Bear --
I may not do it. Like I said, I will try the one box solution first. But, I have had an issue in thepast with the magnetic field radiation being picked up through the amplidier and being heard through the speakers. I figured that getting the transformer into a separate box would eliminate this. Plus, being that I would be using chokes in a CLC configuration, I would avoid any interference from those as well. I also thought that 16 gauge would be good in that it would add a little resistance that would add a slight amount of filtering to the suppy line.
Again, I may be off base on all these counts. That was just my thinking.
Thanks,
Steve
I may not do it. Like I said, I will try the one box solution first. But, I have had an issue in thepast with the magnetic field radiation being picked up through the amplidier and being heard through the speakers. I figured that getting the transformer into a separate box would eliminate this. Plus, being that I would be using chokes in a CLC configuration, I would avoid any interference from those as well. I also thought that 16 gauge would be good in that it would add a little resistance that would add a slight amount of filtering to the suppy line.
Again, I may be off base on all these counts. That was just my thinking.
Thanks,
Steve
Hey Bear,
What do you mean by this?
I was thinking the following: The signal ground would be going to the star ground between the last bank of caps in the amplifier box. From the star point, the umbilical would carry the ground back to the power supply case to the earth plane of the original filter caps. Form that point, it would be grounded to the case via a thermistor (or resitor, or whateve means you like).
At least that was my plan.
Thanks,
Steve
Imo, better to keep it simple.
The F5 case is generally big enough, due to heatsinking, to allow the transformer to be far enough from the input circuits. The gain is low enough too, resulting in a low hum sensitivity. Short wires are often better. Taking care not to create ground loops being the most important thing.
The F5 case is generally big enough, due to heatsinking, to allow the transformer to be far enough from the input circuits. The gain is low enough too, resulting in a low hum sensitivity. Short wires are often better. Taking care not to create ground loops being the most important thing.
I have remarkably low noise in my F5's -- I mount the power transformer on the front of the case -- run the high current wires on the bottom, away from the PCB's -- all of the signal wiring is at least 2 inches away from the power supply leads. As NP suggested I use a CL-60 ground breaker, and a pair of CL-60's on the primary of the trafo. Noise is under 30uV when one amp is wired in. With 2 it goes up to ~96uV.
I use some industrial strength 5/16th inch cap screws to mount the transformers (ANTEK) -- fugly -- but it's DIY after all.
Net, net -- not necessary to mount the power supply with an umbilicus.
I use some industrial strength 5/16th inch cap screws to mount the transformers (ANTEK) -- fugly -- but it's DIY after all.
Net, net -- not necessary to mount the power supply with an umbilicus.
Hey Jack,
I will try the one box solution first. But, I built an Aleph J and I had/have some issues there with the transfromer's magnetic field inducing some noise into the circuit. The input wires are pretty far away from transformers and other PS wiring. But, I think some is being picked up from the ckt board. The closest edge of the circuit board is about 2.5 inches from the nearest transformer (2 for dual mono).
The F5 amp may be somewhat different with respect to noise susceptibility. I'll have to wait and see.
Thanks,
Steve
I will try the one box solution first. But, I built an Aleph J and I had/have some issues there with the transfromer's magnetic field inducing some noise into the circuit. The input wires are pretty far away from transformers and other PS wiring. But, I think some is being picked up from the ckt board. The closest edge of the circuit board is about 2.5 inches from the nearest transformer (2 for dual mono).
The F5 amp may be somewhat different with respect to noise susceptibility. I'll have to wait and see.
Thanks,
Steve
Hi steve,
Perhaps shielding your transformer would be easier. I used magnetshield
Magnetic Field Shielding Materials
It's only $4.50/ft. I used about 1.5ft around a 300VA antek transformer. It noticeably reduce hum in my first F5 build (due to poor placement of transformer - see post 3783)
It is possible to create a ground loop with the shield so be sure to have it connected at the bolt on one end and leave some clearance on the bottom.
Quixote's enemies were only somewhat imaginary
The schematic is correct, Q3 is on the positive rail side and should open when voltage at the gate is (sufficiently) lower than voltage at the source.
Just a glance at the 4.2V voltage drop at Q1 JFET side shows that Q3 should be P-channel, IRFP9240.
(a P-channel MOSFET is positive at source and drain, negative at the gate side)
Just a glance at the 4.2V voltage drop at Q1 JFET side shows that Q3 should be P-channel, IRFP9240.
(a P-channel MOSFET is positive at source and drain, negative at the gate side)
