Blending Fender and Marshall (Page 1 of 2)

Well, certain amps run 180 degrees out of phase with each other, and so there could be buzzing.

I was looking into the radial bigshot, but apparently with high gain amps this can cause a pop when switching. The model that doesn't cause popping, is £200 more. So if the two amps are in phase with each other and neither need the ground lifted it'd just be a case of finding a good aby pedal without popping.

If its out of phase just reverse it at the speaker, ie flip the leads around, or you can flip one side of the wiring iside of the speaker cable (from head to cab).  If its a ground issue just get the ground lifts you would use in your home (the ones that convert new appliances for old style receptacles) from your hardware store/home depot/lowes.  That elimates the ground wire of the cord elimintating your ground loop.  You can use the Voodoo Labs Amp Selector, which has ground lifts, tuner out, and can either do 4 amps, or 2 amps and an aby for use of 2 different guitars (instead of unplugging and switching guitars).  It's built like a tank, I have one.

Ben

I advise so strongly against this method.  It is extremely dangerous for both amp and YOU!  Sure, the chances of something happening are slim, but why take the chance of your body becoming the amp's path to ground?  Amps are designed with a ground wire for a reason, don't mess with it.

1.  when you run two amps at the same time, you are providing two paths to ground.  this can cause a nasty buzz, often called a ground loop hum.  this can actually happen with pedals also.  when i run a pedal (powered by the dc jack) in the fx loop of my vintage modern, there are two paths two ground - the ground through dc power supply, and the ground through the amp.  the solution was to either run the pedal on a battery or disconnect the ground of the cables going into both the fx send and return.

2.  phasing issues may occur because it possible that the both amps wont output the signal in the same phase.  one amp may be 180 degrees out of phase with the other.  joe gives a pretty good description of this on one of the sticky threads in this forum.

3.  a morley aby would be great as an amp selector, but it won't cure the above to problems.

hope this helps.

what ever you DO NOT disconnect the amps safety ground (using an adapter that turns the plug from three prong into two).  the amp uses a three prong plug to ground the chassis.  the chassis is metal and capable of passing current.  if the you disconnect the safety ground, there is a risk that the chassis may become "live" if something shorts to the chassis inside the amp (there wont be a way for the current to go to ground). this means that if you touch the chassis, that current will pass through you!  this can be FATAL, especially if it is AC!  either way it will still hurt (every touch a filter cap?).  furthermore, you will void the warranty and potentially surrender any legal claims you may have arising out of your injuries or death.

Just don't touch both amps at the same time.  Why would you be grabbing both amps together at the same time anyway?  And if you are, well wear rubber soled shoes .  Also, you'd only have to do it to one amp.  Just think of all of those lamps/appliances you have around your house with 1) zip cord, and 2) two prong plugs.  Those lamps/appliances are wired so you don't get shocked... the grounded conductor is part of the casing of the lamps/appliances.  That grounded conductor meets with your grounding conductor back at the main panel of you residence.  Unless your house is extremely old and those crazy electricians back in the day wired it for reverse polarity (I've learned about these careless old timers the hard way), you don't have an ungrounded conductor running through the metal casing of anything, otherwise most of us would have our hair permanantly teased like the 80's.  Old amps used to come with a two prong plug - not to many people had a problem then.  And why take the chance you ask, well I want a quiet rig that where the hiss/hum doesn't out shine the sound you are trying to produce.  No biggie though and if anyone else gets shocked from touching your rig, well they shouldn't have touched you amps .  If your using pedals, run it off of a dedicated power block like the Voodoo Labs, its the industry standard and the grounds are isolated there as well eliminating said ground loops.

Lastly, just be careful!

Insulate and Isolate,
Ben

PS - Don't get the Morely its terrible on your tone .  A Monster Power Conditioner would work as the grounds to each receptacle on the back are isolated.  Plus they make the amps sound better by cleaning up all of your dirty power genereated from everything electric in your house.

I am sorry Ben, but you are giving extremely bad advice that can get some one killed.   You may have experience, but why recommend this to someone with out the same eduction about electricity?  It is just plain irresponsible.  There is no way of knowing what kind of electrical system someone would be connected to, especially when gigging! 

I don't mean to start trouble, but guitarists die from this every year.  Look what happened to Keith Relf from the Yardbirds.  Ace Frehley thank g-d survived.

A guitar amp is not the same thing as a toaster or a lamp, which would most like trip the circuit breaker or GFI if there was a short. 

This has nothing to do with touching two amps at the same time, although that is a great way to earth ground the ungrounded chassis.

Yes, the neutral and ground wires do meet at some place in the house, BUT that doesn't mean they have same reference.  Neutral can float, while earth ground will be 0.  This means that neutral can have a higher reference point than earth ground.  The amp will still function without out being connected to the safety earth ground because all that a current needs is to flow from a higher reference point to a lower one, which DOES NOT have to be 0.  This means that a current finding earth ground will go to earth ground rather than neutral.

When you disconnect the SAFETY (yes, it is called that for a reason) ground, everything that was connected to that earth can "float up" because it will be searching for a new reference. This means that even without a fault in the amp, something bad can happen.  Because of the nature of the AC filtering in tube amps, it is possible that the metalwork and everything connected to it on the amp (which is a lot of the circuitry and this includes the guitar strings because the input jack was safety grounded) could now have an extremely high reference point and can cary very lethal current.  It could be half that of the mains - thats AC! And in the UK, thats double than the US! If your guitar strings become earth grounded, your amp could fry.  If you are the connector between the current and ground, the current will carry across your heart and you could die.  Things in your house are connected to earth ground, like the plumbing and baseboard heating for example.  Things at gigs are earth grounded everywhere.  You don't know what is and what isnt.  Or as you said, touching two amps at the same time could do it.  You could even just touch your guitar strings and the grounded amp to adjust it and boom.  The most common way to achieve electrocution is to be holding the guitar strings and grabbing a mic that is earth grounded through the PA.

Here is very good article that explains what I mean by float up:   http://www.soundonsound.com/sos/aug06/a … 0806_4.htm
And some more in depth reading:  http://www.ssguitar.com/index.php?topic=288.0

If there is a fault in the amp, there is even a higher chance that the chassis could become "live."  The designer of the Vintage Modern explains:  http://marshallvintagemodern.com/viewto … amp;t=4187

Risking this is not worth eliminating the buzz because that can be achieved in SAFER ways.

I have an education in electrical engineering for audio application.  I have built amplifiers.  I have wired studios.  I have even discharged the filter caps through my fingers accidentally (its not fun).  I have been lucky, but there is no reason to mess around with this.  A few bucks on an isolation transformer or your life?  You chose.

Well, you are prob. right about giving this type of info out.  I am an electrician though and do know the safeties and understand how grounding and bonding works in houses and buildings.  I know the hazards, but I guess explaining it and working/understanding electricity is a difficult subject.  Being 21 and full of gas and vinigar has something to do with it too lol.  I have done it on occasion in a pinch, but found other ways previously mentioned (voodoo labs amp selector and monster power conditoner).  Sorry, next time I will watch what I say for safety sake.   

Ben

PS - No trouble started, we do this all the time here.

I have never had a chance to use a monster conditioner.  My pedal board says its a power conditioner, but I don't know how will it works.