1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
     
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

Effects Loop vs Preamp Out/Power Amp In

Discussion in 'Amps and Cabs [BG]' started by Joe Ty, Mar 13, 2017.


  1. Hi

    Sorry, still new to this forum and did some searching on this but didn't find a good consensus answer. I currently run my Fender Jazz into a Tech 21 Sansamp DI and then into the PowerAmp Input, bypassing my Preamp entirely. It's an early 80's Peavey TKO 65. It weighs about 60 pounds and I don't like lugging it to our friend's house to jam anymore. I'm trying to find something a little lighter that I can rig up the same way. Most of the smaller combo amps don't have this feature. I found an Orange Crush Bass 50 that weighs 32 pounds (much more manageable and yet still has enough oomph) and has an effects loop. My son's guitar amp has an effects loop, but he still uses the preamp to plug his guitar into. Can I use it the same way I do on my Peavey and just plug right into the "return" of the effects loop?
     
  2. tech21nyc

    tech21nyc Commercial User

    Aug 17, 2010
    Manufacturer: Tech 21
    They are pretty much the same thing but labeled differently. An effects loop send and return or preamp out/power amp in are basically an insert point between the amplifiers preamp section and power section. There are exceptions. The Orange should work fine for your purposes. You could also use the Aux in with an adapter as well. Who knows, you might just like the amp's tone in general and keep the SansAmp for recording or additional tones.
     
    Joe Ty and el murdoque like this.
  3. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    If you ever have the choice of plugging into either an effects return or a power amp in, go with power amp in. On many amps inserting a plug into the power amp in will disconnect the amp's preamp from the power amp. This will eliminate any signal noise coming from the unused preamp. If you are plugging into an effects return, it shouldn't matter but just to be safe in terms of noise, set the amp's tone controls flat and the volume down all the way.
     
    Joe Ty likes this.
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    It depends on what type of effects loop. While most bass amps use series loops that operate at line level, there are some with parallel loops and some that operate at instrument level.

    A series loop at line level almost always functions the same as a power amp in because of the way they are implemented in practice.

    [edit for: auto-correct gibberish, so much for auto-correct auto-correcting]
     
    Last edited: Mar 15, 2017
    JGbassman and kap'n kro like this.
  5. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    I've always assumed that effects returns in general also completely bypassed the preamp (and were the exact same thing as a power amp in) - I'm pretty sure that's how all of the effects returns have worked on all the amps that I've owned. Now I'm filled with self doubt - that isn't the case?
     
  6. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    Ah, must be the seruesblooos ;)

    I think that makes sense, I think that all of the effects sends/returns I've used have all been line level. I don't think I've ever come across one that was instrument level. I guess such versions exist though.
     
  7. mexicanyella

    mexicanyella

    Feb 16, 2015
    I have a Peavey TKO115 (teal stripe, Scorpion speaker, early 1990s I think) that has an effects loop AND preamp out/power amp in jacks. There's a high-pass filter on the effects loop, I think at 200 Hz, designed to limit lows going to the FX in the loop...but I think that's on the send, not the return. I also think the FX return jack is a little more sensitive than the power amp in jack. But still useable for the same thing, if the device that's replacing your preamp has adjustable output level.

    Same deal with my Peavey Special 150 guitar amp, by the way...no HPF on that one, but plugging an external preamp like a Line 6 Pod or something into the FX return requires a little lower output levels on the Pod, and plugging instead into the power amp in jack requires a little more level from the Pod, to get the same volume out of the speaker.

    Both requirements are well within what a Pod can do, in terms of signal amplitude. But I will say that as an experiment I have tried bypassing the preamps in both amps with an old DOD Bi-Fet Preamp pedal, which can add +17 dB of signal boost...apparently less than the Pod. With the DOD running into the power amp in jack the available volume was clearly limited, and it seemed louder running into the FX return jack.
     
  8. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    It depends on the amp.

    A parallel effects loop complicate things, it involves mixing in the effects signal with the preamp signal. There can be gain or impedance stages and pots can be involved to set send and receive levels. How the effects loop is implemented varies from one company to the next. Parallel effects loops can cost more and affect the bottom line, sometimes corners are cut.

