Wow, impedance issue with acoustic pickups REALLY matters.

[aclarson]

Hello, been reading here a lot and this is my first post, hopefully this can be helpful to some the way I've been helped by others from this forum.

So I own a Taylor DN3 (which I adore) that I've installed a K&K Pure Mini in and have been using mostly with less-than-perfect amplification up to this point. I had been doing some open mikes, and a friend had a dinky Crate 15w acoustic amp I'd been using (meh). My guitar with pickup has sounded great direct for most of the things I've tried, but I decided I wanted to step up my game, so I just purchased a Fishman SA220 and LR Baggs PADI.

So I got it an hooked it all up, and while I immediately noticed the clarity and power of the new amp, I also noticed that I seemed to have excessive boominess occuring, and when I got tough on stumming, the midrange would bite kinda hard and nasty in a way that almost sounded like distortion, but I wasn't seeing the clip light go off on the SA220, so I was initially wondering if I had a defect on it in the speakers or something. Within the control of the EQ controls on the DI, I found I had to cut lows and mids quite a lot to mitigate these unpleasant sounds, and I felt like this was an extreme amount of EQ considering I was just wanting to get a nice clear acoustic tone. I went home that night from the studio kinda bummed.

Then I spent the day (at work, away from the setup) reading stuff on forums and found a number of people saying they didn't like too high of an input impedance for the K&K, and that it would cause issues along these lines. K&K themselves recommends a 1M input impedance, and even states on their site that too high would potentially be an issue. Still, I was skeptical - I do electronics for a living and was inclined to think that a higher input impedance would almost always be better, and I didn't think one could really tell the difference between a 1M and 10M. Combine this with the fact that there seems to be many satified users of this combination on these forums and others.

Well, turns out I also have a Sansamp Bass Driver DI with an input impedance of 1M, so I hooked this up, and the difference was HUGE. Boomy bottom and annoying distorted thing was gone, with NO EQ, it sounded absolutely fantastic! I still cut the mids on the SA220 just a hair (DN3 with fresh Elixirs is very present), but I ended up actually BOOSTING the lows on the SA220 when I was cranking my guitar up, and it sounds absolutely delicious.

So, for all you K&K users out there, that impedance thing is no BS. My next step may be to try out a Pure XLR preamp to replace the PADI. Or I've heard good things about the Redeye as well, wish there was a good place to try all these things.

Anyway, hope this helps, please comment if you have had any similar experience with K&K or any other system, or any comments as to what might be good for my setup, thanks.

PS - the PADI seems like a great DI for my electric upright bass, I like it better than the Sansamp, go figure. :-)

[lschwart]

This is interesting, but are you absolutely sure that it's the impedance that was causing the issue with the PADI and not something else about the way you had it set up? I'm not asking to contradict you, but I'm curious about the details given that the more I try different preamps lately, the less I hear really profound differences between them when it comes to basic functions.

Louis

[BuleriaChk]

I play nylon string Flamenco.....

Back in the Dark Ages, when I was using a PUTW SBT (10 Meg, as I remember), I had a boomy response that I couldn't dial out, no matter what I did. I was tearing my hair out, until I purchased an LR Baggs A-Ref in desperation. Still didn't help much, but Brian at LR Baggs suggested that I wire a 1 Meg resistor from signal to ground.

THAT made a HUGE difference, and while the signal still wasn't perfect, it was much, much improved....

Finally the Dark Ages were over when I purchased my first Takamine (TH-5C - and I also now have a TC-132SC), with Palathetic pickup and CTP-2 preamp...... All my problems went away, and I can go into almost any amp with EQ flat.....

[Health Freak]

I've got my JJB 330 (K&K clone) with a 1MΩ output impedance going into my PUTW Power Plug with a 10MΩ input impedance. From the Power Plug (50KΩ output impedance into a DTAR Equinox (4.7MΩ input impedance). I have no issues with boominess or harshness at all. Of course, YMMV.

[lmacmil]

I ran my K&K into a MOSFET boost pedal with 10Meg input impedance until I got my K&K Pure preamp. Didn't really notice any difference in tone.

