Hello. I have 2 ZMACs hooked up as shown in Application Example 6 in the owners manual. I am hearing a pretty loud buzzing noise when selecting any of the 3 amps in ZMACs B.
To troubleshoot, I bypassed the link function from ZMACs A and connected the guitar input directly to ZMACs B. The noise went away.
Anyone have tips on what I could try to do to correct this? I assume it is a ground loop of some sort, but the various combinations of ground lift on the two units did not help.
Hi Dan and Dave,
Thanks for the suggestion and checking in. I did try all different combinations of the passive and active inputs and still getting the loud hum on amps plugged into ZMACs B. I recorded a short video and uploaded to my public dropbox folder below.
The video shows switching between an amp plugged into ZMACs A and another amp plugged into ZMACs B.
I can hear that when you were positioning the cables at the back, I guess that did not change the noise. So that eliminates external interference. Probably the next step would be to try and break the ground loop (assuming this is a loop issue) with an isolator.
Thanks Dan. I just ordered a Lehle isolator, will confirm back once it gets here and plugged in. Would the best place to start be the TS cable between the link output on A and the passive input on B?
I was going to suggest you start with a cheapo one from Amazon first but well… you went for the a good
I think that is a good place, and then the FX loop.
If you have pedals in the front of the amp, power those with a separate power supply (i.e., one that is different from anything in the FX loop); this way there is not a loop between the front and the FX loop.
Haha, thanks Dan. Current signal path has no pedals in front or attenuator in the loop. Tried to get it down to the basics to track down the hum. I’ll drop a line here once I get the isolator.
