Yes I trimmed my J2 boards near the LED and cut off the portion and then made sure that the traces do not touch any of the chassis portion as I had used the 300mm depth chassis.@ meanie and manniraj
Did you trim your boards or are they built differently than mine?
Don
Suggested to have the thermistors "laying" on the top side of the primary wires with the bodies bent up into the air. They will get warm with operation and shouldn't be in contact with anything.
Here's a picture from the F4 6L6 build: IMG_1504_zps2330b348.jpg
Here's a picture from the F4 6L6 build: IMG_1504_zps2330b348.jpg
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My J2 is singing now. I first tested with it my pair of cheap test speakers. She is now hooked up to my Frugel-Horns being feed by my DAP through my Pre Iron SE. Sounds cleaner than my Sony Vfet, so far I have only listened with a glass of red wine in my hand.
The only problem that I have is that the blue leds are too bright.
The only problem that I have is that the blue leds are too bright.
Due to difficulties in sourcing parts, been periodically scouting for the harder to find bits before starting assembly of this amp.The J2 design doesn't use the SJ74/SK170s in a balanced circuit. The SK170's are just implementing a constant current source for the SJ74s (which form a long-tailed pair).
As it turns out, you're actually better off with GR parts for the current source (the SK170s). According to my analysis (with all the usual caveats), you want the total to be 6 - 10mA (so, for instance, a 4mA and a 4.5mA would be ideal).
Like others, I've struggled to find genuine SK170 in GR grade. There are some BL grades being offered currently in the swap meet section in case these are of interest to others.
Would you advise picking up the lowest Idss versions there rather than holding out for a GR grade set? Could get <6.4mA quads.
For reference:
GR = 2.6 to 6.5mA
BL = 6 to 12mA
So a 6.4mA BL grade would technically fall within the bounds of the GR grade, but higher than Jeff's recommended sweet spot.
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