27 May
2008
27 May
'08
3:05 p.m.
Hello.
I often run the PA system for my CU at uni. So far we've been using
jack-jack leads to connect guitars to the desk. However, my Dad has
recently started using jack-XLR leads at my home church and says that
it's much better.
After a very long conversation and lots of googling (which incidentally
provides no info at all on the subject), I'm now completely confused.
Are guitars mic or line or what?
The rationale for using jack-XLR leads and connecting to the mic input
on the desk is that guitars have mics in them so they are mic level.
Apparently the battery unit in the guitar doesn't make it line level,
but I'm not convinced.
The other thing I don't understand is that if that is the case, why do
people use DI boxes? A DI box takes a high impedance (line level - I
think) input and converts it to low impedance output (mic level). If the
guitar is mic level already then what's the point?
Please, could someone shed some light on this because I'm now very confused.
Thanks in advance.
Simon
27 May
27 May
3:16 p.m.
On Tue, 27 May 2008 20:01:43 +0100
Simon Williams <simon(a)systemparadox.co.uk> wrote:
Hello.
I often run the PA system for my CU at uni. So far we've been using
jack-jack leads to connect guitars to the desk. However, my Dad has
recently started using jack-XLR leads at my home church and says that
it's much better.
After a very long conversation and lots of googling (which incidentally
provides no info at all on the subject), I'm now completely confused.
Are guitars mic or line or what?
The rationale for using jack-XLR leads and connecting to the mic input
on the desk is that guitars have mics in them so they are mic level.
Apparently the battery unit in the guitar doesn't make it line level,
but I'm not convinced.
The other thing I don't understand is that if that is the case, why do
people use DI boxes? A DI box takes a high impedance (line level - I
think) input and converts it to low impedance output (mic level). If the
guitar is mic level already then what's the point?
Please, could someone shed some light on this because I'm now very confused.
Thanks in advance.
Simon
Hmmm, can of worms!
A 'raw' guitar pickup gives typically 50-100mV and is generally
regarded as 'high impedance' (that raises many points of contention in
itself), but with built in amplification/processing could be a lot more.
Line level is usually between 500mV and 1V. The nearest you get to a
standard is 775mV in 600ohm, or 1mW.
Microphones vary enormously depending on type, built-in amplification
etc. and can be anywhere between 1-100mV.
So as you can see, there is no simple answer. Welcome to the world of
audio 'standards' :)
--
Will J Godfrey
http://www.musically.me.uk
3:18 p.m.
They are unbalanced Hi-Z (High impedance). Its a different animal
altogether.
Thats why many interfaces have a separate guitar mode/switch.
-Chris
2008/5/27 Simon Williams <simon(a)systemparadox.co.uk>uk>:
Hello.
I often run the PA system for my CU at uni. So far we've been using
jack-jack leads to connect guitars to the desk. However, my Dad has
recently started using jack-XLR leads at my home church and says that
it's much better.
After a very long conversation and lots of googling (which incidentally
provides no info at all on the subject), I'm now completely confused.
Are guitars mic or line or what?
The rationale for using jack-XLR leads and connecting to the mic input
on the desk is that guitars have mics in them so they are mic level.
Apparently the battery unit in the guitar doesn't make it line level,
but I'm not convinced.
The other thing I don't understand is that if that is the case, why do
people use DI boxes? A DI box takes a high impedance (line level - I
think) input and converts it to low impedance output (mic level). If the
guitar is mic level already then what's the point?
Please, could someone shed some light on this because I'm now very
confused.
Thanks in advance.
Simon
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http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
3:50 p.m.
Back on Tuesday 27 May 2008, Simon Williams was like:
Hello.
I often run the PA system for my CU at uni. So far we've been using
jack-jack leads to connect guitars to the desk. However, my Dad has
recently started using jack-XLR leads at my home church and says that
it's much better.
After a very long conversation and lots of googling (which incidentally
provides no info at all on the subject), I'm now completely confused.
