What Marcelo did was great. Loses due to standard patch cables at various lengths. Very informative and awesome playing too.
To verify if any of the pedals you got in the FX loop are suitable for line level, it will be stated in its specifications. May just be on their website or listed as input level +8dBu which is a suitable range for the TC series. The TC can reach that level but to get there you literally need to max out the channel volume and gain on the clean channel.
Not all Boss units are compatible with line levels. Example, the Boss EQ200 has a nominal input of -10dBu and a max of +7dBu. The Boss DD-200 has the same specs. The Boss DD-8, that is -20dBu so it is instrument level only. WazaCraft versions are also instrument level. The JHS clover does not have any input/output specs so it is easy to assume it too is instrument level. If it is not stated in the manual or on their website, it most likely is instrument level and not compatible with line level signals.
Just to point out, I am no expert on what gear is out there. So many products. Hard to make a choice. But after getting burned with the Mark V90, finding out not much will work in the FX loop, I ditch what did not work and found something that will. Strymon. Not always everyone's solution though. I did hold onto the DL4 as a test unit, also the TC flashback 3. Both have issues in the FX loops of the Mark V. That amp runs much higher signal levels typically around +5dBu. I would have to search for that post I did when I measured signal strength on the V, JP2C and the TC50. I am just basing this on my poor memory of what I did.
With that in mind, I believe Radial Engineering has something that will take line level down to instrument level. I got curious and emailed the company on that unit. It has two sets of inputs, XLR in/out and TRS jacks. Mostly for balanced lines, however, the TRS can be used with TS unbalanced connections as some mixers use that vs TRS. This should work with the FX output of the TC. this unit gives you two FX loops and you can blend them. Never tried it so I have no experience with this product.
https://www.radialeng.com/product/extc-sa
Now when considering the long lines on the FX loop, There will be losses on the upper frequency range with standard patch cables. Marcelo made that apparent in his video. So, if you are running lines across a long distance, you probably could use the SGI-44 with the extc-SA and use XLR microphone cables between them. this is just based on information on the products. I would recommend contacting Radial engineering through an email/customer service for more information.
Again, finding new stuff, but yet have so many questions. If I did gig and ran long cable runs, I probably would have some of the devices mentioned or at least have tried them. My pedals are on the floor just below the amp. 10Ft cable is what I am using. That does not work well if you need to have 18 to 100 ft of distance to cover. This is a good topic though. One could always go wireless if there is such a thing for using in FX loops. I am sure that has its headaches too.
Just one thing, I have a DL4 that is instrument level, this unit will not work with the Mark V90, however, I have been able to use it with the TC50 without much if any degradation. Short signal runs. That does not mean it is ideal or will match other gear that is instrument level. That was on the hi/lo gain channels. Since the signal is more compressed, it will not reach the high signal level as the clean channel. It is not that far off from the JP2C at -7dBu to -5dBu range. That is still above the limits for instrument level, more on the consumer line level range. Depends on the buffers of each effect, if they get overloaded, you will have issues with sound quality.
