On 10/9/2012 12:36 PM, James Roth wrote:
> How does one cancel the vertical portion of the signal?

Combine the left and right dhannels of a stereo cartridge.

There are several ways to do that. If your preamp has a stereo/mono 
switch, and you can take your recording feed from downstream of the 
switch, just turn the switch to mono. If that's not available, record in 
stereo, then mix the two tracks in equal proportions in your digital 
editing program. You can also use a couple of Y-connectors between 
cartridge and preamp:

2 RCA-F > 1 RCA-M
1 RCA-F > 2 RCA-M

Connect the first one to the leads from the turntable, then connect the 
second one to the first one and to the preamp inputs.

Or use a mono cartridge; Grado's most recent 78 cartridges have tiny 
wires on them that do the same job as the cascaded Y-connectors.