Mica isolators can come in thicknesses upto 6thou/mil 0.15mm
For our voltages (<150Vdc) in power amplifiers we only need <0.5thou.
You can split mica down to <1thou, or settle for ~1.5thou.
Don't use ~2thou, too much Thermal resistance.
For our voltages (<150Vdc) in power amplifiers we only need <0.5thou.
You can split mica down to <1thou, or settle for ~1.5thou.
Don't use ~2thou, too much Thermal resistance.
F5
Hello together, i use in my f5 lsj74 and lsk170, but I am not sure that pin assigment with originals of TOSHIBA 2sj74 and 2sk170 ithe same. Could you help me, please. That the mistakes can be too expensive. Thank you.
Hello together, i use in my f5 lsj74 and lsk170, but I am not sure that pin assigment with originals of TOSHIBA 2sj74 and 2sk170 ithe same. Could you help me, please. That the mistakes can be too expensive. Thank you.
Same, I have used both Toshiba and LSK in many projects interchangeably without worrying about pinout after verifying on first project using LSK.
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Cool, thank you. I just read somewhere that one of fhe LS tranaistors had been cracked due to reversing the polariry rhat had been used as normal as TOSHIBA. That's why I wanted to secure myself.
I ordered boards to build the F5 without the current limiting circuit and if possible match the output mosfets where no source resistors are necessary. My question is if there is a way to set the bias without the source resistors installed. I think a small value resistor on the mains would work but I have no idea what volt, amp to shoot for.
put 0R1 in one DC rail
you can bypass it later , or not
btw. no need for matching if you're having one output pair
you can bypass it later , or not
btw. no need for matching if you're having one output pair
I thought the output pair would have to closely matched to eliminate the source resistors. What volt, amp would I need on the rail resistor to properly bias the amplifier?
P=I^2 x R
so , if Iq is 1A6 then dissipation on 0R1 resistor is
P=1A6^2 x 0R1 = 256mW
1W will do
if you want to leave it permanently , put 3 watter
no need to match outputs , in any way
so , if Iq is 1A6 then dissipation on 0R1 resistor is
P=1A6^2 x 0R1 = 256mW
1W will do
if you want to leave it permanently , put 3 watter
no need to match outputs , in any way
took it arbitrary
set what you like .... say to 55C at heatsinks , measure just to be sure that both channels are in same bracket and that dissipation is still sane ( which will be , except in case that you are using Gargantuan size heatsinks)
set what you like .... say to 55C at heatsinks , measure just to be sure that both channels are in same bracket and that dissipation is still sane ( which will be , except in case that you are using Gargantuan size heatsinks)
Fired up the F5 but did install .47 resistors but not the current limiting circuit. It is installed on big heatsinks and with .59V bias is running 25C. How high have others biased this amplifier? This is just a project so I am going to turn it up but am just curious how high the other FAB have biased their build. I will turn up till it reaches 55C on the heatsinks close to the mosfets.
Find a cozy place of your own somewhere between
and here.
And never forget the master FAB principle by Papa here.
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As Papa sez, X*?@! is reserved for the more mature constructor. You absolutely qualify beyond reasonable doubt.😀
Right now I have the bias up to .9V and it appears to be running cool directly on the mosfets and around the mosfet at the heatsinks. My heatsinks are so big that the are still around 25C. I am yet to see how it sounds but last night I was surprised on how good it sound. I say this because this is one build I have sighed away from because others have said it would be too bright on horns. It was not the case with my horns.
I have plenty of mosfets indra1 so it is not a big deal if I burn up some. Just playing. Whether they last is another matter. I will keep members informed especially on the difference in sound. Supposedly they sound better the more you run them up.
I have plenty of mosfets indra1 so it is not a big deal if I burn up some. Just playing. Whether they last is another matter. I will keep members informed especially on the difference in sound. Supposedly they sound better the more you run them up.
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Yet we have a body of opinion insisting that semiconductors must run HOT to perform well.
Run them as cool as you can manage and stay within the electrical parameters required for good audio performance.