What do folks do to carry out A vs. B comparisons without being fooled by volume?
 
So, I have a bunch of FX on (say) the master bus (SET UP A), and I want to hear what they sound like versus the dry signal (SET UP B). I want to compare A vs B with one click or even better a keyboard shortcut to switch between the two BUT I do not want to be fooled into thinking the louder one is better. I want to hear purely the effect of the FX in Set Up A. 
 
I have read about Ian Shepherd's Perception - and the video looks very convincing. Any thoughts on this or alternatives plugins or techniques? 
 

This can be useful.
 
https://www.samplemagic.c...g-the-magic-ab-plugin/

$149 seems like a rather inflated price for a plug-in like this.  Sure, if you run a professional studio with high demands for perfection, it could be justified.  But for the typical home-studio producer, that's a lot of money.
 
Unfortunately, we cannot just use our DAWs channel metering and assume matched levels will get the job done unless the spectral content of the comparison signals is very similar.  But what about LUFS meters?  Do these things take Fletcher-Munson sensitivity curves into account?  I must confess, I have no idea.  But if LUFS does account for spectral distribution of audio energy, then I suspect this kind of measurement would in fact be adequate.  Opinions welcome.

Melda MCompare. Haven't compared then feature for feature but it seems to do a lot, and Melda stuff is generally great. And it's on sale right now!

http://www.meldaproduction.com/MCompare

You can sometimes get them even cheaper at Audiodeluxe or maybe other discounters...

I agree. I ise Mcompare for every project and IMO it helps alot. Check it out for tourself and see if it meets your needs.

Thanks for your input so far. There is an interesting debate between Ian Sheppard and the MCompare developer here 
 
I am certainly no professional David, but I think this type of plug could be hugely valuable for an enthusiast like me who has often been fooled into thinking louder = better. 
 
Any further comments more than welcome! 

Mcompare is $34.50 at Audiodeluxe this morning.

Another vote for MCompare.

One thing to bear in mind going forward is that plugins with complex internal routings can just be bypassed to achieve the OP. I have shied away from the one-off plugins recently, since saving complex presets once makes life easier, and Melda's stuff is free upgrades for life and each purchase builds towards the "whole shebang." They are also nicely scripted so you can dive deeper into the guts of them as one feels comfortable.

i think it is still better,
to make these decisions based on sound, not volume.....
 
it's simple to turn the volume up and down to put the playback at what you consider a loud but comfortable level..
 
and THEN make the decision which version sounds better.
 
you do not need any kind of plugin to do this.
 
and it could be, the louder version IS the better version, based on how the compression or limiting or whatever you used to gain the louder volume, did to the low end, high end, and middle....
 
it's pointless to me,
to match volumes for comparison,
when LUFS and your own ears are the best measurement.

and if you are mastering,
you'd better know what you are doing about level matching, as well as tone matching.
otherwise, you are barking up a tree.