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How to attenuate instrument level? Effects Pedals, Units & Accessories
Old 20th May 2018
  #1
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Alon Wolman's Avatar
How to attenuate instrument level?

I've got a guitar amp that I'm trying to use with a theremin. The theremin is supposed to work better with a keyboard amp. To use it with the guitar amp I need to attenuate the output of the theremin. What's the best way to do this?
Old 20th May 2018
  #2
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ProgFree's Avatar
 

something like this:

PDIR01 Palmer PRO DI-REVERSE - Reversed DI Box
Old 20th May 2018
  #3
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Alon Wolman's Avatar
Quote:
Originally Posted by ProgFree View Post
Right now I'm using a True P Solo for this purpose. I plug the theremin into the DI on the front, then set the volume to the lowest setting (input attenuation activated) - then send the output to the guitar amp. This way I can turn the volume knob on the guitar amp to the middle, but I still have to keep the gain turned down to 1. Will the Reversed DI BOX attenuate the signal even more than the P Solo?
Old 20th May 2018
  #5
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Alon Wolman's Avatar
I ended up ordering a JHS Little Black Amp Box Passive Amp Attenuator. This appears to be what I am looking for!
Old 21st May 2018
  #6
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Mikhael's Avatar
 

Quote:
Originally Posted by Alon Wolman View Post
I ended up ordering a JHS Little Black Amp Box Passive Amp Attenuator. This appears to be what I am looking for!
Wow. I would've just stuck a volume pot on it.
Old 21st May 2018
  #7
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Doesn’t your Theremin have a volume control?

The reason they tell you to use a keyboard amp instead of a guitar amp is for the sound.
Old 21st May 2018
  #8
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You only need something like a -6dB attenuator to change its output from Line level to instrument level.
You can buy the RCA type very inexpensively. I used to buy them for under $5.

You can buy a pair of the gold plated metal types here. https://www.parts-express.com/harris...m_campaign=pla Use one if you only want -6DB attenuation, use both in series if you want -12.

You surely don't need to spend any more then this. Line and Instrument levels don't need the transformer of a DI box but you could use one if that's all you had.
You don't have to spend more then $10 on those either. A guitar amp isn't going to produce any frequencies over 5~6KHz or below 100Hz so spending money on a top end DI is a waste of money this one would do the job fine for live or recording. and has a -10/-20dB cut switch which should be more then enough to attenuate the level down. https://www.bhphotovideo.com/c/produ...SABEgKIwvD_BwE
Old 23rd May 2018
  #9
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Alon Wolman's Avatar
Quote:
Originally Posted by kslight View Post
The reason they tell you to use a keyboard amp instead of a guitar amp is for the sound.
I ended up getting a Roland KC 60 keyboard amp and putting it on a stand so it faces behind my head. This is working great so far. The theremin does have a volume control but I like to leave it in the middle because it's for tuning the volume loop.
Old 4 weeks ago
  #10
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Quote:
Originally Posted by wrgkmc View Post
You only need something like a -6dB attenuator to change its output from Line level to instrument level.
You can buy the RCA type very inexpensively. I used to buy them for under $5.

You can buy a pair of the gold plated metal types here. Harrison Labs 6 dB RCA Line Level Audio Attenuator Pair Use one if you only want -6DB attenuation, use both in series if you want -12.

