I have an enclosure which is going to use the layout as in the pics.
It's a two-storied building with an aluminium partition separating them. The toroidals and all mains stuff goes to the lower floor. The secondaries pass through a 2" hole in the aluminium partition to the top floor where 2 stereo plates of my_ref amp are mounted. Additionally there's a cross-over on the same floor.
Should I be worried about hum, emf or some obvious gotchas? I never had trouble with EI transformers because those amps were equally poor. But this is my_ref and toroidals.
It's a two-storied building with an aluminium partition separating them. The toroidals and all mains stuff goes to the lower floor. The secondaries pass through a 2" hole in the aluminium partition to the top floor where 2 stereo plates of my_ref amp are mounted. Additionally there's a cross-over on the same floor.
Should I be worried about hum, emf or some obvious gotchas? I never had trouble with EI transformers because those amps were equally poor. But this is my_ref and toroidals.
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The aluminium plate will do nothing to shield the amp boards from the toroids. You need iron, steel, or mu-metal for that.
Most hum issues are the result of bad grounding. There are a bunch of threads here on grounding. You'll feel lost after reading the first few (at least I did), but keep going and it will start to sink in.
Cheers,
Jeff.
Most hum issues are the result of bad grounding. There are a bunch of threads here on grounding. You'll feel lost after reading the first few (at least I did), but keep going and it will start to sink in.
Cheers,
Jeff.
I've been reading up on toroids. What's kind of interference do transformers create? electrostatic? magnetic? RF?
Also the PCB are going to go right on top of toroids as in the original post (vertical distance between the top of the xft and bottom of pcb around 2"). Are there any changes in the interference on-axis or what?
Also the PCB are going to go right on top of toroids as in the original post (vertical distance between the top of the xft and bottom of pcb around 2"). Are there any changes in the interference on-axis or what?
Electromagnetic (EMI). Not at radio frequency (RF) though. Much lower.
I believe on-axis is worst. That's why I suggested moving the toroids under the cross-over. But I was thinking your cross-over was post-amplification, and looking at your design again it appears to be pre-amplification. So the cross-over will be just as sensitive to EMI as the amplifier input stages, and moving the toroids horizontally won't help.
The EMI field falls off with the square of the distance. So even a couple more vertical inches between the toroids and the sensitive circuits will help. Something on the order of a foot will really help.
Or make your dividing shelf steel.
Or line the dividing shelf with mu-metal.
Or wait until after it is built and see if it's really a problem. (Although it will be harder to fix then if it is.)
Cheers,
Jeff.
I believe on-axis is worst. That's why I suggested moving the toroids under the cross-over. But I was thinking your cross-over was post-amplification, and looking at your design again it appears to be pre-amplification. So the cross-over will be just as sensitive to EMI as the amplifier input stages, and moving the toroids horizontally won't help.
The EMI field falls off with the square of the distance. So even a couple more vertical inches between the toroids and the sensitive circuits will help. Something on the order of a foot will really help.
Or make your dividing shelf steel.
Or line the dividing shelf with mu-metal.
Or wait until after it is built and see if it's really a problem. (Although it will be harder to fix then if it is.)
Cheers,
Jeff.
All of them. EMI = ElectroMagnetic Interference. This is caused by any varying current. A transformer depends on varying currents for it's operation.
varying gaps between the windings does allow some variation in the field around the toroid. I believe this is at a low level for well manufactured toroids compared to the discontinuous windings and exposed core of EI/Ccore/Rcore transformers.
The belly/guass band around the toroid is to smooth out the varying field and wrap it closely around the toroid, thus minimising the external effects.
The interwinding screen is there to reduce the capacitive coupling between primary and secondary. This attenuates the higher frequency interference that is on our mains supply.
So I mounted them exactly as per my pics in the initial post. Dead silent. I put my ear next to the visaton fr10 8ohms and there's "some" "presence" indicating that the amp is on. Zero hum. Beyond 10 inch it's dead.
I was cheap; i put the toroidals on a double sided tape as well as the pcb mounts. Toroids hold well but pcb mounts are shaky. It's okish for temporary mounting and testing if moving things around has any impact. I'll get the aluminium partition replaced by stainless steel once I know how many mounting holes I need (difficult to drill through ss). Would it matter if I order metal that sticks magnets? Because most types of steel doesn't hold magnets. Will upload the pics tomorrow.
I was cheap; i put the toroidals on a double sided tape as well as the pcb mounts. Toroids hold well but pcb mounts are shaky. It's okish for temporary mounting and testing if moving things around has any impact. I'll get the aluminium partition replaced by stainless steel once I know how many mounting holes I need (difficult to drill through ss). Would it matter if I order metal that sticks magnets? Because most types of steel doesn't hold magnets. Will upload the pics tomorrow.
Iron/steel does little unless it *surrounds* the source or destination. A plate, it just goes around, hardly weakened.
Most steel is magnetic, and will act as a magnetic shield (if it encloses).
Most stainless steel is hardly-magnetic, and is a poor magnetic shield.
Sealing transformers, or hot amps, in steel boxes, suggests overheating.
Most steel is magnetic, and will act as a magnetic shield (if it encloses).
Most stainless steel is hardly-magnetic, and is a poor magnetic shield.
Sealing transformers, or hot amps, in steel boxes, suggests overheating.
Hi PRR,
Will a plate increase the distance? In other words if I separate the source and dest with a plate that extends 4" beyond either, and the magnetic field goes around it, does the strength of the field drop off by the square of the distance around the plate?
Still trying to wrap my head around some of this stuff....
Thanks,
Jeff.
Will a plate increase the distance? In other words if I separate the source and dest with a plate that extends 4" beyond either, and the magnetic field goes around it, does the strength of the field drop off by the square of the distance around the plate?
Still trying to wrap my head around some of this stuff....
Thanks,
Jeff.
JeffYoung: I do have the Philips HQ48414P. regardless of the sensitivity, there is 0 hum. But hum is not the only type of noise in a circuit. Hum is low frequency, hiss is high frequency etc. When I put my ear on the speaker, I can tell that the amp is on. I though don't plan to listen it from an inch away 
PRR: If you look at the pics in the initial layout it's all SS except for the partition. If the partition is also replaced with SS then it's all enclosed and surrounded; toroids in their own chamber and amps in their own
PRR: If you look at the pics in the initial layout it's all SS except for the partition. If the partition is also replaced with SS then it's all enclosed and surrounded; toroids in their own chamber and amps in their own
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