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#911 | ||
diyAudio Chief Moderator
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#912 | |
diyAudio Chief Moderator
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#913 | ||||
diyAudio Moderator
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Here's a rough number of currently saved versions that I've tried; variations on this regulator: 397. And these are only the versions that I deemed worth saving, but there are others that I tried and never saved. Code:
$ ls *salas*.asc *reg*.asc reg*.asc | wc -l 397 ![]() |
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#914 | |
diyAudio Moderator
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BTW, salas, I kept forgetting. But if you get a chance, I would recommend that you try in your shunts the mpsa18. You have good ears, and should be able to tell the difference. |
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#915 | |
diyAudio Moderator
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#916 | |
diyAudio Chief Moderator
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#917 | |
diyAudio Moderator
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Hi Andrew,
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However, the contact has not been considered at all. Multi-turn controls are not designed to pass any current through the wiper at all. Minimal at best. They are designed to operate as a potential divider, so you have current that passes through the element, but nothing to speak of through the moving contact. This is a critical error in the use of these parts. Consider a volume control that is familiar to us all. How much current is expected to pass through the element? Through the wiper contact? Consider that this is a huge control with large contact surfaces compared to trimmers. You can not use a trimmer as a rheostat! All, If you need to use an adjustable resistive element, they do make wire wound rheostats for this purpose. You may have seen these in old TV sets or industrial controls. A Lamda power supply comes to mind. If you only need to sample the voltage (ie: no current), then you can use a resistor as the pass element and place a higher value trimmer across this. The wiper then feeds the high impedance point that samples this voltage. jameshillj did suggest this (I think this was your intent?). -Chris
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"Just because you can, doesn't mean you should" © my Wife |
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#918 |
diyAudio Moderator
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Hi Salas,
Remember, darlington transistors are slow. Composite darlington transistor pairs need sufficient base current in the first of the part to be fast. Therefore, unless you are careful, then a composite darlington will also be slow compared t a single transistor. How many RF darlington transistors has anyone seen? -Chris ![]()
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"Just because you can, doesn't mean you should" © my Wife |
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#919 |
diyAudio Chief Moderator
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Slow they maybe, but I am afraid of extreme hfe because the loop gain with the CCS for load is high already in the reg.
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#920 |
diyAudio Moderator
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Hi Salas,
I agree. Just one more thing to consider. It also depends greatly on layout and current levels. -Chris
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"Just because you can, doesn't mean you should" © my Wife |
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