456 vs. GP9

Posted: Fri Mar 01, 2002 3:16 pm

I know this has been brought up before, but its been awhile. In past posts I've read about the GP9, "looping back". What exactly does this mean?
Can my Otari MX5050-8 handle GP9?

Thanks,
Robert

Posted: Fri Mar 01, 2002 8:03 pm

I have a Tascam MS16 that uses 456. I am thinking about changing to GP9 after hearing another studio's drum sound on the same machine - will I have to re-bias my machine?

Posted: Fri Mar 01, 2002 8:15 pm

Quote:

Originally posted by Adam B - Smokin & Jokin:
I have a Tascam MS16 that uses 456. I am thinking about changing to GP9 after hearing another studio's drum sound on the same machine - will I have to re-bias my machine?

You will definitly have to rebias. No way around it. I talked with Quantagy today. Their tech told me that older machines that have wear from using a certain type of tape for so long might have a negative reaction to any kind of tape switch. In other words, if you've run 456 on your machine for a long time, than there will be worn patterns in the parts of your machine that the tape runs across. The change to GP9 is not going to react well to those pre-worn patterns. I don't know what do you think?

Robert

Posted: Sat Mar 02, 2002 12:34 am

Hi guys - Used to work for Memorex as a QA Engineering tech years ago - I haven't heard of the term "looping back" but it sounds like the type of transport problems you can get if tape is either too well polished, backing (mylar)too limp, or both. What happens is that the tape is too conformant to surfaces of the machine (heads, guides, sometimes pinch rollers) so the tape sticks to the guide or pinch roller on its way thru the tape path. This will cause the tape to wind around the pinch roller and ball up -

The other possibility that could be meant by that phrase is that higher output tapes have more of a tendency to "print through" - This is where the "oversexed" magnetic domains on one layer of tape, when left in contact with the next and previous layers, will "print thru" the backing and cause an echo on the next layer. If the recorded tape is stored with the same "wind" as it comes in the box, when it is played back you will hear "pre" echoes. Neat effect if you want it, really bad if you don't. Consequently, virtually all analog tapes are stored "tails out" after recording - this doesn't eliminate the "echo", it just becomes a "post" echo, and sounds more intentional.

"In other words, if you've run 456 on your machine for a long time, than there will be worn patterns in the parts of your machine that the tape runs across. The change to GP9 is not going to react well to those pre-worn patterns. I don't know what do you think?"

I think the Quantegy tech tried to snow you or else didn't know the real reason. Any time you run ANY tape over the guides and heads of a tape machine, you are constantly polishing the surfaces which contact the tape. Mag tape is made in typically 24" to 36" width, then slit down to the final width in stages, and normally doesn't have any noticeable side-to-side differences in stiffness or oxide coating - therefore, if the machine is properly aligned physically, there should be even wear patterns across the width of the heads and guides. As far as wear vs. type of tape, there should be no difference in how a given type of tape tracks through the machine. However, getting back to properties of surface roughness and backing stiffness, these can and will change the coefficient of friction between the guides/heads and the tape. This can cause tension variations along the tape path, stuttering of the tape speed due to stiction (not a made-up word, wet the tip of your middle finger slightly and run it along a smooth countertop at a steep angle, so that it "chatters" along - this is similar to what happens with a highly polished (well-used) tape path and highly polished tape. If you have a copy of Boston's second album (I think that's the one) There's a horror story about their master (and only) 2" tape and too much polishing of tape and machine (100's of passes on same tape) - this is a really severe case of stiction.

If the term means something entirely different, maybe someone who's heard of the term will chip in... Steve

Respected Past Moderator Joined: Mar 13, 2001 Posts: 1256

1. Yes you'll have to re-bias. You should be biasing @ +1.5db over @ 10Khz for 456 @ 30ips. GP9 should be between 1.8db & 2.0db over bias @ 10khz for GP9. If you don't kmow how. 1. Pay a tech a one time fee. Check out what he does. Right it down step by step.
Proper maintenace (i.e. cleanning of all tape path parts: heads, rollers, guides ect ) is essential, of course. Also, GP9 may require a little tweaking of your transport so that it "rides" on the heads right, it's physically a little different than 456.
The short of it is...if your asking...get a tech one time for the setupo and pick his brain. If you know How to align your deck...then do it yourself. Try the 1.8db over bias @ 10k.
As far as the set-up. With the new Tape (GP9) running across the heads; use a flash light and look staright on at the headstack as the tape is running by. You'll need a tech to set it up if you see the tape riding either up or down on the headstack. Noemally you should see the same amount of headstavk peaking out above and below the width of the tape. If this changes, it's because the tension and other adjustments must be corrected.

