We recommend impedance-matching preamps...

[ljguitar]

Originally Posted by krisls

…I can only conclude that most such guitars will work just fine with most gear with tweaks to levels and EQ. There are possibly exceptions but everything I have tried will do the job pretty well.

Hi Kris...

Companies want to make gear that works with a lot of different equipment, and players want a variety of choices of equipment which work well with their gear.

It's been that way since I installed my first Barcus Berry pickup in the mid-1970s, and continues to this day.

It's interesting that the companies that claim their preamps work 'best' with their branded pickup gear advertise widely in order to sell it to people with other brands of pickup rigs in their guitars.

[joeguam]

Thanks everyone for the info and time in this thread. I posted this as a result of some frustration, but the root intentions were based on whether or not I could swap the UST of my Taylor 114ce with their ES-T system with the SBT's of the K&K Pure Mini.

I'm with sdelsolray in the sense that I'd much rather prefer to "buy knowing that it will work" as opposed to "trial and PRAYER" as I like to refer to it. I didn't want to spend a bunch of money on a K&K Pure Mini, "just to try it out" in my 114ce with the Taylor onboard preamp - only for it not to work.

As I thought more and more about this modification, I was able to come up with a great idea to use my wife's GS Mini + Pure Mini, routing through my Taylor 114ce onboard preamp through a cable I spliced as an adapter...and IT WORKED!

Here's the thread where I detailed the process with photos:
SUCCESS: K&K Pure Mini SBT's with Taylor ES-T onboard preamp!

I'm very happy with the results and have purchased another set of Pure Mini SBT's to install in my 114ce permanently.

But, I still think that companies, like Fishman, who make disclaimers so they won't be liable if the buyer isn't satisfied, should provide ample information so buyers can make proper decisions.

Cheers and thanks again everyone, I love the AGF!

...
Joe

[G Miller]

Hello. I'm new to the forum so upfront want to express my appreciation for the wealth of information. I'm a casual player who likes to do his own setups and modifications to low/mid range guitars. Similar to many of you, I'm discontent with USTs and decent saddle to bridge coupling. So now on the quest of wanting to remove the USTs, put in bone saddles, retrofit a different pickup probably SBTs, but want to use the existing preamps in two guitars. I have a Epiphone PR-5E with Esonic preamp/UST and a Fender 400CE with a Fishman Isys III preamp/UST. I've been reading much about the transducer to preamp impedance matching. Haven't found on the forum the specifications for these preamps. I did find on the JJB site some decently priced SBTs (less than the K&K Pure Mini) for a possible source for my 'experiment'. Does any one what the input impedance values are?

[jimmorgan]

I don't have any technical stuff to back this up, but I have used a lot of different passive pickups with a lot of different preamps, and IMHO, if the impedance is greater than 1 MegOhm, you're fine. Going higher may get you something, more bass, etc, but 1 Meg or greater is fine for 99% of pickups.

[martingitdave]

My experience with piezo preamps, and their impedance, for acoustic guitar is this:

K&K PM needs 400kOhm to 1MOhm input impedance to sound clean. Too low and it sounds weak. Too high and it's all mud.

Everything else works find with impedance from about 2 MOhm to 10 MOhm. Most under-saddle piezos sound thin naturally. So the high impedance makes them sounds a little more natural. Most acoustic guitar amps have this kind of very high impedance input. Most mixing boards and PA equipment do not. Therefore a DI box that does impedance matching (i.e high to low) is necessary.

Output impedance of the piezo pickup is not static and actually varies with frequency.

So, with most pickups, it's "horseshoes and hand grenades." You just need to be close to 10 x your output impedance. With the K&K, you need to be a little more careful to get a flat response.

[jonfields45]

An EE's view on this...

The output impedance and the input impedance to which it is connected should be equal for maximum power transfer and highest signal to noise ratio. Line signals through balanced cables follow this design goal.

In the real world of passive signal sources, piezo, magnetic, dynamic microphone, etc. the source impedance is not resistive, but has all sorts of parasitics. A complex impedance consisting of resistance, capacitance and inductance is a function of frequency and a simple single number is not a realistic expectation. Often when you are quoted a number for a mag PUP, you are only being quoted the resistance component. For magnetic pickups it is series inductance which into the wrong load acts as a low pass filter. For piezos it is a double problem of series capacitance (high pass) and parallel capacitance (low pass). For mag PUPs you generally want that 10x (the source impedance) load, or higher across the frequency range of interest, to avoid that low pass filter. For piezos you have a double bound, too low a load impedance and you get a high pass filter, and too high you get a strange sounding low pass filter. This will depend on the construction of the piezo. It is hard to get that too high an impedance input problem with a piezo, but it can happen. Generally a well designed input circuit will be close enough to a simple resistive model.

Seem complex? With liberal return policies it is best to just try it out.

[varmonter]

The output impedance and the input impedance to which it is connected should be equal for maximum power transfer and highest signal to noise ratio. Line signals through balanced cables follow this design goal.

