The Ghost of FM said:
dbx doesnt really eat up your highs as much as using a machine which may have drifted out of calibration or is being used with a poorer tape formulation.
In general though, most cassette based Portastudios will have trouble at the high end of the spectrum because of the inherent short comings of using tape at slower speeds. Generally, the faster the tape travels across the heads, the easier it becomes to capture high frequencies faithfully and is why many Portastudio users graduate to open reel decks which run at much higher speeds and with wider track widths to capture more information.
Turning off the dbx will give you a bit more highs, true; but it will also give you a lot more tape hiss.
Good luck with your sound.
Cheers!
Slowrider. Generally agree with Ghost. Both dolby and dbx got (partly deservedly) a bad rap because manufacturers and marketers didnt want to give the downside to the equation. Or in short, you rarely get anything for nothing.
Analog NR requires the machine and tape combination be
very well aligned, more critically than without NR. That's the big penalty.
But put it this way, if your machine sounds bad with NR switched in, it's out of calibration. But it's also out of calibration
without the NR. It just doesnt sound as bad but it's still not right. Many home users, not knowing this decided NR was crap and soldiered on without it. Result: hissy or distorted (or both) recordings, which were less than what they could have been, even without NR. All that complex processing circuitry gone to waste.
Pro studios used NR from the mid 60's onwards, and to great effect. Almost indispensable with multitrack. But they had the money to pay to have their machines regularly and carefully calibrated.
Cassette recordings benefitted hugely from NR too but only if you had them set up right, like the pro studios did with their reel to reel machines.
Many people have probably never heard a good Portastudio, aligned to a good tape, using say Dolby C or dbx.
There should be no drop off in highs. None at all. Just much less background noise. Even a normal type tape with NR could sound far better than the best, most expensive metal tape available, with no NR.
With dbx if you listen carefully you might hear tape hiss "breathing" especially when something like bass guitar is playing out of silence.
But even with normal tape speed, so long as everything is lined up well with a good tape, the highs should be better with good NR than without, because that's what the NR is doing: working to fit the signal onto the tape far better than you could achieve without it.
There is an extra penalty of more potential for "dropout" which is just a side effect of all the expansion used on playback, so you needed to use good tapes in a well maintained machine or it could sound awful.
Also, NR encoded tapes can be, or become over time, undecodable even on a perfectly calibrated play deck. That is a specialised problem which can be dealt with using the right equipment and know how.
But dont trash NR, whatever brand or type. It was the mainstay of the pro studio world for decades.
I still use it in 2006 in a professional context. It works.
I also have live band recordings done years ago on multitrack cassette with normal tape and normal speed, but with Dolby C (it could have been dbx). The 20db extra headroom is just unbeatable especially with the live recording.
But being a tech I never had to pay anyone to do the alignments for me.
Cheers Tim.
