fx loop??

conisat · 05-07-2009, 09:04 AM

so I am wanting to rebuild an old amp of mine and need some info on fx loop send levels. I want the fx loop as close to the power amp as possible so to capture the tone of my pre-amp and am wondering just how large of a signal will be required. Idealy I would like to send approx 30V P-P. IS THIS TO HIGH OR CAN I INDEED SEND MORE?????

guitician · 05-07-2009, 06:02 PM

An effects loop is just a tap into the junction of the Preamp to Poweramp. The power amps sensistivty should be set to run at "line level", if it requires more voltage you will have to add a stage of gain. If the preamp is putting out more than "Line level", it will need to be attenuated.

http://en.wikipedia.org/wiki/Line_level

GibsonLover · 05-08-2009, 06:28 PM

30Vp-p is pretty hot for an FX loop. For reference, nominal guitar level is referenced to 1V, and -20dBV is the level your floor effects expect to see. That comes to .283Vp-p. Consumer type equipment (RCA) runs at -10dBV, which comes to .894Vp-p. Finally, pro audio has a different reference, where 0dBU comes out to 2.192Vp-p. I have an Alesis Masterlink and an Alesis HD24 that put out +19dBU at 0dB full scale (0dBFS) and that comes to a whopping 19.536Vp-p. Anything more than 3.473Vp-p (pro level +4dBU = 0VU) is asking for trouble when interfacing with FX, mixers, etc.
If you're working with 30Vp-p, for the love of God, dial 'er back a little.

05-07-2009, 09:04 AM	#1
conisat Junior Member Join Date: Apr 2009 Posts: 20	fx loop?? so I am wanting to rebuild an old amp of mine and need some info on fx loop send levels. I want the fx loop as close to the power amp as possible so to capture the tone of my pre-amp and am wondering just how large of a signal will be required. Idealy I would like to send approx 30V P-P. IS THIS TO HIGH OR CAN I INDEED SEND MORE?????

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05-07-2009, 06:02 PM	#2
guitician Senior Member Join Date: Aug 2008 Location: Phoenix Posts: 341	An effects loop is just a tap into the junction of the Preamp to Poweramp. The power amps sensistivty should be set to run at "line level", if it requires more voltage you will have to add a stage of gain. If the preamp is putting out more than "Line level", it will need to be attenuated. http://en.wikipedia.org/wiki/Line_level

05-08-2009, 06:28 PM	#3
GibsonLover Supporting Member Join Date: May 2008 Posts: 175	30Vp-p is pretty hot for an FX loop. For reference, nominal guitar level is referenced to 1V, and -20dBV is the level your floor effects expect to see. That comes to .283Vp-p. Consumer type equipment (RCA) runs at -10dBV, which comes to .894Vp-p. Finally, pro audio has a different reference, where 0dBU comes out to 2.192Vp-p. I have an Alesis Masterlink and an Alesis HD24 that put out +19dBU at 0dB full scale (0dBFS) and that comes to a whopping 19.536Vp-p. Anything more than 3.473Vp-p (pro level +4dBU = 0VU) is asking for trouble when interfacing with FX, mixers, etc. If you're working with 30Vp-p, for the love of God, dial 'er back a little.

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