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

sweetbeats

Reel deep thoughts...
My advice: slow down.

You’re intermixing calibrating the dbx unit and calibrating the Otari. Decide which one you want to do right now and stick with that…one at a time. And be aware you absolutely cannot calibrate the Otari without a calibration tape. There is a process:

1. Calibrate meters
2. Calibrate playback electronics
3. Calibrate record electronics

You have to do them in that order and step 2 requires the calibration tape. Do you have a cal tape? If not, then cal the meters on the tape deck and go back to calibrating the dbx units.

The 150 manual has the nice straight-forward procedure in it I mentioned earlier for calibrating the levels of the dbx units. Just stick to that procedure…page 4 of the 150 pdf manual.

Dbx noise reduction is not “destructive”. It is a broad-band companding processor that compresses the audio ahead of the tape, and then expands it on playback which, in effect buries the tape noise because of the expansion of the program material. It’s a very straight-forward process. Type I dbx works fine for open reel formats such as 1/4” 4-track at 7.5ips and higher.
 

Jzoha18

Member
My advice: slow down.

You’re intermixing calibrating the dbx unit and calibrating the Otari. Decide which one you want to do right now and stick with that…one at a time. And be aware you absolutely cannot calibrate the Otari without a calibration tape. There is a process:

1. Calibrate meters
2. Calibrate playback electronics
3. Calibrate record electronics

You have to do them in that order and step 2 requires the calibration tape. Do you have a cal tape? If not, then cal the meters on the tape deck and go back to calibrating the dbx units.

The 150 manual has the nice straight-forward procedure in it I mentioned earlier for calibrating the levels of the dbx units. Just stick to that procedure…page 4 of the 150 pdf manual.

Dbx noise reduction is not “destructive”. It is a broad-band companding processor that compresses the audio ahead of the tape, and then expands it on playback which, in effect buries the tape noise because of the expansion of the program material. It’s a very straight-forward process. Type I dbx works fine for open reel formats such as 1/4” 4-track at 7.5ips and higher.
The otari was calibrated 3 months ago it's set up really well. I think I got the dbx working right. I got my record level at 0DB with it on and the playback level balanced on the mixer as best I can. The CR1604 meters are not super useful but it's not wonky and blown out or faint sounding. So im going to move forward from here and fine tune if in my next session I am not pleased with the dbx. Thanks for all the help so far!
 

Jzoha18

Member
so my channel 1 which had the most hiss and a slightly off playback VU meter out of the box but recorded and played clear and full seems to be fine and quieter now. What is really shocking me as someone who previously only used built in DBX or Dolby is how low in level i can record on the otari but get full hissless playback without cranking the fader. very impressed. i will have to readjust to the new metering though
 

RRuskin

Rick Ruskin
Once your machine is aligned with the dbx out and th.e dbx is aligned with the 1k tone, you can no longer trust the metering on your machine. You need to use your console meters to judge levels
 

Jzoha18

Member
So update. The recording session went pretty well. I have encountered a problem towards the end of the process though. Basically all tracks recorded and collasped on the otari sound fine. the problem came during the external bounce to the Tascam 112mkiir. ive noticed stereo bouncing back to the otari requires me to balance the stereo field with the otari in repro mode as the channels are off even when input mode plays back through the mixer evenly. Anyways once balanced and bounced back to the otari i got some annoying pumping. not of hiss but more of just a midrange honk. I think i had a effects send of a compressor on the drums and bass before i collasped everything and its settings were off, but i also bounced to cassette with dolby C on. any ideas how to prevent this pumping?
 

RRuskin

Rick Ruskin
Calibrations on analog decks are very touchy. I doubt it stayed in alignment by the time you got it. From your description, that is the only reason you would see the level differences you're getting now.
 

Jzoha18

Member
Calibrations on analog decks are very touchy. I doubt it stayed in alignment by the time you got it. From your description, that is the only reason you would see the level differences you're getting now.
would that explain why im getting pumping though? this didnt arise until after the dbx was installed and i began attempting external bouncing
 

Jzoha18

Member
Possibly but without more details about your bounce procedure & levels, it's hard to tell.
it looks like i hit the cassette deck pretty hard. normally i mix to it with stereo compression dead in the middle of the VU meters so no weird dolby peaks or anything. but just a clean bounce without compression it can spike a bit. I think i just blew out the mix and im paying for it now. Oh well. im using tape machines AND NR systems so im asking for trouble. ill finish the session and move on and keep an eye on it. What kind of calibration are we talking? physical or electronic? i might as well learn to set this otari up. its been restored and wasnt cheap!!! Id like everything working as perfectly as possible
 

RRuskin

Rick Ruskin
You need a calibration tape, an outboard meter you can trust and an o'scope. Alignment procedure should be spelled out in the machine's operation manual. I'm sure you can find one on line if you don't have it.
 

