Q: How can the Tape Monitor output of my stereo receiver be "inadequate"
for sending a good level to my soundcard's Line In?
A: The Tape Monitor outputs in a typical stereo receiver are not amplified
in any way; they simply pass the audio straight from the phonograph
preamplifier through to the Tape Monitor output jacks, with no additional
help from any amplifier circuits.
The phono preamp output circuits found in most stereo receivers are only
designed to work well when connected to the stereo receiver's internal
inputs or the inputs of a cassette deck. They were never designed to drive
more difficult loads like the line input on a soundcard.
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Q: What is so "difficult" about a PC soundcard's inputs?
A: Many people must use long (6 feet or longer) audio cables to connect from
their stereo setup to their computer. It takes extra *current* to drive
the long interconnect cables between the stereo's Tape Monitor outputs and
the soundcard's Line Input, so a phono preamp's outputs may "load down"
while trying to drive the signal all the way to the sound card). This will
result in a very weak signal that lacks highs and lows. The extra boost
provided by a standalone phono preamp or mic mixer will fix this problem.
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Q: Why does this work better with a mixer?
A: An audio mixer has buffer amps at its outputs that are *designed* to
drive difficult loads, like a rack of PA amps and electronic crossovers
located 15 feet away from the mixing position, for instance. Compared to
this, the Line In on your soundcard is a piece o' cake to drive!
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Q: Why do phonograph records need an RIAA preamplifier in the first place?
A: The grooves of an LP record need to be made extremely small in order
to hold all the audio information. At the same time, larger grooves are
needed to reproduce low frequencies. If the grooves are made too large,
the needle will leap out of the grooves on the record surface. To hold
the entire audio spectrum within small grooves, the bass frequencies are
intentionally turned down during the making of the master disk. The LP
record is a copy of this master disk.
When the LP is played back on the listener's record player, an RIAA phono
preamp adds a specifically tailored low frequency boost and high frequency
cut, called the "RIAA equalization characteristic". This results in a
"flat" frequency response during playback ("flat response" means "no
artificial boost or cut of any audible frequencies").
Here is an illustration of the RIAA Frequency Response characteristic.
Notice how the bass frequencies are boosted, the midrange frequencies are
left alone, and the treble frequencies are attenuated. This is exactly
the opposite of what the frequency response is coming directly from the
phonograph cartridge. The end result is flat response, the same as what
was on the original master tape from which the LPs were cut.
Low Frequency Rolloff = 16Hz
| ____ Low Frequency Breakpoint
| / \ = 59Hz (Gain= 29 dB)
+20| / \
G | / \
+10| \ Mid Frequency Breakpoint
A | \ = 590Hz (Gain= 20 dB)
dB| \_____________
I | \
-10| Hi Freq Breakpoint \
N | = 2122Hz
-20| \
+---+-------+--------+---------+--------
10Hz 100Hz 1kHz 10kHz Freq-->
If you connect your record player directly to the Line In of your
soundcard, you will get a faint, "honky", "thin" sound. Please use a
properly designed RIAA preamp for best results.
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Q: How do I hook up my record player (and receiver) into a mixer and then
to my soundcard?
A: LP Record Player RCA plug outputs ---> Stereo Receiver Phono Inputs
---> Stereo Receiver Tape Monitor Out ---> Mixer Line Input
---> Mixer Main Output ---> Soundcard Line In.
Or....
LP Record Player outputs ---> Mixer Phono Inputs (if present) --->
Mixer Main Output ---> Soundcard Line In.
Or for a stand-alone phono preamp...
LP Record Player outputs ---> Phono Preamp Inputs --->
Phono Preamp Outputs ---> Soundcard Line In.
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