I just picked up a Vox AC4C1-BL and I'm really happy with it, but I'd like to add some kind of effects loop so I can put reverb and tremolo after the gain.

Although I'd be willing to try my hands at a full-blown mod, I didn't find any for this amp, and from reading a little, I get the impression that attenuating from the external speaker out and then reamping after the effects is my best bet.

Now, I'd like to keep the solution fairly compact and not too expensive, so I had the following idea, but I'm wondering if it's terrible or not: I want to disconnect the internal speaker from the amp and add a jack for it on the back. Then I'd like to run the speaker out to an attenuator (I'm thinking the 25W Weber Mini MASS) then into my effects (I'm eyeing the Strymon Flint), then into something like the Electro-Harmonix 44 Magnum and then back into speaker of the AC4.

While I expect this will "work", I'm hoping it will also preserve the tone of my AC4, and allow me to expand this to a cab later, if I choose.

Any comments, advice? Is the speaker going to be okay as long as I don't crank the 44 Magnum?
Oof, I would not expect that to preserve the tone at all. Anything that involves knocking a power amp down to line level with an attenuator is getting pretty serious. Then goosing it back up with the 44 (not super transparent) into the original 15 watt speaker seems like a lot of potential issues.

Honestly I think your best bet is to run everything up front, put a distortion in front of the delay and toss a 12AT7 in V1 to keep the preamp low. The AC4 isn't exactly a high-gainer.

Or you could do a simple insert loop addition. But your solution is rather expensive and probably not going to sound great. At the very least it adds a lot of complication and potential frustration for not a ton of payout.
Thanks for your input. Re killing the tone, yeah, I was afraid of that.

As for adding an insert loop -- do you mean modifying the amp circuit to add effects between pre and post gain? If so, where do I start? I poked around a bit for someone who had done just that with this specific amp, but I didn't find anything.

Are amp circuits common enough that I should be able to take a circuit designed for another amp and make it work? And does this really change the problem? Am I likely to be able to splice in somewhere at line level, suitable for effects, or am I still going to have to worry about attenuation?
There is no 'circuit design' here, really. You just find where the preamp ends and the power amp begins, and you put a jack on one side and a jack on the other. That's it. It's only amp-specific in that you need to put the jacks in the right place.

You may have issues with impedance. Most pedals will be fine but that's the drawback of this very simple unbuffered loop. Some pedals might just sound goofy.
What you're talking about is more likely to mess up your tone than not using an effects loop. Run it out front in proper sequence and you will be fine.
Going to ask the obvious.

Unsure how you decided to pick up a new amp and then wished it had an effects loop and now you want to break into the post pre amp stage to mod one in.

Couldn't you have waited until you could get an amp with an effects loop?
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