You surely don't need to spend any more then this. Line and Instrument levels don't need the transformer of a DI box but you could use one if that's all you had.
You don't have to spend more then $10 on those either. A guitar amp isn't going to produce any frequencies over 5~6KHz or below 100Hz so spending money on a top end DI is a waste of money this one would do the job fine for live or recording. and has a -10/-20dB cut switch which should be more then enough to attenuate the level down. Pyle Pro PDC21 Direct Box PDC21 B&H Photo Video
Hi,
i'm joining the conversation since i seem to have some trouble with my keyboards through guitar pedals.
Is 6dB attenuation enough? I based my attenuator cables on this article about the line out jack of a Nord and it tells ~20 dB between instrument and line level which fits with the pad of D.I that is 0 dB for instrument input like a bass and 20 dB for line levels like keys.
Q. How do I hook up guitar pedals to my synth or keyboard? |
I'm fine with understanding the idea of lowering input to avoid pedal circuit overwhelming with strong signal, but they don't mention if after this kind of attenuation the line out of the key is converted to match with the 0 dB instrument input of the D.I..
Is it the case or is there an impedance match concern that comes in here (despite this article says there is none)?
I'm using a Bontempi MS40 through a Boss RV3 (mode 11 reverb, kill dry).
The key only has a headphones output so i'm likely louder than line level with volume set to ~60% to have a good signal/noise ratio without too much headphone amp noise and go to the pedals through the -25 dB jack (10 kohm series, 560 ohm parallel resistors set in the article link above)
I can plug this chain with the 20 dB pad on the BSS AR133 DI and have a correct sound but the input in the mixing console is low since I need to push gain and fader to have something similar to other sources (vox and guitar amp mics) and there is bkgd noise. that likely comes from the mixer preamp gain.
With the DI set on instrument level with 0 dB pad, bkgd noise is awfully strong and if I plug that in my blues jr guitar amp the signal is muck weaker than my guitar so I guess I don’t have something comparable to instrument level but much less.
Is the just the attenuation that is too strong or is there an additional impedance match issue?
I’m looking for advices because we like the simple sounds of these keys in the band and are not that much into MIDI driven ableton live or so. (well, if no other simple and $$ok solution exists we’ll come to that with the regret of losing a bit of originality  )
-Should I try to bypass the headphone preamp to modifiy my key output to line ?
-Accurately measure the strength of the headphone output on a fixed level and calculate the exact attenuation for the resistors to solder in the cable?
-Think of getting a small mixer, plug the key in line in and put the effects as aux?
-Try other reverb pedals till one works? (already tried Trex tonebug, same problem)
I’d be extremely grateful if somebody has answers on this 
Cheers
Old 4 weeks ago
  #11
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Mikhael's Avatar
 

Turn down?
Old 4 weeks ago
  #12
yep
Gear Nut
 

Quote:
Originally Posted by dan173 View Post
Hi,
i'm joining the conversation since i seem to have some trouble with my keyboards through guitar pedals.
Is 6dB attenuation enough? I based my attenuator cables on this article about the line out jack of a Nord and it tells ~20 dB between instrument and line level which fits with the pad of D.I that is 0 dB for instrument input like a bass and 20 dB for line levels like keys.
Q. How do I hook up guitar pedals to my synth or keyboard? |
I'm fine with understanding the idea of lowering input to avoid pedal circuit overwhelming with strong signal, but they don't mention if after this kind of attenuation the line out of the key is converted to match with the 0 dB instrument input of the D.I..
Is it the case or is there an impedance match concern that comes in here (despite this article says there is none)?
I'm using a Bontempi MS40 through a Boss RV3 (mode 11 reverb, kill dry).
The key only has a headphones output so i'm likely louder than line level with volume set to ~60% to have a good signal/noise ratio without too much headphone amp noise and go to the pedals through the -25 dB jack (10 kohm series, 560 ohm parallel resistors set in the article link above)
I can plug this chain with the 20 dB pad on the BSS AR133 DI and have a correct sound but the input in the mixing console is low since I need to push gain and fader to have something similar to other sources (vox and guitar amp mics) and there is bkgd noise. that likely comes from the mixer preamp gain.
With the DI set on instrument level with 0 dB pad, bkgd noise is awfully strong and if I plug that in my blues jr guitar amp the signal is muck weaker than my guitar so I guess I don’t have something comparable to instrument level but much less.
Is the just the attenuation that is too strong or is there an additional impedance match issue?
I’m looking for advices because we like the simple sounds of these keys in the band and are not that much into MIDI driven ableton live or so. (well, if no other simple and $$ok solution exists we’ll come to that with the regret of losing a bit of originality  )
-Should I try to bypass the headphone preamp to modifiy my key output to line ?
-Accurately measure the strength of the headphone output on a fixed level and calculate the exact attenuation for the resistors to solder in the cable?
-Think of getting a small mixer, plug the key in line in and put the effects as aux?
-Try other reverb pedals till one works? (already tried Trex tonebug, same problem)
I’d be extremely grateful if somebody has answers on this 
Cheers
If your keyboard has a volume control, the simplest thing is to just turn it down, which essentially just puts some resistors in series with the output, exactly like the cable in the SOS article you linked to.

