Q23 needs a heat sink. Also only one trimmer on the schematic that I can find (I assume the 10K value is the same?)

Edit: oh you are only using the fine grain 2K control. Interesting. I assume the effect of changing R31, R32, RV1 allowing more adjustment range than the original RV1?

To be clear, the 22K resistor is in a different place in this circuit and you only have a single adjustment point. So, are you saying you turn it on and then use the adjuster to set voltage drop across 22K resistor to 6.55v then the same adjuster to set the voltage to 740v? Or are you adjusting resistor values to get 6.55v? (Sorry it wasn't clear to me)

I am not convinced this will perform better or equal to the KGT2 though. It is easier to build

A simple board to switch between LED bias at LT ref might be fun, for existing T2 owners, similar to the one I did to add low bias, which sits perpendicular to the PCB...

Edited October 19, 201411 yr by luvdunhill

Q23 is on the heatsink in all 4 places.

 

I have edited all 3 boards to make all the horizontal resistors .6 inch

 

waiting on more feedback before I post

 

there is no 22k resistor

http://gilmore.chem.northwestern.edu/t2schemmodified.pdf

 

and the voltage is now 10v on the diff pair.

Edited October 19, 201411 yr by kevin gilmore

R31? Hence my request for clarification.

you mean Q32, heatsinks added

 

http://gilmore.chem.northwestern.edu/t2modified.jpg

 

pot now in parallel with resistor, use one or the other. or pick a higher resistance

and trim down.

 

oh that R31. yeah 22k. but that and the center of the pot is now 10V

Edited October 19, 201411 yr by kevin gilmore

I've never heard one, I can't wait to hear Birgir's tomorrow!

Yes Q32, sorry, but the measurements above would be nice to verify.

If you flip the 6k2 resistor 180 degrees and flip 180 degrees the other transistor and move it behind the one on the little heat sink it might be a bit cleaner... If someone wanted to use 2sc3675 this also seems a bit safer.

I will do a group buy on these transistors if people are interested. Can do a full kit or can do just the Fairchilds. Looks like a good savings can be had.

I'd certainly be interested in some of the old T2 transistors.

"These" means the new production ones here.

Oh, gotcha. Still interested though, JoaMat's mini T2 is something I'd like to build after I finish my kgst (as opposed to "sometime in the future" for the original T2).

like the flip the transistors back to back idea.

I've never heard one, I can't wait to hear Birgir's tomorrow!

 

Mine is still fubar so that won't be happening.  Well we could do mono... 

could go back to my original board and make all the changes to it, but I don't think

anyone would be interested in that.

Would putting in the LT1021 voltage reference but keeping the old sand (2SC3675, 2SA1486, etc) work?

Would putting in the LT1021 voltage reference but keeping the old sand (2SC3675, 2SA1486, etc) work?

Yes, if you make the other changes to the batteries.

/

Edited November 11, 201510 yr by JoaMat

The 10V version has a max voltage noise of 6uV. LEDs should be an order of magnitude less. The things I am not sure of are current noise and tempco. Since LEDs share similar geometry to transistors, this might actually be a case to use LEDs. I just don't know enough to definitely declare the change a winner, other than the goals that JoaMat set out to achieve.

Edited October 19, 201411 yr by luvdunhill

/

Edited November 11, 201510 yr by JoaMat

Slightly change the pot in one of the batteries and monitor the output. Find the point it jumps back down.

Thanks for advise.

 

Edited November 11, 201510 yr by JoaMat

full size layout modified and sent to joamat for checking

 

original board with all the mods

 

http://gilmore.chem.northwestern.edu/staxt26.jpg

 

still needs the pot on the fqpf2145

Edited October 20, 201411 yr by kevin gilmore

Now I am listening totally selfish request but is the 1K trimmer in the exact same location in reference to a mounting hole? I have a hole directly over trimmer locations (also TPs, and LEDs on the bottom, but that doesn't matter as much) as to adjust the amp with the lid on..

Edited October 20, 201411 yr by luvdunhill

Thanks for advise. I'm now back in stereo mode.

Yay! Adjustment of this amp is like dancing on a blade's edge. What about the measurements in #3524 as recompense? :)

none of the board mounting holes or pot locations have changed.

Same spacing as the original board or the slightly smaller one?

JoaMat/Inu: when using LSK389 what are the voltages at all 6 pins with respect to ground? I might be able to suggest a better way to do this.