MRL Question.....

[broken_arrow]

Hey everyone, quick question about MRL tapes..

I need to align my Model 80 as I will be doing some tracking soon. MRL's are expensive, so I instead borrowed a 1/4" MRL from my Professor, sweet! I just saved a hundred(ish) bucks! (or so I thought)

When I got home, I noticed the tape speed of the MRL is 7.5 ips, and the model 80 only runs at 15 ips. I was wondering, since the tape speed is essentially halved, is there any way to align my machine with the 7.5 ips MRL by over/ under compensating the adjustments on my meters? Or do I just have to bite the bullet and buy the correct MRL for my machine? Any advice/ input is welcome, thanks guys

 

[ofajen]

Sure. Check out table 5, page 9 of the MRL guide

http://home.comcast.net/~mrltapes/choo&u.pdf

If the tape is NAB 7.5 ips and you want NAB playback at 15 ips, you want table 5-7. If both were IEC, there would be no level adjustments, you'd just have to be aware that all the frequencies were doubled when playing back at 15 ips. Hope that's clear. If not let me know.

Cheers,

Otto

 

[Beck]

Only trouble with McKnight’s tables in this doc is oddly enough he doesn’t have conversion for 7.5 ips NAB (IEC2) to 15 ips IEC1.

If you can find that information you would also need to compensate for fluxivity differences if any. That info can be found in table 4 on page 8. For example if the MRL tape you have is 250 nWb/m you would need to compensate levels to get the M80 set correctly to 320 nWb/m

If you have a 7.5 ips cal tape it’s most likely NAB. The Foxtex M80 needs IEC1 15 ips 320 nWb/m.

You can do the most basic level set @ 1 kHz using table 5-7 because 1 kHz is the same with NAB and IEC1. And then compensate for any flux level differences with table 4.

It starts to get a bit complicated when you’re dealing with different speeds and different flux levels… just plain screwy really.

 

[ofajen]

Only trouble with McKnight’s tables in this doc is oddly enough he doesn’t have conversion for 7.5 ips NAB (IEC2) to 15 ips IEC1.

If you can find that information you would also need to compensate for fluxivity differences if any. That info can be found in table 4 on page 8. For example if the MRL tape you have is 250 nWb/m you would need to compensate levels to get the M80 set correctly to 320 nWb/m

If you have a 7.5 ips cal tape it’s most likely NAB. The Foxtex M80 needs IEC1 15 ips 320 nWb/m.

You can do the most basic level set @ 1 kHz using table 5-7 because 1 kHz is the same with NAB and IEC1. And then compensate for any flux level differences with table 4.

It starts to get a bit complicated when you’re dealing with different speeds and different flux levels… just plain screwy really.

Thanks. I wasn't sure what eq the machine would have.

It's not too bad. You can use table 5-6 to go from 7.5 NAB to IEC, and it's the same at 15, but the playback frequency is doubled. The difference in level is no biggie. Its just a constant amount up or down. Easier to just calibrate to the level of the tape, do the frequency adjustments and then readjust level at 1k at the end. Done!

Cheers,

Otto

 

[broken_arrow]

You. Guys. Rule. Thanks so much, I'm gonna give this a try this weekend, I'll report back with any questions I may encounter. I didn't know this kind of information in the pdf existed, awesome!

 

[Beck]

Ah, here it is... the complete list of conversion tables is in a separate doc. 7.5 NAB to 15 IEC is a bit different than 7.5 NAB to 15 NAB. Whenever you have NAB involved in the conversion, even NAB to NAB, you have to compensate for levels with changes in speed. IEC to IEC you don't. I've worked with different speeds with the same EQ curve but never wanted to mess with going from one curve to another, so I hadn't read this doc very closely before in that regard.

http://home.comcast.net/~mrltapes/eq-shift-tables.pdf

 

[ofajen]

Ah, here it is... the complete list of conversion tables is in a separate doc. 7.5 NAB to 15 IEC is a bit different than 7.5 NAB to 15 NAB. Whenever you have NAB involved in the conversion, even NAB to NAB, you have to compensate for levels with changes in speed. IEC to IEC you don't. I've worked with different speeds with the same EQ curve but never wanted to mess with going from one curve to another, so I hadn't read this doc very closely before in that regard.

http://home.comcast.net/~mrltapes/eq-shift-tables.pdf

View attachment 69256

As I mentioned above, this is precisely the same list of conversion values as in table 5-6 from the MRL document I referenced, except that it takes care of showing the frequency doubling for you upon playback at 15 ips. Jay just assumes that you can take care of the IEC-IEC feequency conversions yourself, so as to avoid publishing multiple tables with exactly the same list of conversion data, which would be tedious.

Cheers,

Otto

 

[Beck]

Would love to know how this all worked out. Otto is a more patient man than I. Mostly want to be sure you're ok and not in a padded cell somewhere from working with the 0.23 and 0.68 dB conversions with all those freakin' tones ringing in your ears.