Adding An Effects Loop to the Fender Frontman 25R SS Amp

[aoresteen]

I have a nice  25 watt Fender Frontman 25R ss amp with an external Peavey Black Widow 12" speaker.

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The iPod plays backing tracks for guitar & lap steel practice & my wife likes the headphones!  I upgraded the amp with a 10" Weber 10F150 speaker.

https://www.tedweber.com/10f150/

The amp is loud enough for small venues and a reasonable drummer

I would like to add an FX loop to the Frontman 25R.

I found this 2019 thread on doing this to a Washburn ss amp:

https://www.ssguitar.com/index.php?topic=5199.msg40778#msg40778


Member phatt posted a solution using two jacks & 2 diodes.  I have twp questions:

1. Where are the diodes placed? How are they oriented?

2. What value diode should be used?


Here is the schematic to the Frontman 25R amp:

https://www.manualslib.com/download/1059221/Fender-Frontman-25r.html

I think I would insert the FX loop just before R55.

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Here's how I think it should be wired but I do not know where to put the diodes

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Any other considerations that I might have missed?

Thanks!

[phatt]

I don't believe I mentioned Diodes as you don't need them,, maybe I'm having a brain fart? (head scratch)
 What you have is correct but Add a low value resistor before the Send otherwise the previous opamp output could get a dead short at some point.
Frankly there is no great benefit I can see to add the Loop, just plug in to the front of the amp,,,, but your choice.
Phil.

[Tassieviking]

I would place the loop between R55 and C33, that way you have resistance on the OP-amp side.
I myself would remove R55 and mount the wires in the holes where R55 was, then I would place R55 in the middle of the wire that goes to the send plug.
You don't have to cut any traces if you do it that way.

[aoresteen]

I don't believe I mentioned Diodes as you don't need them,, maybe I'm having a brain fart? (head scratch)
 ...

Phill,

My bad.  I re-read your post and no diodes are mentioned.  It's my brain fart, not yours. Sorry.

Tony

[aoresteen]

I would place the loop between R55 and C33, that way you have resistance on the OP-amp side.
I myself would remove R55 and mount the wires in the holes where R55 was, then I would place R55 in the middle of the wire that goes to the send plug.
You don't have to cut any traces if you do it that way.

Tassieviking,

Thanks.  I'll take that approach.


Tony