The Effects Loop - threat or possibility?

Your signal path – this is what happened previously:

plectrum made from plastic (or another material) hits the strings resulting in a fundamental wave suitably spiced up with a series of harmonics. A pickup installed in the guitar’s body senses the string vibration and transforms it into an alternating current by means of induction. This tiny little current (our signal) is then transported onwards via the guitar’s electronics and out of the guitar. A cable (or lead) transfers the signal to the amp or to a pedalboard to the best of its abilities. As the signal is rather weak it is subject to many cases of resistance and impedance during its travels. There also might be a series of different effects, which can work in very different ways. The most crucial point, in terms of signal quality, is the point of entry, the input of the first effect. You will find buffered, as well as true bypass effects. Regardless of this difference, they are nonetheless all fed by the same power supply unit. Next, the now effected signal travels on via a cable snake to the guitar amp’s preamp. The signal is fed through a series of preamp valves (tubes), which boost the signal until it is fit for final amplification by the power amp stage.

In the 1980s someone hit upon the bright idea of placing some of the guitar effects between the amplifier’s preamp and power amp sections. This means that these effects are fed a signal overdriven – or distorted – by the preamp stage, resulting in a different sound. Some effects might sound better or clearer if their “wet” signal isn’t overdriven any further. This looks like a great idea on paper, but isn’t as easy to put into practice as it may seem.

The effects loop – a short history

The concept of the effects loop was lifted from recording studio equipment. In a studio the signal is usually sent from a channel insert to an effects rack, before it is fed back into the mixing console. The development of rack effects, channel inserts in mixers, and effect loops in guitar amps go hand-in-hand. Effects racks simply made the jump from the studio onto stage and into a guitarist’s backline. Guitarists wanted to recreate the sounds they got on their records in a live environment, so the rack was dragged on stage and into the limelight. The golden age of the effects rack has long since passed, but there are still many players using (or considering using) an effects loop.  

Some important questions to ponder:

  • Are you sure you’re not simply a victim of peer pressure, who’s reacting to comments in Internet forums that pressure you into connecting your modulation- and time-based effects to your amp’s loop? Have you listened to the sound of your effects in front of your amp, before putting them in the effects loop?
  • Is “your” own signature tone based on preamp distortion? Do you use a lot of overdriven or distorted sounds? If your answer to these questions is “no”, there really isn’t any point in using an effects loop.
  • Are you currently using your loop to hook up effect pedals? Are you aware of the fact that pedal effects are meant to be used with the low signal levels (and very high impedance) of a guitar signal? What’s coming off your effects loop is way too hot for most pedals!

Signal transfer – what you need to know

Guitar pickups induce a small electrical current. A singlecoil pickup might produce 0.25 volts of AC, while a humbucker’s output stands at around twice that amount (0.5 volts). These are the voltages a traditional pedal effect is made for. Your amp’s preamp has to amplify these minute voltages to currents of between one and four volts, before the power amp stage can do its thing, and pump up the signal up to the considerable wattage we need to move our speaker(s) and give our drummer the finger. 

An amp’s effects loop is situated between the preamp and power stages. The – already pre-amplified – signal comes off the preamp and is routed to the effects loop’s send. While writing this article I measured the output of the effects loop sends of a number of different guitar amps. Depending on the master volume settings my meter read between four and 10 volts

A Univibe, for example, is known to be very sensitive regarding input signals. It tends to clip extremely easily, making it very hard to use with an electric piano and even some humbucker-equipped guitars. What do you reckon happens to the Univibe when the input signal increases twentyfold? The same thing that happens to your nice effect pedals – they are going to clip, literally choking on the far-too-hot signal.

The master volume has an effect on the loop’s send!

You may be satisfied with your sound at bedroom levels, but did you know that changing your master volume settings has a direct bearing on the effects loop’s send-levels? At home you’re sending only moderate signal levels to the effects in your loop, but when you turn up to play in a band setting the send-level is raised considerably, changing your effects’ behaviour and your tone. This is probably why you’re never quite satisfied with your live sound… 

And there’s more to come: You may have heard of serial or parallel connections. In the context of effects loops this means that in a serial loop the internal signal path inside the amp is broken and the whole signal is sent through the loop. Thus the effects in the loop become part of the amplifier’s signal path, even when the effects are switched off. If you’re using an old digital effect in series, all of your precious signal is first digitized by a (probably less-than-perfect) analogue-to-digital converter, then processed, and finally converted back into analogue, eating up most of your tone, dynamics, and nuances in the process. Is this the path to “good” tone? I doubt it!

More cables, more trouble

Last, but not least, you shouldn’t forget the rat’s nest of cables you need to hook up more than one effect (pedal) to the loop. The original idea was to have the effect processor or effects rack placed near the amp, and to use only short signal leads. But if you’re bent on using the loop together with a pedalboard, you will need at least two long cables to go between the ‘board and the amp. These two cables will then become immensely important: In case of a faulty lead (in a serial loop) you will experience the embarrasment of drop-outs, or even the amp going completely dead, without any fallback option, but to run over to the amp and disconnect the whole pedalboard.