[aclarson]

Originally Posted by lschwart

This is interesting, but are you absolutely sure that it's the impedance that was causing the issue with the PADI and not something else about the way you had it set up? I'm not asking to contradict you, but I'm curious about the details given that the more I try different preamps lately, the less I hear really profound differences between them when it comes to basic functions.

Louis

That's the only difference as far as I know, and I'm pretty thorough being a major gear geek, I have a recording studio full of equipment. Also, I didn't really wanna believe it was that, but all evidence points to it. It's a very simple setup:

Taylor DN3 w/K&K ----> PADI guitar in (set flat) -----> SA220 (set flat)

vs

Taylor DN3 w/K&K ----> Sansamp Driver DI (either switched off or set flat) -----> SA220 (set flat)

SA220 is providing phantom power to both preamps.

I suppose it's possible the PADI is bad, but that seemed unlikely to me, especially since the high-freq sounds seemed clear.

I also wonder if maybe is has something to do with the guitar itself, it is a very loud acoustic with more low-end resonance than pretty much any guitar I've played, perhaps it's a matter of that + loading being slightly off making something weird happen, I don't know, kinda making stuff up now, though.

Guess I need more DIs to try. I have a Radial ProDI also, but it's only 100k input and passive, not sure that would tell me much, probably would just sound kinda dull and weak would be my guess.

The Sansamp sounds good for right now, so I'm gonna use that for gigs for the time being, but I'm definitely curious as to why the $170 DI I bought sounds so awful. I only arrived at the impedance idea as the only thing I hadn't previously messed with.

[lschwart]

Originally Posted by aclarson

That's the only difference as far as I know, and I'm pretty thorough being a major gear geek, I have a recording studio full of equipment. Also, I didn't really wanna believe it was that, but all evidence points to it. It's a very simple setup:

Taylor DN3 w/K&K ----> PADI guitar in (set flat) -----> SA220 (set flat)

vs

Taylor DN3 w/K&K ----> Sansamp Driver DI (either switched off or set flat) -----> SA220 (set flat)

SA220 is providing phantom power to both preamps.

I suppose it's possible the PADI is bad, but that seemed unlikely to me, especially since the high-freq sounds seemed clear.

I also wonder if maybe is has something to do with the guitar itself, it is a very loud acoustic with more low-end resonance than pretty much any guitar I've played, perhaps it's a matter of that + loading being slightly off making something weird happen, I don't know, kinda making stuff up now, though.

Guess I need more DIs to try. I have a Radial ProDI also, but it's only 100k input and passive, not sure that would tell me much, probably would just sound kinda dull and weak would be my guess.

The Sansamp sounds good for right now, so I'm gonna use that for gigs for the time being, but I'm definitely curious as to why the $170 DI I bought sounds so awful. I only arrived at the impedance idea as the only thing I hadn't previously messed with.

How did you have the gain set on the PADI?

L.

[shawntp]

My Collings OM2h + K&K PWM always gave me wierd issues until I bought a Red Eye Preamp that just made my pickups snap to life.

[ljguitar]

HI folks...

Many of us use these preamps and standard cables (unaltered) without issues.

Comparing the ParaDI to the Sansamp is really two different quality units (the Sansamp being better), and that difference alone could account for differences and erratic behavior.

We are also discussing raw equipment out of context of locations in which they are being set up and operated, which also affects amplification greatly. And it's possible their is something unique with the SA220 rig.

Speakers, just like guitars, are subject to tone shifts depending on the location, design of the room/building, and proximity to walls/corners, floor coverings etc.

Doug Young has already made recordings and demonstrated that wiring up a cable with the resistor makes near-enough-to-zero difference in the recorded sound. Not sure why it would affect the amplified sound...

Also, from personal experience, my best sounding two preamps (DTAR Solstice & Raven PMB) are both 10Kohm input. My Headway EDB has switchable impedance from 1meg ohm to 5meg ohm to 20meg ohm and I can assure you (we tested it thoroughly) you can flip the switch back and forth all day with no affect on anything.

I don't claim to be an expert, but I use 7 different brands of preamps interchangeably with K&K Pure Western mini pickup equipped guitars, without any side effects that simple tweaks cannot correct.

