Effects loop in low-powered amps--why not?

[PB Wilson]

I was wondering why you don't often see effects loops in lower-powered amps (under 20 watts).

I realize that many dual EL-84 or dual 6V6 amps are stripped down designs aimed at the recreational user or for use as a practice amp and effects loops are one of the design features that gets axed, but is there a good reason other than economics? Does power tube clipping and decreased headroom have something to do with it?

 

[Leonc]

Originally posted by PB Wilson
... but is there a good reason other than economics? Does power tube clipping and decreased headroom have something to do with it?

Those are EXCELLENT questions. And I think it's time to throw down the gauntlet. I say to you amp buidlers: get off yer kiesters and figure out how to add great sounding effects loops to your already great low-powered amps. We want 'em and I KNOW you can figure out how to do it! Hell some of you already have.

Start by looking at the Reverend's and Orange Rockerverb's loop designs. The loops in these amps don't result in any tonal degredation, IMO.

 

[gulliver]

As an 18 watt EL84 user, I can tell you they sound so good they don't need effects!

 

[jaclo]

My Groove Tubes Soul-O Single has one. I had a Boodie Studio 22 that had one, also had a Boogie Subway Blues that had one. My old Peavy Bravo 112 had one. They are out there, I never use them though. I may try a pedal in my GT's soon.

 

[John Phillips]

Unless the amp gets the majority of its distortion from the preamp, there's almost no point in an FX loop.

The purpose of the loop is to be able to run some effects after the amp's distortion, so if the amp is getting most or all of it from the power stage (which a lot of small amps do), the FX loop is still pre-distortion so you might as well just put them in front of the amp.

There can be a small advantage in signal-to-noise ratio with a loop, if it's running at a higher level and comes after some of the amp's gain, but it's nowhere near as important, and in any case many loops are designed purposely to bring the level back down to be able to run pedals in them, so you're back where you started.

So you might as well save the extra circuitry, expense and possible tone compromise of fitting one at all...


(I do use the loop on my Blue Angel for my delay and analog flter BTW - partly because the filter is quite noisy, and it does seem slightly quieter in the loop, but mostly because my rack unit sits on top of the amp and it's easier to hook it up that way... )

 

[LaXu]

My 15W Stephenson has a parallel loop in it. Footswitchable too so no tonal compromises. Since I don't own any effects I haven't been able to try it yet though. To me it makes sense having an fx loop for those reverb and delay effects, especially with distortion.

 

[Leonc]

Originally posted by gulliver
As an 18 watt EL84 user, I can tell you they sound so good they don't need effects!

I get a kick when guys say things like this. If use of effects is not part of your style, that's fine. But my sound involves use of effects so if the amp doesn't have built in delay (and some other effects), it literaly doesn't matter how good it sounds without them--I'm still going to be using them and I want them to sound their best. In my experience, this requires a loop or a wet rig.

The wet rig sounds better, but it's a lot more of a hassle.

 

[drbob1]

London Power's 10w amps have effects loops...

 

[bluesdoc]

The Pittbull's loop is also an excellent one, for ex.

jon

 

[John Phillips]

Originally posted by Leonc
If use of effects is not part of your style, that's fine. But my sound involves use of effects so if the amp doesn't have built in delay (and some other effects), it literaly doesn't matter how good it sounds without them--I'm still going to be using them and I want them to sound their best. In my experience, this requires a loop or a wet rig.

Me too, but I'd just got tired of saying it... thanks!

I don't get guys who constantly go on about how an amp (or a guitar, or a player) is "so good that they don't need effects" as if effects are some sort of crutch to cover up poor tone or playing. Actually they help you create interesting sounds that simply aren't possible without them, and often require more skill and learning to use effectively, than simply using the same guitar-into-amp tone all night, IMO. I've yet to hear an amp or a player that can sound like a flanger .

If I'm using an amp with more than a small amount of gain (basically anything with preamp distortion) then an FX loop is a requirement, period. Personally I even prefer a loop to a wet/dry rig, but I know where Leon is coming from too. The only time I wouldn't use one is if I'm using an amp with a limited amount of gain and only power-stage overdrive, so any harder distortion will be from a pedal or outboard preamp... and still before my chorus/flanger/delay-type effects.

It's quite true that a lot of smaller amps are built precisely to get power-stage overdrive, in which case a loop may be of limited use, but the minute you give it a reasonable amount of gain and a MV, you need a loop as well.

Just my opinion.

 

[Leonc]

Excellent points all the way around John!

And it would be intesrting to see just how much gain comes from the power stage in many of teh lower powered amps as it relates to the use of a loop. Of course, it'll vary from amp to amp and circuit to circuit.

I often set my "simpler" amps' volume knobs well before where the amp is grinding in a major way (e.g., it varies but often not much past 12:00). How much of the OD at that point is power stage and how much is pre-amp? Rhetorical question. Of course...it depends on the amp, guitar, etc...

