luvdunhill Posted October 19, 2014 Report Share Posted October 19, 2014 (edited) 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, 2014 by luvdunhill Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted October 19, 2014 Report Share Posted October 19, 2014 (edited) 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, 2014 by kevin gilmore Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 19, 2014 Report Share Posted October 19, 2014 R31? Hence my request for clarification. Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted October 19, 2014 Report Share Posted October 19, 2014 (edited) 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, 2014 by kevin gilmore Quote Link to comment Share on other sites More sharing options...
randerson3024 Posted October 19, 2014 Report Share Posted October 19, 2014 I've never heard one, I can't wait to hear Birgir's tomorrow! Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 19, 2014 Report Share Posted October 19, 2014 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. Quote Link to comment Share on other sites More sharing options...
s_r Posted October 19, 2014 Report Share Posted October 19, 2014 I'd certainly be interested in some of the old T2 transistors. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 19, 2014 Report Share Posted October 19, 2014 "These" means the new production ones here. Quote Link to comment Share on other sites More sharing options...
s_r Posted October 19, 2014 Report Share Posted October 19, 2014 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). Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted October 19, 2014 Report Share Posted October 19, 2014 like the flip the transistors back to back idea. Quote Link to comment Share on other sites More sharing options...
spritzer Posted October 19, 2014 Author Report Share Posted October 19, 2014 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... Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted October 19, 2014 Report Share Posted October 19, 2014 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. Quote Link to comment Share on other sites More sharing options...
s_r Posted October 19, 2014 Report Share Posted October 19, 2014 Would putting in the LT1021 voltage reference but keeping the old sand (2SC3675, 2SA1486, etc) work? Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 19, 2014 Report Share Posted October 19, 2014 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. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted October 19, 2014 Report Share Posted October 19, 2014 (edited) / Edited November 11, 2015 by JoaMat Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 19, 2014 Report Share Posted October 19, 2014 (edited) 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, 2014 by luvdunhill Quote Link to comment Share on other sites More sharing options...
JoaMat Posted October 19, 2014 Report Share Posted October 19, 2014 (edited) / Edited November 11, 2015 by JoaMat Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 19, 2014 Report Share Posted October 19, 2014 Slightly change the pot in one of the batteries and monitor the output. Find the point it jumps back down. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted October 19, 2014 Report Share Posted October 19, 2014 (edited) Thanks for advise. Edited November 11, 2015 by JoaMat Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted October 19, 2014 Report Share Posted October 19, 2014 (edited) 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, 2014 by kevin gilmore Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 20, 2014 Report Share Posted October 20, 2014 (edited) 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, 2014 by luvdunhill Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 20, 2014 Report Share Posted October 20, 2014 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? :) Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted October 20, 2014 Report Share Posted October 20, 2014 none of the board mounting holes or pot locations have changed. 1 Quote Link to comment Share on other sites More sharing options...
GeorgeP Posted October 20, 2014 Report Share Posted October 20, 2014 Same spacing as the original board or the slightly smaller one? Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted October 20, 2014 Report Share Posted October 20, 2014 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. Quote Link to comment Share on other sites More sharing options...
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