I was Googling "HD500 FX Loop Vox AC30CC" and came across this post in the old Line6 forum: http://line6.com/sup.../message/409733
I can't respond to the OP, or others who replied so I thought I'd do it here.
The HD500 into the AC30 sounds glorious! I'd say the biggest issue in using an AC30 in a 4CM is utilizing both the Normal and TB channel in a 4CM is how to go about selecting either channel. The HD500 can act as an AB switcher (two pan effects set to turn on and off alternately with a FS assignment, input B set to "same" into an FX Loop effect) but this blows up when you stick a mono effect before the FX Loop...or you could use a hardware box to do this...but it reduces the all-in-one solution of the HD500.
Or, you could resolve to use the normal channel only using boosts and OD pedals from the HD500 for gain tones.
What I decided to do was not use the 4CM but use the Vox simply as a backend, just like I was using the Valvetronix AD30VT before getting the Vox AC30. It seems a bit shameful not to use the Vox's real preamps....but the problem there is you really need to crank an AC30 to get that tone! Truth is, I can't play that loud at home, or at practice..and stage volume would be too loud if I used the AC30 at "full speed". The switching between the Normal and TB channels meant adding more gear to the mix. I want to keep this simple.
With the Valvetronix, my favorite preamps were the Bassman, the Park, and the 800. With AC30...almost all of the preamps were outstanding in one way or another. I say "almost" because ironically, the Line 6 AC30 preamp was my least favorite. The output is so low, if you wish to keep a clean tone. It seems to me the purpose of the AC30 preamp was its overdrive tone...I guess Line 6 figured, when you have Fender cleans at your disposal....
What I wanted to find was one preamp that could be clean, and then use pedals to dirty it up. The Brit 800 Bright was that preamp. Wow! The cleans are full bodied and have character, and when used with the Chandler Tube Driver just sounds fantastic.
The Park was nice too. Even the Fenders sounded nice but lacked that body like the 800. One preamp that was a standout was the Dr. Z - now I get it! Now, I see that it's a lot like the original Supersonic...and it sounded brilliant. The AC15 model had a robust tone to it...not clean..just on the edge of break up. The Hiwatt was a bit lackluster - but louder when clean than the AC30 model.
I've set the Vox's loop to +4, Master on the HD500 about 3 o'clock, combo amp power. This seems to work great.
So to the OP of that thread...go for it. Try all the preamps...they all sound amazing except for the AC30!
I've been an HD500 owner since late 2010, playing live with a modded (for an FX loop) Vox AD30VT. This worked well - the Valvetronix technology really does have a "give" and "push" similar to a tube amp.
I've used the HD500 pretty much as a front-end, using the combo power amp setting and only using the PRE versions of the amps. My favorites ended up being the Park model and the 800 models.
And, I'll tell you, the feel of this setup...no doubt due to the HD500...was fantastic!
The real shortcoming of AD30 is the size: 10" speaker in a cabinet barely big enough to hold that speaker. The sound was small.
I decided it was time to get a real amp. I was thinking something with an FX return so I could use the 4CM because I really use the effects quite a bit for my sound.
I have a Variax 300, the HD500 so why not the DT25? Possibly a Spider Valve of some sort. I wanted at least a 1x12. Weight is important only so far as tone. I'd deal with lugging an 80lbs 2x12 if I had to.
I tried the DT25...it was good. I tried the Bugera V22 and a Fender Supersonic 22. The Fender was really nice. I also considered a bigger version of the Valvetronix.
What it came down to is this: if I had to buy an amp just for the sake of being a good amp, which would it be?
The Spiders never interested me. The DT25 is not a "real" amp. It's a hybrid and always will be. Flame me later about that...
The Bugera was nice, even impressive for the price but the cleans weren't my taste. The Supersonic...wow! It has those Fender cleans in spades! But, I didn't like the drive sound and there's no master volume. The problem with no MV is that changing volumes for both a clean and dirty channel in different settings means the effects will react differently in different situations - or at least, that's what I expected to be a complication with a non-MV amp.
I just wanted an amp that didn't need firmware updates, needed rebooting, or based on digital technology to be an amp. It had to be a good amp on its own.
I bought a used Vox AC30CC2. I think $1000 US for a hybrid amp like the DT25 is just too expensive. Sorry Line 6 - no matter what, it's not a true blue analog amplifier and I'm afraid resale of a hybrid amp - no matter how snazzy - will fall below an amp of a similar capability in the future.
I can barely get rid of an old Flextone XL at $125... with pedal! I believe the DT line will also end up at the bottom of the list value-wise because of its digital pedigree.