Input Impendance Question

[Spook]

At first I thought.. no way.. has to be a 1MOhm input. I even looked up the manual. You're absolutely correct of course. 47KOhm is the 'High' in. Odd. And I think the consequence is that you need another box to go with it.

If I were you I would get a preamp with the appropriate input impedance and a line out (stereo level) output. Drive the Schertler 100 with the line out from the preamp. You really don't want big impedance mismatches.

[Schau_ins_Regal]

Originally Posted by Spook

At first I thought.. no way.. has to be a 1MOhm input. I even looked up the manual. You're absolutely correct of course. 47KOhm is the 'High' in. Odd. And I think the consequence is that you need another box to go with it.

Yes, I also checked the manual for that. Thought there may be a way to match this without a preamp.

When using a resistor... can´t the 27db attentuator be compansated by just turning up the volume of this channel? Or what problems do occur?

[varmonter]

if one was to go through a di box and use
the amp out on the box to the hi z input of
the jam 100 amp would this effect the input impedance
or is that only the XLR out of a Di that alters
the impedance..??

[SalFromChatham]

Originally Posted by Doug Young

The effects of impedance on passive piezo pickups is absolutely real. But people often get confused about it, and there seems to be a bit of marketing designed to confuse people. James May posted one of the clearest technical descriptions I've seen here recently, so it's worth looking that up. But for K&K's, it's pretty simple, and comes down to anything above around 500K (+/-) is fine, including the 1M, 5M, 10M, 20M, etc. Below 500K or so, you start losing low end. Above that, it makes no discernable difference (you might want to be careful with very long, low quality cables at very high impedances, tho). There are lots of anecdotal reports that contradict that, but it's always with different preamps, different brands, different gain structures, etc. It's not surprising that different products sound different, but there's more to preamps than impedance, and two different designs are, well, different. Get a preamp with variable impedance, like the Grace Felix, and you will be able to compare apples to apples and see when impedance matters and and when it doesn't without changing 100 other variables at the same time.

Of course in the end, it all comes down to "does product X sound good to me". I've yet to encounter a preamp or amp that sounds noticably "bad" with a K&K. Some seem to sound better (with any pickup), but I've never seen anything to indicate that the reason was impedance (unless the impedance was very low, like 47K).

Doug... I cant debate your expertise and I will defer to it. I can say that my J50 K&K through a Baggs Venue made it BOOM. Too much drive/bass ... Switching to the FireEye was a big difference. I am not an engineer. I suppose I cant even say if my experience is perception or reality. I suspect reality, bt not willing to go to the mat i guess...

Cheers

[Woodstock School Of Music]

Originally Posted by themissal

I definitely am one who does not believe the k&k impedance issue is nothing. I have two k&k guitars, I gig in bars with them, and their sound is fantastic with the right setup.

Choices?

1. K&k preamps
2. Fire eye red eye preamp
3. Used older Boss Tuner pedal. $50 or a used TU-3Wazacraft ($80)

I also notice a big difference when I plug my K&K guitars straight into the mixer vs going through my Redeye. Plugged into the Redeye it sounds good right away, plugged into the wrong source not so much.

Some people say the K&K sounds good plugged into anything but that has not been my experience.

[lschwart]

Originally Posted by Schau_ins_Regal

Yes, I also checked the manual for that. Thought there may be a way to match this without a preamp.

When using a resistor... can´t the 27db attentuator be compansated by just turning up the volume of this channel? Or what problems do occur?

It's likely to be very noisy. But how does it sound going straight into one of the high-z inputs on the amp? Is there an actual problem you're trying to solve?

Louis

[Big Band Guitar]

Impedance matching is all about power transfer. When matched maximum power is transferred.

In the extreme the power line coming into your house has a extremely low impedance. If you were to match the same impedance with your toaster it would consume all the power the power company has to offer. One huge flash bulb. Plus the existing power lines would also vaporize. That is the extreme. In reality your toaster has a impedance many orders of magnitude higher than the power line so it just toasts your bread.

In general low impedance power source (your guitar) into a high impedance input ( your amp ). is good. the other way around not so good.

With all that said try whatever you want if you like the "sound" keep it.

[MrErikJ]

Originally Posted by themissal

Doug... I cant debate your expertise and I will defer to it. I can say that my J50 K&K through a Baggs Venue made it BOOM. Too much drive/bass ... Switching to the FireEye was a big difference. I am not an engineer. I suppose I cant even say if my experience is perception or reality. I suspect reality, bt not willing to go to the mat i guess...

Cheers

I think Doug's point is not that you're incorrect in your assessment but that the difference you're observing is not due to impedance. High-impedance is high-impedance, whether is it's 1m or 10m, it's pretty inconsequential to a passive piezo. The difference you're hearing is probably due to the nature of that preamp and not its input impedance. I've heard many people say that the Para DI is too muddy with the K&K and blame the impedance, when in reality, it's probably because that preamp was designed with the Baggs LB6 and Ribbon Transducer in mind, not a K&K Pure Mini. The Venue is mostly the same as the Para but with more features, so it would make sense those issues would apply there.

