ticklemore Posted July 8 Share Posted July 8 We all have heard by now that the JTV magnetic pickups should be between 6K and 8K DCR. We are told below that, the sound will be thin/weak, and above that, rolled off and dull. But that is not true for a "regular" guitar, the pickups sound as intended when wired in a typical guitar with volume and tone pots and pickup selectors. There is some variation with cap and pot values, but nobody recommends a narrow DCR range for a typical guitar unless you are trying to get a very specific sound. PAF? Fine. Duncan JB? Fine. Lipstick pickup? Fine. They sound how they sound, maybe you like it, maybe you don't, but there is no critical operating range for a standard guitar. From this, I conclude that the JTV electronics are not neutral/transparent compared to typical guitar wiring. When in magnetic mode, with or without a battery present, they are somewhere in the circuit and interact with the magnetics in a way that is different from your every day pots and caps. Has this every been discussed/disclosed here? I can't find it. Am I just wrong on my conclusion? If so, how to explain the 6K-8K range? Has anyone done any tinkering/testing to see how the circuit actually works? 1 Quote Link to comment Share on other sites More sharing options...
psarkissian Posted July 8 Share Posted July 8 "... magnetic pickups should be between 6K and 8K DCR. ", and "... sound will be thin/weak, and above that, rolled off and dull. ", yes, correct, very much so. "But that is not true for a "regular" guitar", also correct. This being a guitar with active circuitry (require a power source), as a result, is not a 'regular guitar' with passive circuitry. Pick up companies will have a DCR spec for their products. The pick-up signal goes through the main board, then to the the jack plate. What is in between on the main board I cannot discuss (it's a non disclosure agreement (NDA) thing). I have posted on this subject a number of times, here and on the Facebook Variax group page. "Has anyone done any tinkering/testing to see how the circuit actually works? ", yes, many people have swapped out pick-ups and found out for themselves, and didn't like it. There is a difference in how active verses passive and active filters work, and impedance matching two disparate circuits is key tot that. And I've been the guy at Line 6 who has been doing service and repair on these since 2010. Have been dealing with active circuits for guitars since 1975-76 'ish. 1 Quote Link to comment Share on other sites More sharing options...
ticklemore Posted July 8 Author Share Posted July 8 Thank you for the response, I was hoping you would see this, I have read your contributions to this and other forums over the years and greatly appreciate your expertise and willingness to teach. Glad I was not totally off base with my assumptions. Here is one source of my confusion. You said the JTV has active circuitry, requiring a power source. But, we know that the JTV does not require a power source to pass the magnetic signal, ie, there is nothing active going on at least when the battery is dead or not in place. Under these "passive" conditions, why would there be a DCR range? I guess the active electronics, even when not powered, are able to pass the sound, but still contribute some impedance value? Or maybe there is a passive impedance matcher (like a passive DI) that is always in line and allows the mags to work with the active circuit and therefore always plays a role? Assuming we stay within the 6K to 8K range, would there be an audible difference between the mag sound going through the JTV electronics vs. if they were wired up in the same guitar with typical pot and cap values? In general, I find the JTV sounds a bit darker than what I would expect from the pickups I have in there. FYI, I have a Duncan SSL1 in the neck (6.5K) and a Gibson 57 Classic in the bridge (7.8K). Stock middle. 1 Quote Link to comment Share on other sites More sharing options...
psarkissian Posted July 8 Share Posted July 8 Without power, the relay default position is in passive mode, but it still goes through the main board circuitry, which is fixed, and not to be messed with,... before it goes to the output. The filters are fix, and one can't just put some gum-drop polyester capacitors in there without altering the impedance and filter curve. 6.5k or 7.8k is fine. Also, number of windings of the pick-up coils, gauge of the wire, etc,... plays a part in it as well. Too deep for me to go into here, would be an hour lecture on electronics,... don't want to put anyone through that, too much math. Best to stick with what is specified. There is some lee-way, but not much. Doing mods outside the boundaries on a JTV is not for the faint of heart. I've done a number of mods and Frankie Steins,... so I know the pitfalls. Tread carefully. Good luck. 1 Quote Link to comment Share on other sites More sharing options...
bbehrens Posted July 15 Share Posted July 15 Since the hardware for the James Tyler Variax is no longer made as far as I know, you could end up with a regular guitar with extra knobs that don't do anything at this point in Line 6's guitar ecosystem. Quote Link to comment Share on other sites More sharing options...
psarkissian Posted July 15 Share Posted July 15 Some parts are available, some are not. Would be acquired through Full Compass in the USA, or through authorized service centers as a repair. Quote Link to comment Share on other sites More sharing options...
Dark-Star Posted July 15 Share Posted July 15 Yes! Quote Link to comment Share on other sites More sharing options...
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