That is, a typical volume control does exactly the same thing as a cable with resistors soldered in-line, it just allows you to adjust the amount of attenuation, instead of leaving it fixed in place. From a player's perspective, or for a self-producer/musician, a volume control is actually better than a hardwired attenuator, in just about every respect.

Now, there are three reasons why someone might still want to make or purchase a hardwired attenuator for this task:
  1. The most obvious is if you are running sound in a live or studio environment where you don't trust the players to make sensible gain-staging decisions, either because you don't trust their monitoring, their judgement, their hearing, or their understanding of the volume control. Most live sound guys will check "all of the above", all the time. So you just hardwire the attenuator into setup, and let the talent do what they will.
  2. A corollary to the above is if you just want to idiot-proof your own rig for similar reasons (e.g., gigs where you can't trust the monitoring system to make nuanced gain-staging decisions). This can also be handy for things like on-the-fly patch changes and so on, where the output volume might change from moment to moment, and you just don't want to have to think about this stuff.
  3. Last and definitely least on the list of concerns is the mostly-theoretical possibility that your volume knob might compromise your sound by adding something other than just resistance to the circuit (adding resistance is what it's there for, and what an attenuator does, so it's foolish to worry about additional resistance from the potentiometer in this scenario). If your volume knob is adding noise or capacitance or something, it's probably a better use of soldering time to replace the pot than to make a new attenuator cable.

Hope that helps!
Old 4 weeks ago
  #13
Turn it down! If it doesn't have a properly functioning volume control, use a volume pedal.
Old 4 weeks ago
  #14
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Quote:
Originally Posted by yep View Post
If your keyboard has a volume control, the simplest thing is to just turn it down, which essentially just puts some resistors in series with the output, exactly like the cable in the SOS article you linked to.

That is, a typical volume control does exactly the same thing as a cable with resistors soldered in-line, it just allows you to adjust the amount of attenuation, instead of leaving it fixed in place. From a player's perspective, or for a self-producer/musician, a volume control is actually better than a hardwired attenuator, in just about every respect.

Now, there are three reasons why someone might still want to make or purchase a hardwired attenuator for this task:
  1. The most obvious is if you are running sound in a live or studio environment where you don't trust the players to make sensible gain-staging decisions, either because you don't trust their monitoring, their judgement, their hearing, or their understanding of the volume control. Most live sound guys will check "all of the above", all the time. So you just hardwire the attenuator into setup, and let the talent do what they will.
  2. A corollary to the above is if you just want to idiot-proof your own rig for similar reasons (e.g., gigs where you can't trust the monitoring system to make nuanced gain-staging decisions). This can also be handy for things like on-the-fly patch changes and so on, where the output volume might change from moment to moment, and you just don't want to have to think about this stuff.
  3. Last and definitely least on the list of concerns is the mostly-theoretical possibility that your volume knob might compromise your sound by adding something other than just resistance to the circuit (adding resistance is what it's there for, and what an attenuator does, so it's foolish to worry about additional resistance from the potentiometer in this scenario). If your volume knob is adding noise or capacitance or something, it's probably a better use of soldering time to replace the pot than to make a new attenuator cable.

Hope that helps!
Hi, thanks a lot for your replies,

Well I do trust sound engineers about proper gain staging, my main concern is rather the quality of the signal I will send to them. About this i seem to have myself gain staging mistakes since what comes out of my setup to the PA is either too low for line in and needs lots of gain which then amplifies the setup's bkgd noise a lot for line in and or is too high at some point for instrument in via a DI.

To make it clearer here's a pic of how i use the setup that's made to have a nice sound for both the key and the second mic for desert harmonica. I take advantage of this to also be able to open a second channel wide of reverb to my guitar sound at some places that provides nice dynamics in the songs in a much cheaper way than a second amp.

OD-RV3-installation.png - Google Drive

I'll further try to simply adjust the levels but I'm likely lacking a piece of knowledge somewhere to have this alright so any comment is welcome

Cheers
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