I recently acquired a set of jazz bass activator pickups with a VVT module. I believe this is referred to as a JZ/AE-1 set. I have installed it in a bass and it's working great!


I have attached two photos of the electronics. I think it is a few years old based on the fact that it has two volumes instead of volume and pan, and also because it has a RC4458(?) chip on the filter board.


Questions:
Is the small pot on the filter board for output level adjustment?
Is there a way to adjust the filter Q - resistor value changes, for example?
Are there any upgrades that should be performed?


Anything else I should be aware of?


Thanks in advance for your assistance.

The trimpot is for output indeed, you could add a Q-switch: https://store.turbify.net/alembic/qforac.html

Not sure if I read it right, but based on the stamps I think the set is from 1988?

That add-on Q switch looks like an RC resonance circuit. I'm not looking for on-the-fly resonance control. I'm more interested in being able to tailor the Q for my specific bass/strings. So knowing which resistor and capacitor control the Q might allow me to experiment with different values. And even better, if there was a listing of recommended R/C pairs that produced various Q values, that would be amazing!

The Activator sets with a filter but without a Q switch have an always-on boost of 8 dB for a narrow frequency band around the cut-off frequency. Adding a Q switch actually gives you the option to not have that boost (leaving just the "natural" resonance of the LPF).

There are a couple of variations of the Q switch,  like 2 or 3 positions and various levels of Q boost, but you'd need to confirm what is available for this particular set-up. I had a Spoiler with a 3 position Q switch for 0, 3 and 6 dB, and to my ears a 3 dB difference was fairly subtle, and a 6 dB difference pretty noticeable - but I felt both were an improvement over the original 8 dB, which I felt sounded a bit harsh.

Another update would be the Pan Preamp, which gives you a separate level for each pickup, making it easier to balance their outputs. I think it does replace the two volumes with a volume and a blend.

Having had the variable Q on a Series II, I liked the ability to select the Q values, but then once I had it adjusted to where I wanted it (different for each pickup), I never changed the Q, though I did change the filter cutoff frequency. Having had a bass with Signature electronics, I found that I favoured the 3dB setting.


With the Activators, I'm finding the Q to be higher than I'd like. If it is just a matter of swapping resistors/capacitors, I'd be up for trying various values until I found my sweet spot and then having the new value permanently.

Not entirely sure what you mean by "the filter amount"? But anyway, on a Signature with a 2 position Q switch the setttings are likely to have been 0 and 8 dB, on a 3 position I think they would normally be 0, 6 and 9 - unless you had customized electronics.

Are there one or two components on the filter board that can be changed to reduce the Q?

And one more thing...
When both pickup volumes are on full the bass is silent. But when both (not just one) volumes are off, there is a good bit of noise.
Are the volumes "pre-filter" and is the noise being picked up in the filter circuit?
Do I have some other fault in the wiring/circuit?

Just a long-shot thought, something that happened to me once... verify the pickups are connected in-phase correctly. I don't have any experience with the two-volume harness, but with a set of TC-1 activators I accidentally mounted the modular connector to the the bridge pickup backward. This put that pickup out of phase. The result was similar to what you describe.


At one point, I was receiving a Cuban radio station. I kinda' miss that...

I tried swapping one pickup and got the "out of phase" cancellation with both pickups on full, so I think they are correct.
I may have to look at the control cavity shielding next...