I did a bunch of double blind listening tests using my humbucker equipped strat and my filtertron equipped gretsch. Mostly I found that these circuits behaved very differently from situation to situation depending on the impedance of the signal they were receiving. There wasn't generally a "sound" imprinted by the circuits but rather they affected the signal making it brighter or duller, sometimes improving it, sometimes making it sound a bit worse. Most of them would have benefitted from more headroom. All circuits were the schematics you see above and powered with a 9v batt. I did build the ds1 buffer circuit and thought it sounded good and had plenty of headroom but I didn't bother to include it in my recording/listening tests.

LPB1: Generally sounds good to me but needs more headroom. Sounds great if you want a dirty boost.

AMZ: one of the more inconsistent ones. Sometimes harsh. Sometimes dull and bassy. Often sounds a bit boring. Needs more headroom.

Stratoblaster: Another inconsistent one. Sometimes bright, sometimes dull. Good as a boost.

SHO: Seemed like it sounded good with humbuckers but was very unpredictable with filtertrons. Cool dirty boost tone.

EP3: Mostly well balanced but needs more headroom and doesn't have enough gain to be used as a boost.

I have no plans to build any of these. I went in expecting to find a magic circuit that would just make my sound invariably better but instead I found that the tonal qualities imparted by the circuits vary wildly depending on the impedances involved. I haven't found a magic tone pill but I have gotten a better sense of what impedance is all about.

If you're sticking a buffer somewhere the impedance won't change (say in an effects loop or as the last pedal on your board) then you can experiment and find a buffer that complements that specific situation. If you're looking for something that magically just makes everything sound better regardless of how it is used then a buffer won't do that.

Maybe this is obvious to you guys already but I suppose I'm the sort of person who has to try things out before he can trust in anything.

I didn't build the LPB-1 stand alone, I used that circuit in other situation, inside other pedals. Never built AMZ and Stratoblaster. I'm gonna build the SHO. I built a kind of modified version of the EP3 Echople Preamp.

You can solve almost all that issue (headroom, gain, dull, harsh...) with some mods in the circuit . Replacing transistors, caps, resistors and adding a charge pump.

Or with a dual opamp for a gain stage and a tone control and maybe a voltage doubler or inverter. 

If you want a really clean, totally transparent boost for humbuckers with headroom out of a single transistor running on 9 volts -- you may be asking a bit too much. All of the circuits you tested kinda sorta do that, but they can't outstrip their own inherent limitations. Of course, those limitations are what give these circuits their special characters and tonal signatures, which is why people like them. IOW, a little bit of coloration or dirt is kind of the point. But for that super-uncolored thing, a high input impedance opamp design running on higher voltage is probably your best bet, like a Barber Launch Pad or a variation on one of the MXR designs.
Edit: I see Roseblood11 got his much more concise reply in a few seconds before me, and we are really saying the same thing.

For an off-the-beaten-path opamp option, you can also look at John Hollis's Titan Boost, which works with a dual opamp and a small transformer to produce big boosts on 9v, and can easily be modified into an octave pedal. I've never used nor heard one, so I can't speak to its sound, but those who have seem to like it, e.g. forum member jmusser.

Merlin's Glass Blower is another clean boost that uses some tricks for extra headroom. I've not tried it, but I've never been disappointed by one of his circuits.

Quote from: Ben N on June 10, 2019, 05:40:04 AM
For an off-the-beaten-path opamp option, you can also look at John Hollis's Titan Boost, which works with a dual opamp and a small transformer to produce big boosts on 9v, and can easily be modified into an octave pedal. I've never used nor heard one, so I can't speak to its sound, but those who have seem to like it, e.g. forum member jmusser.

I'd like to find a veroboard layout of the Titan Boost.

Quote from: Elijah-Baley on June 11, 2019, 03:01:44 AM
I'd like to find a veroboard layout of the Titan Boost.

It's go such a low parts count that I doubt very much you'd need one, or, more correctly, that you'd have trouble coming up with your own.

Yes, indeed, in this last months I'm trying to work hard in some veroboard layouts by my own.
But, you know, If there's some verified layout around is better!

I'm guessing this is on perf rather than vero, but just to give you an idea (and this is with a switchable octave):

Thanks! I have the schematic, too.

I think I'm finally gonna build my boost pedal. I've gone with a modified stratoblaster.






I've increased R3 to 56K so I can get a clean sound with humbuckers and use the full sweep of the 50K pot (Changed from B to C taper). I had to change R2 to 220K which sets my drain at 5.2v at maximum gain. My next biggest resistor is a 470K so I think 5.2v is as close as I can get to 4.5v.

Sounds fine on the breadboard. Does the schem/layout look ok?

Looks OK to me.

Quote from: Ben N on June 10, 2019, 05:40:04 AM
For an off-the-beaten-path opamp option, you can also look at John Hollis's Titan Boost, which works with a dual opamp and a small transformer to produce big boosts on 9v, and can easily be modified into an octave pedal.

Looks like it calls for a 1k CT:20k transformer, which Mouser doesn't seem to carry, or my search-fu wasn't strong enough. Any sources for one?

Yeah, that's a problem.    Mouser does carry the 42TM006--alas, the minimum order is 1000. You can find them reasonably priced in lots of 10 on ebay, or unreasonably priced as singles. Maybe 42TM017 (25k:600R) would work?

Circuit built. Works fine. Boxing it up in a 1590A next.