Otari MX 5050 mic preamps

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lazerbeans

New member
I'm a recording novice. A friend gave me a well-worn Otari MX 5050 8 track. It is the earlier one with the 4 stereo preamps separate from the recording unit.

Is there a way to use the 4 stereo sections just for the mic pres?
Are they decent?

I don't want to spend the money on the reel-to-reel section for alignment and tweaks and I don't want to maintain it.

The stereo channels sound good when I use another preamp and send that signal into the unit DI to tape. But when I try to simply plug a mic directly into an Otari mic in and send it out to ProTools the signal is really week and has a nasty hum (on any channel I try).

I know the inputs are unbalanced as I have read. I'm plugging the mic into the 1/4" mic in (the only mic input) with an xlr to 1/4" ts cable. And I'm sending the signal out with the only output (xlr-xlr into a DI channel in my Digi 003).

Maybe the 4 stereo units in the Otari are not actually mic pres since a console would typically be used? But why does it have mic ins AND line ins?

Thanks!
 
lazerbeans said:
I'm a recording novice. A friend gave me a well-worn Otari MX 5050 8 track. It is the earlier one with the 4 stereo preamps separate from the recording unit.

Is there a way to use the 4 stereo sections just for the mic pres?
Are they decent?

I don't want to spend the money on the reel-to-reel section for alignment and tweaks and I don't want to maintain it.

The stereo channels sound good when I use another preamp and send that signal into the unit DI to tape. But when I try to simply plug a mic directly into an Otari mic in and send it out to ProTools the signal is really week and has a nasty hum (on any channel I try).

I know the inputs are unbalanced as I have read. I'm plugging the mic into the 1/4" mic in (the only mic input) with an xlr to 1/4" ts cable. And I'm sending the signal out with the only output (xlr-xlr into a DI channel in my Digi 003).

Maybe the 4 stereo units in the Otari are not actually mic pres since a console would typically be used? But why does it have mic ins AND line ins?

Thanks!
Click to expand...


Are they labeled "Mic" and "Line" or are you assuming that the xlr jacks are mic inputs?
 
If they are XLR inputs they were intended to be mic jacks...I have a yamaha 8 channel preamp that was designed to be a front end to a mixer...they work very nicely.
 
darrin_h2000 said:
If they are XLR inputs they were intended to be mic jacks...I have a yamaha 8 channel preamp that was designed to be a front end to a mixer...they work very nicely.
Click to expand...

Not so. The type of jack/connection does not necessarily denote what kind of circuit is involved.
 
darrin_h2000 said:
Right on...but wouldnt it have been way cheaper and just as good to use other connections?
Click to expand...

The Otari machines were marketed as being upscale from the corresponding Tascam units of the day so in that respect, it made sense to have "pro" gozintas and gozoutas rather than 1/4" or rca types.
 
5050 came in a lot of flavors . . . And Otari, certainly at the time, would have been willing and able to customize connectors for specific installations. Not too extreme a stretch for a recorder to be set up to be fed from 'balanced' outs on a mixer via XLR cables (would have seemed 'cutting' edge at the time) . . . the 'stereo' is perhaps suggestive . . .

In any case see if this: manual helps

Good luck
 
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Kind of out of historic curiosity thought about this issue some more (used a 5050 variation in late 70's) and gut response is that as far as impedance and pot's, amp circuit should accept input from low impedance mics . . . Min impedance was about 150 ohm . . . The pots were 10 kohm but I don't think in original vintage that this would be a device I'd pursue for mic pre's

The amp circuits were pcb and probably migrated to ic's fairly early amps would have been based on 70 dB s/n for the entire unit and guess is overall gain would be less then spectacular

If price is cheap enough and you're looking for the specific character delivered by the approach there is certainly nothing wrong with using these amps

But in terms of modern general purpose recording there are a lot of more effective, more flexible options

and your experience more or less supports my reasoning . . . unit supports nominal impedance but lacks gain, via xlr input, for modern dynamics, attaching via 1/4 in you would expect artifacts (which I would not typically describe as 'hum' but might be characterised as noise) while condesers with external phantom power might fare better I still would not expect exemplary sound

and of course without hands on all of this is pure guess work . . . but depending on age of unit a little mic history research could easily demonstrate why unit could be set up for unbalanced 1/4 in AND balanced XLR but still not be acceptable for modern mics (20 dB s/n leap from tape to entry level digital was a huge leap) all the circuits of all my 70's multitrack tape options were noisey by even entry level standards today
 
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1/4" mic ins - xlr line ins/outs

Thanks, everyone.

The mic ins are, in fact, labeled "mic" and are 1/4". Seemed odd to me but I figured a console and patch bay setup was supposed to sort that out.
The only line-ins and line-outs are labeled as such and are xlr.
There are no other inputs or outputs.

This guy is adamant about the machine being unbalanced:
https://homerecording.com/bbs/showthread.php?t=173053

Oretez, thanks for the thoughts on the mic pres. That is the discussion I need most. With a mic direct in the 1/4" "mic in," the meter shows plenty of signal. But the output has serious hum and low gain. If the signal was clean, I was going to keep the pres for some funky old sound to ad to my more normal pres. I didn't want to regret dumping the machine just since I don't want to use the tape.

The machine sounds really great for its self-contained purpose so I'll probably sell it. Needs a roller resurfaced, alignment, and 2 of the 8 preamps have some noise. Too much investment for my use.

Thanks!
 
Yeah...they seem to look really cool...but not practical by any means today...I was fancying a tascam 8 track similer to this one a few weeks ago...that was on Craigslist...but where go to get the tape?
 
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