 

[R3deemed]

Let me throw a question in here as it's not too off-topic. I'm using a Voodoo Labs preamp into a Mesa/Boogie 20/20. There's no FX loop in the preamp, so I run my time-based FX between the Voodoo and the 20/20. Would you guys suggest something else?

 

[John Phillips]

No, that's exactly how I'd do it too .

Mesa actually suggest trying the same scheme with their own preamps which do have FX loops. The reason is that a lot of digital FX processors introduce latency, which sounds truly awful in a parallel FX loop (which the Mesa ones are, even at full-wet some dry signal leaks through) unless the FX unit is set to wet-only... which you don't always want.


Leon - as you know your question has no easy answer! There are a few amps that get almost all their distortion from the power stage - the 18-watter type circuits are one; with only one gain stage before the PI, there really is no preamp distortion at any volume (unless the input is goosed heavily!). Most more complex amps have a mixture of the two. Which overdrives first depends on the input signal as well as the control settings.

If you have a non-MV amp with a loop, you can find out ... run a volume pedal in the loop, set it full up and turn up the amp until it just distorts. Now back off the pedal slightly - if the distortion goes away it was from the power amp.

FWIW, the reason I like FX loops rather than a wet/dry rig is that I do in fact like a small amount of power-stage distortion after my modulation and delay effects, and it seems to work better when both the preamp and the power amp are part of the same amp, for some reason. I feel it gives a more complex, integrated organic sound - I don't like recording dry and adding effects at the board either, for the same reason. Luckily the recording engineer I usually work with has got used to me and doesn't complain any more .

 

[PB Wilson]

Thanks for the replies. The reason I'm asking is because I am contemplating having a lower-wattage amp built (based loosely on a Tweed Deluxe, 2x6V6 with a half power switch) and was wondering if a loop would be worth the extra cost (not that it's that expensive). I'd basically use it for a bit of delay and perhaps a bit of phaser thrown in. I'm not using any rack effects and don't plan on it in the future. I definitely want the amp tailored for power tube clipping, especially running at half power. I'll chat with the builder and see which way he leans. Thanks again.

 

[PB Wilson]

You learn something new every day. I am REALLY glad I got on this forum. The signal to noise ratio is pretty damn high in here. Thanks!

 

[haslar]

That signal/noise ratio is often a big problem with effect loops.
I've given up using mine on my Rivera M60: the hiss is not acceptable.
Many effect loops are poorly engineered, it seems, and using them leads to a WORSE sound than plugging your pedals up front.

 

[Voodoo Amps]

You can install FX-Loops into 5, 10, 18, 20, 25 watt amps as well as higher wattage amps. Over all it depends on the design of the amp.

Generally speaking; Vintage amps derive their gain from the phase Inverter tube and when the amp is cranked up really the high the power tubes also kick in more distortion. FX-Loops go before the Phase Inverter tube so in vintage amp designs it tends to change the feel, gain and over all character of the amp's initial design (which a majority of players dislike).

For amps such as a JCM800 2204/2203 (or other higher gain amps) where the Master Volume comes before the Phase Inverter tube, you can install an FX-Loop with great results.

Again this is just a generalization and naturally this does not apply to all amps.


Hope it helps
Trace

 

[kipknee]

Thought I'd jump in on this topic. I primarily use the effects loop in my amps for the purpose of running a volume pedal.
My current (small) amp is a Mesa Subway Rocket.

Like this...

Guitar -> Compressor -> Sparkle-Drive -> Barber-LTD -> Boss CE-2 -> Subway -> Volume Pedal -> Boss DD-3 -> Subway

This setup works very well for me. The pedals can still excite the preamp section sufficiently, but I can still control the overall volume.

Bob

 

[utterhack]

Reverend Goblin 5/15 rocked the effects loop. Sadly discontinued now...

 

[Bad Back]

You can install FX-Loops into 5, 10, 18, 20, 25 watt amps as well as higher wattage amps. Over all it depends on the design of the amp.

Generally speaking; Vintage amps derive their gain from the phase Inverter tube and when the amp is cranked up really the high the power tubes also kick in more distortion. FX-Loops go before the Phase Inverter tube so in vintage amp designs it tends to change the feel, gain and over all character of the amp's initial design (which a majority of players dislike).

For amps such as a JCM800 2204/2203 (or other higher gain amps) where the Master Volume comes before the Phase Inverter tube, you can install an FX-Loop with great results.

Again this is just a generalization and naturally this does not apply to all amps.


Hope it helps
Trace

OT- Looked at your site, and I see you install solo boost mods.

That is of real interest to me. I didn't see any sound clips (or I missed it). If no sound clips yet, I would be most interested in simply hearing a scale with it off, and then on.