Many people really like a Fire Eye with a K&K and I'm sure they are a great complement, but it's probably due to the preamp's voicing and not its input impedance. Many people also like the Tonebone PZ Deluxe and PZ Pre with the K&K and it also has a 10mohm input impedance, but unlike the Baggs, it's designed to be very neutral and clear in its sound. It isn't trying to warm-up a bright sounding pickup.

Impedance mismatch refers to running something high-impedance into an input that's low-impedance, not running high-impedance into something marginally more or less high-impedance. Once you get in the high-impedance realm, it's more or less the same.

[sdelsolray]

Originally Posted by MrErikJ

...
Impedance mismatch refers to running something high-impedance into an input that's low-impedance, not running high-impedance into something marginally more or less high-impedance. Once you get in the high-impedance realm, it's more or less the same.

To add to this, there are two categories involving impedance:

1) Matching Impedance: This involves signal transmission which requires identical impedance values between two units. Early analog telephones did this (600 Ohms). In modern settings, this "matching" is found when connecting digital devices, such as 75 Ohms for wordclock or SPDIF or 110 Ohms for AES3 (aka AES/EBU). Both the source output and the input load must match, i.e., have identical impedance, in order for the circuit to work as designed.

2) Bridging Impedance: This is different and involves feeding a lower impedance source output into much higher input load impedance, usually at a minimum of a 1 to 5 ratio. Most connections in a studio or in sound reinforcement involve bridging impedance. For example, a mic with an output impedance of 300 Ohms should be connected to a preamp with an input impedance of at least 1,500 Ohms. There is no "matching impedance" here. Running a mic at 300 Ohms into a preamp input of 300 Ohms will not work well.


All impedance discussions involving passive pickups (such as the K&K mini) connecting to a preamp involve bridging impedance, not matching impedance.

To complicate things a bit, passive pickups have a variable output impedance, depending on the specific frequency and to some extent upon amplitude. The K&K mini has variable output impedance in the range of thousands of Ohms to over a 100,000 Ohms. This is a "high impedance" source. Applying bridging impedance discussed above, the input receiving that signal should have an input impedance at least 5 times higher than the highest output impedance of the pickup, which is why the suggestion of 1,000,000 Ohms is used.

[martingitdave]

Originally Posted by sdelsolray

To add to this, there are two categories involving impedance:



1) Matching Impedance: This involves signal transmission which requires identical impedance values between two units. Early analog telephones did this (600 Ohms). In modern settings, this "matching" is found when connecting digital devices, such as 75 Ohms for wordclock or SPDIF or 110 Ohms for AES3 (aka AES/EBU). Both the source output and the input load must match, i.e., have identical impedance, in order for the circuit to work as designed.



2) Bridging Impedance: This is different and involves feeding a lower impedance source output into much higher input load impedance, usually at a minimum of a 1 to 5 ratio. Most connections in a studio or in sound reinforcement involve bridging impedance. For example, a mic with an output impedance of 300 Ohms should be connected to a preamp with an input impedance of at least 1,500 Ohms. There is no "matching impedance" here. Running a mic at 300 Ohms into a preamp input of 300 Ohms will not work well.





All impedance discussions involving passive pickups (such as the K&K mini) connecting to a preamp involve bridging impedance, not matching impedance.



To complicate things a bit, passive pickups have a variable output impedance, depending on the specific frequency and to some extent upon amplitude. The K&K mini has variable output impedance in the range of thousands of Ohms to over a 100,000 Ohms. This is a "high impedance" source. Applying bridging impedance discussed above, the input receiving that signal should have an input impedance at least 5 times higher than the highest output impedance of the pickup, which is why the suggestion of 1,000,000 Ohms is used.

Excellent post!

[Doug Young]

Originally Posted by MrErikJ

I think Doug's point is not that you're incorrect in your assessment but that the difference you're observing is not due to impedance.

Exactly. Different gear sounds different. Trying to figure out why gets trickier, and assuming it's only due to impedance is likely not the answer, unless you're down in the range where it matters (very low impedances). You can do tests where you change only impedance, using preamps that support variable or switchable impedance, so that all the other variables are kept constant. There you are changing only one factor, and you can hear what the effect of impedance is, without any other factors to confuse things (I posted a recording of one example - and there are differences with some values - check it out).

When you compare a PADI vs a Red-Eye, you're getting many other variables, and it's hard to say why you might prefer one over the other. I have never used a PADI, so I have no thoughts on it. I do have a Red-Eye and it sounds quite nice to me, but I suspect it's the clarity, simple clean circuit, and the treble control, which is very effective (tho that's just a guess - who knows why it sounds good). But I have a bunch of other preamps, Venue, Felix, SPS-1, Raven Labs PMB-1, all of which also work great with K&Ks even tho they have different impedances.

[gfsark]

Interesting discussion. My limited experience is that my K&K equipped guitar always sounds better when run through a preamp. For small gigs, I run straight into a Fishman Mini, which sounds good, but when I’ve used a better external preamp (T1) it always sounds better. Probably because the external preamp is more capable than the onboard preamp that comes with the mini.