414 mkII: noise reduction my a**

[Vagodeoz]

I got some brand new high bias and I gave them a try with my drumkit, and after recording like half an hour, I realiced that I was recording with noise reduction off, then I started hitting myself in the head.
So I put play to check the difference, and I switch it on and off (the noise reduction) and when it's off, it sounds good, I don't distinguish any noise while the drums are playing, and when it's on, it removes most of the highs, and it's almost like it has a gate that when it reaches certain threshold it closes, so I hit a cimbal and one second later I hit another one. With "noise reduction" on, the cymbals sounds at a normal volume for half a second, and the other half second it drops several dBs, and then the other one comes with full volume.
Adding to that the SEVERAL change in frequency response and you get a pretty awful sounding tape.

 

[The Ghost of FM]

dbx noise reduction is a two stage process which encodes during recording and decodes on playback.

You can not make a recording without it and then attempt to apply it afterward. It simply doesn't work that way. It will literally scramble the signal just as you described.

You can either complete your current production without it or start over again. Unfortunately, those are your only choices.

Cheers!

 

[Vagodeoz]

Wow, good to know that. thanks!
I thought it was a standart process that could be applied in recording, reproduction or both to have a better performance. dumb me...
Thanks a lot!

Edit: By the way, those new TDK SA-X Type II tapes WITHOUT noise reduction sound way better than regular Type I TDK tapes WITH noise reduction.
To all of you savers, go get decent tapes! seriously!

 

[jjones1700]

I recently did a recording outdoors (just outside the garage of the my motorcycle...........trying to find a rattle.......I know, kind of odd) with my 424 mkII and dbx on during recording. I played it back and WOW, it sounds pretty damn good. I played it again without the dbx, it sounded terrible. I guess dbx acts as a noise reduction and compressor.

 

[The Ghost of FM]

dbx compresses and expands all at the same time!

It works dynamically, depending on what's going on in the signal. Generally, things that it sees below a certain db threshold will be boasted and signals above that line will be compressed and then on playback, the exact opposite algorithm is used and the end result is that dynamics are preserved and steady state noises like tape hiss get pushed down lower then Dolby could ever do.

It's not a perfect system and especially so on cassette but it is very usable and solves more problems then it creates....usually!

Cheers!

 

[Vagodeoz]

I played it back and WOW, it sounds pretty damn good. I played it again without the dbx, it sounded terrible.

Same happened to me. So I guess it applies both ways, if you recorded with NR and play back without it, you will get an awful signal (waaay worse than if you would have never used it).
Maybe the dbx system also uses a little system I forgot how it's named, that first (on encoding) it boosts high frequencies (since noise is mostly in high frequencies) and then on decoding, it lowers the high frequencies back to a normal level (and therefore reduces the noise).

 

[jjones1700]

dbx compresses and expands all at the same time!

It works dynamically, depending on what's going on in the signal. Generally, things that it sees below a certain db threshold will be boasted and signals above that line will be compressed and then on playback, the exact opposite algorithm is used and the end result is that dynamics are preserved and steady state noises like tape hiss get pushed down lower then Dolby could ever do.

It's not a perfect system and especially so on cassette but it is very usable and solves more problems then it creates....usually!

Cheers!

I was thoroughly impressed with it. I know the purists and digital pundits would turn their nose up at it, but for me it works well. My question is, if I record with dbx on my 424 mkII, and then play it back on another (414, 424, etc. for example) player/deck with dbx, will it sound the same? I'm just curious if that algorithm is fixed or if it tends to vary by machine.

 

[jjones1700]

Same happened to me. So I guess it applies both ways, if you recorded with NR and play back without it, you will get an awful signal (waaay worse than if you would have never used it).
Maybe the dbx system also uses a little system I forgot how it's named, that first (on encoding) it boosts high frequencies (since noise is mostly in high frequencies) and then on decoding, it lowers the high frequencies back to a normal level (and therefore reduces the noise).

That makes me wonder about Dolby NR. I remember having a decent (read: not top of the line) Pioneer deck with Dolby B/C noise reduction. I always hated the way it sounded and I never used it on playback. I was ignorant of how noise reduction worked back then and here in the last month I have started to understand how it works. I just wonder if I go back through some of my pre-recorded cassettes (if I can find them.) and find ones that were specifically recorded in either Dolby B or C, if they would sound better with the appropriate decoder turned on. However, I have heard (and keep hearing) that Dolby wasn't/isn't as good as dbx, yet Dolby was everywhere, and I never even heard of dbx until I started getting into vintage audio gear in the last year.

 

[The Ghost of FM]

I was thoroughly impressed with it. I know the purists and digital pundits would turn their nose up at it, but for me it works well. My question is, if I record with dbx on my 424 mkII, and then play it back on another (414, 424, etc. for example) player/deck with dbx, will it sound the same? I'm just curious if that algorithm is fixed or if it tends to vary by machine.

So long as the different recorders are all calibrated to the same levels, you should be OK to swap the tape into another machine. But, if the machines are out to each-other, then some degree of pumping and breathing will be heard.

Cheers!

 

[The Ghost of FM]

Maybe the dbx system also uses a little system I forgot how it's named, that first (on encoding) it boosts high frequencies (since noise is mostly in high frequencies) and then on decoding, it lowers the high frequencies back to a normal level (and therefore reduces the noise).

dbx does use a similar process to Dolby B noise reduction along with its compression/expansion scheme though it works in a slightly different way which was probably by design so that they could avoid the Dolby licensing fees! That part of the dbx process only contributes about 25 ~ 30% of the noise reduction effect that dbx has though.

Cheers!