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Overbias levels
Old 13th November 2002
  #1
Capitol Studios Paris
 
jon's Avatar
 

Overbias levels

Hi all,

A quick survey here:

What overbias levels do you guys like for 1/2" and 2" at 30 ips using Emtec 900 and GP9?

Are you recording 10k or 20k when doing it?
Old 13th November 2002
  #2
I'm doing a 1.25 over with 20khz on a Tascam ATR 80
Old 13th November 2002
  #3
Lives for gear
 
drundall's Avatar
 

I think I've got 10K 1.25 over on a JH24 at 30ips with 900. I follow factory guidelines from the tape manufacturer for my machine. Varies with brand/headgap.
Old 14th November 2002
  #4
Capitol Studios Paris
 
jon's Avatar
 

We wanted to double-check the levels for 1/2" GP9 on a Studer A820 today. Pete Schwier (freelance UK engineer) and I called to various folks in the UK and the US. One advised +4dB with 20k for 30ips. Another advised +2 with 10k. The third advised +3.6 with 20k.

More opinions? Which would you use?
Old 14th November 2002
  #5
member no 666
 
Fletcher's Avatar
Every batch is a little different... so... I used to make sure the budget bought more tape than I thought we'd need, then dedicate one reel for alignments. Each studio on the project got it's own alignment section... with a 'record pad' at the end of the 'alignment reel' [how's that for pissing away money? It was usually the only extravagance on one of my gigs].

On the alignment reel, at the start of the project, I'd run a 10Hz tone into the machine, the dick with the bias until I got what I determined was a good balance between the noise, popcorn, and modulation noise. Repeat over like half a dozen tracks. Then I'd run 10kHz onto the tape, and measure what the hell it was I did at 10Hz... take kind of an 'average' of what I found between the half dozen tracks, and you're in the ballpark.

There were times when I would go a little bias light or a little bias heavy on certain tracks as I knew what was going to end up there, and whether or not I'd have noise problems, or wanted that track a hair brighter...

I rarely ever trusted anyone with my alignments... that way if it was ****ed up, there was no one to blame but me... that and it's better to keep your mouth shut and be thought a fool... then to open it and confirm everyone's suspicions [sorta like now].
Old 14th November 2002
  #6
One with big hooves
 
Jay Kahrs's Avatar
I do 1.5-2dB over with 10khz at 30ips for GP9 on a JH-24. At 30ips I usually do 3.5 or 4 over at 10khz. What's the advantage to using a 20khz tone? I've never experimented with bias all that much and just do what I was taught. Also, which way makes it brighter vs. noisier? Help an analog youngin' out.
Old 14th November 2002
  #7
Jay Kahrs:
I do 1.5-2dB over with 10khz at 30ips for GP9 on a JH-24. At 30ips I usually do 3.5 or 4 over at 10khz. What's the advantage to using a 20khz tone? I've never experimented with bias all that much and just do what I was taught. Also, which way makes it brighter vs. noisier? Help an analog youngin' out.

My ATR 80 manual wants you to use 20khz for bias. Theres alot of adjustments on this deck, the 10k is called mid frequency and you use 18khz
for high frequency. Its a bit more of a pita to align but the deck sounds real good and punches great. I just got my heads redone by John French what a treat.
Old 14th November 2002
  #8
member no 666
 
Fletcher's Avatar
Quote:
Originally posted by Jay Kahrs
I've never experimented with bias all that much and just do what I was taught. Also, which way makes it brighter vs. noisier? Help an analog youngin' out.
Brighter and noiser go hand in hand... less bias give you a brighter tone, and more noise... more bias makes it quieter...

The general idea is to get a good balance between the two... but you can fudge a little bit here and there if you know what effect you're looking to achieve [you can experiment on less important demo clients as part of the learning process.
Old 14th November 2002
  #9
Lives for gear
 
drundall's Avatar
 

Jon,
I've gotten differing opinions on OB levels from different techs also. In the end I decided to go with the manufacturer's spec. Was very frustrating in the beginning though
Old 14th November 2002
  #10
One with big hooves
 
Jay Kahrs's Avatar
On a related note I have a minor sort-of problem with my A80mkII 1/4" deck. I use either 456 or SM911 at +6/185 running at 15ips. After I bias the deck and I'm setting the record levels 1khz and 100hz come up fine and have plenty of room to swing but for some reason 10khz comes up at 0VU and there's no room to back the trim pot down. So it's not a problem because the level is fine but if it's ever hot I won't have room to back it down which is a bit disturbing. FWIW, I'm about 1dB up at 15khz. Any thoughts on what the problem might be? Is this a sign that I might need caps? They look ok, nothing is bulging.
Old 15th November 2002
  #11
Capitol Studios Paris
 
jon's Avatar
 

For 2", I have been using 1.7dB overbias at 30ips with GP9 tape on the 2" Studer A820...as per the advice of Quantegy's tech at the factory.

The A820 is a damn handy machine...you just enter in the overbias number you want, and it auto-biases for you in about one minute of time and tape usage using 10k tone at 30 ips. Or, you can fully auto-rec-align the machine (bias, 1k, HF, LF) instead, which takes all of 3 1/2 minutes of time and tape. Much faster than doing it by ear...and it sounds just as good. In fact, it sounds great.

For other machines, like my JH24, I follow the guidelines of the machine's manual, the booklet that comes with MRL alignment tapes (some very good stuff in there), and the tape manufacturer -- and since they are often contradictory, by ear using a mix of all three.

1/2", in contrast, is not a daily thing for me here...we don't own one yet...and the local rental machines have been pretty dodgy. We had both ATR102 and A820 1/2" machines rented in this week. The Ampex had a PB amp problem, and the Studer...well, first we thought it was a bias or azimuth thing...we re-azimuthed, we re-biased using 2dB over at 10k based on advice from Real World Studios, then checked to see how far away was 4dB over at 20k, but it still didn't sound good.

Mike Spitz at ATR Service recommended 3.6dB using 20k with GP9 on an ATR102, suggesting that maybe a bit more would be needed with an A820 due to the different head gap. Quantegy recommended 4dB using 20k for GP9 at 30 ips with both machines.

Fletcher, speaking of different tape batches, would you re-bias the machine if you bought more tape mid-project?

How many of you guys out there are biasing by ear?
Old 15th November 2002
  #12
Capitol Studios Paris
 
jon's Avatar
 

Quote:
Originally posted by Jay Kahrs
On a related note I have a minor sort-of problem with my A80mkII 1/4" deck. I use either 456 or SM911 at +6/185 running at 15ips. After I bias the deck and I'm setting the record levels 1khz and 100hz come up fine and have plenty of room to swing but for some reason 10khz comes up at 0VU and there's no room to back the trim pot down. So it's not a problem because the level is fine but if it's ever hot I won't have room to back it down which is a bit disturbing. FWIW, I'm about 1dB up at 15khz. Any thoughts on what the problem might be? Is this a sign that I might need caps? They look ok, nothing is bulging.
I'm not an analog tech, but offhand, given the probable age of your machine, the trim pot bit isn't unusual. You can try replacing composants or the cards if it becomes a problem. When that machine was built, 185nW/m was normal flux and 250 was considered elevated level...so you are using the machine at levels it wasn't initially designed for, which may or may not be a problem. Modern elevated level tapes like 911 are also heavier/thicker than the tapes the machine was built to use...I don't know if that's an issue with 1/4"...it can be one with 2". 1dB up at 15kHz is audible...if you like it, cool. If not, bias a little higher (more overbias). What is the head condition btw...have they been relapped or optically aligned...
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