To be honest I am not sure it is oscillations - or if it is, something else in the circuit must be off/broken. I’ve seen OPA2132 behave in seemingly much worse situations...?...
But if it turns out it is oscillating and nothing else is faulty I’ll try with the 33pF caps, thanks for the tip
Here it is. just turned it on and immediately it starts whistling like crazy.
Iphone microphone 2 inches from the horn tweeter - but sitting in the listening spot you hear it just as good.
can't wait to have you guys tell me what you think this might be... :-/
PS Edit: the file didn't upload. I need to convert it somehow. This is gonna be fun. Be right back...
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Wow -- -- bet that is REALLY hard to put up with!
Sounds like something with a medium-performance microprocessor in it. There's too much structure to it for it to be something random like intermittent oscillation.
You wouldn't happen to have a mod-ed 1990's-era CD player nearby with its cover off ..? or plugged into the same outlet ..?
I sure feel your pain. That's awful.
Rick
-- bet that is REALLY hard to put up with!Sounds like something with a medium-performance microprocessor in it. There's too much structure to it for it to be something random like intermittent oscillation.
You wouldn't happen to have a mod-ed 1990's-era CD player nearby with its cover off ..? or plugged into the same outlet ..?
I sure feel your pain. That's awful.
Rick
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Wow --
Sounds like something with a medium-performance microprocessor in it. There's too much structure to it for it to be something random like intermittent oscillation.
You wouldn't happen to have a mod-ed 1990's-era CD player nearby with its cover off ..? or plugged into the same outlet ..?
I sure feel your pain. That's awful.
Rick
I have a 1987 Revox B226 used as drive and an SMSL SU-8 DAC. Maybe I can plug them in a different power strip from a different outlet and see if that helps?... :-(
ok...
unplugged both CD drive and DAC won't change a thing.
Unplugged WiFi and TV box won't change a thing.
Unplugged monitor audio wireless transmitter (plugged on a tape out of my preamp, it sends bluetooth music to my bedroom where the receiver is) won't change a thing either :-(
what bugs me is if it's really interference somehow it would change even so slightly when I open or close the enclosure, except maybe if it comes from the mains.
unplugged both CD drive and DAC won't change a thing.
Unplugged WiFi and TV box won't change a thing.
Unplugged monitor audio wireless transmitter (plugged on a tape out of my preamp, it sends bluetooth music to my bedroom where the receiver is) won't change a thing either :-(
what bugs me is if it's really interference somehow it would change even so slightly when I open or close the enclosure, except maybe if it comes from the mains.
Ah. Maybe time to ditch and cut your losses
This is ******* me off so much. what in hell could cause this?
I've tried every other outlet and disconnect all possible sources of interferences in the house, no results
I don't get it
it won't be a big financial loss but that thing has so much potential to sound good - guess I'll be stuck with my old TDM crossover again. which is dead silent - but doesn't sound half as good.
OK another update:
I put back the original JRC NE5532 in.
the whistling noise seems to be gone (but I will leave it on all day to check if it comes back...)
...if the whistling noise indeed goes away when I put the slower NE5532 in the circuit, that means either:
-OPA2132 was oscillating and that what we heard (although how can OPA2132 oscillate in all but the most inadequate circuit is beyond me, it's like the easiest chip to use as upgrade) maybe because I put a FET op-amp in a circuit made for bi-polar devices?
-the presence of faster chips makes the circuit prone to pick interferences, but interferences should vary depending on location, etc... here it doesn't seem to.
The reason why I bought this crossover was not to use it with any faster IC op-amp... I wanted to use it with Sparkos discretes, wich are supposedly triple compensated etc to make them almost universal. I wonder how those would behave in this circuit. I know Sparkos Labs would let me re-send them for a refund if they don't work in my device but I need to be sure I don't damage them...
I put back the original JRC NE5532 in.
the whistling noise seems to be gone (but I will leave it on all day to check if it comes back...)
...if the whistling noise indeed goes away when I put the slower NE5532 in the circuit, that means either:
-OPA2132 was oscillating and that what we heard (although how can OPA2132 oscillate in all but the most inadequate circuit is beyond me, it's like the easiest chip to use as upgrade) maybe because I put a FET op-amp in a circuit made for bi-polar devices?
