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Old February 24th, 2008, 03:34 PM   #1 (permalink)
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Line vs. Instrument vs. Speaker vs. Mic Levels

I've always been a bit confused about how each of these was defined.

Could anyone give me a quick primer on these, perhaps perhaps defining the +/- db parameters of each? Maybe an example or two to help me understand?

One of the things that made me think of this again (I've always wanted to learn it) was a recent message in which the poster was using the line out of his Roland Microcube into another tube (?) amp which he was using as a slave.

Wouldn't this be an impedance mismatch?

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Old February 24th, 2008, 05:48 PM   #2 (permalink)
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Quote:
Originally Posted by postjob62 View Post
I've always been a bit confused about how each of these was defined.

Could anyone give me a quick primer on these, perhaps perhaps defining the +/- db parameters of each? Maybe an example or two to help me understand?

One of the things that made me think of this again (I've always wanted to learn it) was a recent message in which the poster was using the line out of his Roland Microcube into another tube (?) amp which he was using as a slave.

Wouldn't this be an impedance mismatch?
No the line out is made to do such a thing go from the line out to another amp or mixer. If you do not have a line out you can use a Passive DI box and run from a external speaker out if you have one to the High in on the DI box using a shielded guitar cord and run a mic cord with a quarter inch jack on one end for a high impedance mic from the low Z out to the High impedance input of the amp. Do not go to the normal channel but the High one if there is more than one input. The transformer in the DI box allows you to do this safely. When you do this you still have to have a speaker working in the first amp your running the line out of to the DI box. If you do not have a External speaker out jack you could make a jack with a couple of clips on it and clip it to the speaker and run a guitar cord out of that to the DI box. OR like most will say here use a MIC on the speaker. Myself I use a line out from a smaller tube amp to a larger SS amp for more stage volume.
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Old February 24th, 2008, 09:00 PM   #3 (permalink)
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I'm pretty sure a speaker level signal is one that's been through a power amp already, and can only be plugged into a passive speaker.

Mics usually need phantom power from whatever they're plugged into.
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Old February 24th, 2008, 09:34 PM   #4 (permalink)
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In order of voltage you have:
  • signal level around 1-10mV e.g. output from pickup or microphone
  • line level around 1V e.g. output from mixer, pre-amp, line out, RCA outputs from CD deck or tuner
  • headphone out - not sure of voltage but comparable to line level
  • speaker level - lots of volts e.g. output from power amp

Any of the first three can be input to a guitar amp or mixer.

With line and headphone signals particularly, you should do the connections with all volume levels set to zero and bring them up gradually. If I am running line level (and even humbuckers sometimes) into a guitar amp, I use the lo-gain inputs if they are available.

Line level and headphone output also have enough gain to drive a power amp so you can, for instance, run the output from a CD deck straight into a power amp.

I have not run speaker level output into anything except an appropriate speaker since an expensive accident when I was a gormless youth. I know some DI boxes accept speaker level output but there seems to be some caveats around this. If I need to record guitar, I mike the amp or use line out.

Phantom power is not so much related to levels as to powering condenser (but not dynamic) microphones and some DI boxes. It is simply the mixer sending sufficient power (typically 48V) down the balanced microphone lead to drive the device.


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PS A turntable puts out signal level. Its output needs to go through a special phono pre-amp that boosts the lower frequency component of the signal as well as bringing the signal up to line level.

