If you think the hum eliminator will work with the mimiq power source, just use the internal battery. I doubt it will change the hum issue. Most switch mode power supplies that are commonly used for small pedals are typically double isolated. Not sure if the hum eliminator will do much.
If you are looking at this unit, it is not compatible with instrument level signals. This is line level only and will not work in front of the amp. I was curious and read its description. It is in the right arena though but not going to give you what you need.
https://www.morleyproducts.com/hum-eliminator/
First time I saw Lehle has a stereo version of the P-split. Cool. I have the single version so I can run two amps with one isolated. but when running two amps with FX on the front end, you need to be able to isolate the left and right signals. This will work just like the single. I have used the single with the input and then isolated output (not using the direct output) to I could run three amps with the Mesa Switch track (tuner out is not isolated and that resulted in some issues when I tried to connect the JP2C in the two Mark VII amp configuration. The P-split helped to isolate the JP2C from the other two amps.
I think this would work and is suitable for instrument levels. Also works in the FX loops too as I have use one to split the signal to slave into another amp. What is cool about the P-split, it does not require any power to use it. It is completely passive.
https://www.lehle.com/lehle-p-split-stereo
I opened up one of the Mesa Switch track units, it does have dual transformers, one for each output A and B. I assume the Radial bigshot ABY may be similar but not all ABY switches have dual isolated output, usually just one has the isolation transformer and the other does not. I looked up the bigshot on Radial engineering website as I wanted more details. It only has one isolation transformer on output B. The isolation transformer is what provides the DC ground isolation between the two amps to cut out that hum or buzz. It also has a phase switch and ground lift to disconnect the common ground between the two amps. Sometimes if you are using two of the same amp, for example, two Badlander 100W amps, it may not matter much if the two amps are not isolated when there is a common ground. The same can be said with the TC100. It may be possible to run the Mimiq between the ABY switch and the amps. Just know once you run any FX unit between the amp and the isolated ABY switch that has stereo in and out will no longer have the dc ground isolation between the two amps. Most FX units have a common ground. The output and input grounds are not isolated between the left and right circuits. This does not seem to be an issue with FX loops with different amps if and only if they have a solid ground connection since the chassis should be earth grounded and the ground on the SEND and RETURN jacks are connected to chassis ground. That is usually safe to run to a stereo FX unit and best if the two amps have a balanced output or are the same model and type.
What I am trying to say if you have the mimiq connected between the amps and the ABY switch, expect to have that hum problem. I have the mimiq pedal too as it was suggested by another person who runs stereo TC100's. Similar to the Strymon Deco. When I have run a stereo double tracker, it is usually taking the mono guitar input, splitting to stereo and each stereo output is going to a separate Mesa Switch track that is connected to two amps on each. 2BAD and 2Mark VII. I could probably run the mimic to the 2 badlanders without needing isolation between the two amps. However, the Marks seem to be very sensitive on the inputs. This holds true to the JP2C as well. When using two Mark amps, even if they are the same, I have to have the ground lifted on the Mesa Switch track to prevent noise and ground loop hum. Nothing can be inserted in between the ABY switch and the amps unless they are separate devices. I just got done reviewing the Mimiq manual, it states you can use it in the FX loop even at line level but does not indicate if it is line level compatible. That is one location I have not tried with the Mimiq. I favor the Strymon Deco as I can set it up as a doubler, delay or even chorus. Mimiq has more of a chorus effect. Curious how it would sound in the FX loop assuming it does not get burdened by the output levels. Using any pedal including the Strymon Deco in between the ABY switcher with an isolated output and any tube amp will lose that isolation you got from the ABY switch since the device does not run fully isolated channels. I did test the input and output terminals on the Mimiq, the outer rings are all connected to chassis ground. If you must use that in front of the amp, I would recommend the Lehel P-Split and select the noisy amp (probably the JP2C) and run the mimiq output to the input and then the isolated output to the amp. That would isolate the amps input from the common ground. If using in the FX loop on both amps, with the amps plugged into their respective power, you can use a digital meter to test for circuit ground connections of both amps meaning the jack outer ring or the sleeve of a guitar cable plugged into the send jack. Test between both amps. Do not power up the amps, just test for common ground on the FX jacks. If they are earth grounded through the chassis and the ground prong on the plug it would be fair game to use the Mimiq in the FX loop of both amps. This is assuming the output levels of both amps are at the same level. If they are different, one amp will have more influence on the FX than the other. Generally why I run two identical amps when running stereo FX units. Tried it with the Mark VII and JP2C, it was not a good match. However, the Reissue and the JP2C were perfect matches on the FX levels. As I said, I have never tried the mimiq in the fx loop as it is described in the manual.
Interesting the Deco can handle line level signals so may be ok in the FX loop. However it has a boost to it so that may not be ideal for the FX loop. Thanks for bringing up the Mimiq. Been a long time since I had it out of its box.
