samhay

If you are really tight on space, you could split the control cavity. You could put the controls on the other side of the bridge (so you could see them with the bass on) and run the wires to the 'existing' cavity, perhaps via the pickup route. As the buffers would go before the controls, these would be low impedance, so shouldn't pick up much/any noise.

Nice, but no volume control?

This is looking quite stunning. >What do I need to know before glueing in the neck? I guess that you have the neck angle correct and have fine-sanded any bit that are going to be really difficult to reach once the neck is on?

[quote name='Andyjr1515' timestamp='1490791836' post='3268007'] [/quote] Could you not alternatively fix the bridge to the neck side of the cavity (by flipping upside down from the above orientation)? I would imagine this would make it stronger...

This looks to be interesting. >Hidden magnetic pickup >At the moment in that proposal, the pickup is deeper than the body... Are you planning on burying that pickup in/under the fingerboard, or have you given up on the hidden aspect? In either case, seeing as you are pushing the boat out, why not wind your own pickup to fit?

As you mentioned, you can get chassis mount type 1/4" jacks with short barrels, which can be mounted with a mounting plate like in a telecaster (some mounting hardware is quite discrete too - see below). However, you still have to be able to accommodate the length of the jack when it is plugged in. The 1/4 jack is ~ 32mm long, which is why your barrel jack is 33-34 mm long, to hide the jack when it is plugged in. In summary - whatever you try, the jack will hit the PCB when you plug it in! http://www.stewmac.com/Hardware_and_Parts/Jack_Plates/Electrosocket_Jack_Mount.html

>I then remembered the copper I use for shielding. With a small offcut, I soldered a tab to the earth wire: That's how I've always done it, but I also fold the tape over the wire to make a little pocket. I wasn't convinced when I started reading this thread, but like others, I have come around. You have done good work sir.

^Fair point. I keep discounting this as it doesn't work very well with the cheap 16mm pots I often use for those 'little boxes full of Steve's lovely bits'. (ooh arr) Creeping towards genius territory now though.

>Does anyone know of an electronics genius that could retrofit a passive tone control to my existing electronics? Do you have much room in the control cavity? If so, it would be easy enough to replace one of the tone controls with a dual-gang pot and wire the second gang as conventional tone control. I expect you would also want to bypass this when the preamp is engaged, which may also involved replacing the switch. This won't work if you don't have any room to play with, but is fairly straightforward if you do (and I am not even a genius). The rub is that your preamp almost certainly won't use 250k tone pots (looks like 50k or 100k), so you will lose some range (brighter settings) as finding dual gang pots with 2 different resistances is not easy.

Nice job. I suggest you scrape the flake out of the neck pocket then tape this off. Otherwise, you are going to have some fun when it comes time to put it all back together again.

I was bound to have one of those one day. If you go that route, you may have to rethink the passive aspect too.

That top is too nice to put a pickup in. Seeing as it is semi, semi acoustic, why not go piezo? You could be Derby's Rob Allen.

You don't need to convince me - I'm quite fond of bone nuts too. And bone dust doesn't smell very nice either.

I got the issues with the zero fret, but was wondering more on the choice of nut material - brass vs. bone vs. synthetic stuff, etc.

Looking and sounding good. Did you use the brass nut for the sake of authenticity, or is it your/Pete's preference?

High pass and low pass are easy - you only need a resistor and capacitor. For high pass, put a capacitor between the pickup and volume pot (i.e. in series with the pickup). If you are using a 500k volume pot, then try cap values of about 2.2n (0.002). Bigger values give more bass/lower corner frequency and vice versa.

