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How to feed a preamp with line level signal?
Old 30th May 2007
  #1
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Farshad's Avatar
 

Exclamation How to feed a preamp with line level signal?

Hi guys,

I am wondering how you feed a preamp with a line leve signal to add some character to it. Is it always necessary to use a pad or you can basically lower the output volume? Will also a lin eleve signal ruin a preamp?

An comments would be much appreciated.
Old 30th May 2007
  #2
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Farview's Avatar
 

You could just lower the gain on the preamp if you can turn it down far enough. If the preamp has a pad, use it. A direct box could help.
You won't hurt anything.
Old 30th May 2007
  #3
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Thank you for the reply Jay,

Sure I can turn up the gain on my preamp. How about turing the volume of the line level feeding the preamp down?

Cheers
Old 30th May 2007
  #4
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AlexLakis's Avatar
 

Check out the Shure ATTY. Great tool! thumbsup
Old 30th May 2007
  #5
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Barnabas's Avatar
 

Quote:
Originally Posted by Farshad View Post
Sure I can turn up the gain on my preamp. How about turing the volume of the line level feeding the preamp down?

Cheers
Yes, you can change the gain on the line-level source.
Old 30th May 2007
  #6
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poncival's Avatar
How about a nice direct box before the preamp?
Old 31st May 2007
  #7
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Quote:
Originally Posted by poncival View Post
How about a nice direct box before the preamp?
Will it sound better this way?

Cheers
Old 31st May 2007
  #8
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Farview's Avatar
 

You can turn down the source, but then the preamp will be bringing it back up to where it was, so there isn't any point. In addition, you would be raising the noise floor by doing that.

The DI would be the standard way for sending a line level signal into a preamp.
Old 31st May 2007
  #9
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Quote:
Originally Posted by Farview View Post
You can turn down the source, but then the preamp will be bringing it back up to where it was, so there isn't any point. In addition, you would be raising the noise floor by doing that.

The DI would be the standard way for sending a line level signal into a preamp.
Hi, Thanks for the clarification. I want to use the pre mainly to colour the sound. Seems the DI is the way to go.

Cheers
Old 31st May 2007
  #10
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Farview's Avatar
 

Quote:
Originally Posted by Farshad View Post
Hi, Thanks for the clarification. I want to use the pre mainly to colour the sound. Seems the DI is the way to go.

Cheers
If you get a good passive DI, that could color the sound as well.

There is nothing wrong with just plugging it into the preamp and turning the gain down. Any color or saturation would happen at a certain signal level, not a certain knob position.
Old 31st May 2007
  #11
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mixerguy's Avatar
If I were you, I'd skip the preamp, and save up, and buy a FATSO

just a thought...
Old 31st May 2007
  #12
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Quote:
Originally Posted by mixerguy View Post
If I were you, I'd skip the preamp, and save up, and buy a FATSO

just a thought...
Well FATSO is an interesting idea but I already have two channels of SCA N72 (Neve) which sound wonderful on my mic.
Old 31st May 2007
  #13
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Quote:
Originally Posted by Farview View Post
If you get a good passive DI, that could color the sound as well.

There is nothing wrong with just plugging it into the preamp and turning the gain down. Any color or saturation would happen at a certain signal level, not a certain knob position.
Hi,

I do not have any DI right now. Any recommendations?
Old 30th March 2014
  #14
Question

Quote:
Originally Posted by Farview View Post
You could just lower the gain on the preamp if you can turn it down far enough. If the preamp has a pad, use it. A direct box could help.
You won't hurt anything.
Hello!
I am resurrecting this thread to avoid starting another about the same thing.

I have read quite a bit about this, but I am no clearer about it now than when I first started searching for an answer.

I want to run a stereo mix through a tube preamp to attempt to acquire some colorful distortion.

My interface offers balanced line level outputs.

I was interested in running the line level output of my interface into the mic input on the preamp, with the input gain turned all the way down to avoid instant excessive distortion.

The specs in the manual say that the mic input on the preamp can accept a maximum signal up to +19dBu.
The input impedance for the mic input is variable from 150-3000 Ohms.

My big question is, will I damage the preamp?

Cheers!
Old 31st March 2014
  #15
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Check out this. It does exactly what you want:



Woven Pad LTM37 - Woven Audio
Old 31st March 2014
  #16
Quote:
Originally Posted by Elmbeatz View Post
Check out this. It does exactly what you want:



Woven Pad LTM37 - Woven Audio
Thanks, but that doesn't really answer my question.
I am aware of a whole host of solutions.
I wanted to know if damage will occur to the preamp. I'm asking because I don't want to try it out for real on my equipment.
Old 27th May 2015
  #17
Did you find any solutions to this fred?
Old 27th May 2015
  #18
Wow! Over a year later! Well, no I haven't yet found a conclusive answer.
Old 3rd March 2019
  #19
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Quote:
Originally Posted by the fred View Post
Wow! Over a year later! Well, no I haven't yet found a conclusive answer.
No, you won't damage anything physically.

