SIT-3

[jborden]

The SEAS F8 + SIT3 combination made the stringed instruments sound like they were in the room, spooky indeed. F8's are way out of my price range however.

My favorites were the smaller full rangers. But like I said, with no notes and a memory like a sieve, well you get the idea... 🙂

Arrggghhh ... I have both J2 and SIT-1 ... don't do it ... don't do it 😀

 

[nicoch58]

Those were the 7" SEAS FEA18RCZ, and at $114 from Madisound they are
a bargain. I will get around to publishing their EQ curve for the sealed box.

thanks

 

[Dennis Hui]

Arrggghhh ... I have both J2 and SIT-1 ... don't do it ... don't do it 😀

Do it...do it... 🙂

 

[Dennis Hui]

Those were the 7" SEAS FEA18RCZ, and at $114 from Madisound they are
a bargain. I will get around to publishing their EQ curve for the sealed box.

May I ask how large were the sealed boxes used?

Thanks,
Dennis

 

[Nelson Pass]

Just a tad under 1 cu ft. Mario Yrun made them.

 

[Zen Mod]

Sissy ribbons on top of Sissy DCs

 

[pras1170]

Just a tad under 1 cu ft. Mario Yrun made them.

good
I have sent the sample by China post a few days ago

Please check.

 

[Dennis Hui]

Just a tad under 1 cu ft. Mario Yrun made them.

Thanks for the info. They look really cute. 🙂

 

[Phil Townsend]

Think I would like to build a pair. Like the doubled up plywood edge at a bevel. Plenty stiff sides.

 

[Phil Townsend]

Nelson, can’t tell you how much I am enjoying the SIT3. Well looks like I am telling you.
Anyway... thank you!
Ps the Feastrex with a resistor is quite happy with the 3.. My feastrex is the 16 ohm variety. Onwards

 

[WBS]

While contemplating the simplified diagram of the circuit in the SIT 3 Owners Manual, it made me wonder if it would be possible to adapt the concept to accommodate all of the left over Sony 2SJ28 VFETs out there.

I realize we are talking VFET and not SIT, but would it be possible to find an N channel Mosfet whose Gate voltage is the mirror image of the 2SJ28 and then reverse the voltage to accomplish a similar result?

I'm sure I'm showing my utter ignorance of circuits, but I thought I'd ask anyway. 😱

 

[vdi_nenna]

VFET and SIT are the same.
http://www.firstwatt.com/pdf/art_sit_intro.pdf

The problem is finding pairs of mosfets and vfets with matching Vgs, like you said.
It's been shown before that reversing the polarity in the circuit when using a P-ch device works. But in this case, wouldn't it be a positive supply? The SIT-3 uses a negative supply. Let me check...it does. Shows it right in the SIT-3 manual.

 

[WBS]

Thanks vdi. I've read the publications on First Watt multiple times but can't remember worth a damn. 🙂

 

[Zen Mod]

VFET and SIT are the same.
http://www.firstwatt.com/pdf/art_sit_intro.pdf

The problem is finding pairs of mosfets and vfets with matching Vgs, like you said.
It's been shown before that reversing the polarity in the circuit when using a P-ch device works. But in this case, wouldn't it be a positive supply? The SIT-3 uses a negative supply. Let me check...it does. Shows it right in the SIT-3 manual.

ground is state of mind

SIT-3 uses positive supply , but mind is easily fooled (which I'm confirming several times per day)

 

[Phil Townsend]

HP1 as a pre?

Perhaps there should be some space between the two.

 

[vdi_nenna]

If the lid of the SIT-3 is vented, then yes. Think I read- at least 3" clearance between components.
Surprising amount of heat is generated inside Class A amps; not just from the heat sinks. Heat from the SIT-3 could also heat up the chassis of the HP1.

Good looking couple though. Congrats on the marriage of the two! 🙂

 

[vdi_nenna]

ground is state of mind

SIT-3 uses positive supply , but mind is easily fooled (which I'm confirming several times per day)

Zero is more positive than -23v. Crazy world...🙂

 

[Zen Mod]

any FW amp is too hot for that arrangement , even with 10'' of space above

 

[Phil Townsend]

First Watt on top

First Watt on top...
HP1 Not so hot...

 

[Chul]

While contemplating the simplified diagram of the circuit in the SIT 3 Owners Manual, it made me wonder if it would be possible to adapt the concept to accommodate all of the leftover Sony 2SJ28 VFETs out there.

I realize we are talking VFET and not SIT, but would it be possible to find an N channel Mosfet whose Gate voltage is the mirror image of the 2SJ28 and then reverse the voltage to accomplish a similar result?

I'm sure I'm showing my utter ignorance of circuits, but I thought I'd ask anyway. 😱

Hi WBS, that is what I plan to do in the future. I have some quantity of 2SK28s. We can parallel two 2SJ28s. 🙂🙂
I am not so knowledged but I think 2SJ28 + IRF240 will do the same work as 2SK82 + IRF9240. If not someone please correct me.