Hi all,
At the end of doing my final project for university (making guitar pedals), and have run into a wierd issue. One of the pedals utilises a spring reverb tank to acquire its effect, so i've been following a schematic found online that uses NE5532 opamps to drive, recover and mix the circuit. However, whenever they are plugged into the +15v and -15v power supply, as required, they turn on and off again repeatedly. I absolutely cannot figure out why this is! Any sort of help would be massively appreciated.
See links for the circuits:
https://sound-au.com/articles/rvb-f5a.gif
https://sound-au.com/articles/rvb-f9.gif
https://sound-au.com/articles/rvb-f12.gif
At the end of doing my final project for university (making guitar pedals), and have run into a wierd issue. One of the pedals utilises a spring reverb tank to acquire its effect, so i've been following a schematic found online that uses NE5532 opamps to drive, recover and mix the circuit. However, whenever they are plugged into the +15v and -15v power supply, as required, they turn on and off again repeatedly. I absolutely cannot figure out why this is! Any sort of help would be massively appreciated.
See links for the circuits:
https://sound-au.com/articles/rvb-f5a.gif
https://sound-au.com/articles/rvb-f9.gif
https://sound-au.com/articles/rvb-f12.gif
Drop them to +/- 10 volts, or use 7809/7909 regulators.
5532 can take +/- 22 volts , so you are having an over gain rather than volts issue.
Gain on these is proportional to supply, so that is the easy option, reducing the supply.
Or reduce your guitar output....
And go through that thread, sometimes the fixes are there in the comments section!
5532 can take +/- 22 volts , so you are having an over gain rather than volts issue.
Gain on these is proportional to supply, so that is the easy option, reducing the supply.
Or reduce your guitar output....
And go through that thread, sometimes the fixes are there in the comments section!
A 5532 isn't smart enough to turn itself off. More likely there is a short in the system and your power supply is turning off/on/off to protect itself. One way to make a "short" is to mix the chips' + and - pins. (Backward, the chip looks like a forward diode.)
Things that come to mind:
- Double check for shorts. Turning on and off could be short-protection in the psu?
- See if blocks of the circuit work in isolation.
- Those particular images you linked don't show coupling caps for the power supply pins of the 5532, though I believe they are there in the more complete schematics on the ESP page. You'll want those. 100nF from the power pins to ground, near the chip.
- Make sure your grounding is right. Verify that the input jack of the reverb tank isn't internally grounded.
- Double check for shorts. Turning on and off could be short-protection in the psu?
- See if blocks of the circuit work in isolation.
- Those particular images you linked don't show coupling caps for the power supply pins of the 5532, though I believe they are there in the more complete schematics on the ESP page. You'll want those. 100nF from the power pins to ground, near the chip.
- Make sure your grounding is right. Verify that the input jack of the reverb tank isn't internally grounded.
i just want to add:
try to split your amp in this separate schematic and test each other. if necessary cut some lines. i guess its a short somewhere.check the caps.
chris
try to split your amp in this separate schematic and test each other. if necessary cut some lines. i guess its a short somewhere.check the caps.
chris
Gain of the configured opamp is absolutely not dependent on the supply voltage. Reducing supply voltage will only reduce headroom and overload margins.
Supplies using 78/79 regs can do odd things under light loading. The fix is to add reverse supply protection diodes across the rails and the regulators... its a well documented issue. Make sure the supplies are correct at the opamp terminals when the problem happens.
This has been a common problem. In most cases the pos 78xx-regulator keeps working and delivers the pos output voltage - but the neg 79xx-Regulator puts out something like +0.7V.
Sorry....I meant output voltage is proportional to supply voltage.
Putting a bridge rectifier...how does that sound?
Permanent polarity assurance...
Putting a bridge rectifier...how does that sound?
Permanent polarity assurance...
Clamp diodes across the output of the regulators should prevent regulator misbehavior. (1N4001 should be fine)
Check that you have not reversed the supply connections to the 5532s.
Check that you have not reversed the supply connections to the 5532s.
It seems that you are mixing the input and the output of the reverb tank. Due to the transit time through the mechanical springs, you have a huge phase shift between input and output.
That causes low freq oscillation, and that is what you see.
If you want to verify, disconnect the mixer and you will see it all works as expected.
Jan
Looks like a very conventional reverb circuit to me, the signals are mixed in the final stage and there is no recirculation that I could see which would cause the problem you describe.
Back when I designed MI amplifiers I used a very similar approach which worked just fine.
I am still of the belief that the supplies are probably fighting each other (clamp diodes on the output) or some other mistake that will be obvious once discovered.
Back when I designed MI amplifiers I used a very similar approach which worked just fine.
I am still of the belief that the supplies are probably fighting each other (clamp diodes on the output) or some other mistake that will be obvious once discovered.
Do we know what actually happens? The OP says 'opamps switch off', what does that mean? Do the opamp outputs switch off? Has the OP actually measured what happens to the power supplies, are they switching or is it the opamp outputs that switch?
Jan
Jan
Wierd! You should check if there is any wiring mistake and use clamp diodes (reverse biased) at each regulator output to prevent regulator abnormality.
... and we still don't know what the problem is, but that shouldn't stop us to suggest random solutions, right? ;-)
Jan
Jan
Are there power supply pin bypass capacitors installed at each op amp, to ground from each op amp power supply pin, or across the positive and negative supply pins, 0.10 uF value? An NE5532 will not act right without these.
Regarding connecting the power supply pins backwards to the supply which was mentioned earlier, this will immediately fry and permanently damage the NE5532 and result in unexpected circuit behavior. I’ve done this several times.
NE5532 has 8 pins, numbered 1-8. I propose to measure each pin with a DVM referred to GND, make a according list and show it here.
^^^^^ THAT
Start with this, then we go on.
Even more important:
What is the symptom?
HOW do you know they are "turning ON/OFF" ?????
EDIT: FWIW OP left 5 minutes after leaving this question, 2 days ago (so far) and never returned.
Start with this, then we go on.
Even more important:
what does this ACTUALLY mean?
What is the symptom?
HOW do you know they are "turning ON/OFF" ?????
EDIT: FWIW OP left 5 minutes after leaving this question, 2 days ago (so far) and never returned.
Last edited: