I would change the scope of your request. Analog units dating back to the 70's were a form of magnetic tape that looped around in a spool or cartridge. Back then, most of the equipment was rather expensive and huge. Sometime in the 80's a change in development called the Bucket Brigade Delay (BBD) chip was commonplace and it replaced the bulky tape units at a much lower price point. That technology no longer exists as the DSP (digital Signal Processing) became the norm.
There are some good pedals that emulate the old technology. Unfortunately, I can only reference what I have used, and it is brand specific.
Strymon: I stuck with the brand since these products worked in the Mark V90 FX loop. Even better in my other Mesa amps that do not have such a sucky FX loop circuit like the Mark V.
- Brigadier : DSP form of the BBD that includes the typical decay if you desire to make use of that feature. Decay is in reference to the repeats as they degrade or dissipate over time with more of a natural sound. Strymon had updated the product with a new DSP and it is now called the BRIG. I have the older version which is a nice delay pedal.
- Volante: This is based on the magnetic tape delays. A bit complex to figure out though. I have this too. Prefer the Brigadier. My attention span is too short when it comes to pedals. It does have some good sounds, but it is more of a thing you need to tweak to get into your desires. It does not have much in form of presets like the BigSky, BigSky MX and Timeline, so setup or configuration is what takes too much time. It sounds good once you figure it out.
- Ola: (discontinued) is similar to the Brigadier but more of a chorus type.
- Deco: Not sure if it will work in the fx loop as it does have a gain effect, but the other half is more of a tape effect that can do double tracking, reverb, and some other effects based on how you set the main control. I use this on the front end of the amp in front of two Mesa Switch tracks to increase the stereo effect a bit when I am running 4 amps at once. (Over kill much?). It will work well with a single amp too but more of a front-end unit than loop type.
- DIG: Not what you are looking for but I listed it anyway. This is all digital so the repeats are crisp and do not decay as expected. I have used it but prefer the Brigadier. The DIG is similar to the TC flashback in many ways. I am sure it has a purpose but I prefer more of a natural decay in the effect. This one works but may not be to your liking.
When it comes to the multi-effects, they are preloaded with presets. Consider it a starting point. Some I have made use of and some I do not like. That is always the case for me when it comes to this type.
- BigSky: I use this with all of my rigs. I actually have two of them. Still my favorite for reverb, it is complex with some of the types. Some may be over the top but others are good if you want that big arena sound effect with a slight delay. Carney hall (made a copy of this one and edited it and used it most of the time)
- BigSky MX: A bit more expensive than the older format. Different. Still getting used to it but do like the IR reverb samples. Completely different than the BigSky, does not have the same effects. I am warming up to it after exploring the features. I find it more interesting and rewarding than the BigSky.
- TimeLine: I still have not figured this thing out. Some effects are just bad (one had a specific noise to emulate static and though I had bad preamp or power tubes, there are some effects that are good but will take some tweaking to get it right, I do not use it much but have made use with it in my 4-amp rig to get a ping-pong effect going. I need to spend more time with it as it is a bit complex to figure out. Some of the features of the brigadier and DIG are pack in but also different. If it takes me more than 5 minutes to figure out the first time, I lose interest.
I do not have these but did consider them: El Capistan. I thought there was another but cannot find it now. It may have been the Flint but it changed.
Other brands: Boss DD-200. This one has several modes and delays to select from. I sort of got hooked on the Terra echo function but the delays are decent. Yeah, it works in the FX loop very well. It is also line level rated. Reason why I have the Boss EQ-200 to use with it. Not all Boss units are line level rated. Most of the Stymon units are.
I do not have much other brands, most I have tried got returned as the Mark V90 was the test bed for pass/fail due to its FX loop being the issue.
I do still have the Source Audio Ventris, sort of works but kept losing volume with it. I will have to try this with a different amp as it was the TC50 that I was getting that problem. Not sure it is line level compatible. After using the neuro desktop editor is when I had issues with the fade out issue.
I am sure others will chime in on what delay/reverb effects if you can consider the digital DSP types. Analog is rather a stretch as that tech has been outdated for a few decades now.
