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The Passinwind Open Source Preamp

#344
Feral Feline said:
Yeah, an outer-lug to centre-lug, but from what I understand it changes it to reverse taper, not to the normal audio taper.

It's in RG Keen's article "The Secret Life of Pots".
Click to expand...
It depends on which outer-lug you use. From the article:

"connect a 'tapering resistor' across the wiper and CCW lug" and you got a log pot.

"if you hook up the tapering resistor from the CW lug of the pot to the wiper, the pot emulates a reverse log pot"
 
#346
Feral Feline said:
What about adding a resistor across a couple of a linear pot's lugs?

I've read this can make a linear pot behave more like a tapered pot.
Click to expand...

That tends to work pretty well when one end is grounded, but not always so well in "rheostat" config. Here's another article touching a bit on designing your own pot law: Link Removed
 
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#351
I just took my preamp out of a passive bass and installed it with a set of EMGs in my Modulus. It took a bit if trial and error to figure out the best way to integrate them considering they both need a 9 volt supply and the EMGs are not typically grounded as a passive pickup would be. Best bet is to keep the pickups and preamp V+ isolated and only share the switched ground on the output jack. When simply wired in parallel I experienced a voltage drop and only got about 2 volts to the preamp. Hopefully that'll save you a few minutes on the install.
 
#352
Gfkfloyd said:
I just took my preamp out of a passive bass and installed it with a set of EMGs in my Modulus. It took a bit if trial and error to figure out the best way to integrate them considering they both need a 9 volt supply and the EMGs are not typically grounded as a passive pickup would be. Best bet is to keep the pickups and preamp V+ isolated and only share the switched ground on the output jack. When simply wired in parallel I experienced a voltage drop and only got about 2 volts to the preamp. Hopefully that'll save you a few minutes on the install.
Click to expand...
Thank you.

Would I then use 2 batteries?
 
#353
Loring said:
Thank you.

Would I then use 2 batteries?
Click to expand...
Yup, 2 batteries will ensure that both pickups band the preamp will have the proper voltage and enough current not to squash your headroom. Also, it really helped to ditch the EMG solderless stuff. It was a nightmare getting it to work. After you plug the pickups into their connectors, cut off the connectors and solder it up the old fashioned was and you'll have a much cleaner/easier install. Didn't help that I had a bad cable and a bad connector block in my set right off the bat.
 
#354
Gfkfloyd said:
Yup, 2 batteries will ensure that both pickups band the preamp will have the proper voltage and enough current not to squash your headroom. Also, it really helped to ditch the EMG solderless stuff. It was a nightmare getting it to work. After you plug the pickups into their connectors, cut off the connectors and solder it up the old fashioned was and you'll have a much cleaner/easier install. Didn't help that I had a bad cable and a bad connector block in my set right off the bat.
Click to expand...


These are old - 1980's vintage EMGs. They are already a solder type connection! They are currently wired up volume volume tone (Blech). I think in series also as if both pickups are selected and I kill the volume on one - I get zero output...

Would have preferred a blend control but there you go.
 
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#355
Loring said:
These are old - 1980's vintage EMGs. They are already a solder type connection! They are currently wired up volume volume tone (Blech). I think in series also as if both pickups are selected and I kill the volume on one - I get zero output...

Would have preferred a blend control but there you go.
Click to expand...
I prefer blend as well, it's just a more elegant design.
initially I had the same issue with one pot interfering with the volume of the other and what solved it was swapping the output and input on the pot.
Look up a classic jazz bass wiring diagram and wire it that way with the cumulative negitive and positive from both pots going to the input and Input-Ground of the preamp opposed to your usual tone pot and you'll be good to go; both volumes will be totally independent as they should be.
 
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#356
Gfkfloyd said:
I prefer blend as well, it's just a more elegant design.
initially I had the same issue with one pot interfering with the volume of the other and what solved it was swapping the output and input on the pot.
Look up a classic jazz bass wiring diagram and wire it that way with the cumulative negitive and positive from both pots going to the input and Input-Ground of the preamp opposed to your usual tone pot and you'll be good to go; both volumes will be totally independent as they should be.
Click to expand...

they also go to a selector switch...

I imagine best place to do the reversal is there?
 
#359
Loring said:
The selector is kinda redundant I would think. Unless the bridge pickup still effects the neck pickup at 0.
Click to expand...


You're absolutely right. Once the volume pot wiring is redone to resemble a jazz bass, you won't need the switch to have one pickup one with the other off without this all or nothing issue you're having now.
Keep us updated with your build, I'm looking forward to seeing how it'll turn out!
 
#360
parts are on the way. I have 3 knob holes, a selector hole and 2 mini dip holes...

one of the mini dips will likely get the mid selector mod (eventually lol). I am hoping the selector hole is the right size for an extra pot...

2 pickup volumes will feed the preamp or would I be better off changing that to a blend? use a master volume post?

I may switch out the pots on the BOM for some stacked ones to clean it up a bit...

Be nice to have resonance and freq. on a stack... Maybe volume and blend as well. still need four knobs then...
 

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