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Author Topic: Enthusiastic with tape alignment  (Read 14443 times)

Nick in 't Veld

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Enthusiastic with tape alignment
« on: October 29, 2006, 09:51:01 am »

I'm very enthusiastic with the alignment of my tape machine the last days (luv it). I've always left the servicing to a company here, but now I want to do it (as I should) before every session just like demagnetizing and cleaning.

I've also checked and adjusted the head (hight/tilt and Tangency)
All done by reading hardest output level (db) and then fasten the screws (offcourse with a MRL tape) Do you recommend it this way ?
After this I played the test tape with a high frequency (12,5khz) and applied light pressure to the tape with my thumb to see if there was a volume boost. There was no volume boost, so looked like I adjusted it right (?)

With checking azimuth (also by reading hardest output of 8 channels summed to one channel) I noticed not so much difference in volume on the db meter. Is this common ?
When checking with oscilloscope (unfortunately can't set to X/Y) does the two "graphs" needs to be exact the same ?
I checked this with channel 1 and the last channel: 16. They are quite the same/in sync.

I assume the amplifier and eq adjustments needs to be done after azimuth ? I did this because some channels had a little bit of overs at 0,5 db.

Thank you.
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scottoliphant

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Re: Enthusiastic with tape alignment
« Reply #1 on: October 31, 2006, 11:45:41 am »

Quote:

I've also checked and adjusted the head (hight/tilt and Tangency)
I don't have zenith on my 2 decks, so can't talk to that.
Quote:

With checking azimuth (also by reading hardest output of 8 channels summed to one channel) I noticed not so much difference in volume on the db meter. Is this common ?
I'm not quite sure what you are doing here. I've done a down and dirty azimuth alignment by running channel one and then channel 16 (or 24 with a 24 track) flipping phase on one or the other, and adjusting for the lowest db reading (you can find this method online if you search around). I prefer the dual trace oscilloscope. the two sine wavs (from channel 1 and 16 / 24) should line up. you can use 1k for rough, and 10 -16 k for fine adjustment off your mrl. you can then set the record head azimuth in sel-rep by putting the machine in record and sending tones from a tone generator. After this, I'd adjust your bias, then do your record cal (gain, eq, etc). BUT, if you've had it professionally set up, I bet the azimuth and all are probably still ok, and you may want to not mess with it before you wind up all out of whack. There are a lot of folks here with a lot more experience than me who may be able to offer up more detailed advice. good luck!

Justin from Queens

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Re: Enthusiastic with tape alignment
« Reply #2 on: November 01, 2006, 01:25:18 am »

What type of machine do you have?

= Justin
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Nick in 't Veld

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Re: Enthusiastic with tape alignment
« Reply #3 on: November 01, 2006, 09:48:30 am »

It's is a Fostex G16, nice machine for a 16 track 1/2 inch.
Are there portable machines with more bandwidth, like 16 track 1 inch ? (I do almost all the time location work)

When checking levels I was setting the erase head Embarassed
That's why the levels didn't change very much Laughing

All is set now. But I was wondering when checking for Rep EQ setting, I saw that the company that serviced the machine a half year ago setted the levels at 12,5 Khz to 1 DB exactly.
Maybe they did this to achieve more high frequencies, is this good  ? The manual tells me it has to be set to 0db.
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scottoliphant

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Re: Enthusiastic with tape alignment
« Reply #4 on: November 01, 2006, 12:49:30 pm »

Quote:

Are there portable machines with more bandwidth, like 16 track 1 inch ?
there are 1" 16 tracks, but, they are not very portable, several hundred pounds (like my mx70).

Quote:

All is set now. But I was wondering when checking for Rep EQ setting, I saw that the company that serviced the machine a half year ago setted the levels at 12,5 Khz to 1 DB exactly.
Maybe they did this to achieve more high frequencies, is this good ? The manual tells me it has to be set to 0db.
Sounds like they may have been calibrating your machine for one EQ with a MRL set for another. We have an IEC MRL for the 2", every once in a while I have to load up an older session that was done NAB, and there is a chart available from the mrl manufacture that will let you convert the settings to what you need (ie, set NAB eq with a dif tape). What EQ does your MRL reference?

check out page 8 in this pdf:
http://home.flash.net/%7Emrltapes/choo&u.pdf

Nick in 't Veld

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Re: Enthusiastic with tape alignment
« Reply #5 on: November 05, 2006, 08:47:10 am »

It's an IEC1.