Working from this schematic: http://www.flyguitars.com/gibson/bass/EB3_schematic.php I see the filter as the GA-90C inductor/choke and the 20n (0.02u) cap. In series, this gives a notch filter, which is what I understand the varitone to be. In my simulation: L1 and R4 are the FB pickup. I didn't model the other pickup, but this won't change the position of the notch. Pickups have both series inductance and resistance and a typical guitar pickup might have about 5-10k DC resistance and 2-3 H inductance. The mudbucker, being the beast that it is, seems to be closer to 30k and 65 H. R3 and C3 are the tone control rolled all the way up. This doesn't do much to the frequency response, as one might expect. The notch filter is L2 C2 R2. R2 is the inherent DC resistance of the inductor/choke used and I guessed at the value of 150 ohm. If this is higher/lower it will not move the notch position, but make it less/more deep. C2 is the 20n cap. You can ignore R1 - this is a way of essentially switching this part of the circuit off (sw = 1Meg) to see what the output from the pickups looks like.

^I can just about picture Darth Vader playing an EB-3. Probably not a fan of funk. The specs of a classic mudbucker seem to be ill-defined, but it seems that 30k and 65 H seem to be a reasonable guess. If we assume the varitone choke they used is similar to Andy's transformer - 1.5H and 150 ohm DC resistance, we get this (red trace) with the tone control all the way up (no treble cut): Edit - the notch is at ~900 Hz. Because 65H is about 20-40 x higher than a normal pickup, I also simmed this with more sane pickups with 5H and 15H inductance (green and blue traces).
 If you remove the inductor from circuit, you can see how much treble is naturally rolled off as you increase the inductance of the pickup (grey is 65H).
 
 3below - I use LTSpice and have included a screen shot for your perusal.


^sorry, missed that post. Happy to model the mark 1 circuit. Do you know what the inductance of the choke/inductor they used is?

Thanks for recording the sound clip - the notch settings definitely sound quite useful. Might have to cobble something together myself. Happy to impart a little knowledge too - I am fairly sure we aren't even yet as I have learnt quite a lot reading through your build threads.

[quote name='Andyjr1515' timestamp='1476981331' post='3159008'] If I understand the figures above, doesn't the 220n knock out the low frequency 280Hz? (It must be said that I probably don't understand the figures above ) [/quote] That's correct for the notch filter. The corner frequency will be different for a more conventional low pass filter (tone control), but vintage p bass tone controls use 100n, which most consider to be about as dark as anybody would ever need. 220n is darker.

220n would make for an incredibly dark tone control on a passive bass or guitar. In any case, I have a good stash of caps and am happy to pop some in the post if you want to try other values.

No problem - happy to help. 22n = 0.022 uF gives a notch at ~880 Hz. The original varitones had caps ranging from 1n (0.001 uF) to 220n (0.22 uF) and they used an inductor of 1.5H, which is helpful. Here are some common cap values and the notch frequency: 1n, 4110 Hz 2.2n, 2770 Hz 3.3n, 2260 Hz 4.7n, 1900 Hz 10n, 1300 Hz 15n, 1060 Hz 22n, 880 Hz 33n, 715 Hz 47n, 600 Hz 68n, 500 Hz 100n, 410 Hz 150n, 340 Hz 220n, 280 Hz Do you have any/many other cap values you can experiment with?

Great - sound like we are on the same page. Below is the simulated frequency response of an RLC filter (image a few posts above) with your transformer (1.5H inductance and 148 ohm resistance in series with this inductance) and a 22n capacitor. The top graph shows the output when driven by a perfect voltage source. The bottom graphs shows the same filter driven by a simulated guitar (not mudbucker) pickup. Notice how there is a lot more treble rolled off, and this will get worse with a bigger pickup like the mudbucker. In both cases, the resistor is varied from 1k-100k. As the resistor gets larger, two things happen: 1. The notch gets broader 2. As this resistor works as one half of a voltage divider with the volume pot (I asssumed 500k here), larger resistances give additional signal lose at all frequencies. Bottom line - less resistance is more signal. Also, the original varitones switched in a range of capacitors, and this is still a good thing to do with the rotary switch. I can suggest values if you tell me how many values to suggest... p.s. look like a resistance of about 10k would be a good choice, so it seems the computer agrees with your ears.