Are guitars mic or line or what?
Hi-Z Line level. (The output level can vary quite drastically depending on the
type of pickup though)
The rationale for using jack-XLR leads and connecting to the mic input
on the desk is that guitars have mics in them so they are mic level.
Apparently the battery unit in the guitar doesn't make it line level,
but I'm not convinced.
A battery is for active pickups. Pickups that don't need batteries are
passive.
The other thing I don't understand is that if that is the case, why do
people use DI boxes? A DI box takes a high impedance (line level - I
think) input and converts it to low impedance output (mic level). If the
guitar is mic level already then what's the point?
The DI converts a line level (regardless of impedance level) signal to Low-Z
mic level. The reason for this is that line level signals can't travel long
distances without degrading, but Low-Z mic level signals can go much much
further. I wouldn't run a -10 dBu signal much futher than 20 feet. (A +4 dBu
line level signal can go quite a long distance though) Most sources like
keyboards are -10 dBu though, and levels on guitars can be all over the
place.
A DI is used because it can take a wide range of signal levels and change them
all to a uniform Low-Z mic level signal that can travel a long distance.
They also usually have a ground lift switch for when your FOH and Stage power
are sourced to different grounds to prevent ground loops. (The hum you
sometimes get when plugging in a guitar or keyboard) Some can be placed in
between a head-amp and cabnet. Some have pad switches. Some are active, some
are passive. Some are crap. (I'm talking about you, Behringer)
Please, could someone shed some light on this because I'm now very
confused.
I wouldn't recommend plugging into a line jack, or a mic preamp. Both can be
made to work, and both can be a mess. I would recommend getting DI boxes.
The cheap ones that still work good, are the passive IMP DI boxes made by
Whirlwind. (~ $40)
I prefer active DI boxes because they have a better frequency response, but
they cost quite a bit more.
I recommend:
BSS AR-133 - Great for keyboards because of the pad switch
Countryman Type-85 - Great for guitars because they can also go in between the
amp and cabnet. They're also indestructible.
Anything made by Radial.
-Reuben
Thanks in advance.
Simon
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4:20 p.m.
On Tue, May 27, 2008 at 02:49:29PM -0500, Reuben Martin wrote:
Back on Tuesday 27 May 2008, Simon Williams was like:
Well, I'd say they are neither. Typical levels for a guitar are
well below standard line level, and on many pro equipment the
line input Z could well be as low as 10k so, which is too low
for a guitar. It can work, but the sound won't be the same.
This is because the impedance of a typical guitar is not only
high but also inductive, and in many cases (depending on the
setting of the controls on the guitar) this can resonates in
the audio band with the capacitance of the cable. Connecting
it to a medium Z line input will kill that resonance. Guitars
expect at least a few hundred k.
Use an active DI-box, in particular if the guitar output has
to be split for a guitar amp as well.
The only reason why guitars are as they are is historical.
The first ones were built at at time there were only tube
amps. This can easiliy have an high imput impedance. Making
the pickup high-Z enabled it to produce an higher output
voltage, and require one tube less in the amplifier. For
the same reason you could buy high-Z mics 50 years ago.
These would be hard to find today. Guitars are unbalanced
also only because it's cheaper.
Today (and for the last 30 years) it would be perfectly
possible to make guitars low-Z, balanced, and compatible
with a normal mic input. It would save all of us a lot of
trouble, and would also allow for phantom-powered active
electronics in the guitar. So why didn't this happen ?
Because a guitar manufacturer would push himself out of
the market by doing it. People expect any guitar to work
with existing guitar amps.
Ciao,
--
FA
Laboratorio di Acustica ed Elettroacustica
Parma, Italia
Lascia la spina, cogli la rosa.
Are guitars mic or line or what?
Hi-Z Line level. (The output level can vary quite drastically depending on the
type of pickup though)
5:03 p.m.
