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Impedance Matching - is it actually important?
Old 24th January 2007
  #1
Here for the gear
 

Impedance Matching - is it actually important?

o does anyone know much about impedance matching and whether its particularly important when Re-Amping signals?


For instance, Say you've got a Synth track in your DAW (Cubase, Logic etc) and youwant to run it out of the computer and through some old Guitar FX Stomp Box or through a Guitar Amp and then record the results back into the Daw.

Currently I'm just going:

DAW/Soundcard Track -> Mixer Channel --> Mixer Send --> FX Box / Amp --> Mixer Channel --> Soundcard/DAW

so the thing is the Mixer Send is outputting a High Level, Low Impedance signal but really the Guitar FX and/or Guitar Amp are expecting a Low Level, High Impedance signal.

Should I use a ReAmp box before the FX Box? (They seem rather expensive)

What are the problems with not doing it?
Old 24th January 2007
  #2
Gear Maniac
 
theoryinmotion's Avatar
 

I personally can't see any reason.
Give it a try, not like you fry the inputs or anything...the real issue is that the guitarFX may distort the audio.....if it doesn't distort then go for it.
Old 24th January 2007
  #3
Here for the gear
 

Well yeah I am doing it that way at the moment.

However sometimes i find it sounds a bit "funny". (yes thats a Technical term )

The question is whether it would make a difference?

Why does it matter the other way around? why do you need a DI to get a good tone form a guitar (when not using an AMP)?
Old 24th January 2007
  #4
Lives for gear
 
pounce's Avatar
 

well, yes impedence is important.

basically, impedence is frequency specific resistence. getting something like a reamping box or DI or something in the path may be a big help. obviously, you are running through all that stuff to create a certain sound. but if the synths sound funny because of stuff like impedence, you are removing some of the benefit of the process. get the impedence right and you might be in business again, which would be good.
Old 24th January 2007
  #5
Gear Head
 

I find that with improper impedance, the pedals/amps still work but are a hell of a lot noisier. sometimes to the point of not being useful. i recently rewired my whole guitar pedal board and took a lot of care with power distro. and signal matching and my noise floor dropped an incredible 24dB odd.... depends on whether you can stand the imperfections in an unmatched signal.
Old 24th January 2007
  #6
Gear Maniac
 
theoryinmotion's Avatar
 

Found this in a manual from a isntalled audio company.


"Some folks seem to believe that balanced/unbalanced lines and impedances are related; or even worse that they are associated
with a particular type of connector. Not so. Unbalanced signals are not necessarily high-impedance and balanced signals/
lines are not necessarily low-impedance. Similarly, although 1/4-inch jacks are typically used for things like guitars (which are high-impedance and unbalanced), this does not predispose them to only this usage. After all, 1/4 inch jacks are sometimes used for loudspeakers, which are anything but high-impedance. Therefore, the presence of 3-pin XLR connectors should not be construed to mean that the input or output is low-impedance (or high‑impedance). The same applies to 1/4‑inch jacks.
So, what is really important? Signal level, and (to a much lesser degree), the impedance relation between an output (signal source) and the input that it connects to (signal receiver).
Signal level is very important. Mismatch causes either loss of headroom or loss of signal-to-noise ratio. Thus, microphone inputs
should only see signals originating from a microphone, a direct (DI) box, or an output designated microphone-level output. Electrically, this is in the range of approximately -70 to -20 dBm. Line inputs should only see signals in the -10 to +24 dBm/dBu range. Guitars, high-impedance microphones, and many electronic keyboards do not qualify as line-level sources.
The impedance relation between outputs and inputs needs to be considered, but only in the following way:
Always make sure that a device’s input impedance is higher than the output source impedance of the device that drives it.
Some manufacturers state a relatively high-impedance figure as the output impedance of their equipment. What they really mean is that this is the minimum load impedance that they would like their gear to see. In most cases, seeing a output impedance
figure of 10,000 (10K) ohms or higher from modern equipment that requires power (batteries or AC) is an instance of this type of rating. If so, then the input impedance of the succeeding input must be equal to or greater than the output impedance of the driving device."


Hope that helps
Old 24th January 2007
  #7
Here for the gear
 

Quote:
the impedance relation between outputs and inputs needs to be considered, but only in the following way:
Always make sure that a device’s input impedance is higher than the output source impedance of the device that drives it.
ok. so to me this would imply that as a guitar is high impedance / Low signal then guitar gear must have a high impedance.

thus it will always be of a higher than a line level signal from a mixer / keyboard. so it should be ok.

Thanks!
hey do you have the source?
Old 24th January 2007
  #8
Here for the gear
 

Well ok i found something else as well:
http://www.tape.com/cgi-bin/SoftCart...2923+995498793


