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JMON
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Components used during our jazz session were the following.

Premium tube preamp - Don Sachs  

Amp - First Watt F3

DAC - Holo Audio Spring 3

Speakers - Lii Audio F-15 in parallel with Lii Audio Silver 8 drivers. Impedance drops to about 4 ohms in this configuration. 

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Got a F8 hooked up. OMG!  I find it both smoother and clearer than my F3 and Xa25.  Somehow it is more transparent than the xa25, but smoother.  Clearer and more aggressive than the F3, but just as smooth, or smoother.

this is better in all categories for my system. Did just what I wanted, smoother, but more clear and transparent at the same time.

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48 minutes ago, VDS said:

Got a F8 hooked up. OMG!  I find it both smoother and clearer than my F3 and Xa25.  Somehow it is more transparent than the xa25, but smoother.  Clearer and more aggressive than the F3, but just as smooth, or smoother.

this is better in all categories for my system. Did just what I wanted, smoother, but more clear and transparent at the same time.

 

Single ended amplifiers are my favorites and the F8 is a great one!! Power Jfet output and current feedback topology yes please. Great design!!

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45 minutes ago, captainbeefheart said:

 

Single ended amplifiers are my favorites and the F8 is a great one!! Power Jfet output and current feedback topology yes please. Great design!!

I’ve only had one SET tube amp, but this really has some similar characteristics. 

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9 hours ago, VDS said:

I’ve only had one SET tube amp, but this really has some similar characteristics. 

😀

 

SET sound using SS devices. Shame those power J-fets are no longer available for diy'ers. Discrete audio transistors are not profitable to design anymore. The old ones are slowly being phased out. 

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On 2/25/2022 at 7:12 AM, henry4841 said:

😀

 

SET sound using SS devices. Shame those power J-fets are no longer available for diy'ers. Discrete audio transistors are not profitable to design anymore. The old ones are slowly being phased out. 

 

It's strange because Jfet's are much cheaper to produce vs Mosfets. My guess is with all the high speed switching applications the high capacitance of a Jfet isn't good for much of today's applications.

 

For the masses linear amplifiers are being phased out to Class D switching amplifiers. The new zetex chips are supposed to be the next level for Class D amplifiers as it addresses a lot of their shortcomings. And of course switching amps are going to use Mosfets.

 

Another thing is Jfets are all depletion mode, or always on transistors. They will pass IDS with VGS=0, again less application uses.

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  • 3 months later...

It's been a while now but I picked up a First Watt SIT-3 amp.  I haven't had a whole lot of free time to listen but have had sufficient time to believe this is unquestionably the best solid-state amp I've ever owned.  In fact, I'm really having trouble differentiating the sound from the other tube amps that I own.  I certainly need to spend more time listening and comparing them, but I could absolutely live with any of them as my only amp.  The SIT-3 seems to only be at it's best when connected to a certain pre-amp that I have that has a higher output level than the others.  But when it is with that particular pre-amp it sounds wonderful.

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On 6/7/2022 at 12:15 PM, JMON said:

It's been a while now but I picked up a First Watt SIT-3 amp.  I haven't had a whole lot of free time to listen but have had sufficient time to believe this is unquestionably the best solid-state amp I've ever owned.  In fact, I'm really having trouble differentiating the sound from the other tube amps that I own.  I certainly need to spend more time listening and comparing them, but I could absolutely live with any of them as my only amp.  The SIT-3 seems to only be at it's best when connected to a certain pre-amp that I have that has a higher output level than the others.  But when it is with that particular pre-amp it sounds wonderful.

when you get tired of it... :)

 

I almost bought a F8 a couple weeks ago based on the the comparisons of former owners of the f7/f8/SIT III, However the Sit III is at the delta of what I am seeking. I know there are a couple for sale on the bay and US Audio. good to hear you are enjoying them... with which speakers are you running them?

 

I have been reading that they mate well with highly efficient speakers, but are underwhelming with demanding speakers or if you like to live at reference levels... is that your assessment?

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1 hour ago, Schu said:

when you get tired of it... :)

 

I almost bought a F8 a couple weeks ago based on the the comparisons of former owners of the f7/f8/SIT III, However the Sit III is at the delta of what I am seeking. I know there are a couple for sale on the bay and US Audio. good to hear you are enjoying them... with which speakers are you running them?

 

I have been reading that they mate well with highly efficient speakers, but are underwhelming with demanding speakers or if you like to live at reference levels... is that your assessment?

Get in touch with Mark at Renohifi about your desire for a SIT-3. Give him a call. Almost bet he will find you one with some kind of warranty. USA Pass dealer. 
 

https://renohifi.com/Instocklist.htm

 

I assume you know the F8 is a power J-fet vs true SIT's in the SIT-3. Big difference, but I am sure both sound excellent in their own way. 

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When considering a SIT (static induction transistor) think in the terms of triode tube sound, 300B, in a SS device. The F8 is supposedly an improved J2, probably the best seller of the Firstwatt brand. Nelson's stash of SIT's, his private made transistor, and the power J-fet made by the SemiSouth, are almost depleted. SemiSouth is no longer in business. The SIT's made by SemiSouth were original made for the military because of their fast speed in radar. Contract ran out and one more batch made for Nelson and soon after SemiSouth closed the door. Just some history. 