Fons Adriaensen wrote:
On Tue, May 27, 2008 at 02:49:29PM -0500, Reuben
Martin wrote:
> Back on Tuesday 27 May 2008, Simon Williams was
like:
lol Reuben- what mail client do you use?
Well, I'd say they are neither. Typical levels for
a guitar are
well below standard line level, and on many pro equipment the
line input Z could well be as low as 10k so, which is too low
for a guitar. It can work, but the sound won't be the same.
This is because the impedance of a typical guitar is not only
high but also inductive, and in many cases (depending on the
setting of the controls on the guitar) this can resonates in
the audio band with the capacitance of the cable. Connecting
it to a medium Z line input will kill that resonance. Guitars
expect at least a few hundred k.
Ok that explains that.
Use an active DI-box, in particular if the guitar
output has
to be split for a guitar amp as well.
What if I can't afford DI-boxes? Which is best to use?
Thanks.
Simon
5:30 p.m.
On Tue, May 27, 2008 at 11:00 PM, Simon Williams <simon(a)systemparadox.co.uk>
wrote:
A DI-box is a really small investment.
The cheapest one my regular music store carries is Alto DI-1 (about $67 USD)
and Zzsounds have a Behringer GI100 Ultra G for $35 USD. You can also check
the classifieds.
--
Anders Dahnielson
<anders(a)dahnielson.com>
Use an active DI-box, in particular if the guitar
output has
to be split for a guitar amp as well.
What if I can't afford DI-boxes? Which is best to use?
5:46 p.m.
On 27/05/08 22:00:15, Simon Williams wrote:
What if I can't afford DI-boxes? Which is best to
use?
I would try it, listen and decide.
The other possibilty - if the guitarist has a guitar amp and you have a
spare microphone you could mic the guitar amp. Many guitarists like
this approach anyway because they chose a guitar and amp that sound
good together and that's the sound they would like to hear recorded (or
amplified further for FOH).
Steve.
6:05 p.m.
Back on Tuesday 27 May 2008, Simon Williams was like:
There's really no good way to get around using DI boxes. If you google for
IMP2 Whirlwind boxes you will find places selling them for 39.99. That's
really not a bad deal if you're strapped for cash.
-Reuben
Fons Adriaensen wrote:
Kontact / Kmail
On Tue, May 27, 2008 at 02:49:29PM -0500, Reuben
Martin wrote:
> Back on Tuesday 27 May 2008, Simon Williams was like:
lol Reuben- what mail client do you use? Well, I'd say they are neither. Typical
levels for a guitar are
well below standard line level, and on many pro equipment the
line input Z could well be as low as 10k so, which is too low
for a guitar. It can work, but the sound won't be the same.
This is because the impedance of a typical guitar is not only
high but also inductive, and in many cases (depending on the
setting of the controls on the guitar) this can resonates in
the audio band with the capacitance of the cable. Connecting
it to a medium Z line input will kill that resonance. Guitars
expect at least a few hundred k.
Ok that explains that.
Use an active DI-box, in particular if the guitar
output has
to be split for a guitar amp as well.
What if I can't afford DI-boxes? Which is best to use?
6:41 p.m.
Reuben Martin wrote:
Back on Tuesday 27 May 2008, Simon Williams was like:
> What if I can't afford DI-boxes? Which is best to use?
There's really no good way to get around using DI
boxes. If you google for
IMP2 Whirlwind boxes you will find places selling them for 39.99. That's
really not a bad deal if you're strapped for cash.
Well, considering the desk was not more than a few hundred it's quite a
bit, and I'm going to need 2-3 at least I think.
Actually, what instruments actually need DIing? Acoustic guitars fine.
What about electric guitars and bass guitars?
Thanks.
Simon
7:14 p.m.
On Tue, May 27, 2008 at 11:37:43PM +0100, Simon Williams wrote:
Actually, what instruments actually need DIing?
Acoustic guitars fine.
