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Posts by kevin gilmore

On the T2, the high end Vishay resistors caused a problem because they leaked current to the ground plane. Due to the super thin coating on these resistors. So running a resistor at 500v ( a few at 560v) for a resistor rated at 350v did not turn out well. Lifting the resistors .25 inch above the board did help, but still not a great idea. Stax used xicon resistors rated for voltage for a reason. And the same resistors are highly recommended if you build a diy T2.   I...
 definitely. But others helped too. Justin, Kerry,Ari,Marc,Craig and Mitsuru Very few of you are going to know the last 2.
2sk389/2sj109 came out sometime in early 1980's timeframe. At least that is the oldest datasheet I have on those parts.
You should probably test the output of the transformer with a 120pf load and look at it with a scope to see if there are any ringing problems before you hook it to the headphones.
That particular amp has output transformers. So yes it can run dynamic headphones. The malvalve amp also has output transformers and runs dynamic headphones.
this is what a diy-T2 looks like http://gilmore.chem.northwestern.edu/t2chassis29.jpg   more solid state than most solid state dynamic amps
You would have to make up a very custom cable to plug those headphones into a BHSE. Including a male stax plug. And wire it for balanced operation. A BHSE can source about 20ma max, so unlikely any damage to the headphones would occur. In any case its clear abuse of the headphones and is not covered under any of eBay's guidelines. Tell the clown to go and pound sand.
a thing of beauty for sure.   frank has retro down to a science.
this http://gilmore.chem.northwestern.edu/bamaslama.jpg but you have to change to driving the grid of the bottom of the tube. this is the idea, then you wrap the gain with feedback around this http://gilmore.chem.northwestern.edu/idea1.pdf what you do is pick R2 for the tube and mosfet current you want such that the output voltage is about +25 volts, then the servo will take it down to zero and keep it there. C1 allows the output tube to keep gain to max. ksa1156 is...
large voltage swings without feedback on a 6sn7 are going to be in the 2 to 3 percent thd range. you really need feedback. other power tubes are going to be similar. the output stage really does need to be dc coupled with a bipolar power supply. as simple as fixed bas, but better with a ground referenced servo and a high voltage pnp transistor similar to my old bamaslama design. then capacitor grid drive from an opamp with feedback
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