    My point was more, if in doubt when it comes to pluggin into either an effects return or a power amp in, go with power amp in.
     
    kap'n kro and Joe Ty like this.
  9. Thanks, everyone. I'm looking at another option(s) with Ampeg equipment. The SVT-210AV cabinet weighs four or five pounds less than the Orange combo I was looking at and gives me more options than just a practice/small venue amp. I could pair it with SVT Micro VR 200 head which has an effects loop or the Portaflex PF-500 head which has BOTH an effects loop and preamp out/poweramp in. I think the PF-500 is meant to be used on much bigger stacks and the Micro VR has more unique tone options as well as meant to be paired with that cabinet, so I'm leaning that direction. Looking at the schematic, and I'm no engineer, the Micro VR effects loop is exactly how Tech21NY describes above. On the PF-500, the effects loop is more complicated "upstream" and the preamp out/power amp in looks like more of a clean cut-off right before the power amp.

    I am leaning towards the Micro VR option. Plus it looks more rugged.
     
  10. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    It seems like you're off of the Orange Crush 50 at this point, but one of the rehearsal spaces I use infrequently has one of those 50w 1x12 combos (that I use with a Sansamp going into the input incidentally), and I'm pretty sure it doesn't have an effects loop (just an aux) - maybe there are different versions?

    EDIT - NM, it looks like the newer version that Orange has listed on their website (still not on commercial sites) seems like it DOES have an effects send/return.

    Anyways, if you could afford it, I'd maybe reconsider the PF-500 over the VR 200. I'm not sure how much more rugged the VR 200 may or may not be, but that difference in power will be noticeable if you ever decide to upgrade your cabs. There's a big cost difference there that likely isn't inconsequential, but IMO there's a reason for that as well.
     
    Last edited: Mar 15, 2017
    Joe Ty likes this.
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    That was a pretty odd auto-correct into gibberish, right??? Yes, different loops do exist, a few parallel, and a few that are instrument level (like the Walkabout, which is ~instrument level because of the way the signal take-off is done to work with the unique tube driven output stage).
     
    kap'n kro likes this.
  12. Thanks, Kap'n. Would you have any concerns running a 500 watt amp through a 200 watt cab? Obviously I would not push it on the volume. Sweetwater has a demo available for $360, so it's only a $60 lift from the smaller head.

    I just heard from Ampeg technical support and here's what they said:

    "Hi Joe, In this particular amp, yes, you can use it in the same fashion as the ‘power amp in’. In this case, the signal path is pre-volume knob, so it’s not a true ‘power amp in’, which would bypass all preamp circuitry. Effects Loop VS preamp out/PA in can be used interchangeably. I would say the only difference, and this would be purely nit-picking, would be the position in the signal path. Effects loops would generally come before the amp’s volume, where the preamp and power amps would be split completely."
     
  13. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    This too depends completely on the architecture as most stand alone power amps have sensitivity or volume controls as well.
     
    kap'n kro likes this.
  14. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    First off, the PF-500 is only rated at 300w at 8ohms, so as long as you’re running just the one 210av, that’s what you’d be looking at (likewise that VR would only put out 150w into 8ohm).

    The amp also has a volume knob, so it’s entirely possible to be responsible with it and never push it into the danger zone.

    With that being said, the smaller the rig, the larger the likelihood that in a burst of enthusiasm you may push the speakers too hard, and since it’s a quieter rig to begin with, the higher the likelihood that in that situation you won't hear the cab’s calls for help.

    When I first started playing bass, the initial iteration of my first “real” bass rig was a GK 700RB-I into an Avatar B210: 225w @ 8ohm into a single 2x10. It did get me by for a good while with various pit gigs and rehearsals, but when I started venturing into the rock/club world, I was super glad that all I had to do to upgrade to the next level was to get another 8ohm cab – at which point my head went to 360w @ 4ohm into two 8ohm Avatar cabs.

    For what it’s worth, more volume will be much more about speakers than additional wattage, but I’m pretty sure I’d want more than 200w in that “next step” extension cab scenario if you ever decide you need it. Just my 2c. YMMV
     
  15. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    I just love thinking about "seruesblooos" in terms of the name of some very esoteric technical component. It still makes me giggle every time I think about it. People in my office are looking at me funny...
     
    agedhorse likes this.

  16. Thanks, again. One of the reviewers of the cabinet said he was going to eventually buy a second cabinet and a PF-500 to push them both, so that makes sense. I'd sure rather haul around two 26 pound cabs than a single 60-100 lb cab, not that that is an exact comparison.
     

Share This Page