-the presence of faster chips makes the circuit prone to pick interferences, but interferences should vary depending on location, etc... here it doesn't seem to.
The reason why I bought this crossover was not to use it with any faster IC op-amp... I wanted to use it with Sparkos discretes, wich are supposedly triple compensated etc to make them almost universal. I wonder how those would behave in this circuit. I know Sparkos Labs would let me re-send them for a refund if they don't work in my device but I need to be sure I don't damage them...
Okay, Rf interferance.
Is it in a steel box connected to mains safety ground or water pipe from water table? Is there a choke on each + and - from power supply - I use 11 turns on toroid form. If AC driven, is power supply walled off from circuit by ferrous steel? Toroids move to board side of wall. Do all entry signals to quiet compartment have 33 to 68 pf disk caps to signal ground on them? Does line level exit have a choke in series with it? 11 turns around china marker is usual.
If not you have more work you can do. Plus the feedback resistor bypass caps. What slew rate is OPA amp, 20 v/usec? I'm not looking up, I don't want one. NE5532 is 6.
Is it in a steel box connected to mains safety ground or water pipe from water table? Is there a choke on each + and - from power supply - I use 11 turns on toroid form. If AC driven, is power supply walled off from circuit by ferrous steel? Toroids move to board side of wall. Do all entry signals to quiet compartment have 33 to 68 pf disk caps to signal ground on them? Does line level exit have a choke in series with it? 11 turns around china marker is usual.
If not you have more work you can do. Plus the feedback resistor bypass caps. What slew rate is OPA amp, 20 v/usec? I'm not looking up, I don't want one. NE5532 is 6.
Here's a picture; there's no chokes as far as I can tell, and the PSU section isn't separated from the rest. Do you think a simple steel plate around the PSU could help?
Attachments
Yes if it is not self-oscillating. Plate has to be bonded so it is connected electrically to the safety grounded case. Transformer can stop RF but the wires to it from line cord have to be short so they don't act as transmitters. There are IEC sockets with RF trap in them if this has unprotected one of those to the line cord.
I tack the 33 pf caps right on top of the feedback resistor with short leads. I don't see them. 22 or 47 could help too.
I tack the 33 pf caps right on top of the feedback resistor with short leads. I don't see them. 22 or 47 could help too.
If you look at the picture there's a thick white line on the board; it looks like it was meant to accept some kind of shield, there are even pads... I should check if those pads are connected to ground.
I tried an Eupen filtered cable with magnetic powder coating, but it's just a add-on, it doesn't come to the IEC socket, it comes between the power strip and the device's mains cable. It didn't help. I put small ceramic caps between hot and ground on the RCA jacks; it didn't help. The RFI (if it is RFI) must enter someplace else. Maybe the whole pCB acts as an antenna...
Your line cord acts as an antenna. Inductive trap for RF has to be near the entry of line cord to enclosure.
There are packaged coils you can buy, dead flat screen TV's & switcher power supplies are full of them. About 8 turns standing up. The ones at the exits of PA amps are about 10-14 microH - or 11 to 14 turns 1 cm diameter.
Yes, the line between power supply & quiet zone looks like good place to put a steel bulkhead. Stainless star washers on scratched paint can bond a steel plate to another plate (like the grounded case) if held tight enough. Realize when steel case top is off shielding bulkhead is only effective against hum, not RF.
Whole pcb will act as antenna if RF is not kept out of the case.
There are packaged coils you can buy, dead flat screen TV's & switcher power supplies are full of them. About 8 turns standing up. The ones at the exits of PA amps are about 10-14 microH - or 11 to 14 turns 1 cm diameter.
Yes, the line between power supply & quiet zone looks like good place to put a steel bulkhead. Stainless star washers on scratched paint can bond a steel plate to another plate (like the grounded case) if held tight enough. Realize when steel case top is off shielding bulkhead is only effective against hum, not RF.
Whole pcb will act as antenna if RF is not kept out of the case.