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Input Impendance Question
Hi,
I have a question to the electronics guys here. Let´s say I have a K&K PWM and a Schertler Jam 100. The K&K wants to see 1mOhm input impendance but the Schertler high-z inputs have 47kOhm. What I read here several times is that many people just solder a 1mOhm resistor into the guitar cable from tip to ground. I think in this case it wouldn´t change anything because the two resistors are now parallel which means the resulting resistance will be less than 47kOhm. I think that 1mOhm should just be soldered to the lead of the jack but not to ground so that a series connection of the resistors is established. Am I right or am I not seeing something here?
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Goodall Grand Concert Italian spruce/EIR Taylor GS-mini mahogany In process of construction: 0-12 (own build) |
#2
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Quote:
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James May Audio Sprockets maker of ToneDexter James May Engineering maker of the Ultra Tonic Pickup |
#3
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Okay, so what would be the best solution in this situation?
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Goodall Grand Concert Italian spruce/EIR Taylor GS-mini mahogany In process of construction: 0-12 (own build) |
#4
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K&K works well with anything from 400 to 1mOhm. This is from their own documentation. My advice... Do nothing. It probably won't sound any better (or possible any different at all) with a 500 kOhm change.
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"Lift your head and smile at trouble. You'll find happiness someday." |
#5
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An easier solution may be to add an active enpin preamp to your Pure Mini as I've never heard of a high-z input only being 47kohm. I've heard anything over 500k is sufficient for most passive pickups but 47k is pretty chill. To James' point, adding a resistor will attenuate your signal so your next best option (to me) besides changing the Schertler is preamping your signal before it reaches it. An endpin preamp or beltclip unit should buffer it enough to reduce any impedance issues.
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Alvarez MC90 Guild GAD-50 w/Seymour Duncan Mag Mic Taylor 352ce Taylor 514ce Zoom AC3 https://linktr.ee/erikjmusic |
#6
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Attenuation and frequency response are the only two things you can change by messing around with resistors - What is the objective you want to achieve?
Personally, I wouldn't do anything to it. |
#7
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Totally agree. All this impedance talk is mostly the Emperor's New Clothes. Plug it in and play...I bet it sounds killer.
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2017 Alvarez Yairi OY70CE - Sugaree c.1966 Regal Sovereign R235 Jumbo - Old Dollar 2009 Martin 000-15 - Brown Bella 1977 Gibson MK-35 - Apollo 2004 Fender American Stratocaster - The Blue Max 2017 Fender Custom American Telecaster - Brown Sugar Think Hippie Thoughts... |
#8
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you mean from 400 Ohms or from 400 kOhms?
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Goodall Grand Concert Italian spruce/EIR Taylor GS-mini mahogany In process of construction: 0-12 (own build) |
#9
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Input Impendance Question
K ohms. Typing on phone. Sorry. Also, I thought you said your amp was 470 kOhm, not 47 kOhm. I was on the go. If you want to match impedance you’ll probably need an active/preamp or DI. However, I think Schertler is supposed to sound very good with K&K straight in.
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"Lift your head and smile at trouble. You'll find happiness someday." Last edited by martingitdave; 01-03-2018 at 02:47 PM. |
#10
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47K ohms is unlikely to sound good with K&K. People who try the resistor trick are trying to lower a 10 M impedance down to K&K's claimed 1M. In reality, anything over 500K or so will work fine with K&K (including 10M or even 20M) in my experience. However, below 500K you will start hearing low end roll off. 47K is likely to be pretty thin sounding. This amp would work fine with active pickups that have low impedance outputs, it's unlikely to sound good with a passive piezo. Of course, depending on what you like, you never know. Some people's objection to K&Ks is too much bass, and 47K would definitely solve that!
BTW, here's an impedance test I did a while back with various impedances. I don't have a 47K example, but I have 330K and 10K. 47K would be in-between, closer to the 10K. (10K is the 3rd sample in the list) impedance sequence: 1M, 10M, 10K, 1M, 20M, 330K
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#11
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Such a low input impedance on the "High-Z" inputs on an amp designed to be used with amplified acoustic guitars seems like an odd design choice, given that many guitars have passive piezo pickups that wouldn't sound good into an input like that. Are we sure that that's actually the right figure for the input? I can't get clear information poking around on line, but several sources indicate that the high-z inputs have a "bootstrap" design that adapts the impedance to the nature of the signal.
Bottom line: try it first. If it sounds good, it's likely because it's designed to work properly with a signal like the one that comes from a K&K mini. It would be odd if it weren't so designed--although it's possible, I suppose. If it does sound bad, and you don't want to get a different amp, get a preamp or EQ pedal with at least a 1mOhm impedance to buffer the signal. Or a DI box to go into one of the mic inputs. Louis |
#12
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I do find it to be telling when a company doesn't provide good specs. I know Schertler is a reputable company, but pro-quality gear generally provides detailed specs. When I see specs that only say things like "high impedance", a voice whispers "run the other way". (I have heard good things about the Jam 100's tho - they appear to be nice amps)
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#13
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Louis |
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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)
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i got tired of updating my guitars. Last edited by SalFromChatham; 01-03-2018 at 09:48 PM. |
#15
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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).
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