Maybe I'm missing something. Ive read the eilliot section and the HiFisonix. I have not seen anything discussing a sitiuation where noise is happening when the Case IS earthed AND the signal 0V is floating until and NOT connected to the case or earth.
In every other component (15 of them) you connect it to another unit that will connect to earth via a plug in one location (In my case the bluray player)
Jean has given up but also for me not explained which subsection or other subtle naunce I have missed. I can and will continue and try the loop breaker but to me it looks like my problem is there with no loop in any case ?
In every other component (15 of them) you connect it to another unit that will connect to earth via a plug in one location (In my case the bluray player)
Jean has given up but also for me not explained which subsection or other subtle naunce I have missed. I can and will continue and try the loop breaker but to me it looks like my problem is there with no loop in any case ?
When noisy it's like this, very loud buzz
Then when this it's lost the buzz and 'quiet' but still some general noise just enough 'hiss' to be needing a bit more work to get inaudible at the seating position. All my other amplifiers are near silent and totally silent unless you are literally 6" away from the speaker
Then when this it's lost the buzz and 'quiet' but still some general noise just enough 'hiss' to be needing a bit more work to get inaudible at the seating position. All my other amplifiers are near silent and totally silent unless you are literally 6" away from the speaker
Are you sure this amp is not oscillating? It would only take a few hundred mV at HF for a problem like this to manifest. How this works is the HF oscillation (100's of kHz up to a 1-2 MHz typically) is modulated by any mains magnetic fields that may be around - e.g. wiring or stray transformer fields. This HF is then demodulated - usually in the small signal sections of the amplifier - and it appears at the output as buzz. One of the sure signs of HF oscillation like this is a 'shhh' or hissing sound with the inputs shorted. On a modern power amp with moderate gains (25-30 dB), there should be absolutely no hiss from the speaker with the inputs shorted.
The other thing that may be taking place here is that you inadvertently have 2 connections to ground/chassis in your amp. When you then connect the earth, an existing ground loop condition causes current to flow between the two earth connections, causing a small volt drop, which is then injected into the signal path. Ground loops almost always manifest because the loop current flows through the signal return, thus appearing in series with the signal and ultimately degrading the SNR.
Can you confirm you have absolutely NO connection to the transformer mounting bolt and that it only makes connection to the chassis on one side? What happens if you remove the transformer from the chassis and just run long twisted wires from the transformer secondary to the PSU?
The other thing that may be taking place here is that you inadvertently have 2 connections to ground/chassis in your amp. When you then connect the earth, an existing ground loop condition causes current to flow between the two earth connections, causing a small volt drop, which is then injected into the signal path. Ground loops almost always manifest because the loop current flows through the signal return, thus appearing in series with the signal and ultimately degrading the SNR.
Can you confirm you have absolutely NO connection to the transformer mounting bolt and that it only makes connection to the chassis on one side? What happens if you remove the transformer from the chassis and just run long twisted wires from the transformer secondary to the PSU?
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Is your RCA ground connected to the chassis? If so, there would be a ground loop if both your amp and your source are earthed.
I would say try another amp that you know it is quite by its alone. If it has the same issue, you got ground loop between audio components. Stop messing around the circuitry inside.
I would say try another amp that you know it is quite by its alone. If it has the same issue, you got ground loop between audio components. Stop messing around the circuitry inside.
A good point, I will try and speak to the manufacturer as these are set at 50KHz and perhaps I can simply add something to remove the bulk of the high frequency requirement - I use these from 3-40 Hz for subwoofers. I will check the dB gain as well today. I can see the resistor that adjusts sensitivity is set to 500mv and I can swap to move to 775mv
I have checked with my meter and the GND does not connect to the chassis anywhere until I make the connection
Yes the transformer mount bolt does make contact with the chassis and the hat holding the transformer in place on top. I have checked connections as none of this connect to the transformer. The transformer sits on a rubber pad on a painted metal support, the hat clamps the transformer top via another rubber pad
I have managed to remove 99% of the buzz by trying capacitors as the link from Chassis to GND when the chassis earth connection is in place. With a number of .1uf variants the TDK ceramic was the best. If I add a resistor 20 Ohms or so it's fine as well with both attached.
The 'hiss' and general amplifier noise is still there as I say it's not super loud, but just audible at the seat some 3.5m away from the sub, replace the amp with a 500 plate amp and silent at the approximate same output level. I could be persuaded about 'Shhhh' as this noise comes through when I turn the amplifier off as the caps discharge
The only connection form the RCA to the chassis is when I make the connection. The problem is the same with both my BK 1000 MF amps and not there with any of the other sub amps (all BK BPSP 500 amps)
Are there any pieces of gear in your system using SMPSU? What happens if you connect the earth to the chassis but unplug the source, leaving the interconnects in place?
