Re: Impedance converter for electric guitar

On 2008-05-21, Eeyore <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:
Andre Majorel wrote:

My search engine skills must suck. I've been looking without any
success for the schematics of a DI box. The goal is to plug an
electric guitar or bass into a line input.

Would a TL072 voltage follower with a 5 M resistor to ground on
the non-inverting input do ? Or is there more to it than that ?

A TL071 might be more suitable ! ;~)

I wouldn't make the loading as high a 5M though. 1M ought to be more
than enough. Basically, you're on the right track however. Don't forget
a resistor in series with the output of around 150 ohms though. The
TL07x series tend to like to oscillate when driving capacitive loads
(i.e any length of screened cable) in voltage follower mode
particularly.

Thanks. I used a 3 M to ground and a 220 ohms in series with the
output. Left the offset nulling pins floating and didn't even
bother decoupling the op amp. It's night and day compared to
going straight into the mixer. Not bad for 0.4 EUR worth of
components.

--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
"Cette supposition rappelle assez celle de ce prédicateur qui, en
pleine chaire, faisait remarquer à ses fidèles la bonté de Dieu qui
avait placé les rivières auprès des villes." -- Alexandre Dumas
.

Relevant Pages

  • Re: Impedance converter for electric guitar
    ... electric guitar or bass into a line input. ... Would a TL072 voltage follower with a 5 M resistor to ground on ... a resistor in series with the output of around 150 ohms though. ...
    (rec.audio.tech)
  • Re: Impedance converter for electric guitar
    ... - one high impedance input, ... Would a TL072 voltage follower with a 5 M resistor to ground on ... TL07x series tend to like to oscillate when driving capacitive loads ...
    (rec.audio.tech)
  • Re: 4-20mA Analouge input
    ... Im sure there is a standard im meant to be following but im not sure what it is. ... you do that via a 24 volt supply through a resistor ... basic ohms law of the source resistor you're using. ... just put this into a op-amp as a voltage follower. ...
    (sci.electronics.design)