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The ultimate DIY? A Stax SRM-T2!


spritzer

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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 by luvdunhill
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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 by kevin gilmore
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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.

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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 by luvdunhill
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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 by luvdunhill
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