Bonsai, hi
There are no SMPS in the system other than a laptop power supply that controls the DSP (Which seemingly has no effect if unplugged). Today for some reason whilst taking a few more measurements, seems the single cap (the Blue 100nf TDK ceramic) providing the only connection is not performing like it did last night and the buzz is back a little, if I bridge by hand with a resistor or another cap it's as good as it was last night, bizarre. The cap is a 250V ceramic, I will solder on a large resistor (the 10 Ohm as recommended) and swap this for a 630v DME for the time being.
I do hear shhh when I turn the amp off. I'll drop a not on my source GND and the links as it's quite convoluted but on the BR player has GND to the earth pin, all the others are either double insulated or each connected to chassis only
There are no SMPS in the system other than a laptop power supply that controls the DSP (Which seemingly has no effect if unplugged). Today for some reason whilst taking a few more measurements, seems the single cap (the Blue 100nf TDK ceramic) providing the only connection is not performing like it did last night and the buzz is back a little, if I bridge by hand with a resistor or another cap it's as good as it was last night, bizarre. The cap is a 250V ceramic, I will solder on a large resistor (the 10 Ohm as recommended) and swap this for a 630v DME for the time being.
I do hear shhh when I turn the amp off. I'll drop a not on my source GND and the links as it's quite convoluted but on the BR player has GND to the earth pin, all the others are either double insulated or each connected to chassis only
If you are touching any part of the circuit and there is a change in buzzing it’s likely you have HF demod taking place. Have you got a scope?
Let me reword my sloppy statement above: if you touch any part of the metalwork incl the heat sinks, and there is a change in buzzing/hum/hiss it’s likely you have HF demodulation taking place.
Is the plug earth on the BR player connected to the signal ground at the BR player output?
Is the plug earth on the BR player connected to the signal ground at the BR player output?
Here's the base amplifier as I picked them up , I did put a pot in series but have bypassed now until the noise is sorted. So the inlet is RCA and the GND is only contacted via a resister now (10 Ohm) and a 0.1uf Film cap, I might pop the Ceramic back at some point.
The layout is as shown here, the connector is a Powercon 32A connection. I'll tidy it all up when I settle on a quiets solution. I also have a few cheap pre-amp boards as I have never been a fan of no preamps, I have tried using an old AV2 as a direct pre amp and that didn't solve any noise issues
The layout is as shown here, the connector is a Powercon 32A connection. I'll tidy it all up when I settle on a quiets solution. I also have a few cheap pre-amp boards as I have never been a fan of no preamps, I have tried using an old AV2 as a direct pre amp and that didn't solve any noise issues
I did speak to Tom at BK and he could not see why there might be an issue with my configuration. I will try adjusting the frequency in the band filter (I think the schematic is incorrect and have two 900pf in series so I think it's band is 2-3Hz to 75KHz, so will bring this down to under 1kHz, I think a 0.1uf will be circa 350 Hz
I'll also try reducing the sensitivity a bit
I'll also try reducing the sensitivity a bit
What is that wire going to the pot?
I would keep all input wiring completely away from the pot until the noise issue is sorted IOW remove the pot completely
I would keep all input wiring completely away from the pot until the noise issue is sorted IOW remove the pot completely
I don’t think reducing the amplifier bandwidth is the right thing to do. You should find the root cause IMV.
Oh that wire is only the GND, but I could just remove the pot completely even though its not connected and bypassed now
You should remove all possible confounding factors - I’d make sure there were no connections to that pot whatsoever. It looks like you have connected the black wire from the input RCA to the pot housing which is conductive and connected to the chassis and then off the input RCA taken a pair- one of them being signal return - off to the amplifier input.
Am I reading this right?
Am I reading this right?
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Tks, My set up has additional GND leads, to keep 0v as closest 0v as possible, the BR player feed analogue out to 4 pre amps (all run from one power supply, naim Supercap) and they are connected to 9 power amps (bi amping fronts). I've followed the naim topology for the power and pre amps so all signal GND goes via the Supercap. The noise is now as below and still just a little too loud, I'll remove the lead from the redundant pot.
The black RCA is just an additional GND connected or disconnected the measurements are the same
Pot will be completely removed, I'll listen and measure again. The connections are Powercon top right, pot top left, RCA GND black Signal in and Signal GND (Screened cable), bottom Speakon out
At the moment the Pot is not in circuit (I will unsolder all GND connections), the signal goes via a small screened cable to signal in and the speaker is connected via the same cable I use for the subs
The black RCA is just an additional GND connected or disconnected the measurements are the same
Pot will be completely removed, I'll listen and measure again. The connections are Powercon top right, pot top left, RCA GND black Signal in and Signal GND (Screened cable), bottom Speakon out
At the moment the Pot is not in circuit (I will unsolder all GND connections), the signal goes via a small screened cable to signal in and the speaker is connected via the same cable I use for the subs