My preamps include:
K&K
DTAR Solstice
Raven PMB
UltraDI Plus & UltraDI Max
Baggs ParaDI

My gigging partner has
Fishman Platinum
Sansamp
Old (very old) simple Fishman preamp (nearly 20 years old)

In addition, our church sound team have several ParaDIs and an UltraSound UltraPlus which we use interchangeably (and the UltraDI have 1meg ohm in).

All of these work just great with K&K equipped rigs, and with under saddle rigs as well. Very full, fat and warm sound through a variety of amps and PA systems.

We could start a war over this, but my take is if you must be absolutely certain everything is impedance matched, purchase the rigs which are already matched. Then at least you have the peace of mind it's all 'kosher'.

If you are not particular, and your rigs are working fine without impedance matching, then enjoy your rigs.

I'd say for the original poster it's essential to impedance match with his new rig. For me it's absolutely non-critical.

I'd bet we could gig together, and the audience would just sit back and enjoy the music totally aware we are each achieving the quality sound we accomplish with different methods.

[Doug Young]

The funny thing about this whole impedance thing is that what people claim is somewhat at odds with the way electronics work. The high impedance (10M) is loading down the K&K *less*, therefore allowing the true sound of the K&K to come thru. It should sound better, one would think. (That's why so many preamps are made to be high impedance - it's a good thing!) As you lower the impedance, you generally get a sort of tone control effect, as the pickup gets loaded down, and in particular, what K&K seems to suggest is that it reduces the bass a bit. That's fine if your guitar has too much bass, but there are these handy controls on most preamps that can be used to adjust things like bass! Cool thing about tone controls is that you can also add bass if that's what you need, or if you have a really good EQ section, do a lot more fine tuning than that - like picking the frequency of the cut or boost on a parametric control. In any case, as long as the input impedance of a preamp is the same or greater than the pickup, the effect of changing impedance should be negligible. Certainly, if you go lower (below 1M in this case), you can hear the effect of impedance (just try plugging a passive pickup like a K&K into a 600 ohm mic input, to hear the effect!), but 1M, 10M, you shouldn't hear any difference. You *might* also hear a difference with a really long, or very low quality guitar cable because high impedances and long cable runs, or high capacitance cables don't work well together.

What generally gets reported is much like this post: someone tries two totally different preamps, and they sound different, and they conclude that the difference must be due to the impedance, ignoring the possibility that it's two completely different circuits from different manufacturers, with different EQ curves, different gain structures and so on. If you want to see how much difference impedance makes, get a preamp like the Headway that has switchable input impedance, so you can change that and *nothing else*, and see if you hear a difference. If you do, please post a recording - it will surely be audible if you can really hear an obvious difference. (In spite of years of internet lore about K&Ks and impedance, no one has yet demonstrated the difference. If you can, please do!) If not, it's possible that the real subject line here should be "Wow, using completely different gear really matters".

[guitaniac]

FWIW, I've found that my Fishman Platinum Pro EQ preamp works much better with the K&K Pure Western mini than does the Baggs PADI. I have no idea why, since both preamps have a 10Mohm input impedance, according to the specs. Its possible that some other factor(s) may be responsible for the PADI's incompatability with the mini-Pure.

[Pnewsom]

I think the name of the game is massaging the output signal of a pickup system to appeal to the amplifier. Do that and you're good to go.

I recently bought a RedEye on the recommendation of some posters on this board. I am very pleased with the results so far.

I recently gigged it with my upright bass equipped with an Underwood pickup and I was able to get fantastic sound out of my regular electric bass amp, an Eden WT550, with 210XLT cabinet. Normally this amp is almost unusable with this bass, and I would be dialing the Eq a lot to suppress feedback, but with The RedEye, I was able to get loads of volume, great bottom, and no boxiness to the sound with amp's controls set flat. Not only that, but it greatly improved my Fender Jazz bass sound as well. I have an Acoustic Image amp that I normally use for upright bass, but it doesn't hold a candle to the power of the Eden rig. My upright sound just got a whole lot better.