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1 hour ago, henry4841 said:

The F8 is supposedly an improved J2

 

I have the J2 and really like it. Got rid of my VRDs and Wright 2A3 mono blocks and have zero regrets. My only beef with the First Watt lineup is that more of them don't have balanced connections. I'd likely try a few more variants beyond the J2 if only they were.

 

EDIT: Just looked back at the first page. I'm now so old I'm repeating myself. 😲

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1 hour ago, rplace said:

 

I have the J2 and really like it. Got rid of my VRDs and Wright 2A3 mono blocks and have zero regrets. My only beef with the First Watt lineup is that more of them don't have balanced connections. I'd likely try a few more variants beyond the J2 if only they were.

 

EDIT: Just looked back at the first page. I'm now so old I'm repeating myself. 😲


— admitting you’re old is step one to total enlightenment - (proverb from the sticks) 😎

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I also have the J2 because I wanted balanced inputs. I'm very happy with it on my Lowther / Oris horns. It seems like it takes a little bit to warm up. After a few hours of playing the soundstage is holographic if that makes sense.

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10 hours ago, rplace said:

My only beef with the First Watt lineup is that more of them don't have balanced connections. I'd likely try a few more variants beyond the J2 if only they were.

 

6 hours ago, capo72 said:

I also have the J2 because I wanted balanced inputs. I'm very happy with it on my Lowther / Oris horns. It seems like it takes a little bit to warm up. After a few hours of playing the soundstage is holographic if that makes sense.

 

This is easily solved by using a high quality Jensen ISO-MAX transformer to allow Balanced to Unbalanced equipment use with full high quality signal integrity in my experience.

 

I highly recommend using a Jensen PC-2XR or the PI-2XX (which can be ordered as a PI-2XR if wanting the RCA OUTPUT Connector installed on unit versus using a short Balanced to RCA interconnect cable with the PI-2XX). 

 

The PC-2XR has a 4:1 Step-down Transformer and is beneficial in situations where you have to much gain in the system leading to the amplifier or an amplifier with a high sensitivity input.

 

The PI-2XX (PI-2XR) has a 1:1 Transformer and is best used when the system gain isn’t an issue or in the specific case with amplifiers having typical or low input sensitivity.

 

The First Watt F3 for example will work well with either but my preference and my opinion having used both ISO-MAX units is the F3 benefits from strong input drive and gives maximum quality and output level when using my McIntosh C50 with the PI-2XX (with the proper balanced to unbalanced adapter cable).

 

 

On the topic of warm up with the first watt amplifiers I have experienced the same as you in that the imaging and tonal balance of the F3 takes a minimum of 30 minutes to 1 hour to fully develop and stabilize and is easily among the best I have experienced even when compared with my Cary CAD2A3-SE tube amplifiers.  FYI: I have actually measured both of my F3 amplifier’s heat sinks and temperature stability is reached at 130 Degree Fahrenheit in approximately 1hr.

 

 

miketn

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The F3 was the first of Nelson's power J-fet amplifiers. The others are the J2, really popular, and the newer F8. It is a known fact that the hotter you run a transistor the better it will sound. That is until it burns up. Your F3 is running at it's intended range of 55C. The mosfets Nelson uses are generally rated at max 150C so the 55C is a very safe range for them. Most that own a class A amplifier can hear the difference from cold startup and when it reaches it's intended operating range. This is not to say it will not sound really good cold, just better when warmed up. With an A/B amplifier you normally listen to transistors just barely warm all the time. Another reason class A is called by the first letter in the alphabet. 

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2 hours ago, henry4841 said:

t is a known fact that the hotter you run a transistor the better it will sound. That is until it burns up.

 

That raises a question in my mind: what's the life expectancy? If J-fets are no longer available, how does one get service?

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On 6/10/2022 at 4:56 AM, henry4841 said:

When considering a SIT (static induction transistor) think in the terms of triode tube sound, 300B, in a SS device. The F8 is supposedly an improved J2, probably the best seller of the Firstwatt brand. Nelson's stash of SIT's, his private made transistor, and the power J-fet made by the SemiSouth, are almost depleted. SemiSouth is no longer in business. The SIT's made by SemiSouth were original made for the military because of their fast speed in radar. Contract ran out and one more batch made for Nelson and soon after SemiSouth closed the door. Just some history. 

I wish I had learned something new today... but I guess it's a little to early and the rest of the day is open for someone to actually enlighten me. One can only hope.

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2 hours ago, michaelwjones said:

 

That raises a question in my mind: what's the life expectancy? If J-fets are no longer available, how does one get service?

 

I’m personally not concerned due to knowing that these are high quality and relatively simple designs with low parts counts and Nelson Pass knows very well how to spec parts and choose operating  parameters for very reliable long life span designs. I’m not aware of any issues of getting parts for repair service being reported by First Watt and if anyone is concerned about available parts (I believe they maintain a reserve inventory just in case a need for servicing might arise) for servicing of a First Watt Amplifier I would suggest contacting them directly. 

 

I’ve only read of one instance of a First Watt F3 amplifier that needed a solder joint on the Jfet of an F3 reflowed. I’ve not read of any other repairs being required on a First Watt amplifier and would be curious if anyone else knows of any that required service.

 

 

miketn

 

 

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