How do I add a line-out?

[tubelovin]

Is there a formula to use or is it just a basic circuit that works on most amps? I would like to try a wet/dry setup but I don't want to fry anything.

[Cliff Schecht]

There's always a formula to use. It's simple Ohm's law and cutoff frequency calculations though, nothing too crazy.

[iknowjohnny]

very simple. A couple resistors and a jack. Go to schematicheaven.com and look at some newer amps like marshall jcms on up. Most will have a DI taken directly from the speaker jack which is great because it gives you a signal representitive of the entire amp. that way you can use most anything as your effects return amp and still get a good sounding signal to it. I use the wet/dry setup myself like this and it works great. any small amp works fine as a effects return, even a cheap 15 watt SS amp will do unless you use a lot of effects. I just use a little bit of verb or delay and occasional chorus. set your effects to fully wet and no dry signal if possible. Oops, sorry for the leacture on wet/dry, you probably know all that. But in any case go there and look at some later marshalls like the 2204 or soldonos etc etc. Most fairly modern amps have a DI out from the speaker.

[MasterDisaster]

This is a Voltage Divider calculator you can use.
http://www.raltron.com/cust/tools/voltage_divider.asp

R1=Series Resistor
R2=Parallel Resistor or Pot

A 100w amp will give you about 40V into a 16ohm load and a 50w amp about 20V into a 8ohm load.

Some common values are R1=47K and R2=5K.
Normal Line Voltage is 2V.

Mike

[tubelovin]

Thanks guys, I'll give those links a look. Basically I should be shooting for about 2v into my effects then?

So on the JCM800 the DI on the back is a line-out? I've got one of those and never really thought about what that jack as for.

[MasterDisaster]

I would recommend that you use a pot for R2 so you can adjust the level.
You might have to tweak these values depending on amplifier output and input impedance of your target.

*Log in for schematic.

Mike