Last edited by Robin Nahum; February 25th, 2008 at 03:34 AM.
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Old February 24th, 2008, 11:28 PM   #5 (permalink)
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So what are the caveats for using a DI Robin? On the Behringer Passive DI there is a jack for speaker out to run from any speaker out jack. SO it is acceptable. I asked about this at the Gear Page and it was explained to me its perfectly acceptable as long as One the DI box is Passive not active. Two the speaker is still being used by the primary amp for a load on the amp and the cord is used in an EXTERNAL or parallel speaker jack out. Three the Low Z mic cord is plugged into the High side of the input if the amp has both high and normal input jacks for best results. I tried it with my Peavey DI box and it worked great.
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Old February 24th, 2008, 11:38 PM   #6 (permalink)
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So I can come out of my Classic 30 Speaker out to a passivs DI, into my interface? And this still uses my Preamp/effects? That'd be awesome if so.
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Old February 24th, 2008, 11:59 PM   #7 (permalink)
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What do you mean by an interface? You can use this to go to an other guitar amp or a PA mixer or powered mixer or powered speaker. What ever you use to amplify it will amplify the signal you would hear out of the speaker which would include any effects being used. Just make sure the DI is a Passive one and not an active one. The Passive ones have the transformer that makes this possible.
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Old February 25th, 2008, 01:41 AM   #8 (permalink)
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So what are the caveats for using a DI Robin? On the Behringer Passive DI there is a jack for speaker out to run from any speaker out jack. SO it is acceptable.
I have a Behringer DI4000 which is a four-way powered DI.

I have just retrieved the manual from:

http://www.behringer.com/DI4000/index.cfm?lang=eng

and attached the relevant bit which says that it will accept speaker out (up to 3KW!) but you do need to watch out for a couple of things.
Attached Files
File Type: pdf DI4000.pdf (130.5 KB, 36 views)
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Old February 25th, 2008, 01:50 AM   #9 (permalink)
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And at

http://www.soundonsound.com/sos/apr9...html?print=yes

Quote:
SPEAKER DI

Sometimes it's desirable to take a DI feed from the speaker output of an amplifier, and both active and transformer DI boxes can do this, as long as they are fitted with an input designed to accept speaker-level signals. Amplifiers' speaker outputs carry signals of several tens of volts, while line-level signals are usually only around a couple of volts, so it's evident that plugging a speaker signal into a line-level input would overload it massively, probably to the point of causing damage. Mic inputs are designed to accept signals of typically only a few thousandths of a volt in amplitude, so the effect of plugging in a speaker signal would be even more serious than in the case of the line input. DI boxes with speaker input jacks should also have thru connectors allowing connection to either the original speaker or to a dummy load. The DI output signal will be at either mic or line level and can be fed to the appropriate console input.
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Old February 25th, 2008, 03:05 AM   #10 (permalink)
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I suppose it depends on the unit. I know it works fine with my Peavey ID box and it seems like from the post I have read on this more than a few folks have used DI boxes for this purpose.
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Old February 25th, 2008, 03:10 AM   #11 (permalink)
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Which is why I said you have to have the speaker of the amp hooked up and being used and you hook up from External Speaker jack which is normally parallel to the speaker jack or speaker being used. It is also why I specified using a DI box with a transformer in it which is of the passive type.
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Old February 25th, 2008, 12:02 PM   #12 (permalink)
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Which is why I said you have to have the speaker of the amp hooked up and being used and you hook up from External Speaker jack which is normally parallel to the speaker jack or speaker being used. It is also why I specified using a DI box with a transformer in it which is of the passive type.

Uh, thanks.

I think.
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Old February 25th, 2008, 04:59 PM   #13 (permalink)
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OK, here's the deal. Tube amps don't like being run with the output unconnected. It needs a load to dissapate the power the tube is trying to make or it will fry the output transformer.

This load is simple. An 8-10 ohm resistor rated at enough watts to soak up what the amp is producing. Voila, the amp runs safely and makes no noise. You can still borrow some of that signal to drive a preamp, albeit at rather high level.

This is EXACTLY how my Hammond M3 organ drives my Leslie amp. The output of the organ's amp is loaded by a power resistor, and the remaining signal drives the phase inverter in the Leslie amp. (No preamp in a leslie - that's always in the organ.)

So yes, Virginia, you can use the output of a power amp. You just have to load it. Some DIs do this for you and some don't. Read the manual.

As for levels, the voltage levels were about right, though guitars are more like 200-250mV for a tele. About twice that for a Les Paul.

