I've got many treble boosters from the very cheapest to fryer and guild models and ALL do the job, don't waste your money on an expensive fryer model. The cheapest Covington one is decent and also has a high 35db output.
I would say save up your money and get the Fryer one if that's what you really want. It's a false economy to get a cheaper brand if you are intent at some point in acquiring the more expensive one. That's a mistake I learned with buying guitars: best to save up until you have enough for the one you really want rather than settle for a lesser model (because you never will "settle" -- you will never be content until you get the one you really wanted in the first instance). So I gradually went through a Hohner Arbor, a Fender "Hank marvin" Squier and a Westone Prestige until I bought my Gibson Les Paul. But I wish I had saved up for the Les Paul in the first place! (The LP is now long gone, sadly, and I still miss it) :(
There is a markable difference in the sound achieved by different boosters. The three boosters within the Greg Fryer range offer different output levels and their for different sound characteristics.
If you are looking to achieve a Brian May sound you need to remember that he has, through the years, used different types of boosters.
False economy spending less rather than buying the most expensive? NO
It would seem that at the moment Brian isn't using Fryer Boosters. Greg Covington produces high quality gear at affordable prices and has spent time designing Treble Boosters which are simlar to the TB83 and TB83 extra. Both of which were associated with Brian's classes tone long before Greg Fryer was asked to build something more modern and able to stand the harsh treatment of life on the road.
It would be worth trying out the Voltage Pickups Booster. The worse thing would be buying blind then finding it doesn't do what you want it too.
To get close to the Brian May sound you will need an AC30 normal channel driven at full volume with a treble booster, which drives the amp into a kind of saturated distortion. The guitar volume pot is what will give you the clean warm sounds right up to the overdriven sound when playing live. When recording their are other ways to achieve the sound. But remember technique is important too. If you can't copy Brian's playing style the equipment will be of no use.
"False economy spending less rather than buying the most expensive? NO"
You've missed my point so let me put it slighty differently. It's probable that if someone wants a Brian May Red Special (for example) they will never be quite happy with anything less so it's best to save up for the RS rather than go for lesser models which will likely lose money when resold. This is a separate point from how things sound: my Westone Prestige was a lovely guitar and could do a lot of the things my LP could. But it's the LP that has the real mojo and the LP will never lose it's value whereas the lesser models likely always will.
I have to agree with Holly, I have spent 30+ years buyinhg guitars and drums and every time I have bought something other than what i had my heart set on it has been a mistake. I simply ended up buy the real thiong months later.
I always wait until I can buy the original thing I wanted.
Regarding the BM sound, the new AC30's come with a Vol and master vol so you can actually get the BM sound at lower volumes, interestingly I have found two ways of doing this, first as Brian does Normal channel full up with a Fryer booster, or alternatively, Top Boost Channel at low volume with a fryer booster. put the top boost vol at full and the master vol at 1/4 and you get a very good BM sound at lower volumes
The Amp is still bloody weighty to get around so think before you buy how much you will be moving it, evertime I go out I have to brace myself to get it in and out of gig, which is usually miles away from where I can park
The true BM tone is achieved by plugging into the normal channel, via a treble Booster, on an AC30 with the volume turned up to max. The tone is a pure tone, ie no bass, mids or treble, are added on the amp.
Using the top boost add's gain to the sound, from low guitar volume the sound will be coloured all the way to full volume.
If you take a look at the Vox AC30 BM model, they are stripped of everything but the normal channel input because the rest is of no use.
The amps BM uses live have the unwanted circuitry removed. If you are ever fortunate enough to stand in the same room as BM is playing in, you will realize that his sound is powerful and loud and not typical of what most AC30's sound like.
Indeed but the point i am making is that the current production run of AC30's come with a master vol, which when used in conjunction with the trebel boost pedal and set as described allows the user to get a good Brian may tone at low vol for the first time.
You still have the option of using the Normal channel with the tone controla rolled off and the vol up full to get the real thing.
I have used the BM amps and they are great if thats the only sound you want, but somewhat limiting if you want to play other types of music, they dont for example do a very convincing British 60's tone.
BM's own amps are hand wired and concert ready, i have actually been in a small ish room with him demostrating them when he appeared at a music show in London in the 90's His tone was amazing as always, but way too loud to be practical in anything other than a studio, so I think the new AC30's are the best yet in terms of being a home plus gig amp.
Mine now has Blue Alnico speakers and new tubes fitted from Watford Valves. Couple that with a fryer pedal and a BM guitar and you can't get any closer to his sound without him being there.