First Watt SIT-4

cjfrbw

Well-Known Member
Apr 20, 2010
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Pleasanton, CA
Double post because new product:
I will let you know when my Protos arrives!
Nelson Pass is releasing another First Watt single ended SIT, the SIT-4, made with Tokin SIT rather than his previous radar SIT. Amp is spec'd at 10 watts per channel, but the Tokin device has potential anode dissipation of hundreds of watts (radar SIT had anode dissipation of about 50 or 60 watts). It is both voltage and current amplifier with a mu type MOSFET binary with no feedback fronted by NP's favorite JFET buffer.

Likely due to the massive reserve of the Tokin device, the amp has a lazy distortion curve that goes to about 20 watts @ 5 percent or so distortion, and probably can punch out higher transients than that, so not so lightweight as it seems from basic specs. $5K, so maybe a 'poor man's' Aries Cerat triode transistor type.

NP is also planning monoblocks for heat sinking purposes to push the base power up to 20 watts or more per channel.

I suspect this one will be a favorite of the low power high efficiency crowd, if it is anything like the single ended VFET Sony 2SK60 that I built from Pass DIY site.

Morricab's reports will be interesting on the AC units, but I have only read good things about them.
 
I just received mine. It’s only played for a day but offhand two immediate observations. First, it’s a lot more powerful than the spec would indicate. I also have the J2, SIT3, and F8 and this one plays the loudest with the volume knob static. According to the FW website, its gain is higher than the others so that’s likely the contributor, but with only 10 wpc into 8 ohms (5 into 4 ohms) it's nonetheless impressive.
The other thing is it’s much hotter to the touch than the others. This is due to its higher bias but must be right on the edge of what is permissible.
Again, I’ve only been listening for the past 24 hours but right away it’s got that lovely SIT bloom. It’s replaced the XA25 and while I rate that one highly, the new SIT is noticeably more musical with much better depth and nuance especially in the mids and highs.
I intend to compare it back to back w the SIT3 later this week.
But suffice to say I think Nelson has another hit on his hands.
 
Congrats. A new report after a couple of hundred hours of use would be welcome. However, I notice that the SIT products I have sound quite good even without a lot of warmup (as opposed to the M2 which doesn't come into form for at least an hour or two).

I gather NP may have a few SIT designs in the future with the Tokin SITs. I might buy one of the commercial products after we see what he rolls out.
 
monos to follow! ❤️❤️
 
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Any further updates or reviews on the SIT-4?
Would love to see a picture of the inside.
Not much posted about this amp. Maybe there are not many in the field yet?
 
I have the J-2. It’s no SET killer, that’s for sure! I find its highs too grainy on my La Scalas, whereas my various SETs (45s, 300Bs, WE 421a) sound simply sublime. I hope the SIT-4 sounds better. Someone should compare it to a great 300B SET. The wattage looks about the same.
 
I have the J-2. It’s no SET killer, that’s for sure! I find its highs too grainy on my La Scalas, whereas my various SETs (45s, 300Bs, WE 421a) sound simply sublime. I hope the SIT-4 sounds better. Someone should compare it to a great 300B SET. The wattage looks about the same.
Funny you should say that… I recently had a J2 in my kit for a while because so many have called it a darling of the First Watt series. On my field-coil T3’s it placed a broad grayish, somewhat grainy, upper frequency haze between us and the music compared to my triode based OTLs. I have recently been looking into low watt alternatives to the OTL format. This has included Atma-Sphere’s own D-class. Both of these fine solidstate amps imho are headed in the right direction, but neither has supplanted the larger power consumption tube based OTLs. Some might have said, well dah!… obviously. But I prefer to listen (with an open mind) and let that do the deciding and would have warmly embraced either had it worked out sonically different.
 
Received the sit-4 over the weekend and wow it is amazing. I can't think of any aspect of the sound that it does do exceptionally well in my system, considering that I have a subwoofer array in place and rendering its bass performance less important. By far the best solid state amp I've had in my system and possibly one of the best low-powered amplifiers of any kind in existence.
 
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Funny you should say that… I recently had a J2 in my kit for a while because so many have called it a darling of the First Watt series. On my field-coil T3’s it placed a broad grayish, somewhat grainy, upper frequency haze between us and the music compared to my triode based OTLs. I have recently been looking into low watt alternatives to the OTL format. This has included Atma-Sphere’s own D-class. Both of these fine solidstate amps imho are headed in the right direction, but neither has supplanted the larger power consumption tube based OTLs. Some might have said, well dah!… obviously. But I prefer to listen (with an open mind) and let that do the deciding and would have warmly embraced either had it worked out sonically different.

I have the J-2. It’s no SET killer, that’s for sure! I find its highs too grainy on my La Scalas, whereas my various SETs (45s, 300Bs, WE 421a) sound simply sublime. I hope the SIT-4 sounds better. Someone should compare it to a great 300B SET. The wattage looks about the same.
Ouch! Two strikes against the J2, and I'm assuming your speakers remain well above 4 ohms, especially in the midrange and above, as JA cautions here. https://www.stereophile.com/content/first-watt-j2-power-amplifier-measurements

Troy Crowe is building my new speakers, which except for the back loaded horn will resemble this. https://josephcrowe.com/products/speaker-system-no-2095 My sealed Altec 416-8B woofers and the same ES450 horn but with B&C DCM50 midrange and Troy's Fostex tweeter/lens combo.

Should have the speakers around end of summer, while meanwhile deciding on a DAC.

Actually, I've never once powered the J2 up since I purchased it from Reno hifi years ago. So, to protect the aging supply caps I will FIRST have to soft-start it via my pair of el cheapo Technics SB2760 speakers.

Hoping to report happy sounds from them with the J2, which I hope will outweigh the bad of its power draw and heat emissions.
 
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I’m not sure what systems others are using w their J2 but mine with a Pass XS Pre and Wilson Alexia 2 is terrific. In contrast to the F8, SIT-3 & 4 it’s still a favorite with certain tracks.
 
What are some good pre-amp options for the SIT-4, or other First Watt varieties including the Pass XA25?
I’m running a J2, and it is prickly with some of the pre-amps on hand. The best is actually a Bryston headphone amp which can be used as a pre-amp too. Short term solution, and apprehensive on trial and errror of the dozens and dozens of pre-amp options available.
 

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