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Do I need a DI box for this?

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Do I need a DI box for this?

Postby CrayMo » Wed Dec 02, 2020 7:32 pm

I've got a Yamaha MT120s 4track and tons of music recorded on tape. I'm planning on ingesting it through my MOTU M4. The hitch is that two of the inputs on the M4 are balanced while the outs on my 4track are unbalanced. So two tracks are coming in at super low volume.

If I put a DI box between the 4track and the M4 on those 2 channels, would that take care of the volume problem?

Thank you for any advice on this.
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Re: Do I need a DI box for this?

Postby Sam Spoons » Wed Dec 02, 2020 9:05 pm

Welcome to the forum. I'm guessing you are using the XLR mic inputs for two channels? The will be more sensitive than the line inputs (i.e. the line inputs will record a lower/quieter signal into the DAW). A DI will not help as they reduce a line level signal to something appropriate for a mic input.

In theory you should be able to send the MT120 outputs to the line ins on the Motu (all four are balanced BTW) and if you record to 24 bit files, while they will show very low* on the waveform display, you should then be able to increase the gain to a reasonable level. Simple TS jack to TS jack cables will deal with the balanced/unbalanced connections.

* I assume the MT120 outputs 'consumer' -10dBV line level for sending to a hifi or similar, the MOTU is configured to receive a +4dBU line level.
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Re: Do I need a DI box for this?

Postby CrayMo » Wed Dec 02, 2020 9:28 pm

Yes, that's exactly it. Thank you.

So assuming I'm recording at 24bit and I boost the audio in the DAW, I shouldn't be losing too much of that audio?
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Re: Do I need a DI box for this?

Postby Sam Spoons » Wed Dec 02, 2020 9:38 pm

Once you have the audio in the DAW, even with very low levels you can boost it considerably before noise generated by the MOTU starts to be an issue. The simple way to find out is to give it a try. Obviously get the levels as high as possible into the MOTU, if the faders control the individual outputs then max them out. Then a gain plug in or normalise the tracks (to, say -12dBFS peaks) and see what happens. BTW which DAW are you using?
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Re: Do I need a DI box for this?

Postby innerchord » Wed Dec 02, 2020 9:56 pm

Are these important tracks? If so, please consider using an interface with matched inputs. There can be a marked difference between mic and line inputs on some devices. You just shouldn't be getting into impedance losses and level matching.

You might be surprised at how little you'd need to spend; a cheap interface may be all that's required. For example, the humble Behringer UMC404HD would be an excellent choice. Yes, really, a Behringer...

Feel free to spend more if the thought of a B@!&$% scares you!
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Re: Do I need a DI box for this?

Postby CrayMo » Thu Dec 03, 2020 6:19 pm

Sam Spoons wrote:BTW which DAW are you using?

Logic Pro X. Also have Adobe Audition, if that makes any difference.

I did what you suggested here and it actually sounds much better than I thought it would. Especially for something coming off of tape. It doesn't sound half bad at all.

innerchord wrote:Are these important tracks?
Heheh well, yeah - to me.

And thank you for this recommend!
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Re: Do I need a DI box for this?

Postby Sam Spoons » Thu Dec 03, 2020 6:59 pm

The headroom of the digital system, recording at 24 bit is way better than that of the tape that is the source (circa 120dB compared to the around 50 dB 'downhill with the wind behind it' of a cassette tape recording). That gives you a lot of 'free' gain available to boost the level in the digital domain.

I use Reaper and don't know much about Logic (or any other DAW TBH).

Glad it's worked out ok.
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Re: Do I need a DI box for this?

Postby Tomás Mulcahy » Thu Dec 03, 2020 7:48 pm

I had exactly the same issue. The audio interface has two inputs with gain, and two without. You are doing it the best way possible. Sam's advice is correct. Don't be tempted to use any of the outputs on the Yamaha that have gain. Stick with the direct tape outputs, it's noticeably cleaner sounding that way.
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Re: Do I need a DI box for this?

Postby CrayMo » Thu Dec 03, 2020 8:46 pm

This great info.

Thank you, everybody!
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Re: Do I need a DI box for this?

Postby ef37a » Fri Dec 04, 2020 9:35 am

CrayMo wrote:This great info.

Thank you, everybody!

You are using RCA (phono) to MONO TS jack plug cables? I ask because I am doing a similar thing dubbing from a domestic, neg ten Sony Dolby S cassette deck to the line inputs, 3/4 of an NI KA6 and I get easily enough level.

Dave.
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Re: Do I need a DI box for this?

Postby Tim Gillett » Fri Dec 04, 2020 10:18 am

Sam Spoons wrote:The headroom of the digital system, recording at 24 bit is way better than that of the tape that is the source (circa 120dB compared to the around 50 dB 'downhill with the wind behind it' of a cassette tape recording).

The MT 120s had the option of DBX noise reduction which the manual recommended using, so these recordings may be DBX encoded. If they are, and DBX decoded on playback, the noise floor may be a lot lower than 50 db down, probably more like 80 down or more. With less than ideal gain staging, and lots of gain boosting in the DAW what may seem like tape noise may be added noise after the signal leaves the tape deck. I'd check this carefully.
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Re: Do I need a DI box for this?

Postby Tomás Mulcahy » Fri Dec 04, 2020 8:06 pm

MT120 doesn't give SNR input to output (i.e. including the tape and the electronics). It says 84dB for the tape alone, with dbx in. The MT4X (which I have) is a superior machine, manual gives input to output SNR as 75dB with dbx in. I would say that they didn't include the MT120 electronics in the SNR because they're definitely not gonna add less than 15dB to the SNR :D

The MOTU line in noise floor is -115dB IIRC.

Can you do the math? I think it's a safe bet: 24 bit + digital gain FTW.
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Re: Do I need a DI box for this?

Postby Tomás Mulcahy » Fri Dec 04, 2020 11:52 pm

Oops I meant subtract :headbang:
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Re: Do I need a DI box for this?

Postby Tim Gillett » Sat Dec 05, 2020 4:14 am

Tomás Mulcahy wrote:MT120 doesn't give SNR input to output (i.e. including the tape and the electronics). It says 84dB for the tape alone, with dbx in. The MT4X (which I have) is a superior machine, manual gives input to output SNR as 75dB with dbx in. I would say that they didn't include the MT120 electronics in the SNR because they're definitely not gonna add less than 15dB to the SNR :D

The MOTU line in noise floor is -115dB IIRC.

Can you do the math? I think it's a safe bet: 24 bit + digital gain FTW.

You may be right that even with a DBX recorded and decoded tape, and gain and possible impedance mismatch there will be no losses but I wouldnt bet on it. I'd want to test it, as Sam suggested the OP do.
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Re: Do I need a DI box for this?

Postby CrayMo » Sun Dec 06, 2020 4:28 pm

ef37a wrote:You are using RCA (phono) to MONO TS jack plug cables? I ask because I am doing a similar thing dubbing from a domestic, neg ten Sony Dolby S cassette deck to the line inputs, 3/4 of an NI KA6 and I get easily enough level..

Yes, that's exactly it and that's good to hear!

Tomás Mulcahy wrote:Can you do the math? I think it's a safe bet: 24 bit + digital gain FTW.

I cannot do the math, so thank you!

Yeah, I've tried it on a number of tracks now and even with considerable gain - I'd say the most I've used on one track is +18db - it really sounds great. Or at least so much better than how I thought it would sound.

So again, thanks for the guidance!
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