Just loaded a tape which was recorded before my alignment.
It sounds more dull now, but I guess that is normal because the machine wasn't well aligned back then ?
Maybe it's also the Rep EQ, that was set higher.
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bushwick

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Re: Enthusiastic with tape alignment
« Reply #6 on: November 09, 2006, 09:37:28 pm »

If a machine is set up for IEC1, you are going to have repro electronics set about 2.5 db down at 10k and up 1.5 db at 100hz to acccomodate more high frequency hitting the tape in record mode. This is the advantage of IEC1 at 15ips and its the equivalent of the 30ips AES eq curve. You get more high frequncy level while you record giving you better S/N ratio. I have run my 1/2" machine in both modes and at the moment I like NAB at 15ips better. Mmmmmm. Noise.

josh

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Joshua Kessler
bushwick  studio
brooklyn, ny
www.bushwickstudio.com

Nick in 't Veld

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Re: Enthusiastic with tape alignment
« Reply #7 on: November 10, 2006, 11:40:52 am »

Hey Josh,

I don't exactly understand that.

- If set 2.5 db down at 10k and 1.5 db at 100hz, you have more low end... ? Or do you mean 2.5 db over the 0 db with 10 khz ?
- Setting voor Repro, how does that effect Recording ?
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siolle

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Re: Enthusiastic with tape alignment
« Reply #8 on: November 10, 2006, 11:47:58 am »

Hi, if my merory serves me right the standards is:
NAB 15 ips 3180 and 50 microseconds (meaning bass roll off -3dB at 50Hz and + 3dB hi end boost at 3180 Hz, then 6dB per octave)
IEC 15 ips 35 microsecons (meaning +3dB point boost at 4500Hz)
IEC 30 ips 17,5 microseconds (meaning +3dB point at 9000Hz)
Eq-curves reversed at playback.

Europe was mostly aligned for 0dB at 320 nWb, or 510 nWb for some studios and most broadcasters.
US used was more of a 200 nWb country.

Level on tape was the same, it was more a question of how hard you likeked to drive the electronics in the recorder, different ideas different sound.

nWb is nanoWebers per square meter or something totally beyond understanding for normal people....

regard
Olle
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scottoliphant

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Re: Enthusiastic with tape alignment
« Reply #9 on: November 10, 2006, 01:01:10 pm »

Quote:

Hey Josh,

I don't exactly understand that.

- If set 2.5 db down at 10k and 1.5 db at 100hz, you have more low end... ? Or do you mean 2.5 db over the 0 db with 10 khz ?
- Setting voor Repro, how does that effect Recording ?



It gets confusing. If you have an IEC tape and want to set the machine for IEC, you still align VU to 0. You are basically setting the eq curve. IEC at 0 is 2.5 db down at 10k from NAB at 0. You make up this difference when you do your record cal. Search the internet, there are several great "intro to tape cal" things out there that will help you out. Or have someone come show you.

bushwick

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Re: Enthusiastic with tape alignment
« Reply #10 on: November 10, 2006, 06:01:56 pm »

On your MRL tape it should have printed the Nw/M level - on the box and on the reel itself. What does it say?

josh
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Joshua Kessler
bushwick  studio
brooklyn, ny
www.bushwickstudio.com

Nick in 't Veld

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Re: Enthusiastic with tape alignment
« Reply #11 on: November 11, 2006, 07:35:24 am »

Yes, G320 nWb/m Reference Fluxivity
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bushwick

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Re: Enthusiastic with tape alignment
« Reply #12 on: November 11, 2006, 05:57:52 pm »

Okay here is what you do:

320nWb/m is 5db over 185nWb/m. 185nWb/m is referenced to 0db in the world of tape engineering. This means that you are going to be shifting your VU meters -5db referenced to 0db. What does that mean to you....?

You are going to be using tapes such as 456 or GP9 or one of the newer tapes that has come out. Each of these has a different amount of fluxivity or magnetism headroom that they can maintain with out distorting the waveform. In the case of 456, it is a +6db over 0vu type of tape (referenced to 185 nWb/m). This means that if your calibration tape were 185 nWb/m (not the 320 nW/m tape you have) and you were calibrating to use 456 you would set your repro electronics at 1k, 10k, 100hz to read -6vu while doing the repro alignment. You would then set your record electronics to read 0vu after the repro electronics had been set during the record alignment.

So what does this mean to you...?
With your MRL tape you are going to cal your machine like this:
1) Demag the tape path. (Make sure you know how to do this properly and have a powerful enough tool for the task. Han-D-Mag is the guy to get. Also, if you do this wrong you can actually magnetize the heads. So know what your doing.)

2) Clean the tape path with 99.9% isopropyl alcohol. Do NOT clean the rubber components with this. If at some point you do need to do clean the rubber use Fantastic Orange Action. This was recommended to me by the tape machine techs at Sony Studios here in NY. I think it works great too and won't eat up or dry out the rubber.

3) Put the MRL tape on the machine. Make sure the machine is not record enabled.