What you're not taking into account is impedance. A guitar pickup works well into a tube amp because the amp has high imput impedance (Z). This means lots of resistance, so the pickup doesn't get loaded down much. Lower Z means some of the signal gets shorted and you lose high end. Plug into a mixing console (low Z input) and see what I mean.

--Rob
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Old February 25th, 2008, 05:28 PM   #14 (permalink)
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OK, here's the deal. Tube amps don't like being run with the output unconnected. It needs a load to dissapate the power the tube is trying to make or it will fry the output transformer.

This load is simple. An 8-10 ohm resistor rated at enough watts to soak up what the amp is producing. Voila, the amp runs safely and makes no noise. You can still borrow some of that signal to drive a preamp, albeit at rather high level.

This is EXACTLY how my Hammond M3 organ drives my Leslie amp. The output of the organ's amp is loaded by a power resistor, and the remaining signal drives the phase inverter in the Leslie amp. (No preamp in a leslie - that's always in the organ.)

So yes, Virginia, you can use the output of a power amp. You just have to load it. Some DIs do this for you and some don't. Read the manual.

As for levels, the voltage levels were about right, though guitars are more like 200-250mV for a tele. About twice that for a Les Paul.

What you're not taking into account is impedance. A guitar pickup works well into a tube amp because the amp has high imput impedance (Z). This means lots of resistance, so the pickup doesn't get loaded down much. Lower Z means some of the signal gets shorted and you lose high end. Plug into a mixing console (low Z input) and see what I mean.

--Rob
While having a load resistor is a good idea if you do not want to run your speaker with this set up I think most folks using a small amp into a larger one would want to use their speaker as the load I know I do and then run the line out from the external speaker jack into a DI into the slave amp or mixer. My self I would want the amps speaker working and the line going to the slave amp. When you do it this way you can set the slave amp vol for what ever you want and the first amps VOL will control both. Good idea on the load resistor. If you run your speaker for the load and run an external speaker jack or a parallel jack off the speaker and the speaker is running going into a PASSIVE DI with a transformer will do the job with no worries remembering to run the Low z into the high Z input of the slave amp if there is a hi and low input. Pretty simple as long as you remember passive and keep the speaker in the set up for the load.
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Old February 25th, 2008, 07:37 PM   #15 (permalink)
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Line vs. Instrument vs. Speaker vs. Mic Levels

Quote:
Originally Posted by postjob62 View Post
I've always been a bit confused about how each of these was defined.

Could anyone give me a quick primer on these, perhaps perhaps defining the +/- db parameters of each? Maybe an example or two to help me understand?

One of the things that made me think of this again (I've always wanted to learn it) was a recent message in which the poster was using the line out of his Roland Microcube into another tube (?) amp which he was using as a slave.

Wouldn't this be an impedance mismatch?


Impedence mismatch would be the wrong terminology. Impedence is related to hooking up a Marshall stck with Fender 212 cabinets.


+/- db parameters of each


Check out this link:
http://www.cdc.gov/niosh/mining/topi...trolBasics.pdf
Interesting Pages of Above Link
page - 13/55
page - 26/55


This is also a good link:
http://www.fenderplayersclub.com/fro...ce/quartet.htm
Small Concert Sound System
I would suggest a Peavey XR680


Line Out:
Usually used on Bass amplifiers so the Bass can be put in the P.A. Speakers and keep the stage volume comfortable. It also reduces the bass from bleeding into other microphones.

Instrument:
Usually they are played through an amplifier. Acoustics are usually ran through a D.I.

Speaker:
To understand this you may want to study up on Ohms Law.
eg:
Marshall Head
200 watts @ 8 ohms - (using one speaker cabinet or combo amp
400 watts @ 4 ohms - (using two speaker cabinets)
The 8 and 4 may be in the wrong spot. I play a combo amp.


Mic Levels:
Simply put they are a volume controlled by a mixer.
-If anyone tell you a Shure Beta 58 is better because it's louder than a Shure58 mic they are wrong. It's like comparing a Les Paul and a Tele. The Beta is a hotter mic.

