We recommend impedance-matching preamps... - Page 3

G Miller · #31 05-23-2018, 05:40 PM

Thanks guys. I'll write Epiphone and inquire about the spec as I got it from my manual as well as the link you posted. The 4.7M Ohm makes more sense. For the other guitar with a Fishman, they did reply to me and said their input impedance spec for the ISys III is 1M - 10M Ohm. Others though have discussed that Fishman may use a DC bias voltage with the signal riding on it so I need to look into that as well. Anyone know about this? Anyway I was playing the Fender last night partly to evaluate do I really want/need to do anything except refit a saddle, change the crappy stock tuners, slot the bridge pin holes, for my personal preference and the darned G string broke (new set of strings too). So while changing the string breaking up a set I realized there is a significant break angle between the nut and tuners whereby a little rounding of the headstock side of the nut slots is warranted. Fun

lkingston · #32 05-29-2018, 05:12 PM

How do passive pickups sound with a simple active directbox? It seems like that would be what they are designed for? It should match the impedance and boost the level to where it would be on a passive directbox with an active guitar preamp. Why not just do that?

jonfields45 · #33 05-29-2018, 05:41 PM

Quote:

Originally Posted by lkingston

How do passive pickups sound with a simple active directbox? It seems like that would be what they are designed for? It should match the impedance and boost the level to where it would be on a passive directbox with an active guitar preamp. Why not just do that?

If such a box was around 1M ohm input impedance, both K&K's and Magnetic pickups would work well.

martingitdave · #34 05-29-2018, 06:19 PM

Quote:

Originally Posted by lkingston

How do passive pickups sound with a simple active directbox? It seems like that would be what they are designed for? It should match the impedance and boost the level to where it would be on a passive directbox with an active guitar preamp. Why not just do that?

Some do exactly that. The RedEye, for instance does that, plus adds a treble control. The K&K usually needs some highs added.

lkingston · #35 05-29-2018, 08:24 PM

Quote:

Originally Posted by jonfields45

If such a box was around 1M ohm input impedance, both K&K's and Magnetic pickups would work well.

That is exactly the published input impedance of the Samson MDA1 active directbox I got today. They are about $35 everywhere online. I got it specifically because at this one open mic I do, there is one guy with a factory passive pickup in his Martin. I haven’t tried it yet with that guitar, but it sounds great at home with everything I’ve tried it with so far. Outward construction is thick metal and surprisingly good. The appearance on par with what you would expect from a Radial DI. It can be powered either by a 9v battery or phantom power.

My understanding is that active directboxes are much less expensive because they don’t require really expensive Jensen (or similar quality) transformers in order to sound good. To me the output sounds like the input.

I wouldn’t be able to tell the sound of this and an active Radial DI apart by the sound. On the other hand, I have no trouble at all distinguishing between the sound of a Radial Technology and a cheap passive DI.

G Miller · #36 10-11-2018, 05:21 PM

I never really found out the truth on the Esonic preamp input impedance so all I have to go on is the written spec of 4.7KOhm. However, I had JJB electronics make me a three 15mm sensor SBT similar to the K&K Pure Mini. I needed to use the 15mm diameter transducers due to limited bridge plate space. After making a custom jig to mount all three sensors at the same time my initial test was successful. My initial test was with a quickly roughed in saddle and with strings that were over due for a change. The sound difference between having the UST interfering with the physical coupling of the components at the bridge and the SBT was like the difference between an old set of strings and new ones both playing amplified and unplugged. I did not notice an overly tinny or mud sound at all. The guitar is a slim body acoustic and the sound was much richer 'leaning' towards a full depth dreadnought. While it would be nice to know the 'numbers', I was happy with the initial results. I'll give another update once I finish fit a saddle and give it a run over some time. Regards to the group.

varmonter · #37 10-12-2018, 08:13 AM

Quote:

Originally Posted by ljguitar

Hi Joe...

Fishman isn't alone. K&K makes similar allegations.

The reality is I own 5 different brands of preamps, and they all work fine with any passive undersaddle or bridgeplate transducers which we've run through them for the past few years.

I seriously doubt that any but the matching-name-branded ones would qualify as a 'perfect' impedance match for the pickups.

I treat these statements with the same seriousness I do when a product from Sony or Panasonic suggests that I must use their brand of batteries and even offers order blanks and product numbers to get them. My grandmother is the only person I ever knew who actually ordered batteries from them for her small recorder.

This.. Perhaps we put entirely to much concern and thought
into this issue. Suffice it to say if you have a passive
pickup you will need some sort of device to match
the impedance to the board. One with sweepable
midrange eq control is always preferred . Yes i suppose
the proprietary preamp made specifically for the
pickup might be ideal(kk comes to mind) .It is seldom necessary.
I try to buy pickups in the 1mgohm range Kk pure mini.. baggs m80 ..etc.
just to keep things consistent. You can bite the bullet
and buy a preamp like the felix which has switchable input impedances.