4) Play the 1k tone off the MRL tape. With your 320nWb/m tape you are going to set the "level" of your repro potentiometer to read -1vu for a +6 tape and -4vu for a +9 tape. 456 is a +6 tape. GP 9 is a +9 tape. 499 is also a +9 tape.

5) After you set your 1k tone, do the same thing for 10k and then the same thing for 100hz. The 100hz however will get set properly during the record alignment and you are only ball parking it now.

6) After you have finished the repro. Do the record cal.

7) Take the reel of tape you are going to record on. If its a new tape, put the reel on the right hand side otherwise know as the "take-up side" upside down. Rewind the tape onto the left side, called the "supply side". You do this so that the tape is stored "tails-out" and this will diminish the effects of "print through".

Cool Splice leader tape on the front of the record reel.

9) The first thing to set is over bias and now that your repro electronics have been adjusted to give reference for your record levels, send 10k to your machine with the machine set to input mode. Set the meters for 0vu by adjusting the send from your console/DAW. Then switch the machine to repro and hit record. Turn the treble potentiometer counter-clock-wise til the needle falls to -80db or until you have no level. Start turning the Treble pot clockwise until you see the needle peak. At that point, continue turning the Treble pot clockwise while the needle starts to "fall backwards" towards the quiet side of the meter counting db until you are at the correct number of db of "over-bias".

9b) Every type of machine has different electronics and head construction. I am going to tell you how to set bias on an ATR-100. If you have something different this may not apply to you. Setting bias is directly dependent on tape type and speed. Limiting the conversation to 456 and GP9, 15ips and 30ips you will over-bias like this: At 15ips you will over-bias aprox. 4db with 499 and GP9; 3db with 456. At 20ips you will over-bias approx. 1.75 db with 499 and GP9; 1.5 db with 456.

9c) My machine has slightly different heads from stock so its a tad different from stock ATR settings. Also, over-bias is not exact. You will get different sonic effects from varying the over-bias. Someone went into that in detail a while back on these forums I think. Do a search and you will find it. A brief description of over-bias: It is high frequency magnetism that puts the magnetic particles in a state of motion as they pass over the record head so that they will record the audio portion in greater detail. This is a crude explanation, very lay, but should help you visualize whats going on. In the case of setting large over-bias settings, it might be useful to you to send the machine less than 0vu of the 10k tone so that you have enough room on the vu meter to watch and accurately calculate see where the needle peaks.

10) After you set over-bias, set the record level. Send 1k to the machine with the machine set to input mode. Set the meters for 0vu by adjusting the send from your console/DAW. Switch the machine over to repro, hit record and set the "level" potentiometer on the record card/electronics to 0vu. Do this for 10k as well, adjusting the Treble pot.

11) Then send 100hz to the machine with the machine set to input mode. Set the meters for 0vu by adjusting the send from your console/DAW. Switch the machine over to repro, hit record and adjust the repro electronics Bass potentiometer for 0vu. You will notice that there is no adjustment for Low Frequency on the record electronics so this is how you set the low end on your machine.


IMPORTANT: All of this is predicated on a machine that has had proper I/O and VU meter calibrations and proper azimuth adjusments performed. Its been made clear to me that really the best way to feel good about your azimuth is to use a Oscope set to xy and to get your outside channels to make as close a straight line on the diagonal from 7:30 to 2:30 if you were to visualize a straight line connecting the dots on a clock face.



Good luck with it,
josh




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Joshua Kessler
bushwick  studio
brooklyn, ny
www.bushwickstudio.com

Han S.

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Re: Enthusiastic with tape alignment
« Reply #13 on: November 12, 2006, 06:00:27 am »

The Fostex G16 is a machine that operates at -10dB and it has only one head for record/repro, like the Tascam MSR16/24.

So 0 on its meters (ledbars) will be -10 on its output.

Aligning a machine like this isn't as easy as a three head machine like the professional machines have.

On your question about the 16 track machines with wider tape: the best sounding tape machines are those with 16 tracks on two inch tape.
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Nick in 't Veld

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Re: Enthusiastic with tape alignment
« Reply #14 on: November 12, 2006, 08:54:18 am »

Thank you, Josh, for the enormous post.

Sorry to say that I readed your post wrong about: "If a machine is set up for IEC1, you are going to have repro electronics set about 2.5 db..."

I thought you meant setting 2.5 db down at 10k and 1.5 db at 100hz on the VU meter with an IEC1 test tape gives better S/N ratio.
But this is offcoarse done when setting IEC1 to 0DB.

Han, more difficult in my opinion is only you have to record and then playback to tweak with record levels and eq.

I know 2 inch sound better, but I need a machine that is portable and hoped there is a machine out there which is portable enough (for location work) and is 1" 16 tracks.


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