PL 700 II Clair Bros Rising from the Ashes
- Thread starter Peter S
- Start date
Peter, if those wires going to the switch are still in the circuit, it will still create an EM field that can induce (either capacitively or inductively - it doesn't matter, probably some of both) into the input. They, the wires going to the switch, have to be totally disconnected from the AC. Even one end connected to the AC is enough to create the EM field.
QUESTION: What is the audible difference in the scope photos?
QUESTION: What is the audible difference in the scope photos?
Hi Jim;
From what I gather from Henry Ott's book; if a wire is only connected at one end, current cannot flow and therefore can only radiate noise electrostatically. Twisting the radiating conductor would not completely reduce that effect. With power being supplied via IEC jack, through power switch and thermo switches, it appears that my twisting has not had any effect;
From what I gather from Henry Ott's book; if a wire is only connected at one end, current cannot flow and therefore can only radiate noise electrostatically. Twisting the radiating conductor would not completely reduce that effect. With power being supplied via IEC jack, through power switch and thermo switches, it appears that my twisting has not had any effect;
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Jim;
Regarding the audible difference" between scope traces, it seems like the larger traces is audible at 6" and I pretty much have to wear my test speaker like headphones to hear the smaller trace. (However my workshop has a little higher ambient noise than the listening room.
Joe;
I used 16 awg for the AC. My OCD seems to always kick in. Even with # 18, it wouldn't fit in the corner with the under-size Clair Bros chassis. I guess Perry was right about just using a new WO chassis..
---Wouldn't running along the bottom still be close to input wiring (inputs on terminal strip) What if 'rev H' had the inputs at the top!
Regarding the audible difference" between scope traces, it seems like the larger traces is audible at 6" and I pretty much have to wear my test speaker like headphones to hear the smaller trace. (However my workshop has a little higher ambient noise than the listening room.
Joe;
I used 16 awg for the AC. My OCD seems to always kick in. Even with # 18, it wouldn't fit in the corner with the under-size Clair Bros chassis. I guess Perry was right about just using a new WO chassis..
---Wouldn't running along the bottom still be close to input wiring (inputs on terminal strip) What if 'rev H' had the inputs at the top!
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- Halfbiass...Electron Herder and Backass Woof
- Joined
- Jan 14, 2011
- Messages
- 74,829
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
Good Morning Folks;
Hi Blue, yes, noise is noise. I was thinking that magnetically induced noise would be more of a problem because non ferrous shielding is not effective. Regardless, I have a routing problem.
Glen, I will be raising the control board, thanks for the pictures. BTW, love that copper busbar! I thought mine was over the top.
Any thoughts about an aluminum or steel shield under or around the control board?
Hi Blue, yes, noise is noise. I was thinking that magnetically induced noise would be more of a problem because non ferrous shielding is not effective. Regardless, I have a routing problem.
Glen, I will be raising the control board, thanks for the pictures. BTW, love that copper busbar! I thought mine was over the top.
Any thoughts about an aluminum or steel shield under or around the control board?
The Control Board does not require shielding. Most of the current flow on the Control Board is DC, with very low level AC current flow. DC only generates external electromotive force (EMF) if the wires move, as in a generator. Because none of the traces on the Control Board move, almost no DC EMF is electrostatically or electromagnetically generated by capacitive or induced coupling into active signal wires that would result in hum. (thanks BlueCrab)
The primary source of radio frequency (RF) EMF is the 60Hz AC power wires in the amplifier. The solutions are to: 1) create separation between the power (radiator) wires and the signal (receiver) wires and, 2) shielding either the radiator or the receiver wires. This is why we shield the input wires going to the Control Board; they are the most sensitive to RF interference (hum) because any induced RF EMF will be amplified along with the input signal. We also try to cross any AC wires at right angles to reduce any capacitive coupling that might occur if the wires run parallel to each other, even for a short run.
Joe recommends tucking the smaller 18AWG M22759/11 60Hz AC wires along the edge of the bottom of the amplifier. This Mil-Spec wire is capable of handling 15 Amps at 80 deg (C) and tucking the wire into the 90 degree channel will theoretically reduce the EMF by 50%. (ref: https://www.coonerwire.com/amp-chart/ )
Thoughts?
The primary source of radio frequency (RF) EMF is the 60Hz AC power wires in the amplifier. The solutions are to: 1) create separation between the power (radiator) wires and the signal (receiver) wires and, 2) shielding either the radiator or the receiver wires. This is why we shield the input wires going to the Control Board; they are the most sensitive to RF interference (hum) because any induced RF EMF will be amplified along with the input signal. We also try to cross any AC wires at right angles to reduce any capacitive coupling that might occur if the wires run parallel to each other, even for a short run.
Joe recommends tucking the smaller 18AWG M22759/11 60Hz AC wires along the edge of the bottom of the amplifier. This Mil-Spec wire is capable of handling 15 Amps at 80 deg (C) and tucking the wire into the 90 degree channel will theoretically reduce the EMF by 50%. (ref: https://www.coonerwire.com/amp-chart/ )
Thoughts?