With acoustic guitars it depends on the type of pickup. A piezo-
electric one (very high Z, normally directly connected to a guitar
amp) needs a DI-box. If it is actually a miniature electret mic with
it's own battery/preamp unit maybe the preamp output can go directly
to a mic input. Depends on the wiring. Be careful with phantom power
in that case - it could destroy the preamp if that is not designed
for it.
Professional sound engineers will use a DI-box for everything
that doesn't have a balanced XLR out. Even for high-level synth
outputs etc. which in theory could go directly to a line input.
What about electric guitars and bass guitars?
You need a DI-box for these.
Ciao,
--
FA
Laboratorio di Acustica ed Elettroacustica
Parma, Italia
Lascia la spina, cogli la rosa.
11:18 p.m.
On Tue, May 27, 2008 at 6:37 PM, Simon Williams
<simon(a)systemparadox.co.uk> wrote:
Reuben Martin wrote:
Well, considering the desk was not more than a few hundred it's quite a
bit, and I'm going to need 2-3 at least I think.
Cheapest DIs I've seen are from audiopile.net. I have an active DI
from there, and it works fine (to my ears). They have 4 channel
versions too, $75 passive, $125 active. I've ordered cables from them
a few times (cheapest cables, too!), and have no complaints.
Even cheaper solution: DIY. Schematics are provided on the Jensen
website: http://www.jensentransformers.com/apps_sc.html#musical
Find a compatible transformer to the Jensen part in the schematic
(Jensens are too expensive).
29 May
29 May
3:39 a.m.
On 2008-05-27 22:00 +0100, Simon Williams wrote:
Try it and see but I bet they both will sound muffled. If you have
a bipolar supply hanging around, you can make an unbalanced buffer
for cheap.
Tip of jack from guitar to ground via a 1 M to 5 M resistor and to
the non-inverting input of a TL071. Output of TL071 to its
inverting input and to a 220 ohm resistor. Other end of resistor
to tip of jack to line input. Leave the offset adjust pins
unconnected. Sleeve of both jacks to ground.
^ +15 V
|
-----------
| _ | |
| 2| -_7 |
--|- -_6 | 220
| _---+--^v^v------\ /| TO
FROM |\ /-------+---|+ _- TL071 \/ | LINE
GUITAR | \/ | 3|_-|4 _______| INPUT
OR BASS |_______ < | |
| > 1~5M | ---
--- < v -15 V
|
---
You could surely do something similar with a unipolar supply (9 V
battery or wall wart) but I don't know how. There is probably a
bipolar supply inside your mixer, though. If it doesn't exceed
+/-18 V, you could use that. Shouldn't be a problem, a TL071 draws
very little current.
--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
Do not use this account for regular correspondence.
See the URL above for contact information.
Fons Adriaensen wrote:
Use an active
DI-box, in particular if the guitar output has
to be split for a guitar amp as well.
What if I can't afford DI-boxes? Which is best to use?
4:02 a.m.
On Thu, May 29, 2008 at 09:39:36AM +0200, Andre Majorel wrote:
^ +15 V
|
-----------
| _ | |
| 2| -_7 |
--|- -_6 | 220
| _---+--^v^v------\ /| TO
FROM |\ /-------+---|+ _- TL071 \/ | LINE
GUITAR | \/ | 3|_-|4 _______| INPUT
OR BASS |_______ < | |
| > 1~5M | ---
--- < v -15 V
|
---
You could surely do something similar with a unipolar supply (9 V
battery or wall wart) but I don't know how. There is probably a
bipolar supply inside your mixer, though. If it doesn't exceed
+/-18 V, you could use that. Shouldn't be a problem, a TL071 draws
very little current.
Two 9V batteries should be fine. I'd add some 0.1uF caps
between the power supplies and ground, mounted as close as
possible to the chip. Also one in series with the input.
There are other chips you could use, even double or quad
opamps such as the LM series from Texas.
Ciao,
--
FA
Laboratorio di Acustica ed Elettroacustica
Parma, Italia
Lascia la spina, cogli la rosa.
4:10 a.m.
