Outside foil in Pultec MEQ-5 filter section

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soapfoot

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This seems like it ought to be an easy question, but I'm not sure how to figure it out and would appreciate any help!

Building a pair of MEQ-5s, I've tested and marked all of my capacitors for outside foil. I just want to double-check my reasoning of where outside foil should be connected (apologies for the quality of the attached schematic).

  • The "mid dip" section is easy--all of the capacitors connect directly to ground on one end.
  • For the "high boost" section, all capacitors connect directly to "VOUT" on one end, which directly couples to the grid of the 12AX7 in the following stage. So I'd assume to not connect outside foil here, and to connect the outside foil of each capacitor to the switch instead (where it would have a path to ground through the inductor coil and a few potentiometers and resistors). Seem logical? I'm unsure here
  • For the "low boost" I'm even less sure. The input transformer is a 600Ω:600Ω (Triad HS-56), for the record

Thanks for any insight!

 

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abbey road d enfer

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soapfoot said:
This seems like it ought to be an easy question, but I'm not sure how to figure it out and would appreciate any help!

Building a pair of MEQ-5s, I've tested and marked all of my capacitors for outside foil. I just want to double-check my reasoning of where outside foil should be connected (apologies for the quality of the attached schematic).

  • The "mid dip" section is easy--all of the capacitors connect directly to ground on one end.
  • For the "high boost" section, all capacitors connect directly to "VOUT" on one end, which directly couples to the grid of the 12AX7 in the following stage. So I'd assume to not connect outside foil here, and to connect the outside foil of each capacitor to the switch instead (where it would have a path to ground through the inductor coil and a few potentiometers and resistors). Seem logical? I'm unsure here
  • For the "low boost" I'm even less sure. The input transformer is a 600Ω:600Ω (Triad HS-56), for the record

Thanks for any insight!
You shouldn't worry too much about it. Whatever effect parasitic coupling may have will be negligible, because the conduction path is dominant by several orders of magnitude.
Actually the differences between connecting in one or the other direction will be so tiny I don't think they would be measurable, much less audible.
 

soapfoot

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abbey road d enfer said:
You shouldn't worry too much about it. Whatever effect parasitic coupling may have will be negligible, because the conduction path is dominant by several orders of magnitude.
Actually the differences between connecting in one or the other direction will be so tiny I don't think they would be measurable, much less audible.

Understood, thanks for your input!

I also suppose, since this will be inside a shielding can, it should matter even less than it ordinarily would. I was just trying to dot every i and cross every t, but I won't worry about it
 

abbey road d enfer

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soapfoot said:
Understood, thanks for your input!

I also suppose, since this will be inside a shielding can, it should matter even less than it ordinarily would. I was just trying to dot every i and cross every t, but I won't worry about it
Actually, there are two diiferent aspects to consider:
[list type=decimal]
[*]Hum susceptibility: indeed, the fact that the whole assembly is in a shielded container takes care of that
[*]Interaction between nodes: this is where the minimalistic effects could be noted
[/list]
 
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