Ceriatone Forum

How do I add an effect loop to the plexi? is it as simple as taking the signal to power amp and turn them into a jack?

yes, but you'll need a dumblator

i think there is some on There (http://ceriatone.com/tlbrBorderSub/modifications.htm)

I am not an electrician, but I have been wiring guitars and cables for almost 40 years. I am sure I could manage this little mod myself - the diagram is great. Thx. for that.

One stupid question: what is a dumblator?

And will it work with pedals and fx-units with different impedances?

Cheers Brett

It is not as simple as splitting the signal path.  The effects loop needs to be buffered. 

The "Dumblator" is just an outboard buffer for an effects loop, but traditionally the buffer is built-in and driven either by a tube or an op-amp. 

Hi wyatt, thanks.

I looked at the schematic and the wire between the treble pot and the resister gets split - the point of inception for the interupt loop (lol).

If I understand that correctly then I do not need anything else - right? You mention buffer but I do not need to add anything physically or do I? I am blindly trusting the schematic...

One question still left - if the line to the resistor is cut to the fx-loop and imagine the fx-loop is unused (for whatever reason...) then surely the treble pot becomes deactivated? I would need a short cable from Send&Return I guess..

Looking forward to any replaies - Cheers Brett

i never used to have one of the fx loop, or to use fx loop on any of my amp, my knowledges about it and how they work are limited.
i dont know about buffer etc.
Also yes the fx loop get splitted between the treblepot and the input of the phase inverter.

for the other question, if you look at this schematic (http://ceriatone.com/images/mods/Plexi50-with-interrupt-styl.jpg)
i can be wrong but i think when you keep the fx loop jack empty they switch(the jack) to original setting.
ie: they get bypassed and A is connected directly to B.
we can see This schematic too (http://ceriatone.com/images/mods/FX-Loop.jpg) wich have a bypass switch.

Well, the effects loop referred to in these schematics is a straight "insert" effects loop, which is okay for line-level (2-watt, 0db) outboard effects but won't cut it for many instrument level (.5 watt, -20db) effects (in short, in a simple insert loop, some pedals may sound like crap).  You have to have a buffer in there to correct for line-level or instrument-level effects.  On most factory amps, this is part of the amp design (most commercial amps don't use simple insert loops), they use a tube or op-amp gain stage in front to buffer the signal going into the loop (and another for mixing the return in parallel loops) to correct for that instrument-level signal. 

Now it is possible to do this outboard, which is what a device like the Dumblator does.  And some buffered effects do a decent job correcting for non-buffered effects placed after them. 

Actually, I have a tube spring reverb right after the insert loop, which nik says it automatically buffers the signal anyways since if you really think about it, the reverb first boosts the signal before going into the tank then boosts again to line level after leaving the tank...

I don't think so. The fender spring reverb units do buffer the signal but they produce less output than what goes into them.

I thought Nik offered this mod as an extra option along with master vol(PPIV)?.