My First Watt F2 was recently re-worked by Nelson with J-Fet's in place of the original Mosfets. Thought I would write a few words about it.
As usual, the unit requires 15 minutes of warmup to sound good, and 30 minutes for critical listening. It does not take long to realize this is a special amp. Although it is difficult to recall the exact nature of the F2 mosfet sound, this amplifier is obviously cleaner, with lower distortion. The "rose shaded glasses" effect of the F2 is now gone. But, more importantly, the sound is now much sweeter, as if cut from whole cloth and part of the musical fabric. Imaging seems improved, but that my be more my memory than fact.
As before, very dynamic when mated with efficient speakers. The current source F2 may require a special filters to sound its best with different speakers. For more information, see the White Paper "Current Source Amplifiers and Sensitive Drivers: by Nelson Pass" on the First Watt site. With only 5 watts, high efficiency speakers are a must.
As an extra added prize, the LED's have been dimmed. So last night was a late night listening session. Vinyl was spinning, the lights were off, and a bit of cognac involved. But it was the sound which was truly intoxicating. Extended listening showed no signs of "listener fatigue", and the few words above do not accurately portray how much fun it is to hear this amp. Very, very nice.
As usual, the unit requires 15 minutes of warmup to sound good, and 30 minutes for critical listening. It does not take long to realize this is a special amp. Although it is difficult to recall the exact nature of the F2 mosfet sound, this amplifier is obviously cleaner, with lower distortion. The "rose shaded glasses" effect of the F2 is now gone. But, more importantly, the sound is now much sweeter, as if cut from whole cloth and part of the musical fabric. Imaging seems improved, but that my be more my memory than fact.
As before, very dynamic when mated with efficient speakers. The current source F2 may require a special filters to sound its best with different speakers. For more information, see the White Paper "Current Source Amplifiers and Sensitive Drivers: by Nelson Pass" on the First Watt site. With only 5 watts, high efficiency speakers are a must.
As an extra added prize, the LED's have been dimmed. So last night was a late night listening session. Vinyl was spinning, the lights were off, and a bit of cognac involved. But it was the sound which was truly intoxicating. Extended listening showed no signs of "listener fatigue", and the few words above do not accurately portray how much fun it is to hear this amp. Very, very nice.
well Jon , I'm glad that you're glad .
funny thing is - that nothing less we don't expect from Papa .
funny thing is - that nothing less we don't expect from Papa .
Nelson, is there a hand drawing of the new schematic to share?
I have some of the R100's that could be used.
I have some of the R100's that could be used.
greedy boy .........
I hope it was the F1 as I am building one, that being said I would like to hear both as I am sure they are different sounding...
Regards, Elwood
Regards, Elwood
Oops, The F2 I was referring to, and I have SemiSouth SJEP120R100's.
The F2 is the first pass amp I built. It's worth revisiting.
Cool 🙂
I'm wondering if can be changed to provide more power, even leaving class A...? Any tip?
You can have more power with higher voltage on the rails and more output devices, but as far as I can see neither F1, F2 or J2 can leave class A with the power on...
F1 and F2 are good candidates for higher rail voltage, the J2 with tiny Jfets on input are not so good at higher voltage without some work.
highly refined 45 amp vs. F2J
Can you quantify the difference between the F2J and high quality DIY 45 amp.
A friend tells me he prefers the F2J (his 45 is not out to mine-best active and passive parts through trial over several years, Hashimoto Trannies, EML rectifier and output tubes, JJ drivers)
After 45 years of refining my system, I am done and off the merry-go-round.
I have your M2 which is a fine amp, but...
I imagine the F2J has more detail. Could a die hard 45 lover "warm up" to a F2J?
I'm sure the F2J is excellent-can it eclipse a good 45?
BTW-Have found "my last speaker". A true marvel-Mark Audio Alpair 12P drivers ($157/each) in their Super Pensil transmission line enclosure. Made for 45s and, I believe about the only true full range single driver. Amazing sound.
Thanks,
Mike
Hi Nelson,
Can you quantify the difference between the F2J and high quality DIY 45 amp.
A friend tells me he prefers the F2J (his 45 is not out to mine-best active and passive parts through trial over several years, Hashimoto Trannies, EML rectifier and output tubes, JJ drivers)
After 45 years of refining my system, I am done and off the merry-go-round.
I have your M2 which is a fine amp, but...
I imagine the F2J has more detail. Could a die hard 45 lover "warm up" to a F2J?
I'm sure the F2J is excellent-can it eclipse a good 45?
BTW-Have found "my last speaker". A true marvel-Mark Audio Alpair 12P drivers ($157/each) in their Super Pensil transmission line enclosure. Made for 45s and, I believe about the only true full range single driver. Amazing sound.
Thanks,
Mike
Doesn't sound to me like you're off the merry-go-round. 😉
I couldn't possibly tell you which is better - that is to say which will sound
better to you in a given system.
I can only tell you that the F2J is easier and cheaper to build than a 45, so
it should be reasonable for you to build it and find out.
😎
I couldn't possibly tell you which is better - that is to say which will sound
better to you in a given system.
I can only tell you that the F2J is easier and cheaper to build than a 45, so
it should be reasonable for you to build it and find out.
😎
well , it somewhat rude (here in Papaland) to even mention any speaker smaller than 15" in diameter
Mike,
The A12p SuperPensil is a really good system (we helped Jeff aka VinylKid a set) but the A10p goes lower, reaches higher, has greater DDR/detail, and is less than a dB less efficient. And EnABLed they are even better.
dave
- Status
- Not open for further replies.