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How to use fx-loop of a guitar amp? Multi-Ef­fects Plugins
Old 3rd January 2011
Lives for gear
audiothings's Avatar

How to use fx-loop of a guitar amp?

I am looking at a tube amp with an fx-loop and no on board reverb. So if I were to hook up, say, an EH Holy Grail or some such to the fx loop, how will I control the amount of reverb coming back, given that there is no output level control on the Holy Grail... I can set the mix knob to taste, but then I will be getting back some part of the original signal as well, through the return of the loop (albeit through the EH converters)... is it not? What am I missing? Oviously I don't want the original signal degraded by bany cheap converters...
Old 3rd January 2011
Gear Nut
Dudevico's Avatar

There should be knobs for send and return on the amp (could also be one knob called mix or something). With those you controll the output signal to the reverb and input back into the amp.
Old 3rd January 2011
Gear Maniac
BasHermus's Avatar

Well... in my experience on most tube amps (or of any type of guitar amp for that matter) there is no mix/send/return knob on them.

So you'll have to use the mix knob of the effect pedal.

But, the FX loop of many amps is parallel, so if your effect is able to send an effect-only signal and you can control its volume, your original signal is not altered by the pedal (nor the cables that you use).
Old 3rd January 2011
Lives for gear
Broadly there are two aspects to guitar amp effects loops:

1. Is it buffered? Many loops are a simple break in the circuit just before or after the last gain stage, and offer the wrong impedance to guitar pedals resulting in a loss of high end. Rack gear is more forgiving of this. You can buy a tube buffer for your effects loop, the Vox 847 (discontinued) being the least expensive on Ebay.

2. Is it parallel, series or switchable. A series loop requires you to use the mix function on your pedal, and will be affected if the pedal digitizes the dry signal, not a great solution IMHO. For serial loops and non-dry bypass gear, you can buy pedals that allow you to set bypass/mix amounts. A clean boost after the reverb pedal will bring up the level. Parallel loops work with effects that can be set for 100% wet and preserve your amp tone well, and many of them have level controls to match levels. By far the best solution to your problem...
Old 4th January 2011
Lives for gear
audiothings's Avatar

So I need to find out if the fx loop on the Ibanez Tube Screamer amp is parallel and buffered... no info on their site and no manual either... What I do know is that there is no send/return level control.

Old 4th January 2011
Gear Maniac
BasHermus's Avatar

Finding out whether it is parallel is easy.

Just insert two cable into the FX in and out (and don't connect anything to the other end of the cables).
If you still have sound, its parallel.
If you don't have sound, it series.

Don't know a simple trick to check whether it is buffered (but to me this is less important. I even prefer a bit of high-end loss in my delays and reverbs).
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