So NP or anyone, i'm trying to understand just how far I can go with biasing my amp. I'm running 42 vdc rails with large heatsinks for a 200W amp into 4 ohms. I have the original 4 pair of outputs and .68 ohm emitter resistors. I have each transistor running at 30mA. Is this a problem? Can I go higher? The heatsinks are just barely warm after 15-30 min. can I just base it on heatsink temp as far as biasing higher?
Take a look at how well the bias is matched between devices and how
stable it is with temperature. You might be able to reduce those Emitter resistors
and/or increase the bias.
stable it is with temperature. You might be able to reduce those Emitter resistors
and/or increase the bias.
So after an hour of biasing at 30mA per transistor in a room at 30c my heatsinks are 31c. I will move up and keep monitoring temps.
Ok so biased at 63mA per and heatsink temp stable at 93 deg F. Room is at 83 deg.F
Seems like there is plenty of headroom.
Seems like there is plenty of headroom.
So I have just noticed a potential problem in my build. One channel I have used 220 ohm base resistors and the other channel I have used 180ish resistors. Will this cause any problems in operation. Should I change the 180's out.
these resistors are meant to prevent potential oscillation.it seems to me that 100 or 200 is not that important - if no oscillation. I like it if everything is the same on both channels but value are not critical 180 or 200 or 220.
Nelson Pass posted his full and complete Gerber CAD files (the "blueprints" for a PCB) here in the thread. You could send them off to a PCB fab in China and have 10 copies made for $35 including shipping back to Kansas. Use one, sell or give away the rest.
I have a couple of boards here in Oklahoma. I went to PCB fab in China. Mine are 1.6mm thick but more than $35. Mine cost 70 with shipping. I would only sell 2 at $10 each to cover shipping. Let me know
It is possible to pay $70 to have ten AB100 boards fabbed and shipped to you. As shown in the quote below, from a website I highly recommend (pcbshopper dot com), it is also possible to pay $29 for 10 boards.
Click on the image and then click on the white "X" at bottom left, to see it full size.
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Click on the image and then click on the white "X" at bottom left, to see it full size.
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Hi Mark,
Thanks for the info about pcbshopper; it's great to get one-stop comparisons.
I'll definitely check before ordering pcbs next time.
Cheers,
Dennis
Thanks for the info about pcbshopper; it's great to get one-stop comparisons.
I'll definitely check before ordering pcbs next time.
Cheers,
Dennis