Effect loop problem

I picked up a used but in great shape mark V a few months ago. Today I tried using a 10 band mxr eq in the loop but something is wrong. As soon as I plugged a cord into the send the sound level drops dramatically. Even with nothing in the return. Any ideas?

It's a serial effects loop, you will have to complete the signal chain going back into the return, enable the effects loop switch and make sure the level knob on the back is adjusted so that the volume is the same when you engage and disengage the effects loop.

I would think though that just plugging something into the send wouldnt affect the output when nothing is plugged into the return. No? Plus with an mxr ten band eq in the loop I have to crank the level nob on the back all the way up and still dont even come close to the same level.

possibly, i don't recall the behavior when the return is not connected. Did you try another pedal or device ? maybe to rule out the MXR.

firmani99 said:

I would think though that just plugging something into the send wouldnt affect the output when nothing is plugged into the return. No? Plus with an mxr ten band eq in the loop I have to crank the level nob on the back all the way up and still dont even come close to the same level.

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The loop is essentially an insert point between the preamp and the power amp. By plugging into the send only (with nothing in the return jack), you have basically broken the connection between the preamp and the power amp.

I also have an MXR ten band EQ, and have had no problem at all achieving unity gain with it in the Mark V loop, so it's likely that you have your levels off somewhere. The MXR has two gain controls (these are the sliders on the far left and far right), and with them in the center position you should have unity gain when the rest of the sliders are in the center position.

Steve, That's what I was thinking too about unity gain. Something is definitely wrong with my amp. I'm hoping it's just a tube.