Successful dbx DX-4 noise reduction mod.

  • Thread starter Thread starter samth3mancgp
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samth3mancgp

samth3mancgp

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It's great to be able to sort out any problem here with just one quick search on this forum. :)

https://homerecording.com/bbs/showthread.php?t=271661&highlight=dbx+dx+4+mod

Thanks evm1024 for the very simple fix. Just 1 simple solder bridge.

It seems to be working fine! I hear a sort of deep pumping sound on the stuff that was not recorded with it. and a very noisy tinny sound to whatever i recorded with it on (when i turn it off while it's playing.)

It all sounds good when it's playing with it decoding. Does the noise reduction alter the frequency response at all? and it definitely looks like it can be calibrated. maybe i should do that?

Thanks again.
 
Just FYI, if you recorded with dbx NR, you need to play back with dbx NR.

If you recorded without dbx NR, do not play back with dbx NR.
 
Yea I knew that. ;) I was just describing what happened when I played something that was done without it through it. and what something that was done with it sounded without it so I could see if it was working properly :) Does the sound i described seem like it is working properly?
 
What you described sounds right.

I've found that dbx noise reduction often attenuates the high-end frequencies (8k and up) so I sometimes boost these frequencies when playing back for mixdown. Low frequencies also tend to build up, so I'll often cut below 100Hz if it's not a bassy instrument. The latter could be a nuance of the particular machines I'm using, so your mileage may vary.
 
Haha, well what you described sounds quite like the results I got with some acoustic guitar. :) I guess the high frequencies can be compensated for much easier now since the hiss is effectively gone right? It could make mistakes in tracking like not EQing before going to tape so that bringing up the highs later also bringing up the hiss during mixing irrelevant. It would be easier to get the tracks down. not to mention that the hiss is very annoying to alot of people I know that automatically associate hiss with bad quality :rolleyes:

This thing sure does use a crap ton of cables for only 4 channels. (and I need to get 1 or 2 more of these for the 8 track! :eek:)
 
You are welcome. Glad to see the info put to use.

Playing encoded tapes with out decode and un-encoded with decode will introduce all kinds of non-linear sounds (pumping etc) as you describe.

There are artifacts when the encode and decode (transfer functions) don't match. Calibration will help remove those as best as can be.

These units are old and the caps have changed most likely. Recapping can make a significant difference. I think I wrote about that when I recapped one of sweetbeats units. So I think that recapping then calibration will be useful.



--Ethan



samth3mancgp said:
It's great to be able to sort out any problem here with just one quick search on this forum. :)

https://homerecording.com/bbs/showthread.php?t=271661&highlight=dbx+dx+4+mod

Thanks evm1024 for the very simple fix. Just 1 simple solder bridge.

It seems to be working fine! I hear a sort of deep pumping sound on the stuff that was not recorded with it. and a very noisy tinny sound to whatever i recorded with it on (when i turn it off while it's playing.)

It all sounds good when it's playing with it decoding. Does the noise reduction alter the frequency response at all? and it definitely looks like it can be calibrated. maybe i should do that?

Thanks again.
Click to expand...
 
I noticed when I had the unit open that there were many pots there for calibration. How do I go about calibrating it and how do I know if it needs it?

Anybody have the manual? :)
 
Are the cal pots on the DX-4 internal? I have the 150 and they are on the front. Just wondering.
 
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