HRM board to ground question

[moj067]

I'm currently finishing up a HRM skyliner 100w and am having second thoughts about some decisions made while building. Is the 100R resistor to ground from the HRM board to cathode grounds necessary? I don't see it in the HRM 101 schem and on an older layout by Normster. Yet see it in some builds- or is it a Bluesmaster thing? Thanks in advance.

[Funkalicousgroove]

The mid control should connect directly to ground just like a marshall or Bassman, the 100K is from the wiper of the treble pot to the top of the OD volume control.

[tubedogsmith]

I think he's talking about the 100r resistor on the HRM board to ground from that mid trim pot. I can't hear any difference.

[moj067]

Yep, that's the one Tubedog. I just have a wire instead of the resistor there. Thanks!

[ic-racer]

I was also wondering about this. Doesn't seem like 100r would do much. I guess its variable as to if they have it or not.

[ic-racer]

duplicate

[Funkalicousgroove]

I see, that's a tail resistor. I've seen HRM's with the mid set at like 500 ohms, maybe that's like a minimum setting? I saw one that was all fixed resistors, no trimmers!

[rackandroll]

The 100 ohm resistor in this application, seems to me an effort to avoid any noise induced through the audio ground. Often this is done to break a gound loop. I am guessing that since the small board with the trimmers was added after the main preamp board was populated, the best ground point may have been under the blue(or black or whatever color) goop.

100 ohms (or less); I have used this technique in addressing similar issues. That is what you don't here it.

Well, that is my best guess at this.

Alex

[ic-racer]

The 100 ohm resistor in this application, seems to me an effort to avoid any noise induced through the audio ground. Often this is done to break a gound loop. I am guessing that since the small board with the trimmers was added after the main preamp board was populated, the best ground point may have been under the blue(or black or whatever color) goop.

100 ohms (or less); I have used this technique in addressing similar issues. That is what you don't here it.

Well, that is my best guess at this.

Alex

I'll probably put it in mine then.

[Funkalicousgroove]

I've built lots of these, it's really not necessary. The board grounds at the cathode grounds for that stage.