#1
Hey UG, I think I'm possibly over complicating the assembly of a set-up I'm looking to build next year, so may need some help... Sorry, this is a long one!

My current amp set-up is a Marshall JCM900 (4100 head) with a Marshall 1960A 4x12 cabinet. I've recently stumbled onto a friend's Peavey Classic 50 (the old tweed covered one) as a combo and fell in love with it! After finding that they also made one as a head, I've been trying to work out how to utilise both heads if I were to get one. Reasons being that I love the clean on my Marshall and use pedals to get my overdrive sounds through it, but I love the overdriven tone of the Peavey, so would use the Marshall +/- pedals for the majority of my sounds, but the Peavey so a different overdrive sound. But the reasons aren't that important.

My problem comes with the fact that I would want to put the same pedals through the effects loop of both amps. The attached flowchart looks alright to me, but would love some opinions on how effective it is, and whether there's an easier way..

To explain the chart if necessary... my guitar signal will go directly into what I've called the "O/D stage" of my pedalboard, where my wah and various overdrive pedals live. From that it'll go into the input of the amp switcher which will be a ToneBone "HeadBone". That will then send the signal to the pre-amp sections of amps A and B. The effects loop "send" on each amp will go to a switch which will send one of these signals through the "FX stage" of my pedalboard, delay, chorus, reverb etc. After that, another switch will send that processed signal to the power amp section of amp A or B, which will then go back to the HeadBone.

So that all the necessary switches will occur at the right times, I'll put the two switches shown in the flowchart on the 3PDT footswitch, where the third pole will act as a remote "slingshot" switch for the HeadBone.

My main concern is that I don't know how either amp will respond when its effects loop is connected, but not completed if the signal is not being sent back to it after the "FX stage" of my pedalboard.

So...thoughts?
Attachments:
Dual_Amp_Setup.jpg
PRS SE Chris Robertson
PRS SE EG
PRS SE Angelus Custom
Yamaha SF1000 (Both of 'em)

Laney L20H Lionheart
Marshall 1936 w/ Eminence

Rather large pedalboard..
#2
Serial effect loops close the circuit from the preamp output to the power amp input when there are no plugs inserted in the Send and Return jacks. If you plug a cable into either or both FX loop jacks, integral switches in the jacks will open the circuit between the preamp and power amp, re-routing the preamp output into the Send cable and the power amp input from the Return cable, regardless of whether the cables actually go anywhere.

Parallel effect loops are quite different. The preamp and power amp stay connected (the dry signal) and there is another path from the preamp to the power amp that goes through the Send and Return jacks (the wet signal) with a blend knob to mix the dry and wet signals (there could be some amps out there with parallel loops and no blend knob, so be warned). Parallel loops dont care what happens at the Send/Return jacks if the blend pot is set to full dry. As you roll the blend pot towards wet, the dry signal level lowers. At the same time, the wet signal level increases, assuming there is a complete circuit between the Send/Return jacks.

A good example of a parallel loop is the reverb circuit in an amp; the Reverb pot being the blend control, sort of (it is actually just a volume pot for the reverb circuitry). The reverb circuitry goes in between the preamp and power amp and there is a fixed resistor across the reverb circuitry to divert some of the signal around the reverb circuit. Without the resistor across the reverb circuit, the reverb would be in series with the signal path and not sound too good (I've tried it). It goes like this (ignore the break in the line):

preamp output-->reverb driver-->reverb tank-->reverb recovery-->reverb level control-->power amp input
             |                                                                       |
             |_________________________________Resistor____________________________|

Hope this helps...
Last edited by Invader Jim at Nov 18, 2013,
#3
Quote by Invader Jim
Hope this helps...


I'm gonna sound stupid, but I'm terrible at absorbing such dense text and am struggling to find the important parts of what you've written..

Are you saying that I should use either a parallel or series, and how would I go about doing either/or?

Sorry!
PRS SE Chris Robertson
PRS SE EG
PRS SE Angelus Custom
Yamaha SF1000 (Both of 'em)

Laney L20H Lionheart
Marshall 1936 w/ Eminence

Rather large pedalboard..
#4
Don't worry, so am I.

I just re-read your post and flowchart and I think I made an ass of myself.

This should work fine as you have it, as long as you switch the loops and the heads at the same time. I don't know what you mean by "remote slingshot switch" for the head switcher.

You may be able to replace the two "switch" boxes with Y-splitters to feed the "FX stage" to both amps at once, negating the need for more switches. This way you can just focus on the HeadBone and not worry about killing your signal by having one of the fx loop switches set wrong.

Or it could affect the impedances of the amps and change your tone, noticably or not. You could try it though.

I've been awake for too long.
#5
The "remote slingshot" is what they call a switch for the HeadBone that you can wire externally from the main unit, so you can have short cables going from the HeadBone to the amps and just one long one to a remote switch on your pedalboard

The reason I was looking at using switches rather than Y splitters was that I've had problems with signal strength and consistency with them before - admittedly mostly with headphones, but guitar signal and tone needs to be even more stable yet, so I figured switching would avoid all that.. I'd need a switch anyway to control the HeadBone, so I figured I might as well just wire up a 3PDT switch and do the whole lot in a single "stomp" as it were.
PRS SE Chris Robertson
PRS SE EG
PRS SE Angelus Custom
Yamaha SF1000 (Both of 'em)

Laney L20H Lionheart
Marshall 1936 w/ Eminence

Rather large pedalboard..
#6
That works. I was just thinking it'd be good to have one less switch to worry about. But it would be better to have shorter cables between the amps and one longer cable for the switching.