DannyG wrote:I've been reading a lot about amp switchers and ground and phasing issues. I understand the grounding aspects but why do some switchers offer phase reverse options and some don't. Is the phase problem when both amps are on or one or the other? Please offer advise.
Also, best bang for the buck. I really don't want to spend a ton of money. Maybe $150 tops. I've heard Radial, Lehle and Voodoo Labs are good. I heard Loop Master makes a good one but no phase option. What's your input?
At the risk of being redundant, the phase switch can be used in a multi-amp setup to quickly match the phases so that the speakers of both amps are pushing air in the same direction at the same time. If the signals are out of phase, the result is that one amp's speakers are driven forward at the same time as the other amp's are driven backwards. The tone suffers because the sound waves partially cancel each other, or it causes a phaser effect.
A quick way to test for phase alignment is to play with both amps facing the same direction and listen to the sound. Then, turn one amp around and listen again. If it sounds better with one amp turned around, the amps are out of phase. This is where you could use the phase switch to correct the problem by switching the phase of one signal path on the switcher. Without a phase switch, you would have to reverse the polarity of one amp by swapping the positive and negative wires on the speaker cable.
As was mentioned earlier, it is important to do this with everything hooked up; otherwise, pedals can introduce phase issues.
Keep in mind that ground loops and hum can be caused when the power (amp OR pedal) is not shared by both rigs. To minimize noise, you need to make sure that the amps are powered by a common outlet and the signal path to each amp is completely isolated. Sharing pedals by both amps may cause hum unless the effects loop/switcher has a ground lift feature.
Always, ALWAYS test outlets for a proper grounding and DO NOT use ground lifters on power plugs. Improper grounding in multi-amp rigs can kill you. I feed all my amps through a single inline ground fault power cord and I test the outlet I plug it into with an outlet tester (Home Depot - $10). Joe said in one of his posts that he's been zapped more times than he can remember - perhaps that is one of the reasons why he uses a wireless setup.
Hope this helps.
EDIT: Here's a link with a good illustration of the grounding concepts mentioned above http://www.pedalsnake.com/page.php?id=1113
Guitars: '79 LP Custom, '01 Dickey Betts Goldie - 80 of 114, '00 Chandler Lectraslide
Amps: '00 Marshall 1987x, '70 Marshall 1959 SL, 4x12 JBL D120s
'64 Vibroverb - JBL D130, '66 Super Reverb - CTS Alnicos
'77 Peavey Deuce (great for melting stubborn ear wax)