[panfilero]

hello,

I'd like to make a sine wave generator that I can play through a
guitar amp... or bass amp for that matter... I imagine the signal
coming out of a guitar into an amp is pretty tiny... I was wondering
if anyone could tell me around what amplitude range I should make my
signal so that it's comparable to that of a guitar or bass....

also, is there any kind of impedence matching or anything I need to
check with the amplifiers input impedance and the circuit I'm making?
I would guess not, because I just tried to measure the resistance
looking into my amp... and it's like a meg.... but i hear a lot about
impedence matching and speakers being 8-ohms and 4-ohms and such....


much thanks!

 

[panfilero]

Output from guitars can be as low as 10 mV and as high as 1 V or larger
(especially in the case of active pickups or active circuitry).  But for
passive pickups somewhere in the 50 to 200 mV range is typical.

As for impedance matching, don't worry about it.  Impedance matching is
important for power transfer -- like when you go from your amp's output
transformer into speakers -- but is irrelevant at the other end of the
signal chain.  You're interested in good *voltage* transfer basically,
which means that you should try to keep the output impedance of your
device well under 1 megohm, which by the way is a typical input
impedance for most guitar amps.

cool, thanks that's exactly the info I was looking for!

 

[Eeyore]

hello,

I'd like to make a sine wave generator that I can play through a
guitar amp... or bass amp for that matter... I imagine the signal
coming out of a guitar into an amp is pretty tiny...

Errr... NO ! When played hard it can be as high in the volts range (
depending on pickup type and make ). Ditto for even low impedance
microphones used close up believe it or not. I'd suggest a generator that
can produce up to 'line level' ( around a volt ) to make it versatile.

Impedance is not an issue, audio is not 'matched' as much as people seem
to think. Make your generator low impedance output ( say a few hundred
ohms in series with an op-amp output to avoid capacitive loading problems
from any long cable causing instability problems - that's the only reason
).

Graham

 

[Eeyore]

Output from guitars can be as low as 10 mV and as high as 1 V or larger
(especially in the case of active pickups or active circuitry). But for
passive pickups somewhere in the 50 to 200 mV range is typical.

As for impedance matching, don't worry about it. Impedance matching is
important for power transfer -- like when you go from your amp's output
transformer into speakers -- but is irrelevant at the other end of the
signal chain. You're interested in good *voltage* transfer basically,
which means that you should try to keep the output impedance of your
device well under 1 megohm, which by the way is a typical input
impedance for most guitar amps.

Yes, 220k or even 100k are typical.

All good advice.

Graham

 

[krw]

Huh? 0dBm = 1.5492V P-P across 300 Ohms.

He didn't say "0dBm". He said "0db", whatever that is ;-)

0dBV is 1Vrms (impedance not specified).

 

[krw]

All of which does nothing to enhance the OP's knowledge.

Perhaps not. Misinformation doesn't enhance the OP's knowledge
either.

Try this and try Google next time before asking a question. Google
electric guitar pickup voltage level
and see how many answers you get like this one

Why? Doesn't interest me.

answers.yahoo.com/question/index?qid=20080609130810AAnq2T5 - 29k -

<yawn>