Quote:
I'M CONNECTING TWO AUDIO DEVICES. IS IT IMPORTANT TO MATCH THEIR IMPEDANCES? WHAT HAPPENS IF I DON'T?
First some definitions. When you connect two devices, one is
the source and one is the load. The source is the device that
puts out a signal. The load is the device you are feeding the
signal into. The source has a certain output impedance, and the
load has a certain input impedance.
A few decades ago in the vacuum tube era, it was important to
match the output impedance of the source to the input impedance
of the load. Usually the source and load impedances were both
600 ohms. If the source impedance equals the load impedance,
this is called "matching" impedances. It results in maximum
POWER transfer from the source to the load.
In contrast, suppose the source is low Z and the load is high
Z. If the load impedance is 10 times or more the source
impedance, it is called a "bridging" impedance. Bridging results
in maximum VOLTAGE transfer from the source to the load.
Nowadays, nearly all devices are connected bridging -- low-Z out
to high-Z in -- because we want the most voltage transferred
between components.
If you connect a low-Z source to a high-Z load, there is no
distortion or frequency-response change caused by this
connection. But if you connect a high-Z source to a low-Z load,
you might get distortion or altered response. For example,
suppose you connect an electric bass guitar (a high-Z device)
into an XLR-type mic input (a low-Z load). The low frequencies
in the signal will roll off, so the bass will sound thin.
We want the bass guitar to be loaded by a high impedance, and
we want the mic input to be fed by a low-impedance signal. A
direct box or impedance-matching adapter does this. Such
adapters are available from Radio Shack.
The adapter is a tube with a phone jack on one end and a male
XLR connector on the other. Inside the tube is a transformer.
Its primary winding is high Z, wired to the phone jack. The
transformer's secondary winding is low Z, wired to the XLR. You
plug the guitar cord into the phone jack, and plug the XLR into a
mic input in a snake or mixer. Use it with a bass guitar,
electric guitar, or synth.
This impedance-matching adapter works, but is not ideal. The
load it presents to the bass guitar might be 12 kilohms, which
will slighly load down the high-Z guitar pickup, causing thin
bass.
An active direct box solves this problem. In place of a
transformer, the active DI usually has an FET (Field Effect
Transistor). The FET has a very high input impedance that does
not load down the bass guitar.
Old 25th January 2007
  #9
Gear Maniac
 
theoryinmotion's Avatar
 

Sure, Symetrix Inc user manual for the 528e - page 25 of the pdf I believe.....
you can find it at www.symetrixaudio.com
Old 25th January 2007
  #10
Lives for gear
 
Tibbon's Avatar
You generally don't want to match impedence with modern equipment.
Old 30th May 2018
  #11
Gear Head
 

I just 'DI' from the SEND of the FX LOOP or use a Y-SPLITTER from the guitar or pedal to record

I then output from the headphone jack of my MultiTrack into a miced Amp/Cab...

Am I doing something WRONG?
Old 30th May 2018
  #12
Gear Guru
 
fiddlestickz's Avatar
11 year necro revival, cool...!!
Old 30th May 2018
  #13
Woah! Big time OG necro!

Here is the deal. Does it matter? Sometimes. I know a fair amount of people just blast guitar pedals with hot synth or DAW output signals, and attempt to attenuate the signal in some way. This can be achieved sometimes by simply turning the gain down on the synth, or hitting a mixer and attenuating on the channel fader. Often, everything is cool, no problems.

What can happen at times IME, is a signifigant anount of noise will come into play. Most often, this occurs with pedals that are very gain dependent like distortion or overdirve pedals, sometimes a little noise isn’t a big deal in this situation, but sometimes it sounds like crap. It also can get real annoying with pedals clipping.

Here’s my thing. I have thousands of dollars in HW synthesizers, several pricey guitar pedals, expensivie wires, hi-end convertors, all of this fancy gear, and always hoping to make the best possible recordings while listening through my quality monitors in my treated listening environment. So why is it always a question about whether I’m going to buy a hundred dollar reamp box to ensure that I’m going to get the very best out of my guitar FX?

Its a no brainer. Sometimes it doesn’t matter much, sometimes it matters A LOT. It depends on the signal strength, the type of patch, be it a plucky bass, or a smooth pad......so just buy a reamp and be done. You never have to worry again about impedance mismatch, clipping, or any problems.

I’ve never been big about bringing audio out of the computer, and going back in. However, sometimes using an analog fuzz or dirty analog delay on a softsynth can sound quite nice, and in the end, thats all that matters.

I have a Radial Reamp, and Pigtronic Keymaster. Both do the job fine, but the Keymaster allows for two sends serial/parallel, or I can do a stereo out of the DAW and run a drum bus or something like that, into an overdrive to give it a little something extra.

They make passive ones, active ones, ones with fx loops, and even multichannel ones. If you enjoy guitar pedals, I think anybody should have one.

Certain really popular pedals, like the RE-201 or to a lesser extent, El Capstan, can both clip rather easily. This will put a stop to that, and ensure you are getting the very best out of your pedals, by affording them with the appropriate amount of headroom to function optimally.
Old 30th May 2018
  #14
Gear Head
 

Quote:
Originally Posted by fiddlestickz View Post
11 year necro revival, cool...!!
;-p
That's how I roll..!!

(Have to admit, though, it DID get me to thinking/make me paranoid -delete where applicable!- that I might be making a glaring error!?

I mean, I certainly DO use DI boxes on stage but when ReAmping recordings I try to use as little as possible in the signal path)
Old 30th May 2018
  #15
Gear Guru
 
fiddlestickz's Avatar
Quote:
Originally Posted by merseymale View Post
;-p
That's how I roll..!!

(Have to admit, though, it DID get me to thinking/make me paranoid -delete where applicable!- that I might be making a glaring error!?

I mean, I certainly DO use DI boxes on stage but when ReAmping recordings I try to use as little as possible in the signal path)
that's what forums are for don't sweat it, ask questions to things you want to know, ignore the idiots and take your answers and learn your craft.
Old 4th June 2018
  #16
Gear Head
 

Thanks Fiddlestickz
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