Have fun...and happy recording

Posted: Sat Mar 02, 2002 12:06 pm

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Posted: Mon Mar 04, 2002 9:42 am

Quote:

Originally posted by RecorderMan:
1. Yes you'll have to re-bias. You should be biasing @ +1.5db over @ 10Khz for 456 @ 30ips. GP9 should be between 1.8db & 2.0db over bias @ 10khz for GP9. If you don't kmow how. 1. Pay a tech a one time fee. Check out what he does. Right it down step by step.

You're correct, partly. You have the right bias amounts for 30ips. At 15ips you have to double those bias amounts. I have a friend who's using GP9 on his JH-24 16 track at 15ips and he said he's going +7 over at 10khz and it's smooth. I haven't tried it myself.

Also if you're trying to set the bias and it's really wacked try setting with a 1khz tone first. That'll get you in the ball park, then align the rest of the channel, go back and do it with 10khz for bias and it'll be right on.

If you switch from 459 to GP9 you can also adjust the operating level from +6 over 185 to +9 over 185. If you don't have an alignment reel get one and learn how to do this yourself. It's not hard, more time consuming then anything else.

Posted: Mon Mar 04, 2002 10:00 am

Quote:

Originally posted by Jay Kahrs:
If you switch from 459 to GP9 you can also adjust the operating level from +6 over 185 to +9 over 185.

True, you could, but it depends on your recording style. I did a lot with 996 at "just" +6 over 185 and enjoyed the extra headroom. It's nice to have the option.

Dang, as much as I like the GP9. I still miss 996. That was nice tape. . Hopefully the GP9 will last longer than the 996 before baking is required.

-dave G

Posted: Mon Mar 04, 2002 11:07 am

What do you guys think of Emtech (BASF) SM911?
My understanding is that it sheds less than 456,
and it has the same bias settings as 456.
Does shedding affect the heads as long as you clean them often BTW?

P.S. There's a new website for reel to reels
called Reel2Reel.info

Posted: Tue Mar 05, 2002 9:35 am

I've only gone through a few reels of SM911 but so far I like it. The midrange is a little different then 456, maybe a tad less upper mid, but I prefer the hiss from it. Go figure. While we're on the subject I've found that I don't really like the sound of SM900. It sounds great until the breaking point where it goes into compression. At that point it gets glassy and hard to my ear. I've been having better luck running it at +6 rather then +9.

Posted: Tue Mar 05, 2002 10:03 am

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Posted: Wed Mar 06, 2002 1:34 pm

Quote:

Originally posted by Adam B - Smokin & Jokin:
I have a Tascam MS16 that uses 456. I am thinking about changing to GP9 after hearing another studio's drum sound on the same machine - will I have to re-bias my machine?

I have the same machine. Last I checked GP9 wasn't available in the 1 in. format. I've also heard from others (no personla exp. I use 456) that the record and/or bias circuits don't have enough oomph for GP9. Some people even have trouble getting enough for 499 on the MS-16.

Posted: Wed Mar 06, 2002 9:28 pm

I have a 2002 catalog from Total Media in Hackensack, NJ (I buy my tape there) and they have 1" GP9.

Posted: Wed Jan 19, 2005 7:15 pm

Hi all.

I'm new here (lurker <g>) and have been reading through some of these tape threads.

I am considering buying a used Studer A807 mkii 1/4" machine and was planning on using GP-9 tape with it.

Any thoughts on what I might expect?

TIA

Posted: Wed Jan 19, 2005 9:07 pm

Quote:

Any thoughts on what I might expect?

Yes: expect some difficulty finding tape. At least until Quantegy gets sorted out. Do a search on Quantegy.

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