Setting up a pair of DBX 150's with an Otari MX5050bqii 4 track

Jzoha18

Member
Hello!
My otari has been killing it under regular recording circumstances (one collapsed bounce to channel 4 and 3 more channels for a total of 7 tracks). It's a truly pro level unit and I wanna shift the majority of my recording to it. Unfortunately it's only 4 channel's and 1/4 mds-36 tape I use ain't cheap. So I use it at 7.5 IPS and I've been very happy. But trying to do stereo bounces to my mixdown deck (tascam 112rmkii, I know not optimal but USB interface is unusable too much interference) and back I realized the pair of DBX units I got for it need to be installed if I want to get away with 8 track mixes at this speed and probably at 15ips too under my current constraints. Hopefully it improves the outcome. Does anyone know if it's difficult to set these NR units up? Do I just plug the 1&2 rack into channel 1&2? And the other rack with it's matching channel numbers? I've heard some say it needs to be biased and others say it's simply level Matching. First time using a seperate NR system and I would like my beautiful otari as optimized for my needs as possible. It's too much machine to not constantly be tracking too. Anyways sorry for the essay!
 

sweetbeats

Reel deep thoughts...
Got it. This one, yes?

https://dbxpro.com/en/product_documents/150-owners-manualpdf

If yes, you’ve got the right idea. If you didn’t have the manual, you do now. It has some really good straight-forward instructions for connections. But yes, one of your two dbx 150 units will encode and decode noise reduction for two of your Otari tracks, and the second 150 will handle the other two tracks.

I don’t know anything about “bias” with dbx noise reduction units…there may be internal trimmers for detailed operational calibration, but those don’t typically need messed with, and you’d need the service manual, oscilloscope, pulse generator, etc to do this. SO…fuggedaboudit. Don’t worry about the internal stuff. BUT you see the trimmers in the front. That’s just for calibrating the input and output levels. Similar to level calibration on a tape machine, making sure whatever signal level goes in is the same as what comes out across all channels. There’s a procedure in the manual for this. It’s not mandatory that you do it, the units will operate without having all the levels lined up, but knowing and being able to trust what “0” on your meters actually represents and that levels are consistent across all tracks is essential IMO. But you can plug them up and take them for a spin before you worry about calibrating levels.
 
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RRuskin

Rick Ruskin
1kHz is the only frequency that dbx doesn't mess with. Align your machine with dbx in bypass. Afterward playback a 1kHz tone @ 0Vu and compare the level with decode in and out. Anything within +- 1 db is fine. Then record a 1kHz tone @ 0Vu and compare the level with encode in and out. Anything within +- 1 db is also fine. Do not record ultra hot with dbx.
 

Jzoha18

Member
Got it. This one, yes?

https://dbxpro.com/en/product_documents/150-owners-manualpdf

If yes, you’ve got the right idea. If you didn’t have the manual, you do now. It has some really good straight-forward instructions for connections. But yes, one of your two dbx 150 units will encode and decode noise reduction for two of your Otari tracks, and the second 150 will handle the other two tracks.

I don’t know anything about “bias” with dbx noise reduction units…there may be internal trimmers for detailed operational calibration, but those don’t typically need messed with, and you’d need the service manual, oscilloscope, pulse generator, etc to do this. SO…fuggedaboudit. Don’t worry about the internal stuff. BUT you see the trimmers in the front. That’s just for calibrating the input and output levels. Similar to level calibration on a tape machine, making sure whatever signal level goes in is the same as what comes out across all channels. There’s a procedure in the manual for this. It’s not mandatory that you do it, the units will operate without having all the levels lined up, but knowing and being able to trust what “0” on your meters actually represents and that levels are consistent across all tracks is essential IMO. But you can plug them up and take them for a spin before you worry about calibrating levels.
Should I just use the 10k and 1k internal Oscillator my Otari has to do the level Matching?
 

sweetbeats

Reel deep thoughts...
No need for the 10k tone. Just use the 1k tone. Look on page 2 of the linked manual under the Quick Set Up section. There’s a nice little procedure for the level calibration.
 

Jzoha18

Member
No need for the 10k tone. Just use the 1k tone. Look on page 2 of the linked manual under the Quick Set Up section. There’s a nice little procedure for the level calibration.
Ok I'll give this a look. Hopefully this DBX quiets it up enough. Proper hiss reduction and this machine would be killer
 

Jzoha18

Member
this is a rats nest trying to get these units figured into the otari which is in a patchbay but ill figure it out. say i just remove the patchbay and do this Otari and mackie CR1604 and DBX units. how do i translate this image?
 

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sweetbeats

Reel deep thoughts...
The Mackie is the mixer on the left, your Otari is the bottom tape machine, and your two dbx units are the bottom two in the pic. Does that help?
 

Jzoha18

Member
The Mackie is the mixer on the left, your Otari is the bottom tape machine, and your two dbx units are the bottom two in the pic. Does that help?
I'm not using the patchbay until after the dbx is setup correctly. Basically the direct outs of the Mackie are the buss outs in the diagram and the inputs on the manual would be the inputs to the Mackie correct?
 

sweetbeats

Reel deep thoughts...
Yeah I think you’ve got it right. The direct outs on the console go to the “from console outputs” jacks, and the inputs on the console that you want sourced to the tape machine outputs connect to the “to console inputs” jacks. Hope that helps.
 

Jzoha18

Member
Yeah I think you’ve got it right. The direct outs on the console go to the “from console outputs” jacks, and the inputs on the console that you want sourced to the tape machine outputs connect to the “to console inputs” jacks. Hope that helps.
Thank you! I'll take a shot at it tommrow I'm cooped up at work!
 

Jzoha18

Member
im having some trouble im all set up and i turn on the internal 1k and set the line input knobs to 0db with DBX in OUT. I begin recording and when i hit IN the tone gets quieter but the meters stay the same no matter how much i touch the rec trimmer. on playback the playback trimmer makes a difference in the tones level but not on the meters. Im doing the record adjustment with the otari set to INPUT and the playback with the otari set to REPRO. Am i missing something?
 

Jzoha18

Member
im testing a drum machine out and the record adjustment seems to affect the otaris meters now? just not with the internal osc?
 

Jzoha18

Member
i used a tablet sending a osc at 1k and sort of figured this out. i think the alignment on channel 1 is hotter than the rest and that explains the noise. im doing a rough level balance with the tone and testing record and playback with a drum machine. it wont be perfect but the hiss is gone and i should be ablew to get a better mix out of it now. ill see what happens. how destructive is type 1 dbx to audio at 7.5 IPS?
 

Jzoha18

Member
so i recorded a stereo bounce from before and finished it up and the hiss is lower so thats good. levels arent all over the place between channels. This will be have to be fine tuned. I need to record fresh on all channels with DBX to really know for sure.
 
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