Effect Blocks Between Amp and Cab or IR Blocks?

[erniedenov]

I've noticed some of you do this. I never thought about it before; I've always put effects like reverb, modulation and delays after the cab. What is the advantage and/or difference in sound?

[jbuhajla]

It's kind of like running effects in your effects loop of your amp (not exactly I know, but close). The effects loop signal gets processed, then to the power amp, then speaker.

 

In the Helix, the cab block is like a mic'ed cab. So if you run effects after the cab block, it would be like running effects on the mic input signal from the mic in front of your amp into your main mixer. 

 

Putting the effects in between amp/cab (like in your "real amp's effects loop) gets processed by the cab block and tends to "soften" things up a bit. Give it a try for yourself. Put two effect in between and the same two after, assign them all to a single foot switch, and toggle between the two options.

 

Another thing to keep in mind is that everything in front of the cab block gets summed to mono as it goes through the cab/IR block. Don't waste DSP power by putting stereo effects in front of the amp/cab. Because of this, I'll put at least a stereo reverb after the cab/IR to get things back to stereo again. Everything in front is mono, everything after is stereo if you want stereo. Stereo effects use more DSP power. That is why you are wasting processing if you put them in front.  

[zooey]

Difference will be subtle, and depends complete on what FX and settings and original sound, but it is different. Experiment, which is fun with everything Helix, and simple and free, once you've got the box, unlike doing a lot of this IRL.

[amsdenj]

If the system between the output of the amp model and the output of the IR is essentially linear, then it may not make much difference at all. You're putting the same input signal through the same linear block transforms so they should produce similar results regardless of the order.

 

Now convolution is not linear, so it may make some difference where it is placed in an otherwise linear signal chain. 

 

Of course any distortion in the signal chain would have a big effect since its very nonlinear.

[Verne-Bunsen]

Why it's different I don't know, but I know that the spring reverb (regular spring, not the '63) and the bias and optical tremolos only sound "right" to me between the amp and cab. The nice thing is you can try stuff out in different spots in the signal chain without it being an hour long pedalboard re-build. Move things around and see what your ears tell you!

[PeterHamm]

I also like most delays and time-based FX after the cab... BUT... there is a different sound when they are before the cab, more like a real-world FX loop on an amp, and some FX, notably spring reverb and amp tremolo, sound way better to me in that spot than anywhere else.

[erniedenov]

It's kind of like running effects in your effects loop of your amp (not exactly I know, but close). The effects loop signal gets processed, then to the power amp, then speaker.

 

In the Helix, the cab block is like a mic'ed cab. So if you run effects after the cab block, it would be like running effects on the mic input signal from the mic in front of your amp into your main mixer. 

 

Putting the effects in between amp/cab (like in your "real amp's effects loop) gets processed by the cab block and tends to "soften" things up a bit. Give it a try for yourself. Put two effect in between and the same two after, assign them all to a single foot switch, and toggle between the two options.

 

Another thing to keep in mind is that everything in front of the cab block gets summed to mono as it goes through the cab/IR block. Don't waste DSP power by putting stereo effects in front of the amp/cab. Because of this, I'll put at least a stereo reverb after the cab/IR to get things back to stereo again. Everything in front is mono, everything after is stereo if you want stereo. Stereo effects use more DSP power. That is why you are wasting processing if you put them in front.  

 

You had me until you mentioned that everything in front of the cab block gets summed to mono. Still, I will check it out and thanks for the replies, everybody!

[jbuhajla]

You had me until you mentioned that everything in front of the cab block gets summed to mono. Still, I will check it out and thanks for the replies, everybody!

The signal going into the amp and/or cab block gets turned into mono, even if it was stereo before that. That's why you just want to use mono effects before you amp or in between your amp and cab block, so you don't use up DSP power unnecessarily. Use stereo effects after your cab or IR. 

 

Give it a try with headphones on. Put no effects after your cab block and have a listen. Then put a reverb (all reverbs are stereo in Helix) after the cab block and have a listen. 

[erniedenov]

The signal going into the amp and/or cab block gets turned into mono, even if it was stereo before that. That's why you just want to use mono effects before you amp or in between your amp and cab block, so you don't use up DSP power unnecessarily. Use stereo effects after your cab or IR. 

 

I knew that, just didn't know about it going between the amp and cab since I never thought about trying that idea. I've yet to worry about wasting DSP power since my patches are relatively simple with one serial path. When I was using a Line 6 Vetta, I used to use two amps and two cabs all the time; just haven't felt compelled to do that with Helix... yet.