On Thu, May 29, 2008 at 09:53:32AM +0200, Fons Adriaensen wrote:
There are other chips you could use, even double or
quad
opamps such as the LM series from Texas.
Oops, should be LF of course.
--
FA
Laboratorio di Acustica ed Elettroacustica
Parma, Italia
Lascia la spina, cogli la rosa.
4:15 a.m.
On Thu, May 29, 2008 at 10:01:09AM +0200, Fons Adriaensen wrote:
On Thu, May 29, 2008 at 09:53:32AM +0200, Fons
Adriaensen wrote:
Oops again. I really need to wake up.
Final version:
There are other chips you could use, even double or quad
opamps such as the LF series from National.
Sorry for the noise !
--
FA
Laboratorio di Acustica ed Elettroacustica
Parma, Italia
Lascia la spina, cogli la rosa.
There are other chips you could use, even double
or quad
opamps such as the LM series from Texas.
Oops, should be LF of course.
12:27 p.m.
On Thu, May 29, 2008 at 3:39 AM, Andre Majorel <aym-psd(a)teaser.fr> wrote:
On 2008-05-27 22:00 +0100, Simon Williams wrote:
Try it and see but I bet they both will sound muffled. If you have
a bipolar supply hanging around, you can make an unbalanced buffer
for cheap.
Tip of jack from guitar to ground via a 1 M to 5 M resistor and to
the non-inverting input of a TL071. Output of TL071 to its
inverting input and to a 220 ohm resistor. Other end of resistor
to tip of jack to line input. Leave the offset adjust pins
unconnected. Sleeve of both jacks to ground.
^ +15 V
|
-----------
| _ | |
| 2| -_7 |
--|- -_6 | 220
| _---+--^v^v------\ /| TO
FROM |\ /-------+---|+ _- TL071 \/ | LINE
GUITAR | \/ | 3|_-|4 _______| INPUT
OR BASS |_______ < | |
| > 1~5M | ---
--- < v -15 V
|
---
You could surely do something similar with a unipolar supply (9 V
battery or wall wart) but I don't know how. There is probably a
bipolar supply inside your mixer, though. If it doesn't exceed
+/-18 V, you could use that. Shouldn't be a problem, a TL071 draws
very little current.
Wouldn't any non-"True Bypass" stomp box do the same thing?
Fons Adriaensen wrote:
Use an
active DI-box, in particular if the guitar output has
to be split for a guitar amp as well.
What if I can't afford DI-boxes? Which is best to use? 
1:39 p.m.
2008/5/29 Paul Coccoli <pcoccoli(a)gmail.com>om>:
Wouldn't any non-"True Bypass" stomp box
do the same thing?
Indeed. A guitar pedal that won't produce any sound when it's not
being powered usually can act as a DI box when powered and in bypass
mode, my Boss DS1 for instance does just fine.
4:04 p.m.
On 2008-05-29 12:26 -0400, Paul Coccoli wrote:
On Thu, May 29, 2008 at 3:39 AM, Andre Majorel
<aym-psd(a)teaser.fr> wrote:
In most cases, yes. The only two caveats are that a) some stomp
boxes are reputed to have a less than transparent bypass channel
and b) since stomp boxes do not *have* to have a low output
impedance, some might have a high output impedance. I'm not sure
why someone would design a stomp box that way but people do even
weirder things every day, so...
--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
Do not use this account for regular correspondence.
See the URL above for contact information.
On 2008-05-27 22:00 +0100, Simon Williams wrote:
Wouldn't any non-"True Bypass" stomp box do the same thing? What if I can't afford DI-boxes? Which is
best to use?
Try it and see but I bet they both will sound muffled. If you have
a bipolar supply hanging around, you can make an unbalanced buffer
for cheap.
27 May
27 May
5:09 p.m.
