bartolini mk1 active and passive (samples inside)

[leitmo]

Hi TBers!

i've read several threads before starting a new one about bartolini mk1 pickups and switches active/passive and i always wondered how my Cort A5 sounded passive?

so i gave it a try, downloaded schematic from Cort

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and my active/passive test began:

- play bass only bridge pickup (active bridge.WAV)
- play bass only neck pickup (active neck.WAV)
- soldered bridge pickup to output jack (passive bridge.WAV)
- soldered neck pickup to output jack (passive neck.wav)

there's no EQ, no compression, just adjust level for similar perceived volume (active bass was 4 to 5 dB louder).

Looking at schematic i'm confident enough to convert EQ on/off switch to active/passive switch

Here are results, waiting your opinions:

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[SGD Lutherie]

when you soldered the pickup to the output jack, did you remove the preamp's output first?

[leitmo]

I'm absolutely sure preamp is not in the signal path.
I removed battery to ensure pickups are passive.
i also removed solder connection between pickup and input preamp so signal goes from pickup to output jack.

[SGD Lutherie]

Originally Posted by leitmo

I'm absolutely sure preamp is not in the signal path.
I removed battery to ensure pickups are passive.
i also removed solder connection between pickup and input preamp so signal goes from pickup to output jack.

OK, but did you leave the output of the preamp connected to the jack? If you did, it will affect the tone of the pickups in a bad way.

[leitmo]

Of course not, i desoldered volume pot to output jack and solder a wire from pickup to output jack

[leitmo]

Preamp has no wire attached to signal path

Please don't judge my player technique, just hear differences.

Don't know how much current does other active basses drain but Cort A5 begins to fail when battery measures 7'8 volts.....this test is just to confirm i like passive tone

[leitmo]

anybody?

for those interested i'm pretty sure i've found the way to implement active/passive switch in Cort active basses,

suggestions/corrections will be welcome

[SGD Lutherie]

Originally Posted by leitmo

anybody?

for those interested i'm pretty sure i've found the way to implement active/passive switch in Cort active basses,

suggestions/corrections will be welcome

Both diagrams look the same. If the volume control is after the preamp, it's probably rated for a low impedance signal. So it's probably something like 25k to 50k. That wont work when the preamp is bypassed because it's too low for passive pickups.

So a way around this is to replace the output volume control with a regular 500k pot before the preamp, and after the blend. Then when you switch the preamp out, you would switch the wire from the volume pot from the front of the preamp to the output jack, and the output of the preamp would also be removed from the output jack. Also, the input to the preamp should be going to ground when it's bypassed.

[leitmo]

volume pot is already 500k in original schematic

Diagrams differs a lot if looking closer:

factory setup drives pickup signals to preamp to act as buffer, goes through blend pot and back to preamp for EQ (switchable on/off), finally passes through 500k volume pot

my mod is simple: blend pickup signal with 250 or 500k blend pot, go to active/passive switch, if active goes to preamp and EQ, if passive runs straight to vol pot

The only component i must change is original 25k blend pot and get a 250 or 500k blend pot

[SGD Lutherie]

Oh yeah, I see that now. I have to say though, a buffered blend works a lot better than a passive blend. Passive blends tend to work over a very small range past the center detent.

I'm not exactly sure what you have to gain here. If you just want an unbuffered tone, I'd try some small value caps to ground, connected to the pickup inputs to roll some high end off and simulate the capacetance of the cable. That's the only reason why passive basses sound different.

I'd try that method and keep the buffered blend.

[leitmo]

I'm sure buffered blend works better than passive but, same as transistors are more efficient than tubes and parametric EQ gives more freedom to tweak but i prefer to get my tone with subtle changes....

I was also thinking about getting out preamp and have a totally passive bass with 2 volume pots and 2 tone pots....i'm still not sure about 5th pot and switch

[SGD Lutherie]

Originally Posted by leitmo

I'm sure buffered blend works better than passive but, same as transistors are more efficient than tubes and parametric EQ gives more freedom to tweak but i prefer to get my tone with subtle changes....

Subtle is how you use it. You have EQ on your amp right? Same thing. Just because a knob goes to 10 doesn't mean you need to turn it past 2. I generally have a little bass boost going on all the time, and then I either boost or cut the treble depending on the song. I leave my amp fairly flat.

With my passive basses, I can only cut the highs, and can't boost them.

One you will accomplish going passive is loosing high end. So you have a sort of preset EQ that you can't change, so in the end you have less tonal options.

There seems to be this misconception that passive basses are more "organic" or "purer" in tone, but every bass is an electric bass, so they are all active. It just depends on where the first gain stage is; in the bass, or at the amp.

Same argument with tubes vs. solid state.

If it's at the amp, you are losing the true tone of the pickups as it travels down your cable, etc.

I was also thinking about getting out preamp and have a totally passive bass with 2 volume pots and 2 tone pots....i'm still not sure about 5th pot and switch

Just check out that you like the tone better. It will be darker passive.

[leitmo]

Great!

Is just a matter of personal preferences

Did you or someone else heard samples? Differences are not so obvious as i could expect

[leitmo]

Finally done!

I went the easy way and make my cort a5 active just passive:

2 vol pots soldered to output jack, simple, nice, warm and less hi-fi sound!!!

I encourage all you are in doubt to try it, you won't be disapointed!

Next step? Maybe 2 or 3 band tone stack......

[dharmaone]

Hey Leitmo,

I'm trying to do the same with my Cort A4 and go from active to passive (fried some surface mount components on the preamp and never liked the hifi active tone anyway..also going to try some flat wound strings for a more vintage tone).

I'm looking at the wiring diagram here: http://www.cortguitars.com/downloads/pdfs/A4.pdf

I could wire the 2 pups straight to the jack, but I'd like to still be able blend between the two pups for shaping tone. How did you do your "2 vol pots soldered to output jack" mod? My cort only has one volume pot. Did you use the existing pots or buy new ones?

Many thanks

[SGD Lutherie]

Originally Posted by dharmaone

Hey Leitmo,

I'm trying to do the same with my Cort A4 and go from active to passive (fried some surface mount components on the preamp and never liked the hifi active tone anyway..also going to try some flat wound strings for a more vintage tone).

I'm looking at the wiring diagram here: http://www.cortguitars.com/downloads/pdfs/A4.pdf

I could wire the 2 pups straight to the jack, but I'd like to still be able blend between the two pups for shaping tone. How did you do your "2 vol pots soldered to output jack" mod? My cort only has one volume pot. Did you use the existing pots or buy new ones?

You would have to remove the entire preamp, since it has a buffered blend control. Then you could wire a new blend, volume and tone, or V/V/T. But there is no way to switch from active to passive with that circuit.

[dharmaone]

Gotcha! Gonna go vvt. Is 500k or 250k linear better with the bartolinis for vol pots? What value cap for tone? Thanks!!

[leitmo]

i didn't use any tone cap, just pickup outputs straight to 250k pot and output to jack

advice: if you are hi-fi, hi-end tone-like you won't like it. Soul, old-school, fat and warm tone lovers will love it!!!

[SGD Lutherie]

Originally Posted by dharmaone

Gotcha! Gonna go vvt. Is 500k or 250k linear better with the bartolinis for vol pots? What value cap for tone? Thanks!!

Barts usually call for 250k pots. 500k will be a little brighter. You can use a standard .047µF cap.