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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: RE: I would not be able to sleep if I had one of those in the house posted by 1973shovel on July 1, 2007 at 06:45:20:
The rule is to use non-inductive caps on each supply rail and no sockets. This is so they will act as close to "ideal" capacitors at the very high frequencies, to provide stability and prevent oscillation. Remember that the op amps we want to use have open loop bandwiths in the MHz range. If you use a 1 uFd dipped tantalum paralleled with a 0.1 uFd ceramic disc or monolithic ceramic, you will not have any oscillation or supply noise issues. Remember to keep the cap leads short. The fact that both of these cap types are not appropriate for audio signal use is irrelevent. They are ideal in this dc application.
You can also add a .001 or .01 cap between V- and V+, (pins 4,8) but it is not essential.
There should also be a cap bypass across each feedback resistor. This is to reduce the op amp gain at very high frequencies. It will also address your slew rate concerns.
If you want to start rolling off the gain at about 100 kHz, use about a 33 pF cap between each output (pins 1,7) to each inverting input (pins 2,6). I generally use a 5 pF or 10 pF silver mica, depending upon the op amp and how much bandwidth I want. I like to minimize phase shift at the highest audible frequencies.
For subwoofer use I would go with an op amp with a bipolar input. Try a National LM4562 or 6172 or a Linear Technology LT1358CN8 or LT1361CN8 for example. Review the applications notes also.
I did find the 1050 service manual. It is pretty thick as service manuals go and it has excellent diagrams, board layouts, schematics, etc. etc. I'll never use it again at this point.
Happy tweaking!
Doggy
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Follow Ups
- RE: I would not be able to sleep if I had one of those in the house - nightdoggy 08:01:38 07/01/07 (0)
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