Effects Loop For Class 5?

Gene Ballzz

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Hey folks,
I've searched everywhere I can and not found anyone who actually installed and effects loop in a Marshall Class 5 amp. I've found many armchair discussions of how it likely wouldn't work well, given that so much of the overdrive characteristics happen at the power tube. I still think that for an echo junkie like me, the amp could easily benefit from a properly placed effects loop. Many folks have added a master volume (that they weren't very pleased with) near R24 of the schematic below. Could some folks look at the scematic and help me decide the most appropriate location for an effects loop attempt? I would likely use a Granger effects loop module! I'm thinking just before the final driver stage of V2B? Possibly just before or after R12?

Thanks For Looking,
Gene

C5_Circuit_Diagram_complete.jpg
 

fitz288

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No clue, same question, here to learn. :coffee:
 

Pete Farrington

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My ‘fx loop’ for power amp overdrive type amps is a mic in front of the speaker (or a line out derived from the speaker output), feeding a delay pedal modded for ‘wet only’. Then into a vol pedal to control the echo level, then a cheapo solid state combo set clean. Or into a PA.

If you’re determined to fit an fx loop, yes, the ‘in’ legs of R12 or R24 look the best options. But most of the clipping will be occurring after those points, ie at the EL84 grid and anode.
 
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Biff Maloy

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My ‘fx loop’ for power amp overdrive type amps is a mic in front of the speaker (or a line out), feeding a delay pedal modded for ‘wet only’. Then into a vol pedal to control the echo level, then a cheapo solid state combo. Or into a PA.

If you’re determined to fit an fx loop, yes, the ‘in’ legs of R12 or R24 look the best options. But most of the clipping will be occurring after those points, ie at the EL84 grid and anode.

Best advice IMO. I did the very same thing with mine years ago. Fed miked signal to a small mixer with chorus, delay and reverb through the mixer's loop then out to powdered PA monitors. Small WDW rig.
 

Gene Ballzz

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My ‘fx loop’ for power amp overdrive type amps is a mic in front of the speaker (or a line out derived from the speaker output), feeding a delay pedal modded for ‘wet only’. Then into a vol pedal to control the echo level, then a cheapo solid state combo set clean. Or into a PA.

If you’re determined to fit an fx loop, yes, the ‘in’ legs of R12 or R24 look the best options. But most of the clipping will be occurring after those points, ie at the EL84 grid and anode.

Best advice IMO. I did the very same thing with mine years ago. Fed miked signal to a small mixer with chorus, delay and reverb through the mixer's loop then out to powdered PA monitors. Small WDW rig.

Yes indeed folks! When I used to use this amp regularly, it was as the "dry" side of a "wet/dry" rig, much as you have described. A bit more elaborate, as I used an attenuator, with a post attenuation line out to an effects unit, into the effects return of an MG100HDFX. Each amp drove two speakers of my 4x12 1960B. The sound was glorious and fully controllable, but dealing with it on a gig to gig basis became rather cumbersome to haul, wire, unwire, etc, ad nauseam! And while a loop in this particular amp may be a small tonal compromise, I'm betting it will be better than running my delay and reverb into the front of the amp or dealing with the overall P.I.T.A. of a "wet/dry" setup!

I've been pleasnrtly surprised by the totally passive (just two jacks) loop I've installed in my generally stock, 5E3 Deluxe clone! It also gets much/most of it's "grind" from the power section. On thing that makes this scenario easier for me is that I don't often venture into high gain usage and I typically live just on the edge of breakup. If it doesn't work well in the Class 5, it will simply be a "white elephant" including a couple unused extra jacks on the back panel!

And while I'm not expecting a passive loop to work in this situation, I'll drill the chassis for the Granger loop to fit and actually try it passive first. FWIW, the Granger loop has the same footprint/jack spacing as a Metro Zero Loss loop. One convenient feature of the Granger loop is that it has both send and return level pots, accessed with a small screwdriver through the jacks. These loops are quite transparent and inert and also allow it to boost the signal a little, if desired! I've used them before and been pleased with the results. Also, note the handy "link" jumpers between C5 and R24, facilitating an "above board" installation with very little potential carnage! The small cost and "maintaining originality" of this fairly cheap amp are not big concerns for me.


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Thanks Folks,
Gene
 


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