| cm961 |
Hey guys,
I was rebuilding my 4 channel gainclone amp today using LM3875s for the tweeter amps and LM3886s for the woofers. Anyway, I keep either blowing fuses or blowing chips (I'm out now actually :( Still have some lm3886 though). I've attached the schematic I'm using. Without input or output attached the chip lets out smoke. The power supply rails are +35 and -35. Power supply is filtered with 6800uF per rail.
Is it the lack of bypassing near the amps that is causing problems? My channels are located within about 3 inches of the power supply's filter caps.
Is it the massive 680uF feedback to ground cap (C1 in diagram)?
Any help greatly appreciated. The amp that I'm upgrading was previously 4 LM12 channels, I believe non inverting. I figured an upgrade to LM3886, LM3875 would help the sound a little.
Pete |
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| cm961 |
Update: I just remeasured my power supply leads. It turns out blue is negative, and red is positive... That solves one problem!
Pete |
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| PauSim |
Greetings to all inmates
Itīs been a month since I started to read this forum with great interest and amusement. I learned a lot here.
Folowing Thortenīs suggestion, I decided to build a GC running on batteries.
I know lm3875īs are specified, but 1875 are far easier to obtain. So...
-Basic NIGC 1875 setup: 47k log pot, 2.2mF cap, 22k res signal-to-ground; 22k + 680 ohm res on the NFL; 1000mF caps on the power rails; no Zobel.
-Two 12v, 7.2AH batteries in series per channel; all grounds merging to the point between batteries (0 volts, I guess).
It should sound great but everytime I turned it on I got this overdrive-type distortion that ruined almost all my speakers even at low volume.
Running on common 9v batteries or even on 4,5v 3r12īs (you know the type?) it does sound great indeed, but they donīt last long enough, of course, so the circuit is well built.
Shouldnīt 1875īs accept 25v per rail (thatīs 25w power) or is 7.2AH too much capacity? I plan to try 3875īs as soon as theyīre available here.
What must be going wrong? Please help!
Thanks |
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| analog_sa |
| You're not using a Palestinian chip by any chance? |
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| DIY_Peter |
| quote: | Originally posted by analog_sa
You're not using a Palestinian chip by any chance? |
They only blow up, when you use them on Morel drivers |
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| analog_sa |
| quote: | | I just remeasured my power supply leads. It turns out blue is negative, and red is positive |
And now - a Morel twist! But which wire to cut? Anyone? Fast! |
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