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Active & Passive Effects Loops

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Active & Passive Effects Loops

Postby Jay Menon » Sat Apr 15, 2017 1:30 pm

On the subject of effects loops, my understanding is that:

A buffered loop: allows the use of reasonably lengthy cables, whilst protecting to some extent against signal degradation. This does not however, affect the level / volume of the signal.

Effect loops may be configured to work with for instrument level effects (-10dBV) or line level (+4dBV) effects. And some loops may well be switchable between the two levels.

If I were to therefore use a boost pedal or a headphone amp in my passive loop (Ceriatone Dumble clone), I could use it with Boss type reverb / delay floor pedal?

Expert opinions deeply appreciated.
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Re: Active & Passive Effects Loops

Postby DC-Choppah » Sun Apr 16, 2017 10:18 pm

-10 dB is still line level. Instrument level is lower by 20 dB. +4 dB is pro line level.

Guitar floor pedals use instrument level. If you run a line level signal into most pedals they will be overdriven so you need a reamp DI box.

If you try to use line level gear with instrument level signals it will be noisy and thin. You need an amp that puts out a line level signal to do that.

I run line level effects - Lexicon MX200 and others in the guitar chain and have to use the special 'to power amp' line level output of my preamp to drive these line level effects. So I have two effects chains. One is instrument level the other line level.
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Re: Active & Passive Effects Loops

Postby CS70 » Wed Apr 19, 2017 7:38 am

Jay Menon wrote:On the subject of effects loops, my understanding is that:

A buffered loop: allows the use of reasonably lengthy cables, whilst protecting to some extent against signal degradation. This does not however, affect the level / volume of the signal.

Effect loops may be configured to work with for instrument level effects (-10dBV) or line level (+4dBV) effects. And some loops may well be switchable between the two levels.

If I were to therefore use a boost pedal or a headphone amp in my passive loop (Ceriatone Dumble clone), I could use it with Boss type reverb / delay floor pedal?

Expert opinions deeply appreciated.

Yes, it's a good trick to use clean boosters or any other clean preamp after an effect in the loop to bring the signal back to line level, provided the effect can work with a line level in. Some pedals do, some sound bad, a few may fry (I guess they're often designed to be attentuate line voltage in the input, but each design may be different of course). Start with zero preamp gain on the amp and get carefully up from there.

For example, my Carbon Copy works fine with the output of my Mesa amp FX loop send, but its own output is too low for the FX return so I need a clean boost if I want to use it there.

In general the easiest is to use either a rack effect or a digital pedal which often is designed to work with a variety of input and output voltages.
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Re: Active & Passive Effects Loops

Postby Wonks » Fri Apr 21, 2017 3:40 pm

Your Ceriatone FX loop is far from passive as it's taken from after the pre-amp. A passive FX loop can only really exist in the signal chain from the guitar to the amp.
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