Onko jäljellä vielä ketään, joka vannoo efektilenkin nimeen? Koska pirujen seinille maalailun sijaan haluan tarjota ratkaisuja, paneudun seuraavaksi niihin. Efektilenkin käyttö on mahdollista, kunhan ymmärtää sen hyödyt ja osaa välttää mahdollisia sudenkuoppia. 

Solution 1 – Don’t use it

What type of music do you really dig? Which decade did your musical heroes create their best works in? My own tastes are rather eclectic. Some of my favourite delay sounds can be heard on records by the Von Hertzen BrothersAmorphis, or Kingston Wall. These guys never used an effects loop.

Amp makers Mad Professor aimed for a traditional guitar tone with their aptly-named Old School -model. They had experimented with an effects loop during the prototyping stage, but finally decided not to utilize a loop. They wanted to build an amp with no compromises, and a loop would have meant compromises in sound quality.

Solution 2 – Move your gain stage

How do you overdrive your signal? Do you rely wholly on preamp distortion? Looking at the frequency spectrum of a signal overdriven by preamp valves, the analyzer will show a curve that is very similar to an overdriven signal produced by the transistors inside a quality overdrive or distortion pedal. Your sound will improve drastically if you lower your preamp gain, instead relying on one or two quality pedals in front of your amp for your distorted tones. The signal levels sent to your modulation and/or delay/reverb effect unit in the loop will be much lower this way, giving the effect more air to breath. Now, signal levels can be changed in front of the amp, before the signal reaches the preamp, making your amp’s signal path more dynamic and much clearer, resulting in a well-balanced, easily-controllable sound.

Solution 3 – Make your own parallel loop

If your amp has a serial loop, you can connect it to a Lehle Parallel L ‑box. This little device turns your serial loop into a parallel loop. First, you have to hook up your effects to the Lehle’s Send- and Return-jacks. Then, simply adjust your digital effect’s mix level to completely “wet”, with none of the “direct” signal added (direct is in inverted commas, because old digital effects also convert the dry signal). The Lehle Parallel L’s mix controls enable you to set your send-, return-, and effect mix-levels independently, keeping your original amp tone intact and all-analogue. 

Solution 4 – Drop your loop’s signal level

You can prevent master volume changes from clogging up your effects in two different ways. The easiest solution would be to use E.W.S.’ Subtle Volume Control. You place the box in your effects loop, and use it to control the loop’s send-level, giving you a sort of “channel volume” control for the loop. A more sophisticated solution would be the aforementioned Lehle Parallel L-box with its separate send- and return-controls. The Lehle lets you drop the send level to suit your effects, while giving you the opportunity to raise the return level to fit your guitar amp’s power stage. 

Solution 5 – Use a professional cable snake

Professional backlines usually empoy the ”four cable method”, when hooking up pedalboards. This means, you have four leads running the length between your ‘board and your amp:

  1. From the wireless receiver (next to the amp) to the pedalboard.
  2. From the ‘board to the amp’s guitar input.
  3. From the amplifier´s Effects Send to the ‘board.
  4. From the ‘board back to the amplifier´s Effects Return.

Many snakes also include an AC-power feed for the PSU on the pedalboard. If no wireless is used, no fourth signal lead is required.

I’ve made many cable snakes to go along with our Custom Boards-pedalboards. All cables are bundled together in a special, sturdy cable sock, giving you a clean, secure, and easy-to-use hook-up solution. Our Custom Boards four cable method snakes are available in three different lengths (six, eight, and ten metres).

Other uses for effects loops

Apart from providing a way to regroup your effects, effects loops can also work in other applications:

  •  Bluetone’s Dusty Road and Wizard model guitar amps come with a buffered effects loop that can be used as an additional gain stage or as a solo booster. An effects loop is the most effective spot to add a booster, because its output is fed straight into the power amp. It works similarly to a booster pedal after a distortion pedal – increasing the volume without changing the amount of overdrive. 
  •  An effects loop is also a good additional tool for the amp repairman, as it splits the amp neatly into its pre- and power amp sections. The loop allows you to test both amplifier stages separately; you can connect the preamp to a different power amp to check whether the fault is in the preamp or the power amp. Locating a problem is much faster this way! 
  • An effects loop also lets you take your sound on the road more easily. It is standard practice with backline rental set-ups to use only the rented amp’s power stage and cabinets, with the sound itself coming from an amp head and/or effects rack, which the band carries with them, placed at the back of the riser. Your rack or amp head is simply inserted into the hired amp’s effects loop. This is a neat way to carry your own sound along to a gig. 

You wouldn’t believe how many bands use a wall of Marshalls for visual effect only, while the sound itself comes from an über-modern modelling amp, like a Kemper or an Axe FX, secretly stashed away behind the cabinets. Fists are punching the air, the audience screams in delight. Rock-concerts are as much about having the right kind of look, and creating the right kind of atmosphere, as they are about the music.

So, there’s some life left in the old effects loop, after all.

27.8.2014 Kimmo Aroluoma (translated by Martin Berka)
The author is one of Custom Sounds’ owners, and an incorrigible guitar and gear enthusiast.