Hello everyone,
I have a strange phenomena that just does not make any sense to me. - ANY IDEAS!!!
I use high level input from the output of my amplifier (211 valve amplifier) speaker terminals to 2 subs, the leads running in parallel, and are identical.
I use two separate BKELEC sub amplifiers that are identical and take high level input with a Speakon connector.
I have a dedicated mains supply with a dedicated consumer unit. I have 8 MCBs running off 2 RCDs (4 MCBs each) Each MCB feeds a single 13Am UK socket with low impedance cable from the consumer unit (30A twin and earth) for convenience of the explanation I have called these socket ABCD and EFGH as they represent the 2 banks of 4
I have painted the sub amplifier boxes (they are not installed in the subwoofer) black and Yellow, for the convenience of the explanation I will call them BKB and BKY they are identical units.
Originally BKB was connected to socket A, and BKY to socket D
When I accidentally swapped the plugs on reinstalling I put BKB to D and BKY to A and I got a very loud SSSSHHHHH noise ARRRGHH what has failed now I thought. But after extensive testing I can confirm that this ONLY occurs with the earth cable of socket D connected to BKB.
no other socket does this
it does not matter if the BK amp is on or off
all physical mains and speakon leads repeat this behaviour
I can disconnect BKY and it makes no difference
testing impedances on BKY and BKB shows no difference
testing impedance on earth on socket A and D measures the same to a consistent reference point
ANY ?IDEAS?
I have a strange phenomena that just does not make any sense to me. - ANY IDEAS!!!
I use high level input from the output of my amplifier (211 valve amplifier) speaker terminals to 2 subs, the leads running in parallel, and are identical.
I use two separate BKELEC sub amplifiers that are identical and take high level input with a Speakon connector.
I have a dedicated mains supply with a dedicated consumer unit. I have 8 MCBs running off 2 RCDs (4 MCBs each) Each MCB feeds a single 13Am UK socket with low impedance cable from the consumer unit (30A twin and earth) for convenience of the explanation I have called these socket ABCD and EFGH as they represent the 2 banks of 4
I have painted the sub amplifier boxes (they are not installed in the subwoofer) black and Yellow, for the convenience of the explanation I will call them BKB and BKY they are identical units.
Originally BKB was connected to socket A, and BKY to socket D
When I accidentally swapped the plugs on reinstalling I put BKB to D and BKY to A and I got a very loud SSSSHHHHH noise ARRRGHH what has failed now I thought. But after extensive testing I can confirm that this ONLY occurs with the earth cable of socket D connected to BKB.
no other socket does this
it does not matter if the BK amp is on or off
all physical mains and speakon leads repeat this behaviour
I can disconnect BKY and it makes no difference
testing impedances on BKY and BKB shows no difference
testing impedance on earth on socket A and D measures the same to a consistent reference point
ANY ?IDEAS?
Those SSSHHH sound probably was regeneration or oscillation. While large currents may flow at output circuitry and placing the ground terminal where also flows minuscle input currents, and being amplification big and in phase, the bad routing of output current effectively can cause regen or oscillations. Those are preciselly the Barkhausen's Criteria for oscillation.
Ok - so this is interesting, and confusing
I had also got a completely new Zzzzzz on my preamplifier recently, not very loud but absolutely not there before. It was on all inputs and I had hypothesised it must be some capacitor or Diode playing up in the PSupply.
Anyway a thought occurred to me with this 4th plug socket out of 8 doing something crazy on the connection between Earth and Neutral, maybe this ZZZzzzz was part of the same story.
I disconnected the IEC from the BK amp coming from the problem socket, and Silence!!! the Zzzz problem, is the SSSSHHHH problem!!!
So I guess the only logical conclusion is this plug somehow is creeping a voltage pathway from E>N?
I will pull off the from plate with the MCB to this switched off, but what should I look for / measure?
Rich
I had also got a completely new Zzzzzz on my preamplifier recently, not very loud but absolutely not there before. It was on all inputs and I had hypothesised it must be some capacitor or Diode playing up in the PSupply.
Anyway a thought occurred to me with this 4th plug socket out of 8 doing something crazy on the connection between Earth and Neutral, maybe this ZZZzzzz was part of the same story.
I disconnected the IEC from the BK amp coming from the problem socket, and Silence!!! the Zzzz problem, is the SSSSHHHH problem!!!
So I guess the only logical conclusion is this plug somehow is creeping a voltage pathway from E>N?
I will pull off the from plate with the MCB to this switched off, but what should I look for / measure?
Rich
If anything was creeping from Neutral to Earth I'd expect the RCD to trip. It sounds like a ground loop issue. I'd check all the earth connections on the MCB to socket run.
We get faulty MCBs sometimes at work,(had a 7A pump tripping a 20A MCB a couple of weeks back. The pump runs fine on all the other available circuits) you could try swapping out D with C and see if the problem moves. Obviously the usual safety disclaimers apply etc.....
Rob
We get faulty MCBs sometimes at work,(had a 7A pump tripping a 20A MCB a couple of weeks back. The pump runs fine on all the other available circuits) you could try swapping out D with C and see if the problem moves. Obviously the usual safety disclaimers apply etc.....
Rob