When we talk impedance are we not talking resistance measured
in ohms.? so the higher the number the greater
the resistance.??so ideally don't we want output from the guitar to
equal to input of whatever we are plugging into. Which is why
we have all this impedance matching stuff to begin with.
Conversely shouldn't any pup of say 1 mgohm (high resistance)
be able to plug into any board if it has a lower number say 600K ohm (low resistance) Without any issues? I know thi isn't so.
I am trying to wrap my head
around why they need to be equal. When i think of resistance
i think of flow.

[jonfields45]

Originally Posted by varmonter

When we talk impedance are we not talking resistance measured
in ohms.? so the higher the number the greater
the resistance.??so ideally don't we want output from the guitar to
equal to input of whatever we are plugging into. Which is why
we have all this impedance matching stuff to begin with.
Conversely shouldn't any pup of say 1 mgohm (high resistance)
be able to plug into any board if it has a lower number say 600K ohm (low resistance) Without any issues? I know thi isn't so.
I am trying to wrap my head
around why they need to be equal. When i think of resistance
i think of flow.

Impedance is a complex number (remember the square root of -1?) whose magnitude is quoted in ohms. For a well designed active circuit (source and load), load equal source is best and by design they will be dominated by resistance.

Passive pickups that have complex impedances (not well modeled by a resistor). In that case equal is often bad for tone (even though it would be best for signal to noise ratio), with some exceptions (like a piezo pickup driving a purely capacitive load). I think in general, this is too complicated for the simple words that get thrown around in the music business. The 10x rule of thumb is generally good enough in most situations for magnetic pickups, but for something like a K&K, you need to stick with their recommendation of a load impedance around 1M ohm (100K to 10M is probably close enough to 1M -- hearing is logarithmic not linear).

I think you are best off trying and returning the infrequent failure.

[Br1ck]

Ideally impedance input would be matched exactly to the pickup used, but this is impractical in the real world, so manufacturers have settled on a value they feel works well with everything.

For instance, my SunnAudio Stage DI was designed to match perfectly with Dazzo pickups, which I have in all my guitars. They spent a lot of effort to get this just right. The reality is this impedance also works well with K&K, JJB, undersaddle pickups, and anything else that has been plugged into it.

The Blender DI SunnAudio built for my open mic gets the gamut run through it, but Dazzos are perfect. Pretty much run flat. Dazzos sound great, but K&Ks don't need EQ either. Once you have a high impedance input impedance, it becomes the circuitry after that tells the tale.

[varmonter]

so would not matching a di output to the board
input also be a good thing . for instance the di
out on my felix is 150k the input impedance
of a touchmix is 100k these seem pretty close
but would i gain anything by matching it perfect
or would i just be splitting hairs.??

[jonfields45]

Originally Posted by varmonter

so would not matching a di output to the board
input also be a good thing . for instance the di
out on my felix is 150k the input impedance
of a touchmix is 100k these seem pretty close
but would i gain anything by matching it perfect
or would i just be splitting hairs.??

In the logarithmic world of audio, definitely splitting hairs. And good advice for best signal to noise ratio was important 100 years ago when vacuum tubes were precious and signal quality was pretty poor across the board. These days there is no need to get too uptight about these things unless you have a noise problem (dramatically awful SNR and the solution to most noise problems is not perfecting impedance matching).

[G Miller]

I found that the Esonic input impedance spec is 4.7 K Ohm. The JJB PPS-200p dual SBT is rated 4M Ohm or less (1M Ohm ideal). What are the groups thoughts on this configuration? What should I expect with 4.7 K Ohm/1M Ohm difference?

[varmonter]

Originally Posted by jonfields45

In the logarithmic world of audio, definitely splitting hairs. And good advice for best signal to noise ratio was important 100 years ago when vacuum tubes were precious and signal quality was pretty poor across the board. These days there is no need to get too uptight about these things unless you have a noise problem (dramatically awful SNR and the solution to most noise problems is not perfecting impedance matching).

thanks this is what i expected. No the felix is really quiet..

[jonfields45]

Originally Posted by G Miller

I found that the Esonic input impedance spec is 4.7 K Ohm. The JJB PPS-200p dual SBT is rated 4M Ohm or less (1M Ohm ideal). What are the groups thoughts on this configuration? What should I expect with 4.7 K Ohm/1M Ohm difference?

http://www.epiphone.com/news-feature...oustic-pe.aspx

It is either going to sound terrible with no bass, or more likey the 4.7K ohm number is wrong. I'm betting on the latter.

[martingitdave]

Originally Posted by jonfields45

http://www.epiphone.com/news-feature...oustic-pe.aspx

It is either going to sound terrible with no bass, or more likey the 4.7K ohm number is wrong. I'm betting on the latter.

Agreed. I've experienced K&K into a wide range of impedance. 100k was about as low as I would go to get a decent sound. 4.7K seems like it would produce a thin irritating sound. Like Jon, I assume it's a misprint and might actually be 4.7 MOhm. 4.7 MOhm might sound too bassy with with the K&K. But, it also depends on the K&k installation. It might be worth a try. Most of this pickup modification stuff is trial and error. I've tried "great" combination suggestions, offered by others on AGF, with little success. Conversely, people have tired stuff I suggested and told me it didn't work. It's truly hit or miss.