Mixing two pickups

[Dave Kerr]

I'm new to this kinda stuff, but how do you go about mounting the circuit? I mean, I've worked with breadboards in the past, but it seems like you'd need to make a PCB for this, right?

Sorry for the noob questions.

Check out Albert Kreuzer's page (Albert's dropped by here now and then) toward the bottom - it can be as simple as mounting perfboard to a pcb-mount pot.

[David Schwab]

Mike, I'm officially saying give it a rest.

Akso, I feel you should have stayed out of the conversation, because starting with your first post, you didn't add anything to the discussion. Not on the subject at hand anyway.

Rick on the other hand pointed out the benefits of buffering and then mixing, which is what Marko was asking about.

[RedHouse]

...you do not have to respond to me if you do not want to argue...

Self incriminating, I rest my case.

[Rick Turner]

Now that we're past the weird stuff...

I'm not here for the sake of arguing, merely to learn and share what I know and have learned both on my own and through working with a series of absolutely stellar audio engineers over about 40 years.

To mix the outputs of two buffers, you'll want to combine through a resistor on the output of each buffer to keep the buffers from loading one another and attempting to push current each into the other. Try 50 K or 100 K mix resistors.

[David Schwab]

Rick, it's great to have you here! I've already learned a few new things. I know we would have loved to have you here the first time we got into talking about horseshoe pickups.

We get into heated discussions at times, but I don't think anyone wants arguments going on.

Back to the subject, yes, resistors at the outputs is a good suggestion.

[RedHouse]

Now that we're past the weird stuff...

I'm not here for the sake of arguing, merely to learn and share what I know and have learned both on my own and through working with a series of absolutely stellar audio engineers over about 40 years.

To mix the outputs of two buffers, you'll want to combine through a resistor on the output of each buffer to keep the buffers from loading one another and attempting to push current each into the other. Try 50 K or 100 K mix resistors.

Yes, and having a mixing stage (Transistor or OpAmp) with a little bit of gain is a good thing. Makes up for the loss in the mixing resistors, just enough gain to bring back to the levels which existed from each individual coil/pickup's buffer's output. As Rick said earlier this a good place for a higher-current device so it can drive the cable with ease.

[Rick Turner]

Yep! The classic is to buffer, run each channel through mix resistors into a line driver. In fact, you can put your master volume before the line driver if you want to have no change in source impedance when turning the volume up and down. In practice, that can sometimes be noisier than putting an attenuator at the end of the on-board circuit...some of this depends on how much current you can burn up on-board. Really low noise circuits and devices tend to be current burners...

Note that the Alembic Stratoblaster is a line driver after the stock volume and tone controls...

That's really an amazing circuit...incredibly simple, works like a champ, and doesn't gobble up much Amp hours of battery juice. BTW, most of the lead guitar parts on Fleetwood Mac's Rumours are Stratoblaster into HiWatts which were blowing up every other night because of poor current limiting in the power supply...they couldn't handle the signal coming in and tried to keep amplifying and drawing too much current from the power transformer. The other great recorded Stratoblaster sound is Lowell George on the live "Waiting for Columbus". That's 12 db of 'blaster into a Dumble Overdrive. It's also my favorite live rock album of all times.

[David Schwab]

I've had a Stratoblaster circuit in many of my basses since the mid 80's. The only change I do is to increase the output coupling cap to 10µF. it really is a great and simple preamp.

I used those as buffer/boosters for some low Z pickups I used to make, one per pickup, with the blend and volume after the blasters. Worked great.

I had a feeling Lowell George was using one. And Buckingham too.

[Marko Ursin]

End of story as far as this bass is concerned. I have a Tillman buffer on each pickup, 25K vol pots after buffers, combined through 100K resistors, 25K master volume pot and 500K master tone pot. Works just great! I can now mix the pickups without them changing their tone (if they change, I can't hear it clearly enough to tell). No difference in volume between neck both or bridge pickup in any mixed position. Just as I wanted.
Many, many thanks to David and Rick for help.
Marko

[RedHouse]

Very cool Marko. Is it getting you the tone's you want now?

Further on the Stratoblaster, I believe Jerry Garcia used that first (the prototype circuit) in his "Alligator Strat" circa '70-'72, it's the one used and seen on the Europe '72 tour and pic's. That Strat had a modified pickguard where the area the controls are located was made removable, many think that was for the battery access for the prototype Stratoblaster circuit. When Alembic offered it commercially they made it into that jackplate assembly thing.

The Dead, like 'em or not, sure tried a lot of new equipment ideas, kind of groundbreakers with some stuff and definately high-tech gear sluts.

[Marko Ursin]

I like the way the pickups mix with each other now so yes, I'm getting the tone I was looking for. At the same time I learned a lot about buffering and mixing. An educative and fun project!
Marko

[Chris Turner]

End of story as far as this bass is concerned. I have a Tillman buffer on each pickup, 25K vol pots after buffers, combined through 100K resistors, 25K master volume pot and 500K master tone pot. Works just great! I can now mix the pickups without them changing their tone (if they change, I can't hear it clearly enough to tell). No difference in volume between neck both or bridge pickup in any mixed position. Just as I wanted.
Many, many thanks to David and Rick for help.
Marko

Any chance you could take a picture of everything mounted in the bass?

[Marko Ursin]

Here you go. Each buffer is hot glued to the volume pot.
http://i631.photobucket.com/albums/u...1/P7250316.jpg

Marko

[Chris Turner]

Here you go. Each buffer is hot glued to the volume pot.
http://i631.photobucket.com/albums/u...1/P7250316.jpg

Marko

Awesome! Thank you! Are you running both buffers off of one 9-volt, or one 9-volt for each?

[Marko Ursin]

I have one 9V battery. Should last quite a long time. If I remember correct one battery last around 600h for one buffer.
Marko