Triple Rec/GCX popping

[metguitar]

The issue I'm having is with my GCX Audio Switcher/Ground Control. I'm using it to control some stompboxes, as well as switch the channels on my triple rec. Whenever I switch one of my presets using the red channel to a cleaner channel, I get that loud popping sound (bad enough where I can't use it in a live situation yet). Switching a clean channel to another clean channel is no problem. I don't think it has anything to do with any pedals because I tried changing the channels with no pedals in the chain, and I still get the popping everytime. Has anyone had a similar problem with a triple rec/GCX combo? I'm using George L cables from my channel outputs into the GCX loops. Could it be a cable issue? I appreciate any feedback or ideas!!

Also, I have had the popping issue with the normal footswitch like many have, but it normally goes away after switching through the channels once or twice.

 

[Gregwor]

There SHOULD be a slight popping the first (and sometimes second) time you switch channels. It's part of the design of the 3 channel recs.

IF it happens all the time with your gcx rig, try only switching the amp channels with the gcx.... in other words, don't try to put in or take out pedals with the gcx. See if it still does it then.

Looking at the schematic (plus I do it in my rig too.. gcx / triple rec), the external switching jacks are working in the exact same circuit the IC is. In other words, there should be no difference channel switching from the footswitch versus the external switching jacks. If you have popping noises and stuff, try to pin point which part of the rig is introducing the problem. Break your rig down and slowly start adding 1 more piece at a time until you hear the problem.. then work with that piece and find out why it is specifically being a piece of crap.

Also, as a heads up to free up some of your gcx loops/switches, you don't have to hook up a cable to the channel 2 external switching jack on your triple.. it's LITERALLY hooked up to air. hahaha. Pretty much, as long as you don't have channel 1 or 3 selected, it will go to channel 2. You'll notice this if you turn on your amp without the footswitch plugged in or your gcx hooked up. It will default to channel 2.

 

[Gregwor]

Ignore the 3 channel thing if you are using an older 2 channel (which is way better in my opinion by the way hahaha)

Either way though, the gcx is just connecting the tip to the sleeve just like the factory boogie footswitch is.

 

[guitarmechanic]

Does the amp pop when switched manually or with the Boogie footswitch?
I know in the Dual Recs, there are several JFETs in the Mute Circuit and sometimes they will go bad and you will get that pop when switching channels. If the amp does it without the GCX, I'd say take it to your tech and have him check those JFETs unless you feel comfortable doing it yourself.

 

[metguitar]

I havent switched channels manually, but when I use the Mesa footswitch I don't have any popping after initially switching through the channels once or twice. So to me, it seems like a GCX issue....I will be talking to them tomorrow when I'm able to actually be on the phone with them from my practice room.

Gregwor, thanks for your input. That tip on the automatic channel 2 switching is awesome because I can always use an extra loop!!

 

[MetalHorse442]

There SHOULD be a slight popping the first (and sometimes second) time you switch channels. It's part of the design of the 3 channel recs.

Glad I own a two channel. Why would Boogie design it to pop on the first or second channel switching? I know I used to have a friend with a nomad that had really bad popping on channel switches.

 

[nemesys]

Mesa uses relays to switch channels. Relays are a nice, reliable solution for this, but they do emit a popping noise when triggered. Mesa designed in a circuit that mutes the signal for a few milliseconds when the relay is triggered, but it doesn't seem to work perfectly the first time after powering the amp on (probably static in the relays or something). It's not really a big deal, I just cycle through the channels once on mine after powering up, which I have to do anyway to make sure they're set where I want them.

 

[msi]

Actually, the reason for the pop the first time you switch is because of the way the amp starts up. The mute circuit relies on the fact that when a relay's coil goes from a power state to an unpowered state there is a discharge of current. Usually this is handled by putting a diode across the relay to allow this current to move across the relay without damaging it. This only happens when the relay goes from on to off. Mesa designed their circuit so that this discharge charges a capacitor and a transistor to short the signal to ground, kind of like turning the volume all the way down. The problem is that when you turn the amp on, all the relays are off, so the first time you switch, there is no relay to create the current that activates the transistor. So a pop ensues. You cannot guarantee the strength of the current the relay produces though, so sometimes the pop is louder than others. There are also relays after the mute point that can possibly cause pops.

The two channel does have a relay in the signal path and no mute circuitry. The reason you never notice is because most people don't bypass their fx loop while playing. Reaching around the amp while playing is difficult. The reason for the switch to relays is probley because the LDR's in the dual rectifier do have a lifespan, that is shorter than relays. Also relays cost less. For LDR's to do the job of one relay requires four LDRs.

Mesa over engineered a solution to a cost saving move.

 

[MetalHorse442]

that makes sense now. I wonder what they did in their older heads? My 2 channel triple doesn't make any weird pops or anything.

 

[msi]

Well, the older heads used LDR's for switching when you change channels. LDR's are not switches, they are variable resistors. The achive switching by making the resistance to certain parts of the amp greater than other parts. Because they are not switches they have no switching noise.

The only relay in the Two channels signal path is the FX bypass and enable. When the effect loop is bypassed (also taking the master volume out of circuit) there is a relay that bypasses V4 and the master volume. This is not foot switchable. So you would probably never notice a pop. Also, it comes after the preamp which is where any pop's would get amplified by distortion. What you could try doing is putting a delay in the fx loop of a two channel, bypass the fx loop (using the knob on back) then switching it back in. There's a chance you might hear a small click or pop in the delay echoes. I don't have a two channel amp to test this on though.

 

[MetalHorse442]

Yeah I notice there is a slight pop if I do that, I have turned the loop on and off while the amp is running, it's not uber bad or anything but yeah. So if the LDRs ever go bad is there a way to replace them?

 

[msi]

Figure out which one it is, get a replacement, and put it in.

 

[metguitar]

So just a follow up to the issue I was having. I figured out my problem for the most part. The majority of issue had to do with the solo volume channel. I was using it to boost the levels on the cleaner channels (1 and 2). I was using loops 5 through 8 to externally connect channels 1-3, plus the solo channel. The way the numbers line up are actually opposite, so channel 1 lines up with loop 8, channel 2 with loop 7....etc. Anyways, the popping stopped when I swapped all the cables and lined up the solo channel last in loop 8, instead of in loop 5. I didn't realize having the solo channel before the main channels 1-3 would cause a pop...but it seems that way.

The weird issue is I still get occasional popping on channel 2 only if the solo channel is in the chain whether I connect it with a cable or let the default switch to it automatically. I've got my presets fixed so I dont need the solo volume boost on channel 2 anymore, so it shouldnt be an issue....but it's still weird that it pops only sometimes. Oh well...the GCX is still really cool and useful either way.