a great amp though. It's a lot like the XA25, just a bit less refined.
Poultrygeist
Lunatic Member
Three watts from my 2a3 SET Bottleheads is more than enough for the Lowther's. I'm considering a 45 SET which makes half that.
nj pheonix
Lunatic Member
F5 turbo in the pipeline. Hopefully done before end of March. Stay tuned
Hobie1dog
subaholic
what he said +1
Damn it, now I need to tell my 10wpc Class A SS amp it apparently does not sound good
Edit: I also have 140wpc and 35wpc available and the 6 and 10 WPC amps get 90% of the listening time.
Lol I did say often not always...
That style of rating is pretty useless unless you're planning to use a power source amp. The vast majority of amps are voltage sources and no speaker is a perfectly flat resistive load. The dB/M/2.83V makes a bit more sense.
so you’re saying a speaker sensitivity measurement is useless when selecting Speakers
mhardy6647
Lunatic Member
One watt is cutting it very, very fine with even very sensitive loudspeakers.
I started my re-entry into vacuum tube amplification with one of Steve Deckert's (then) cheap little SE-84B amps. Single-ended EL84 wired as a triode for somewhere between 1 and 2 watts per channel. It was not quite up to the task of full-range amplification with a pair of 1974 vintage Klipsch Cornwalls (ca. 98 dB SPL @ 1 meter @ 1 watt sensitivity); even "little girl with guitar" music got strained and "hard" sounding at only moderately loud volumes.
Single-ended 2A3 amplification (probably ca. 3.5 watts at 10% THD) was much, much better -- and is what I use to this day albeit with much better sounding, and somewhat more sensitive, loudspeakers (essentially Altec Duplexes (somewhat augmented); ca. 104 dB SPL @ 1 meter @ 1 watt).
What matters for a loudpeaker as it presents itself as a load to an amplifier is its sensitivity and its impedance (and phase) curves. Irrespective of sensitivity, some loudspeakers are just easier to drive than others.
I started my re-entry into vacuum tube amplification with one of Steve Deckert's (then) cheap little SE-84B amps. Single-ended EL84 wired as a triode for somewhere between 1 and 2 watts per channel. It was not quite up to the task of full-range amplification with a pair of 1974 vintage Klipsch Cornwalls (ca. 98 dB SPL @ 1 meter @ 1 watt sensitivity); even "little girl with guitar" music got strained and "hard" sounding at only moderately loud volumes.
Single-ended 2A3 amplification (probably ca. 3.5 watts at 10% THD) was much, much better -- and is what I use to this day albeit with much better sounding, and somewhat more sensitive, loudspeakers (essentially Altec Duplexes (somewhat augmented); ca. 104 dB SPL @ 1 meter @ 1 watt).
What matters for a loudpeaker as it presents itself as a load to an amplifier is its sensitivity and its impedance (and phase) curves. Irrespective of sensitivity, some loudspeakers are just easier to drive than others.
Last edited:
This theme is oft repeated here and elsewhere. Audio consumers listen at different levels, have different speakers and rooms, therefore the variety in watts. I have Nelson Pass amps, doesn't make me any smarter or invested in 1 watt and less output (whoever is hunting down the F5 Turbo, nice path to go!). When I'm really old, maybe 1 watt will do, but for now, not a chance.
You are correct about this
. The discussions always turn into the people that have never done it telling the people that do it everyday how it can't work 
whoaru99
Epic Member
True about speakers not being perfect resistances.
But, it's the relative means of comparison that is the key here. Relative to rated impedance of 8 ohms, 1W vs 2.83V is effectively the same/similar.
4 ohms (or other impedances), OTOH, is where the gotcha lies. For example, 2.83V is 2W @ 4 ohms so rated that way the sensitivity would be shown 3dB higher than a 8 ohm speaker even though on a per-watt basis they may be same sensitivity.
You are correct about this
Yes, folks will continually tell you what you have observed and what works for you is false. Agreed!
Nixxuz
Super Member
It is if you are bi-amping.so you’re saying a speaker sensitivity measurement is useless when selecting Speakers
whoaru99
Epic Member
so you’re saying a speaker sensitivity measurement is useless when selecting Speakers
How ya conclude that?
Its still a meaningful measurement, one of the side effects of bi-amping is you are "basically" increasing the sensitivity of your speakers.
I just re-integrated my power amp into my system, an SAE A-501 with 250 WPC. I was hoping for and got a fuller presentation of the music from my system. During cocktails on Saturday night with the wife we barely grazed 1/8th of 1 watt according to the meters on the amp. It was certainly loud enough for listening while sitting across from the speakers.