I owned a modulus VJ and a Zon Sonus back in the day. Right now I own 2 Klos Apollos. I bought the 1st one about 3 years ago. It's the older style small 2+2 headstock that is currently spec'ed on their "standard" model. The 2nd one is their "custom" model purchased about 6 months ago with the newer 3+1 headstock . Both are superb basses. Although a long-term road test will require a few more years, I can happily say the quality of the necks and overall builds is excellent and on par with the Zon and Modulus I used to own. These necks are also lighter, making the basses lighter overall, with excellent balance. Both necks are super stable, which is particularly sweet up here where humidity varies VERY widely with the seasons. My wooden necks all require seasonal truss rod tweaks in early winter and late spring, but not these.-IMHO there is no quality difference between the 2 necks. The tuners on the "custom" neck are a bit smoother. When they initially came out, a big part of the marketing was that the necks can be easily & rapidly removed because there are perfectly machined/engineered tapped inserts in the body, making it a great bass to travel with. This is all true. The neck pops off in a minute with a provided mini Philips screwdriver and there's no need to readjust anything when it's reattached. . That was the prime reason I bought the 1st one. For that reason the headstock was minimized in length and weight. As soon as I received the bass I realized (and posted on TB) that it was easily good enough to be a #1, even for a picky bassist. As time passed the marketing shifted away from emphasizing the travel-friendliness as much. The instruments stand on their overall merits. That said, I suspect the esthetics of the smaller headstock turned some people off, plus they got into producing fender replacement necks, hence the current "custom" neck with the 3+1 headstock. I prefer passive basses so I can't comment on the Klos preamp, but the ones I have produce excellent, flexible tone with zero noise. Back when I owned the Zon & Modulus those models were available with many custom features (different pup options, many cool finishes, scale lengths, bridges, etc) which is not the case for Klos. That has nothing to do with quality, however. Both Modulus and Zon were born in an excellent economy when the 'net was young and more folks were flush. The current reality is far removed from those days and the barriers to success of a small business selling a discretionary item in a widely populated field are enormous. I am glad the guys at Klos have had the perseverance to stay with it.
I have had zero issues with my 2 Apollos, but have had numerous questions / unusual shipping needs, etc and their service has been rapid, courteous and accurate. I have no affiliation with them. I am simply a thoroughly satisfied customer and I recommend them highly. Mine are both currently set up BEAD, one with Labella low tension flats and the other with DR Pure Blues