If you can plug it in and pump sound through it all you need to do is listen and experiment.

If you can't hear noise then forget about people telling you to worry about noise.

If you like the sound then it's all good to go.

If it distorts too much, you need to bring the input level down (either of the ways mentioned above).

With tubes, there is a sweet spot and that sweet spot varies as much as everyone's taste (and monitoring situation hehe).

Experiment, have fun. Although I assume you've done that by now

Tell us about your results!
Old 4th March 2019
  #20
Quote:
Originally Posted by Greg_KPX View Post
No, you won't damage anything physically.

If you can plug it in and pump sound through it all you need to do is listen and experiment.

If you can't hear noise then forget about people telling you to worry about noise.

If you like the sound then it's all good to go.

If it distorts too much, you need to bring the input level down (either of the ways mentioned above).

With tubes, there is a sweet spot and that sweet spot varies as much as everyone's taste (and monitoring situation hehe).

Experiment, have fun. Although I assume you've done that by now

Tell us about your results!
Wahey! Thank you for stepping in! This thread is pretty old...
I did have a go and it does require some careful fiddling with the input/output level adjustment to not overdrive the signal. Feeding a line level into a preamp can be a little overkill at first. I started at the lowest gain setting and slowly rolled it up. Interesting flavour with the tubes engaged.
Old 4th March 2019
  #21
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Plugging a line level output into a mic level input is going to hiss like an SOB.
Yes you could turn the signal down but all you'll be left with is a highly amplified noise floor.
Running a gain knob at its extreme typically makes for a crappy sounding signal too.

Not only will the slightest movement make the gain jump wildly, but the tape of a pot when its near the end typically has a huge amount of tone suck.

The reason you want to match impedances has a dual purpose. You want to be able to run your gain knobs near the center of their range for maximum fidelity but you also want to do this to keep the noise floor at its lowest.

A simple dual channel DI will do this just fine. I use one for connecting a drum machine to my interface. My unit has 4 mic level inputs and two line/instrument level ins. I use the instrument level ins for Guitar and use the DI to step line level to mic level. This one is only $14. Pyle PDC22 1/4" Direct Box

If you wanted distortion driving a line level into a mic level input is not the best way to get it, and having been an electronic tech who specializes in audio gear I would not take the advice or others when they say no harm will be done. If its a tube preamp, then its unlikely you'd harm a Tube, but a SS preamp is a whole different animal. The biggest enemy of SS is heat. You may not blow the transistors or op amps outright, but that doesn't meant you cant degrade then when driven till they overheat.

I cant count the numbers of times I've heard people take stupid advise and wound up using the excuse "I did that before and never had a problem" Yea you can walk across a highway with a blindfold on and not get hit too. I wouldn't advise others its safe to do that because you happened to have a streak of dumb luck.

There are (7) main signal level types you deal with in audio on a regular and you should memorize how they are different.

Mic level - mics have the weakest signal and need the most gain to amplify.

Instrument level - The instrument outputs a stronger signal then a mic but is too weak to feed a line level input.

Line level pro - use a +4 dB gain structure. This is mainly for feeding signals through older Passive units like Passive EQ's which have no built in preamps.

Line level commercial - use a -10dB gain structure. Most new audio/Hi Fi use active components with hotter signals. Keeps low cost component noise floor low.

Headphone/Line level, This is unique to specific devices which have headphone outs that double as line level. DON'T assume all gear has this - Check your manual.

Headphone only level - Impedance 8 ohms and up. Extremely hot signal headphones only cant be used as a line level unless attenuated and even then noisy.

Speaker level - For speakers only. Depending on the wattage you'll blow any devices you try and connect to it and you'll fry any shielded cables you use from the inside out. There are some DI's which can reduce speaker level to line level but they are typically noisy as well.

Best advice only connect like to like audio devices or be sure you properly attenuate the impedances so that match so you have a proper noise floor and highest fidelity. if you want overdrive, this in not the way I'd advise you get it.
Old 4th March 2019
  #22
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12tone's Avatar
 

Just get something like this?

Avedis Line pads - $35.
LPZ – Line to Mic pad adaptor – Avedis Audio

Quote:
Description

The LPZ is a simple line pad designed to interface Line level audio down to Mic level with the correct impedances. Input impedance is 10k ohms, and output impedance is 150 ohms like a microphone so that you can plug your Line device (such as a DAW or other outboard gear) to a microphone preamplifier. Level loss is approximately 36dB and the signal is balanced throughout, and should not be used unbalanced.
Old 17th May 2019
  #23
Sorry if ive raised an old thread.
Ive had great success with a radial jdi duplex. Balanced xlr line in and balanced xlr mic level out!
Straight from my DAC to stam dual neve pre and it sounds great!
Its a shame radial doesnt advertize this feature a bit more.
The other option im looking at is two warm audio tb12 tonebeast preamps. It has balanced line input as well as mic... great feature
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