The main area of concern is the loading of your amp's tape (line) output.
Assuming that the manufacturer of your amp has made a thoughtful design
consideration to use a buffer/voltage-follower at the output, then
connecting to and using all 3 recording devices at once shouldn't present
themselves to be a problem. But do tread carefully as more often than not,
you will find that buffers aren't used at the output, even in high-end
equipment, on the premise that you will avoid trying to split the signal in
order to avoid a quality problem.
Generally, in amplifier design, a two-way split is acceptable, but anything
further is not recommended and would require a buffer as the device to be
first in-line before splitting out to your various recording devices. This
way we can ensure that there is no excessive loading from all 3 devices and
so the signal remains faithful (or as much as the buffer will allow
depending on component choice).
I've had to do this in a car audio set up where even though the Sony amps
had a line out, it was only for connection to one extra amp and no more to
be "daisy-chained" thereafter. Basically, from a crappy deck (he didn't want
to fork out big bucks for his deck, so he had to live with a single set of
RCA outs), we had 3 amps to drive. Ah well, customer gets what customer
wants. So basically, the deck's output was destined for 2 amps driving one
sub each and one 4 channel amp driving the front and rear. That means a
3-way split and the sound was suffering from just "passive" splitters. It
was distorting, and was clear evidence that the deck's output was heavily
loaded.
Hopefully this makeshift block diagram will explain how I managed the
problem:
DECK --> Buffer1 --> Buffer2 --> Sub Amp 1
--> Buffer3 --> Sub Amp 2
--> Buffer4 --> 4 ch amp
Even though it would have been adequate to use just one buffer (ie. Just
buffer1 and piggy-back/split from there) considering we were dealing with
the same range of amp (and therefore, same input impedance on each of those
amps), it didn't cost much extra for the extra 3 buffers. The key here is
that the voltage remains the same for all line signals to the amps. The
result was a much cleaner sound as it was now remaining faithful, despite
the fact that the op-amps were powered by a single-rail voltage source
(op-amps always work best when powered by a dual-rail voltage source - that
is, +/-12V, not just +12V). Bear in mind that most op-amps operate ideally
at +/-15V but for the sake of an automotive application, 12V was the
available constant (unless you want to use a Jacobs Accuvolt system, which
can regulate (and step-up) voltages up to 16V).
You shouldn't experience any "earth voltage mismatch" if you make sure that
all devices are plugged into the same powerpoint to help minimise (if not
completely eliminate) ground loop issues.
So plug in and listen for any anomalies. If there are, then either don't
record simultaneously, or otherwise, incorporate the use of buffers. Hope
this helps somehow.
Adios,
LarZ
--------------- TAMA - The Strongest Name in Drums ---------------
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf
Of PrinceGaz
Sent: Monday, 19 July 1999 17:29
To: [EMAIL PROTECTED]
Subject: MD: Splitting a Line-out (for my minidisc etc)
I think I know the answer to this question, but would like to run it
past you first, before popping down to Tandy (aka Radio Shack)
and buying the necessary splitters and cables. And knowing me,
wandering around thinking "that's sure to be useful sometime" as
I browse the racks of components and things.
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