At home it has improved the sound of my M1 pickup, and when I get my Pure Mini installed I hope to have good results with it as well.

Very simple effective little DI/preamp with a cool boost switch, and a loop for tuners, Eq, and effects built in. I highly recommend it!

[theotigno]

I'm not sure if this adds anything to the discussion. If not, no worries.

I made a cable a couple of years ago after reading an article on how to match the impedance of an SM57 to your preamp. I made the adjustment to one of the short cables I had and used it ever now and then.

Here's a quick recording I just did that is using:

• The 12-fret guitar I made
• SM58 (a friend of mine has been using my 57)
• Cable (both short, one with a resistor and one without)
• Echo Audiofire 4 (gain turned all the way up)

I compiled them into one WAV file. I have *one* that is just copy and paste. Here is the *other* where I applied a normalize to the tracks.

You should hear a considerable difference in the first. The clip that is using the resistor is the softer passage which falls in the middle. From there, you should also be able to hear an audible difference in the normalized track as well. The impedance matched clip does come in considerably softer as you can hear in the first clip.

Once again, I know that this isn't pickups going into a PA system, but at least it shows the same signal change with one change - the cable. If anything, it was a fun little experiment before going into work

[Doug Young]

Originally Posted by theotigno

The impedance matched clip does come in considerably softer as you can hear in the first clip.

Impedance matching should not by itself make something "softer". But I imagine the effect of your resistor was to alter the gain, so you have less volume. What people claim, at least in the case of the K&K, is a change in tone, not volume. To compare tone, you have to match levels - otherwise the Fletcher Munson curves in our ears play tricks, basically applying different EQ curves in our brains to the 2 different signals. I'm not clear on what you did with the normalized track, did you match the levels of the two different takes? Normalizing isn't guaranteed to really match levels, unfortunately. All it takes is one small peak in one take that isn't there in the other, to throw the whole thing off. Actually level matching 2 different takes, especially ones with different tone or some other change in character, and doing it in a "fair" way is a bit tricky.

[aclarson]

Thanks everyone for the replies so far. I suppose it may be fair to say that I haven't tried an adequate number of different preamps/DIs to say with certainty it's the impedance thing, but for the life of me, I wouldn't expect two active DIs set flat to have a radically different tonal response to my guitar, I mean, they're both supposed to provide clean gain with minimum affect on frequency response. The PADI clearly has significantly more low-end than the Sansamp (in an undesirable way), and the Sansamp just sounds nice and perfectly balanced; much like I would expect from what I've heard from the guitar on other systems, only better.

I can get the PADI to sound ok with a siginificant amount of EQ, but I personally feel if I have to EQ the crap out of it, then something isn't right. Every time you EQ something, you introduce phase shift that will inevitably have some negative affect on some part of your signal. It may be minimal, but if I can avoid this, then that would be ideal. To me, the perfect setup would be no EQ at all. I realize the reality of the circumstances usually dictates some EQ, and having some flexibility for various rooms/venues is pretty key for consistency of tone from room to room, but if I have to peg any of the knobs, then to me, something is not right.

I did play around with the gain on PADI, trying it at all extremes, but it didn't seem to matter too much, by default I set it at 0, but I spent a fair amount of time with it backed off in case I was overdriving the SA220 input. There is a clip light on the SA220, but I have yet to see it light, I know it's possible to slightly clip something without the light turning on, but I continued to back off the gain and still had the annoying sound.

By the way, the room I'm using this in is an acoustically treated recording and rehearsal studio, I have around (20) 2' x 4' rockwool absorbers that are 4" thick. While it is not a huge major label recording studio designed by an acoustical engineer, I find the room to be very well-tamed on reflections and flatter than most rooms. I don't believe what I'm experiencing is due to the room, though my perception of the problems may be enhanced by being in a room with decent acoustics.

I read some stuff about some people trying a Boss TU-2 in front of the PADI to give it the 1M input. It just so happens I have one of these lying around, so maybe I'll give that a try later. Also, my friend has a Behringer ADI21 with a 4.7M input impedance, so maybe I'll try these out later when I get to the studio.