simple LAR/MAR MV installation questions

[Night Owl]

Hi,

The diagram for the LAR/MAR MV for a 100w amp shows connections out to pin 5 of V6 and V7 and pin 5 of V4 and V5. I'm assuming that I just run one of the leads to pin 5 of V6 and run an extra wire from pin 5 of V6 to pin 5 of V7. And similarly, run the other lead to pin 5 of V5 and an extra wire over to pin 5 of V4. Is that correct? Seems simple enough, but I just want to make sure.

I plan to keep both of my speaker jacks operational. And I'm also going to add the zero-loss loop. Any recommendations about where I should locate the MV? I'm planning to put it across from the Middle or Treble knob so the wires will be shorter. Then put the loop a little further down, across from the Treble/Volume knobs.

Thanks!

[chubs]

Look at this layout:
http://home.comcast.net/%7Ejbjdav26/220 ... l%20B+.JPG" onclick="window.open(this.href);return false;

You will notice that the 5.6k resistors on the socket are between the pot and the tube.


As for placement, you want the MV to be as far away from the inputs as possible, because of the large signal that those wires carry. Use shielded fires as indicated on SMD's layouts. Across from the presence pot as much as possible.

Chubs

[Night Owl]

Ahhh...

I should remove the green and orange wires that currently go from the board over the the V4/V5 and V6/V7 resistors, replacing them with the leads to/from the new pots. The whole point is to get the pots into the circuit at that point, instead of just the direct wiring that was there, right? As you can tell, I don't exactly have my PhD in Electrical Engineering, but occasionally something gets through

I could put the MV knob between the power cord and the impedance selector. But it looks like it would be about the same amount of wiring. I guess it would probably be better where I planned to put it, next to the speaker jacks. The connection going into the pots would be shortest that way. That connection is guaranteed to have a higher or equal signal than the one coming out. I guess it's better for the one coming out to be longer than the one going in.

I think I get it now - thanks for the super-fast reply!!!

[Structo]

Yes, I think a lot of guys simply remove one of the output jacks and install the MV there.

You are correct, you need to remove the orange and green wires.
The pot and it's resistors replace the two 220K resistors that are on the board.

Be sure to trim the braided shield off the ends of the shielded cable at the board end and tube end.
Putting the heat shrink tubing there also tidies things up and prevents any chance of the braid touching something it shouldn't.

On the MV pots, you will notice in the notes beside the MV that the shield is not to touch the pot's body or any ground because they are carrying voltage from the board.
You can either heat shrink that or use some stripped insulation and slide it on the wire to insulate that there.

Also pay attention to the polarity of the white and red wires and connect them as the layout shows or it will be out of phase. If it is backwards the amp will shriek in protest.