How to add line-in to a guitar amp?

ozzu2000

Member
2010-12-13 9:32 pm
Hi!
I'm thinking about buying an small 12W amp, (orange crush). The thing is that, unlike it's bigger 20W brother, this one does not have a line-in jack (aux input).
Do you have an idea of how hard is it to add one?
I'm guessing it's just a jack and a couple of resistors in the right place...
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Any help will be very appreciated
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It's hard to give specific advice, especially without a schematic.
This is a solid-state amp?
What do you want to play through your LineIn - CD player without a volume control, or something like an MP3 player with volume control?
For figuring out the values for a resistive voltage divider, one easy tactic is to temporarily wire in a pot, adjust to suit, measure the resistances from the pot, and then replace the pot with a pair of resistors.
I do what NigelWright has suggested - just plug it into the normal input and keep the volume control down.
A lot of the newer cheap amps have pretty flimsy PCB traces- I avoid hacking into them unless it is absolutely necessary.
John
 

wakibaki

Banned
2008-01-08 11:51 pm
Line level varies from ~0.3 - 1.5V rms depending on whether it's consumer (lower) or professional (higher) audio, and which country. They generally have a low output impedance (100R).

Guitar outputs range from 0.1 -1.0V rms. They are quite high impedance and guitar amps have a correspondingly higher input impedance of 500k or greater, so they will not load down the line out.

This means that a guitar amp will generally accept a line level directly into the instrument socket. Depending on the actual line level and amplifier the amp may be slightly underdriven or slightly overdriven, but it should tolerate the overdrive without damage. Just turn it down a bit if it sounds a bit rough.

If you want to run both simultaneously an opamp summer is the best solution.

w