Back on Tuesday 27 May 2008, Fons Adriaensen was like:
On Tue, May 27, 2008 at 02:49:29PM -0500, Reuben
Martin wrote:
Well, to you I would say "neither". To somebody asking if they should plug it
into their mackie mixer line input or mic pre-amp input, I say "line" simply
because I know the chance of them actually going out an purchasing a DI is
kind of low, and if they're going to plug it direct, it's better for them to
stick it in the line input than fry the mic pre-amp. :o)
Back on Tuesday 27 May 2008, Simon Williams was
like:
Well, I'd say they are neither. Typical levels for a guitar are
well below standard line level, and on many pro equipment the
line input Z could well be as low as 10k so, which is too low
for a guitar. It can work, but the sound won't be the same.
This is because the impedance of a typical guitar is not only
high but also inductive, and in many cases (depending on the
setting of the controls on the guitar) this can resonates in
the audio band with the capacitance of the cable. Connecting
it to a medium Z line input will kill that resonance. Guitars
expect at least a few hundred k. Are guitars mic or line or what?
Hi-Z Line level. (The output level can vary quite drastically depending
on the type of pickup though) [...]
Today (and for the last 30 years) it would be perfectly
possible to make guitars low-Z, balanced, and compatible
with a normal mic input. It would save all of us a lot of
trouble, and would also allow for phantom-powered active
electronics in the guitar. So why didn't this happen ?
Because a guitar manufacturer would push himself out of
the market by doing it. People expect any guitar to work
with existing guitar amps.
I think I read an article in TapeOp a while back that Les Paul did just that.
IIRC, he rewired a pickup to be Low-Z because he thought it better retained
it's character by being able to plug it directly into a preamp. Or something
to that effect. I should dig around and see if I can find that article.
-Reuben
6:45 p.m.
On Tue, May 27, 2008 at 04:08:10PM -0500, Reuben Martin wrote:
... it's better for them to
stick it in the line input than fry the mic pre-amp. :o)
Your mic preamp has to be very badly designed if can
be fried in that way :-)
I think I read an article in TapeOp a while back that
Les Paul did just that.
IIRC, he rewired a pickup to be Low-Z because he thought it better retained
it's character by being able to plug it directly into a preamp. Or something
to that effect. I should dig around and see if I can find that article.
If your name is Les Paul you can probably do that without
risking your business.
I actually did the same about 35 years ago for a few friends.
Rewound the pickups manually, using a fixture made of Mecano
parts... Bumped into one of them last year - he's still happy
with the result.
Ciao,
--
FA
Laboratorio di Acustica ed Elettroacustica
Parma, Italia
Lascia la spina, cogli la rosa.
11:42 p.m.
I recommend one the these preamps from k&k for high Z:
http://www.kksound.com/preamp97.html
I use one for my piezio pickup on my upright bass and I LOVE it. I
have also used it in the studio with electric bass.
Peter
On Tue, May 27, 2008 at 3:01 PM, Simon Williams
<simon(a)systemparadox.co.uk> wrote:
Hello.
I often run the PA system for my CU at uni. So far we've been using
jack-jack leads to connect guitars to the desk. However, my Dad has
recently started using jack-XLR leads at my home church and says that
it's much better.
After a very long conversation and lots of googling (which incidentally
provides no info at all on the subject), I'm now completely confused.
Are guitars mic or line or what?
The rationale for using jack-XLR leads and connecting to the mic input
on the desk is that guitars have mics in them so they are mic level.
Apparently the battery unit in the guitar doesn't make it line level,
but I'm not convinced.
The other thing I don't understand is that if that is the case, why do
people use DI boxes? A DI box takes a high impedance (line level - I
think) input and converts it to low impedance output (mic level). If the
guitar is mic level already then what's the point?
Please, could someone shed some light on this because I'm now very confused.
Thanks in advance.
Simon
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21 comments
11 participants
participants (11)
-
Anders Dahnielson -
Andre Majorel -
Christian Delahousse -
Folderol -
Fons Adriaensen -
Giuseppe Zompatori -
Paul Coccoli -
Peter Hartmann -
Reuben Martin -
Simon Williams -
Steve Fosdick