Home |
Search |
Today's Posts |
#1
Posted to rec.audio.tech
|
|||
|
|||
Impedance converter for electric guitar
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. The specs would be : - one high impedance input (couple megohms), - one unbalanced line output, - unity gain, - +/-15 V supply prefered, 9 V supply OK. - preferably only jelly bean components. In particular, no transformers. :-) 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 ? Thanks for your help. -- 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 |
#2
Posted to rec.audio.tech
|
|||
|
|||
Impedance converter for electric guitar
"Andre Majorel" wrote in message ... 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. The specs would be : - one high impedance input (couple megohms), - one unbalanced line output, - unity gain, - +/-15 V supply prefered, 9 V supply OK. - preferably only jelly bean components. In particular, no transformers. :-) 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 ? Thanks for your help. -- 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 A simple voltage follower as you describe would certainly work, but I have to ask:- Why no transformers, why an unbalanced output, and why such a high input impedance? If you're taking the cable any distance, especially in an environment where there are lights and lighting controllers, I would much prefer a balanced connection. If so, then transformers have a great deal going for them, mainly in providing full galvanic isolation between the instrument and the rest of the world. A couple of megohms input impedance also seems very high, is there a reason for it? S. -- http://audiopages.googlepages.com |
#3
Posted to rec.audio.tech
|
|||
|
|||
Impedance converter for electric guitar
In article , 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. The specs would be : - one high impedance input (couple megohms), - one unbalanced line output, - unity gain, - +/-15 V supply prefered, 9 V supply OK. - preferably only jelly bean components. In particular, no transformers. :-) 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 ? Thanks for your help. Your going to have much more than 2 M but thats good. I would rather try an inverting design for stability and protection. Two 10 Megs on the inverting side. Unity gain is not going to work. Its going to be easier getting gain with a non inverting amp. You might be able to modify my basic mic amp. http://www.pitt.edu/~szekeres/sub/mica.gif greg |
#4
Posted to rec.audio.tech
|
|||
|
|||
Impedance converter for electric guitar
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. The specs would be : - one high impedance input (couple megohms), - one unbalanced line output, - unity gain, - +/-15 V supply prefered, 9 V supply OK. - preferably only jelly bean components. In particular, no transformers. :-) 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. Graham |
#5
Posted to rec.audio.tech
|
|||
|
|||
Impedance converter for electric guitar
GregS wrote: I would rather try an inverting design for stability and protection. That will be noisy as hell. Non-inverting is far and away the best method here. Graham |
#6
Posted to rec.audio.tech
|
|||
|
|||
Impedance converter for electric guitar
"Andre Majorel" wrote in message ... 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. The specs would be : - one high impedance input (couple megohms), - one unbalanced line output, - unity gain, - +/-15 V supply prefered, 9 V supply OK. - preferably only jelly bean components. In particular, no transformers. :-) 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 ? Here's a tip, a Behringer DI100 is nearly as cheap as you can buy the parts for, even assuming your time is worth nothing. The performance is quite good, that's why they sell millions of them. If you really don't want a transformer, the DI20 is even cheaper and has dual I/O. However it is better used for a keyboard than a guitar IMO. Both will work on 9V battery or 48V phantom power. Both have balanced output which can easily be adapted to unbalanced if you really must. MrT. |
#7
Posted to rec.audio.tech
|
|||
|
|||
Impedance converter for electric guitar
On 2008-05-21, Eeyore 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 |
#8
Posted to rec.audio.tech
|
|||
|
|||
Impedance converter for electric guitar
Andre Majorel wrote: Eeyore 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. Good to hear you got a satisfactory result. Graham |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Mic for electric guitar recording under $75. | Pro Audio | |||
Guitar cable to rca converter? | Tech | |||
Electric guitar to amplifiers... | Tech | |||
what guitar effect is not use ad-converter in itself? | Pro Audio | |||
Synth through guitar amp -- impedance issues? | Pro Audio |