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From: janpo@leffe.UUCP (janpo)
Newsgroups: sci.electronics,rec.music.synth
Subject: Re: guitar audio signals
Summary: Guitar signal is NOT the same as phono signal!
Message-ID: <45@leffe.UUCP>
Date: 16 Feb 88 08:57:56 GMT
References: <502@m10ux.UUCP> <22670@yale-celray.yale.UUCP> <8948@ism780c.UUCP>
Organization: Philips I&E DTS Eindhoven
Lines: 45

In article <8948@ism780c.UUCP>, gary@ism780c.UUCP (Gary Swift) writes:
> In article <22670@yale-celray.yale.UUCP> lisper@yale-celray.UUCP (Bjorn Lisper) writes:
> >In article <502@m10ux.UUCP> rgr@m10ux.UUCP (Duke Robillard) writes:
> >>
> >>Do turntables put out the same  audio signal as electric guitars?
> >
> >Plug your guitar into "AUX" at your amp. I've been doing this with various
> >keyboards when I've been playing with them at home and it works just fine,
> 
> Were your keyboards (pre)amplified?  I've tried this with a
> (nonamplified) electric guitar and it didn't work, but it *did*
> work by going through turntable inputs.  I don't remember the
> sound quality though.  My experience is that the signal from
> an electric guitar, a microphone, and a phonograph are similar.
> (Hmmm, I wonder if you could plug a microphone into the phono
> jack?)
>
> I alone am responsible for my opinions.
> Gary Swift, INTERACTIVE Systems Corp., Santa Monica, Ca., (213) 453 8649
> sdcrdcf!ism780c!gary


Signals from phonograph and a microphone or electric guitar are
certainly not the same. The phono signal needs a so called RIAA
correction network in the amplifier. On a record, the bass signals
are attenuated and the high tones are emphasized. Consequently, when
the record is played the bass tones have to be boosted and the high
tones have to be attenuated. Why this is done? Well, the strong bass
tones (I.e. drums) cause wide tracks on the record which reduces the
time available for music on the record. That's why collection albums
with many songs on it sound so awfull and Stings' latest album (Think
it's called "Bring on the night"), a two record set actually, which has
only a few songs on it has a very good bass. The high tones are
to reduce the high pitch noise inevitably associated with vinyl records.
For those who are interested in it: The RIAA curve has two poles at
3180 /us (50 Hz) and 75 /us (2122 Hz) and a zero at 318 /us (500 Hz).

What do you get when you plug a microphone into a phono jack? Well, the
bass will boosted by about 20 dB over the midrange frequencies giving
bangs and booms and thuds and thunders through your speaker when the
microphone is only slightly touched and your voice will sound very dull.
You can guess now that an electric guitar will not sound very naturally
when connected to a phono input. A real microphone input will work well
I think because the guitar pick-up element and a dynamic microphone both
work basically the same way and without any frequency compensations.