Jzoha18

Member
i wi
You need a calibration tape, an outboard meter you can trust and an o'scope. Alignment procedure should be spelled out in the machine's operation manual. I'm sure you can find one on line if you don't have it.
l will plan ahead for that. for the time being i might just skip external bouncing and finish vocal stuff on the DAW. Im getting really good results up until the point i leave the otari and honestly bouncing from consumer speed cassette back into the otari isnt that good anyway. Better to just do the instrumentation. mix it down then add vocals later. Money is tight right now. I would need a 7.5 IPS MRL if i want to use 7.5? do i need 15 IPS MRL?
 

sweetbeats

Reel deep thoughts...
Just a general comment, and it’s probably already been mentioned, but dbx Type I and Type II noise reduction processing can get wonky with harmonic distortion. So if the signal on tape is saturating the tape and you’re getting harmonic distortion, that can cause the dbx processing to mistrack between encoding and decoding. This can present as pumping. If your bounce to the cassette deck was hot and you saturated the cassette tracking, I’m not sure what your 150 boxes would do with the saturation artifacts from the cassette sums. Maybe that’s part of the problem, maybe not…dunno. It just crossed my mind so I thought to mention it.

You can use a 7.5ips cal tape at 15ips and vice-versa, but you run into problems if the tone set now falls outside the usable range. Your 10k tone on a 15ips cal tape is goi c to reproduce at 5k at 7.5ips. You won’t be able to properly set azimuth at 5k, or check/adjust HF frequency response. That’s an example.
 

Jzoha18

Member
Just a general comment, and it’s probably already been mentioned, but dbx Type I and Type II noise reduction processing can get wonky with harmonic distortion. So if the signal on tape is saturating the tape and you’re getting harmonic distortion, that can cause the dbx processing to mistrack between encoding and decoding. This can present as pumping. If your bounce to the cassette deck was hot and you saturated the cassette tracking, I’m not sure what your 150 boxes would do with the saturation artifacts from the cassette sums. Maybe that’s part of the problem, maybe not…dunno. It just crossed my mind so I thought to mention it.

You can use a 7.5ips cal tape at 15ips and vice-versa, but you run into problems if the tone set now falls outside the usable range. Your 10k tone on a 15ips cal tape is goi c to reproduce at 5k at 7.5ips. You won’t be able to properly set azimuth at 5k, or check/adjust HF frequency response. That’s an example.
Thanks for the reply!! it looks like the original stereo bounce on the cassette had the same pumping. I dont recall it being present that noticeably on the otari pre bounce. Does Dolby C pump when pushed? i think it might be a combo of the dbx and dolby being pushed too hard
 

Jzoha18

Member
funny enough the pumping has seemed to be coaxed away for the most part in my DAW transfer process LOL idk if its reasons limiter doing its job but it sounds alright! I need to get used to the DBX. On the other hand. The mackies VU meters are complete shit! anyone have a link for a reliable external VU meter i can put in my chain?
 

RRuskin

Rick Ruskin
funny enough the pumping has seemed to be coaxed away for the most part in my DAW transfer process LOL idk if its reasons limiter doing its job but it sounds alright! I need to get used to the DBX. On the other hand. The mackies VU meters are complete shit! anyone have a link for a reliable external VU meter i can put in my chain?
Teac/Tascam MB-20 or MU-40 meter bridge. They aren't frequency weighted and are accurate.
 

Jzoha18

Member
Teac/Tascam MB-20 or MU-40 meter bridge. They aren't frequency weighted and are accurate.
Thank you! My boss CL-50 describes a limiter setting for recording to tape without peaking. I'm aware of compressor to tape as a technique. Would doing this with a VU meter help since hot levels results in errors instead of just saturation?
 

RRuskin

Rick Ruskin
Try recording without any compression. Save that for any track or tracks that need it when you mix. With good NR you can print low, get little to no tape noise, and maintain dynamics. Printing hot enough for saturation defeats the dbx purpose and will almost always introduce unwanted artifacts.
 
Top