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dbx/ hx pro mod

hi,
i have a couple of broken cassette decks. one with dbx, one with hx
pro. was wanting to experiment with tapping into both the dbx and hx
pro circuits (in/out), making them independent processing units. i
would like to use these on other tape based recorders that don't have
them, but could, hopefully, benefit from using their noise reduction/
headroom extension.

i am not a fully knowledgable tech. i can solder and diagnose/
locate minor things, and can repair/ replace parts very well with
direction. my ideas exceed my education. mainly, if someone points
to something or says "this does that, and here's what you need to
do..", i can do it. i don't necessarily know why, but am learning.

i'm really wanting to turn this into a useable project. could someone
with specific technical knowledge let me know (before i tear into my
cassette decks) if it is technically possible to tap into the hx pro/
dbx circuits (through rewiring, ect). i'd like to be able to go into
stereo rca/quarter inch inputs, through the hx pro/ dbx circuit
processing, then out through rca/ quarter inch outs to a separate tape
recorder.

with hx pro, if i'm not mistaken, there is a bias adjustment signal
applied to the tapehead to allow for less high end distortion. would
this change things with the wiring? in other words, would the bias
adjustment signal not be able to transfer through rca/ quarter inch
jacks, but rather have to be hard wired to the circuit of the separate
tape recorder, going straight to the heads (i hope not)?

with dbx, i realize that it's a two way process needing to be recorded
onto tape then used to process during playback. so, would i need two
sets of in/out jacks for compressing (in)/ monitoring (out), and
recorded signal (in)/ expanding (out)?

i feel more interested in the hx pro method, than dbx, but would like
to know about both. i know that there are pro audio independent dbx
processors, but am interested in knowing if a broken cassette deck
with dbx can be turned into an independent processor itself.

specifically, i want to use the hx pro with recording onto 8 track
cartridges. i'd like to extend their headroom, lowering the noise
floor. is this technically possible? does hx pro have some cassette-
specific eq applied to it, that wouldn't work with the 1/4" tape in 8
tracks? seems like it should be able to work, somehow, because - 1)
isn't a circuit, a circuit?! as long as you do it right, can't you
send something through it, getting something different on the other
end...good or bad? 2) even though 8 tracks use 1/4 inch tape, the
track sizes are the same as cassette. the difference being that they
are recorded at 3 3/4 inches per second vs. 1 7/8.

secondarily, i want to use this with vhs and reel to reel technology,
but realize that it may not be necessary since they both have
relatively lower noise floors.

help!
 
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