Will we ever see the schematic for J2 ?
I have been saving parts and home made PCBs of what I think is the schematic (or really close) but never dared to try them in fear of burning my precious FETs...
I'm sure, some day we will. However after receiving the "Amplification Component of the Year" award from Stereophile only 2 months ago, for a 10 year old design no less, it might be a while longer.
I can't think of any reason why Papa would discontinue a successful design that is still selling.
Don't cry LB. With the retirement of several FirstWatt products we should have some pretty interesting reading, and projects, in the near future. Especially if a suitable replacement is found for the Pass SITS found in the SIT-1 and SIT-2!
I'm dying to hear one of the SIT amps. Hoping for a SIT-1 subsitiute.
I had a chance a hear a friend's SIT-1s, but the guy sold them for Class D amps before I could listen to them! What the Fudge!
He must have come to his senses at some point because he now has XA 60.8s, but no joy from the pure single-ended stand point. 
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Which Class D amps did he have? I wonder if the sound gets old after the novelty wears off.I'm dying to hear one of the SIT amps. Hoping for a SIT-1 subsitiute.
I had a chance a hear a friend's SIT-1s, but the guy sold them for Class D amps before I could listen to them! What the Fudge!
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I knew someone would ask.
WOW!! Hypex NC1200!! Those are supposed to be the cat's a$$!!
There are many companies literally just slamming those modules in a box and slapping a $10,000 price tag on them. Then other companies are putting the same modules in a box with a $3,000 price tag. Who would pay the difference??
I was told by a Theta sales rep that Pass was yesterday's news compared to Hypex.
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All I know is this: Every amp with dominate 3rd harmonic I've heard bores me after an hour, although the 1st hour is thrilling. I get irritated and on the verge of anxiety with chip amps and Class D amps, Off goes the power!.
I'd take a SIT-1 any day of the week and twice on Sunday. (I listen more on Sundays. ) Without ever even hearing SIT-1 monos, I'd take them.
I'd take a SIT-1 any day of the week and twice on Sunday. (I listen more on Sundays.
) Without ever even hearing SIT-1 monos, I'd take them. vdi_nenna,
Take the plunge. Exercise you home equity line and get a pair of SIT1s!
I will never get rid of mine. They are the last amplifiers, along with the monoized J2s, I will ever own. If someone improves on them it will be so incremental as to be like the fellow at AUDIO ASYLUM says - if I can hear more difference from moving my head an inch then I do not need another amplifier.
I used my SIT1s for a short while driving two horns from 100 hz on up. I quickly moved them to only 500 hz and above and there they are psychedelic. I cannot imagine anything driving a compression driver better but then I do not expose myself to much that is out there.
Have finally ordered 100 volts transformers and LUNDAHL chokes for a choke input supply for the SITs. I think this will add the final bit of refinement to the sound. It certainly did for the J2s.
Someone made the observation how with better amplification the sound no longer "sticks" to the speakers. A simple idea but it is true. With the choke input J2s the horn they are driving simply disappears. Hoping a similar effect will come from doing the same with the SIT1s.
I will know after this weekend.
Take the plunge. Exercise you home equity line and get a pair of SIT1s!
I will never get rid of mine. They are the last amplifiers, along with the monoized J2s, I will ever own. If someone improves on them it will be so incremental as to be like the fellow at AUDIO ASYLUM says - if I can hear more difference from moving my head an inch then I do not need another amplifier.
I used my SIT1s for a short while driving two horns from 100 hz on up. I quickly moved them to only 500 hz and above and there they are psychedelic. I cannot imagine anything driving a compression driver better but then I do not expose myself to much that is out there.
Have finally ordered 100 volts transformers and LUNDAHL chokes for a choke input supply for the SITs. I think this will add the final bit of refinement to the sound. It certainly did for the J2s.
Someone made the observation how with better amplification the sound no longer "sticks" to the speakers. A simple idea but it is true. With the choke input J2s the horn they are driving simply disappears. Hoping a similar effect will come from doing the same with the SIT1s.
I will know after this weekend.
Interesting stuff Rick. You're a brave dude. I wouldn't risk modding those amps.
Trust me, I have given lots of thought on ways I could get a pair. Its not impossible. I'm just too cheap. Also knowing how to build amps makes buying expensive ones even more difficult to pull the trigger. Only thing in there is the Pass-SIT-1, as far as I can tell, that's unique.
I have the Lamp v193 and CCS. I'm just being greedy.
