Mixiing Actives with passives - circuit related question

[peskywinnets]

Just wondering how it's done in practise?

The output of an active Pickup circuit is low impedance, whereas a passive pickup is high impedance...that doesn't lend itself to joining/blending the two together well....so how do say EMG implement this....is it just a case of a high value in series resistor on the final output of their circuit?

[Steve Conner]

I don't know how it is done, but I would do it by essentially building a little mixer into the guitar, since there has to be power there for the active pickups.

[peskywinnets]

I don't know how it is done, but I would do it by essentially building a little mixer into the guitar, since there has to be power there for the active pickups.

But a 'mixing' method would involVe 'routing' the other (passive) pickups through the active pickup's circuit (vs just dropping in an active into the guitar & wiring it up like a passive...which has got to be the preferred way).

[Steve Conner]

I don't see how it is the preferred way. One benefit of active pickups is that, having a low impedance output, they aren't affected by cable capacitance. Your method throws that benefit away: in cable loading terms, you're downgrading the active pickup to a passive standard. Because that's what you have to do to get them to mix: increase the active pickup's output impedance until it's comparable with a passive one.

Really both methods are mixers. Yours is a passive mixer, the same as the usual arrangement of knobs on a guitar, but I suggest using an active mixer so that the mix output is low impedance. This effectively upgrades the passive pickup to semi-active, I guess.

[peskywinnets]

I don't see how it is the preferred way. One benefit of active pickups is that, having a low impedance output, they aren't affected by cable capacitance. Your method throws that benefit away: in cable loading terms, you're downgrading the active pickup to a passive standard. Because that's what you have to do to get them to mix: increase the active pickup's output impedance until it's comparable with a passive one.

Really both methods are mixers. Yours is a passive mixer, the same as the usual arrangement of knobs on a guitar, but I suggest using an active mixer so that the mix output is low impedance. This effectively upgrades the passive pickup to semi-active, I guess.

Depends what you call a benefit - I wouldn't say that changing the 'end tone' of a passive that the player is already used to (& likes) ...as a benefit

"B-b-b-but hey,listen you've now got back all the high end you lost due to your passives being loaded with cable capacitance, yes, I know it makes your ears bleed & sounds like a different entity, but ahem - it's a benefit! " ;-)

No, what I seek is a way of plopping an active into a std guitar wiring scheme without impacting the tone of the passive pickups already installed.

[ckngumbo]

There is a Stew-Mac sheet on this topic...out this week too.

[Steve Conner]

Well, why would a player who likes the tone of passives be installing an active pickup in his guitar in the first place? I rest my case. Actives are for self-consciously experimental geeks like yourself.

The extra high end could be got rid of by slugging the passive pickup with a capacitor. Or, giving it its own tone knob, then the extra high end could be brought back at will.

[peskywinnets]

Well, why would a player who likes the tone of passives be installing an active pickup in his guitar in the first place? I rest my case. Actives are for self-consciously experimental geeks like yourself.

Because someone may adore the tone of their neck passive pickup, but still want to drop in an active pickup in their bridge, thereby having the other end of the pickup spectrum covered (high output, heaps of high end blah blah).

Ckngumbo...I'll seek it out - tks.

[Mike Sulzer]

Depends what you call a benefit - I wouldn't say that changing the 'end tone' of a passive that the player is already used to (& likes) ...as a benefit

What's the problem here? Why all the moaning and groaning? The passive pickup still sounds like a passive pickup when connected to an internal high impedance amplifier if you put a capacitor across the pickup equal to the cable capacitance and also a resistor to make the resistive part of the impedance the same.

Its been said a hundred times and it is real easy to figure out!

[peskywinnets]

Its been said a hundred times and it is real easy to figure out!

My apologies for asking...I had thought this was a forum - in part for those still learning - clearly I must be intellectually inadequate to even field the question.

Just one thing ....

Has anyone previously mentioned 100 times about the extra noise injected into a passive of doing it this way? (i.e. a passive which was previously minding its own business, prior to being grabbed by the tail wires and forced to chomp its way through an active circuit).

[Steve Conner]

Extra noise? You are the authority on that since you like to design 100 turn pickups hooked to random arrays of op-amps.

Pickups intended for passive use have a sensible number of turns, so noise isn't an issue. They have so much output, they even give acceptable SNR with a tube front end, which any good op-amp can beat. In fact that is the essence of passive pickups, the sound we love comes from a limited frequency response which was a result of the large number of turns Leo needed to get good SNR with his tubes.

So I say noise with a buffered passive pickup isn't an issue, it will beat the active one and not be noticeable with an industry standard tube amp.

By the way, the pickup sound spectrum isn't a line, it's a 2d plane at least. Higher output pickups tend to be darker, but that is a pickup maker's aesthetic choice, not a law of nature. You need several guitars to cover it, or that's my excuse at least.

[peskywinnets]

You are the authority on that since you like to design 100 turn pickups hooked to random arrays of op-amps.

I just like to get my sleeves rolled up, crack out the breadboard, fire up the scope & see what gives (but if the stuff I learn/glean along my journey is going to be the fuel for sarcasm/taunts, then I'll keep myself to myself) - btw, it was never 100 turns of a bog standard single ended pickup - more like 800 turns & bifilar wound/balanced config too ....but, yep, I now learnt the longhand way that it needs more turns than 800 (but probably not considerably more) to get an acceptable SN ratio vibe going down.

[defaced]

This?
http://www.emgpickups.com/content/wi...0230-0095G.pdf

Also, this:
PUPS, Active & Passive..same Guitar?? - My Les Paul Forums

[David Schwab]

Just wondering how it's done in practise?

You have to make the passive active and then blend the two active signals. That way the low Z output of the active wont load down the passive.

You can tailor the input of the preamp for the passive to simulate a passive signal chain, so it doesn't brighten the tone of the passive pickup.

The easy way to do this is to use something like an EMG afterburner or a simple buffer circuit.

Stew-Mac just had an article about this subject:

Trade Secrets! Newsletter at Stewart-MacDonald: Mixing active and passive
pickups in a jazz guitar

[Rick Turner]

Old curmudgeon here....

this is a discussion worthy of about 1975...

If you want it both ways, take the outputs out on separate jacks and use two cables into a two channel amp. You got a problem with that?

And when is a buffered passive pickup not active? Come on now, folks... It's not gain that defines active, it's a transistor of some sort...or a tube if you're really freaky...in the guitar. And the transistor can be part of the front end of an IC.

Been there, done that 40 years ago. No big deal...

Jeez...