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Intermediate Member
Username: lysosome

Post Number: 108
Registered: 1-2006
Posted on Tuesday, August 11, 2009 - 2:40 pm:   Edit Post

Hey guys, it's been a while. I hope everybody is getting along alright.

I was hoping somebody could give me a hand with a wiring diagram. I'm looking at my options for a new set of pickups, and I'm leaning towards the EMG-35DC p'ups for 4 string. Unfortunately, the Alembic AXY's that were my #1 choice are beyond my budget's limitations for now. The bass these are going into isn't an Alembic BTW, so no need to panic ;)

Anyway, EMG has a good selection of pre-wired preamps to go with these pickups. I'd like to go with the EMG-BTC System preamp, but there are a couple of things I want to change.

[Before I go any further, here are a few links to the subject pickups, preamp, and wiring diagram for the preamp...

...just so you can see for yourself.]

Controls for this preamp are as follows: (master) volume, blend, treble/bass stack

With this premap, I like the fact that it's mostly prewired, and designed to go exclusively with the pickups. However, I would like to split the volume wiring so I can have an independent volume control for each pickup. I would also like to install a 4-way selector switch with the same functions as the Alembic version (neck, both, bridge, stand by). Is there a practical way to make these modifications? In the case of this preamp, does the "blend" control make up for dual volume controls? I would be more than grateful for a little guidance.

Being that the people associated with Alembic are the most knowledgable people on the planet when it comes to instrument electronics, I wanted to ask this here first. I don't know enough about this type of thing to try to figure it out on my own.

Thanks for any and all input.

Intermediate Member
Username: benson_murrensun

Post Number: 162
Registered: 5-2007
Posted on Wednesday, August 12, 2009 - 10:36 am:   Edit Post

I got an EMG BTC Control to help out with a wimpy-sounding bass (Steinberger Spirit - great for transporting on motorcycles). It does a good job.
Advanced Member
Username: lmiwa

Post Number: 240
Registered: 2-2008
Posted on Wednesday, August 12, 2009 - 11:49 am:   Edit Post


The BTC System includes the volume and balance controls, with the circuitry on the balance pot. To convert to two volumes, you would need to replace that whole section of the circuit.

Alternatively, you can purchase just the tone control circuitry (BTC Control?) and use the wiring diagrams above to wire up two volume pots.

Since I don't know the actual circuitry of the Alembic pickup switch, I can't say for sure if you could patch it between the pickups and volume pots or not. Depends on whether it provides separate neck/bridge inputs AND outputs or just one set of outputs.

Username: bassilisk

Post Number: 49
Registered: 4-2009
Posted on Wednesday, August 12, 2009 - 12:03 pm:   Edit Post

I have the BTC with the standard Master V and blend on an EMG P/J setup. I also have it as a Vol/Vol/Tone in my Steinberger XL2.

A couple of things. Two volumes give you the most flexibility vs a Blend. The tradeoff is no Master Volume. I have one passive Jazz wired with 2 stack knobs and a Master Volume that pulls up to put the pickups in series. This is a handy set up.

With a Blend control at detent both pickups are full on - turning it in either direction will give you one pickup full on while the other is attenuated. i.e. Turning towards the neck pu just turns down the bridge pickup, leaving the neck pu always at 100%.

With two volumes you can, for example, set one pickup at 35% and the other at 70%.

I don't know about a 4-way (with stand-by position) but you can find a 2 Vol/2Tone/3-Way switch diagram (along with every other combination) here:

I've only rarely used a stand-by myself, but on those occasions I need one I just turn on my tuner and I'm muted. Good luck!
Intermediate Member
Username: lysosome

Post Number: 109
Registered: 1-2006
Posted on Wednesday, August 12, 2009 - 2:41 pm:   Edit Post

Thanks for your responses guys.

I see now. I hadn't looked carefully enough at the BTC Control before. So, that much seems easy now, using the picture on page 2 of the wiring diagram.

I found a 4 position rotary switch. I'm wondering if it will work for what I need..,Product.asp

Any ideas on the wiring?

As an alternative, I could install 2 on/off toggle switches (1 for each pickup) if the rotary switch won't work.

Thanks again guys.
Intermediate Member
Username: lysosome

Post Number: 111
Registered: 1-2006
Posted on Wednesday, August 12, 2009 - 7:48 pm:   Edit Post

I found this diagram on TalkBass. It's almost what I'm looking for...
Advanced Member
Username: dfung60

Post Number: 392
Registered: 5-2002
Posted on Wednesday, August 12, 2009 - 8:30 pm:   Edit Post

You can't do the series/parallel thing with the active EMG pickups like the DCs. These pickups are quite different internally than traditional pickups - they have weaker magnets and less wire on the coils all of which makes a higher-fi sound available, then the output is EQed and boosted by a preamp that's inside the pickup. So you have no access to the individual coils and, even if you did, it wouldn't be particularly useful.

There's some dual sound models in the Extended Series as well, the TW pickups, but they also work in a different way - these pickups have three internal coils and two internal preamps. I personally don't like the sounds of the dual sound EMG pickups, even though I like the "normal" sounds.

Loch has also given you good advice - you can wire twin pickup volumes then send that output to a BTC to do what you want. If you want to add an Alembic-style pickup selector, you're going to have to find a proper switch (it will probably be easiest to get this from Alembic). You insert the pickup selector switch "after" the individual volume pots and before the EQ circuit. And while you're at it, if you want to add a master volume control, you can do that with an EMG 25K volume pot AFTER the EQ circuit and before the output jack - it will work properly with no loss of tone when you turn it down.

Gee, if you want to get really ambitious, you can work out a way to bring the internal DIP switch controls on the BTC that adjust the treble control corner frequency out to a mini switch on the front of your bass, then you'll have extra variations on the treble boost!

David Fung
Intermediate Member
Username: lysosome

Post Number: 112
Registered: 1-2006
Posted on Wednesday, August 12, 2009 - 11:06 pm:   Edit Post

David, thanks for your reply. I should have mentioned that I'm not interested in going the series/parallel route anyway. What I was trying to show with the above photo was that there already exists a setup similar to what I'm wanting.

I am really thankful for all of these ideas. Your idea of having a master volume and boost switch is very cool; not something I had thought of. I'm not savy enough with electronics to work something like this out myself, though. I can put it together from a schematic, but I wouldn't have any idea where to start if I had to make the plans from scratch..

I made up a couple pictures using Microsoft Paint; they're not much, but they convey the message well enough.

This one (above) would be my first choice as a setup. However, the setup below would serve the same functions - just replacing the rotary switch with a toggle switch for each pickup.

Whichever one is easier to configure is the one I'll go with, although I suspect the difference in difficulty is minimal.

Also, David: you said that it would be easiest to get the rotary switch from Alembic. Would the switch I linked to in the above post not work? It seems like the same thing to me.

Thanks again to everybody. I'm almost there.

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