I'm building a lower powered 50w SE Schade amp now.
Hoping to capture some of that magic.
Trust me, I have given lots of thought on ways I could get a pair. Its not impossible. I'm just too cheap. Also knowing how to build amps makes buying expensive ones even more difficult to pull the trigger. Only thing in there is the Pass-SIT-1, as far as I can tell, that's unique.
I have the Lamp v193 and CCS. I'm just being greedy.
I'm building a lower powered 50w SE Schade amp now.
Hoping to capture some of that magic.
Some would say foolish instead of brave!
I like building my own stuff, too. Luckily Mr. Pass made it necessary for me to buy his amps with their unobtanium devices. The enchanting lure of unobtanium is irresistible for me.
With the SIT1s I have, so far, replaced the rectifiers. That's it. I hate binding posts so I did take the output wires to outside of the chassis so I could solder direct to the speaker wire. There is direct connection to the unbuffered input.
I use the amp as part of the crossover - a 0.032 uF cap at the input - the output caps are bypassed and the LC crossover at the speaker handles the DC blocking. Using a Q of 1.3 to get a final response between Bessel and Butterworth. Works extremely well. Used to just have a cap and the passband was extremely droopy as you would expect. Then tried Butterworth and this was better but going beyond Chebyshev was the key. The Qs multiply which took me the longest time to believe! Using REW to see what is happening has been what my experiments were missing.
Getting that region flatter has great effect on how you perceive the rest of the spectrum. The system was transformed. (I had to force myself to write that. It is such a tiresome thing to say but I swear it is true!)
I like building my own stuff, too. Luckily Mr. Pass made it necessary for me to buy his amps with their unobtanium devices. The enchanting lure of unobtanium is irresistible for me.
With the SIT1s I have, so far, replaced the rectifiers. That's it. I hate binding posts so I did take the output wires to outside of the chassis so I could solder direct to the speaker wire. There is direct connection to the unbuffered input.
I use the amp as part of the crossover - a 0.032 uF cap at the input - the output caps are bypassed and the LC crossover at the speaker handles the DC blocking. Using a Q of 1.3 to get a final response between Bessel and Butterworth. Works extremely well. Used to just have a cap and the passband was extremely droopy as you would expect. Then tried Butterworth and this was better but going beyond Chebyshev was the key. The Qs multiply which took me the longest time to believe! Using REW to see what is happening has been what my experiments were missing.
Getting that region flatter has great effect on how you perceive the rest of the spectrum. The system was transformed. (I had to force myself to write that. It is such a tiresome thing to say but I swear it is true!)
That's some analysis and testing. I usually stick with L-R crossovers. My last speaker uses a textbook 12db 2-way passive XO. Happens to sound good although it's probably considered wrong. Also have two FW B4 active XOs. They do all the hard work.
I've heard of soldering the outputs directly to the speakers. Umm, that's commitment.
Anyway, J2 is a nice amp...
I've heard of soldering the outputs directly to the speakers. Umm, that's commitment.
Anyway, J2 is a nice amp...
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It seems the J2 will remain available for the foreseeable future. Does
Stereophile give out an award for amplifier of the decade?
I've been eyeing the SIT-2 for a while but recently pulled the trigger on another
amp. Probably would have made a different choice if I'd known the SIT-2
is soon to be discontinued...
Stereophile give out an award for amplifier of the decade?
I've been eyeing the SIT-2 for a while but recently pulled the trigger on another
amp. Probably would have made a different choice if I'd known the SIT-2
is soon to be discontinued...
One can also make the output wire "pass through" the binding post and then make a mechanical connection to the speaker wire with the said binding post. That way you can swap speaker wires easily for testing.
I do it always...
Cheers,
M.
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Don't cry LB. With the retirement of several FirstWatt products we should have some pretty interesting reading, and projects, in the near future. Especially if a suitable replacement is found for the Pass SITS found in the SIT-1 and SIT-2!
At this time I believe that all the retired FW amplifiers have been documented
sufficiently for DIYer's to build them. The SIT-1 and SIT-2 have also been
documented. At the moment, this leaves the F7 and J2, and there are some
decent examples posted on this forum.
What you may lack is the word "official", which the cloners seem to desire so greatly.
I know there isn’t a reference schematic for the J2, so I already realize I probably won’t get a good answer to my question - but is there any reason to think the gain couldn’t be reduced from 11 to 5? I would halve the feedback resistor, then measure to see if I need to raise the compensation capacitor.