Thanks again for the discussion - am learning/have learned a lot.
So to see if I understand - if one were to build the 2SK77B circuit with a substitution of 2SK182s for the unobtanium would the timing of bias voltage and gate voltage be a concern for theVFET or does the presence of the hockey puck in the CCS mitigate.
Thanks again
Bob
So to see if I understand - if one were to build the 2SK77B circuit with a substitution of 2SK182s for the unobtanium would the timing of bias voltage and gate voltage be a concern for theVFET or does the presence of the hockey puck in the CCS mitigate.
Thanks again
Bob
I only started thinking this way after looking at the CSX1 PS regulation where I saw 3 Zener's in series. And this was on the unobtainium VFET's. So I thought they are probably worth spending another 50cents worth of Zener's to keep from being one VFET short of an amp. And in the case of the Hockey Puck amp, one speaker short of a stereo. Color me yella, fella ;-)
ZM, you are right. I had my share of nightmares on a few 70's vintage PCBs for nixie tubes, and I just wish they never failed. They did and I had sore fingers working the tiny buggers for weeks.
Output cap should take care of this. No need to worry.
I haven't checked on 2sk77 vs 2sk182 to see the differences. If you were extremely lucky you might be able to easily substitute 2sk182 into Papa's 2sk77b amp schematic (a little different than the IXYS schematic we are discussing here)
2 picoDumbs
Thanks for the reply.
I'm going to follow the development of both paths. Thanks to your efforts the Schade is ready to go.
I believe NP at BAF2015 mentioned that the use of the 2SK182 in the 2SK77b would require some tuning.
Best
Bob
Thanks for the reply.
I'm going to follow the development of both paths. Thanks to your efforts the Schade is ready to go.
I believe NP at BAF2015 mentioned that the use of the 2SK182 in the 2SK77b would require some tuning.
Best
Bob
Also bear in mind they are probably only good for 40W dissipation so 40V or 44V supply and around 2A.
Nope, 2sk182e are 500W parts. And they should have a stable bias voltage before the high voltage/current come up.
Is it not safer to slowly raise bias with hv already on than to have full bias and then " turn on " hv ?
In that later case transistor will have full current as soon as hv is comming, I mean that transistor
is "open" by the biasvoltage ?
In that later case transistor will have full current as soon as hv is comming, I mean that transistor
is "open" by the biasvoltage ?
1) I don't see the mountain here. I'm seeing a mole hill
2) Surely the same situation exists with 2sk77b in which case Nelson has already considered it and taken care of it.
Unless someone explains the issue relevant to this amp, then I don't see the problem.
In the case of a depletion mode (normally on at 0 Vgs) mosfet, there maybe some conditions that you might want bias on first to protect the devices from seeing too much current, but if everything turns on together at the speed of light we're talking picoseconds or 3/5 of FA.
Either way I'm not seeing an issue based on point number 2 above but maybe there is something Nelson and I have overlooked. I can't see the problem.
well ........ I know that this isn't exactly written by feng shui rules :
but , I can't find any flaw in that logic
Big Bang moment
cap across zenner (or pot wiper to gnd ) is empty - zero voltage
it goes slowly up
mosfet is enhanced device , meaning - it need some positive voltage to be cranked
so ........ bigger the cap across zenner (wiper to gnd) , soft start is longer
cap across zenner is having no more volts across than zenner is maintaining
simple , isn't it ?
but , I can't find any flaw in that logic
well , if someone toss those pucks in my direction ...... I'll certainly use them
if not , I'm anyways at least 3 amps behind
if not , I'm anyways at least 3 amps behind
What if we just jack the rail to 70V? Would that fry the Jensen's? Or will it rolloff before the 20kHz found by papa. Higher rails are easier to do than to put in new pucks, new thermal solution, etc.
What exactly are you trying to achieve?
Edit: Something worth considering. Assuming your existing speakers are 90dB or less, for less than the price of 2 massive heatsinked cases to deal with over 450W of dissipation, you can buy a pair of 15" Audio Nirvana drivers which are around 98dB/W
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