I've built an active subwoofer filter using a NE5532P op amp and my rail voltages are +22V/-22V. I haven't connected the PS to the board yet. I know some chips have higher tolerances than specified. Anyone overvoltaged (a word?) this chip and survived
Am I really pushing it this time?
Thanks,
David
Am I really pushing it this time?Thanks,
David
According to the data sheet I saw (RS web site) this chip is rated for supply to +/- 22 v so you are within spec ...
(another) Dave
(another) Dave
Check first that you rails really are at +/-22V, unless you have
already done so. I just mean, if the PSU is designed to give that
voltage, it will also have a tolrance and may give a higher
voltage.
already done so. I just mean, if the PSU is designed to give that
voltage, it will also have a tolrance and may give a higher
voltage.
Christer said:
+/- 22V is the actual voltage. I noticed the op amp pec is 22V maximum. Do you think that will be an issue.
It's easier to buy a smaller transformer than desolder the op amp😀
It is unwise to run components at their absolute maximum ratings. You are NOT running it within specs as another member posted, you'll be running it at absolute maximum. So no safety margin. Check datasheets and draw conclusions please. Most critical will be power on sequence when voltages might be higher than +/- 22 V for a short ( but effective ) while. This will certainly be the case if you have a unregulated supply and it will occur with regulators too in a smaller degree.
I would lower the voltage to + and - 21 or 20 V just to be safe on the long term. You've been warned anyway...
I would lower the voltage to + and - 21 or 20 V just to be safe on the long term. You've been warned anyway...
Jean-Paul
You are right, of course, and if it had been a new design, still
on paper only, I would have advised against using 22V.
Running them at the max limit, not over mind you, will probably
only give a slightly increased risk of failure. As I understand it,
the guy already has built this thing, so considering these op
amps cost next to nothing to replace, should they fail, I doubt
it is worth rebuilding the PSU.
I might be wrong, though.
You are right, of course, and if it had been a new design, still
on paper only, I would have advised against using 22V.
Running them at the max limit, not over mind you, will probably
only give a slightly increased risk of failure. As I understand it,
the guy already has built this thing, so considering these op
amps cost next to nothing to replace, should they fail, I doubt
it is worth rebuilding the PSU.
I might be wrong, though.
Only 2 diodes can be enough. I'd prefer a more elegant way though.
Changing/adapting the PSU will be cheaper than replacing a burnt subwoofer....
Changing/adapting the PSU will be cheaper than replacing a burnt subwoofer....
jean-paul said:
Jean-Paul
That last sentence caught my attention! My sub is decoupled w/ 4.7uF. If the op amp fails, could it still damage the sub? I haven't connected it yet, still testing it w/ an old speaker/amp. Seems to be working fine...so far. Wouldn't the op amp warm up if run at maximum, it's runs at room temp now?
David
Op amps can fail even if run within the ratings. Some kind of
speaker protection is always useful.
Maybe Jean-Paul has a differing opinion, but I think the worst
that can happen if an op amp fails due to overvoltage is DC
out. A capacitor on the output should protect the speakers
in this case.
speaker protection is always useful.
Maybe Jean-Paul has a differing opinion, but I think the worst
that can happen if an op amp fails due to overvoltage is DC
out. A capacitor on the output should protect the speakers
in this case.
Christer said:
Agreed, but I'd prefer a capacitorless coupling with the subwoofer and a circuit running below absolute max. to be sure it has a long usefull life. Besides that I think ( no, I am sure ) a 4.7 uF in series with the subwoofer is a tad too small
Please calculate the -3dB point and you'll see what I mean.
I assumed the 4.7uF cap was after the opamps but before the
power amp, otherwise it sounds way off from a reasonable
value.
power amp, otherwise it sounds way off from a reasonable
value.
If you want to be cautious why not try using some 3 terminal regulators, eg LM78 / 79 (or similar), to drop down to +/- 15V ?
The 5534/32's should be pretty bullet proof then ...
I would not use a zener in series with the supply lines (too noisy and poor regulation) or a zener shunt regulator - the 3 terminal regulator would be just as easy to do and will give better results.
BTW - is your +/- 22V supply regulated or just smoothed ?
My **guess** would be that +/-22V will be OK, providing ....
(1) the PSU doesn't go above +/-22V --EVER--.
(2) You don't try to get max output swing into a low impedance load (rated to do 32V swing from +/-18V).
(3) You don't try testing the claim to "indefinite" short circuit protection !!!!
Dave
Dave
The 5534/32's should be pretty bullet proof then ...
I would not use a zener in series with the supply lines (too noisy and poor regulation) or a zener shunt regulator - the 3 terminal regulator would be just as easy to do and will give better results.
BTW - is your +/- 22V supply regulated or just smoothed ?
My **guess** would be that +/-22V will be OK, providing ....
(1) the PSU doesn't go above +/-22V --EVER--.
(2) You don't try to get max output swing into a low impedance load (rated to do 32V swing from +/-18V).
(3) You don't try testing the claim to "indefinite" short circuit protection !!!!
Dave
Dave
Christer said:
I think I'll try either the lm7815 option or replace the transformer. It's only $5 canadian. (about 5c in real money😀 )
Thanks again
Make that LM7818/7918. More headroom and far enough from the max. values. +/- 20 V would be nicer though.
My advice is to better phrase your questions as you see there is confusion. It is also better to reply at the questions members pose.
We still don't know if the PSU is regulated or not, what voltage the transformer is and if the 4.7 uF is in series with the subwoofer or between the active filter and the sub-amplifier.
You see ? A schematic might help as well in confusing items. A simple block diagram will do in this case.
My advice is to better phrase your questions as you see there is confusion. It is also better to reply at the questions members pose.
We still don't know if the PSU is regulated or not, what voltage the transformer is and if the 4.7 uF is in series with the subwoofer or between the active filter and the sub-amplifier.
You see ? A schematic might help as well in confusing items. A simple block diagram will do in this case.
jean-paul said:
The PS in not regulated, the 4.7uF is in series w/ the subwoofer power amp. As for the replies, I have only a few minutes here and there during my day to scan the replies; other necessities
of life preval unfortunately. I'ts more a matter of unintended oversight than anything else.
All your interest and assistance is valuable to me.
David
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