Torpedo CAB M : using the "speaker out" as a FX loop "thru"

[therealdjabthrash]

Hi !

This question has been asked in another general CAB M thread (viewtopic.php?f=75&t=201890), but since it hasn't been asnwered yet, i figured it should have its own dedicated thread, so there you go :

Greetings from Russia, comrades!...)

I have a stupid question:
Will it be safe to use Speaker Out with Fx Loop of an amplifier?

For example:
Preamp->CabM Input ->CabM Speaker Out-> Fx Loop Return
Parallel path: CabM DI Out -> Mixing Desk

Hi !

It seems nobody has answered this question yet, which is far from stupid actually, and it seems that this specific configuration is not mentioned in the user manual or elsewhere.

I have the exact same question, because i want to use a CAB M the same way : in between the preamp and the poweramp (which means : in the FX loop), to be able to get :
1) my dry preamp sound to my power amp (and then to my actual cabinet)
2) my "Torpedo-ed" CAB M output (= dry preamp sound going through the CAB M poweramp + miking sim) to my mixing desk

Is it possible to use the "speaker out" of the C.A.B M as a thru jack output, even if it outputs a preamp signal that goes to the poweramp, instead of outputting a poweramp signal (speaker out) to a speaker (which is the normal case) ?

In other words :
- this "speaker out" of the C.A.B M was originally designed as a THRU in between a poweramp and an actual cab...
- ... but can it be used as a THRU in between a preamp and a poweramp (which would be way more useful in my case) ?
If so, i guess a regular instrument cable can be used (instead of a speaker cable) ?

Looking at the Block Diagram and the Technical Data of the current user manual makes me think that this is possible (and that this THRU jack output is labelled and advertised as a "speaker output" only because nobody considered using it between a preamp and a poweramp), but i need to be 100% before i buy a C.A.B. M and use it this way

 

[plumcrazy]

Hello. First post here. I'm a recent purchaser of the CAB M and have been really enjoying this thing. I had a very similar question. I want to connect from my board to CAB M, go XLR to an interface, and use speaker thru to go to the front of my amp. I tested this and it does seem to work, but it did introduce a bit of hum to the output that I'm trying to figure out. I honestly couldn't hear any difference between direct to the amp vs. having CAB M in line. It would be great to know if this is actually a recommended thing to do, but from my test, I would assume it's safe to use the speaker thru to go back to your effects return.

 

[guillaume_pille]

I did answer that question, if you use the Speaker out as a splitter for a line level signal, it is possible you run into hum/ground loop issues.

this is because we cannot bufferize that output (because it's suppose to be able to handle 50V or more). If you want to use the speaker out as a Splitter, you may need a passive transformer DI box after the speaker out.

 

[plumcrazy]

Great. Thanks for the answer!

 

[therealdjabthrash]

Here are some the answers provided by Guillaume Pille from Two Notes about this subject but on another thread (viewtopic.php?f=75&t=201890) :

viewtopic.php?p=2263374#p2263374

Hi all,

because the SPEAKER out cannot be buffered, the ground of whatever you connect there will be connected to the ground of CAB M and your previous device (a preamp).

It may work and you will not break anything, but it's possible that you experience ground loops doing that. In that case, a DI (with isolation transformer) may be necessary.

When you connect a cabinet on that output, because the cabinet is a floating ground, you have no issue.

viewtopic.php?p=2266949#p2266949

Just to be sure i understand this right, did you mean that to make sure i have no ground loops in my case, i would need to put a DI in between the "preamp out" and the "CAB M input" ?

You won't necessarily have an issue, but in that case a DI can help. It's worth trying it anyway.

Also, let's suppose i skip the "inserting a DI" (to prevent ground loops issues) part, I have a hard time seeing the difference (in terms of ground loops issues) between :
- inserting a regular fx pedal (say a delay pedal) in the fx loop of my amp (which is something lots of people do, and do not seem to have a specific ground loop issue this way)
- inserting a CAB M in the fx loop of my amp

If the CAB M is just connected in and out to your amp, no difference. But if you plug it to your amp on one side, and then into a mixer, a soundcard, another distant device with a different grounding, things can get funny.

viewtopic.php?p=2266978#p2266978

The problem is not with the DI out, it's about connecting the ground of multiple products via the CAB M, which is what you do by using the THRU not for its original purpose.

The ground lift can help, but sometimes it's not enough, it depends on how the noise travels and where it takes its source. That's the case for EVERY product. And if the noise happens because you use the THRU, well, the ground lift on the DI out is useless...

If you don't want to take the risk, do not buy it.