I don't mean to over simplify some of above, but I don't know if you own and operate Concert Sound Systems.

I guess I should have asked this first. Do you own a Sound System? and What do you have? How big a bar do you play in?

That was a good question? Although I did get off on a tangent.
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Old February 25th, 2008, 08:00 PM   #16 (permalink)
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Bandit,

Thanks for the response, and your "tangent" was closer to the mark I was looking for than some others.

Actually, I'm not trying to actually do anything, except educate myself a little abot these different output levels and how they are typically found in real guitar amp situations.

For instance, it would be nice to know if say a particular pedal's output was line level, thus (?) allowing it to be used as a sort of preamp directly in to another amp's "power amp in", or if it would have to go directly into the instrument input on the front of the amp. Also, that Microcube example I mentioned in the OP.

Simple stuff like that.
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Old February 25th, 2008, 08:03 PM   #17 (permalink)
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Hey, by interface I meant a firewire recording interface (M-Audio FW410 in this case). Thanks for the info, I just checked it out and its a great way to use the preamp/reverb on my amp without being subject to the room (mic'ing the amp). I was just worried about plugging a powered output into anything besides a speaker. Success!
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Old February 26th, 2008, 12:57 AM   #18 (permalink)
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Quote:
Originally Posted by postjob62 View Post
Bandit,

Thanks for the response, and your "tangent" was closer to the mark I was looking for than some others.

...educate myself a little abot these different output levels and how they are typically found in real guitar amp situations.

For instance, it would be nice to know if say a particular pedal's output was line level, thus (?) allowing it to be used as a sort of preamp directly in to another amp's "power amp in", or if it would have to go directly into the instrument input on the front of the amp.
Simple stuff like that.
You are saying two things. You like your pre-amp (sound of amp) and you want to add that sound to a more powerful amp. (you want EL84 tones out of a 200 watt amp.)

Your into the half stack or full stack idea. When you say "different output levels" you are into Ohms Law and matching speakers and amps again.

Basically you want to use the pre-amp from a Vox or Dr Z. and run it through a Fender Twin. You want the 30 watt EL84 tube sound, hooked up to the front end of a Twin?

How about a build it yourself amp. Vox pre-amp, reverb and in a Fender Twin case, That would be very cool.

If you want to use a small amp and get gobs of volume run it through a The Mains/House Speakers. The sound man can also add some delay, reverb... to your sound.
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Old February 26th, 2008, 01:48 AM   #19 (permalink)
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You are saying two things. You like your pre-amp (sound of amp) and you want to add that sound to a more powerful amp. (you want EL84 tones out of a 200 watt amp.)

Your into the half stack or full stack idea. When you say "different output levels" you are into Ohms Law and matching speakers and amps again.

Basically you want to use the pre-amp from a Vox or Dr Z. and run it through a Fender Twin. You want the 30 watt EL84 tube sound, hooked up to the front end of a Twin?

How about a build it yourself amp. Vox pre-amp, reverb and in a Fender Twin case, That would be very cool.

If you want to use a small amp and get gobs of volume run it through a The Mains/House Speakers. The sound man can also add some delay, reverb... to your sound.


As often happens with my questions, I must have lacked enough basic knowledge to pose said question clearly.

Actually, I didn't want to do anything proactive except obtain a little information, as stated. What I did or didn't want to do with said information, once ontained, I felt was irrelevant and would only lead to the generous offering of solutions I wasn't seeking to start with...
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Old February 26th, 2008, 01:52 AM   #20 (permalink)
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Quote:
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As often happens with my questions, I must have lacked enough basic knowledge to pose said question clearly.

Actually, I didn't want to do anything proactive except obtain a little information, as stated. What I did or didn't want to do with said information, once ontained, I felt was irrelevant and would only lead to the generous offering of solutions I wasn't seeking to start with...

Well one thing about forums your going to get info and suggestions and in some cases they will go off the deep end into other subjects not even related to your origional question. All part of how folks interpert what you say or what your trying to say or ask.
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