Studer 827 question for keith or anyone else

got an 827 that 3 channels do not align properly. If running audio into it and the machine in input without recording I get 1K = 0 VU @ +4. If I run my alignment MRL I can get all channels to meter properly per desired calibration level of +6/185. When I go do my record alignments channels 11,12, and 24 do not even come close to being the right level. 24 comes closest @ -2VU and that is with the REC level all the way up at any frequency 10K,1K, or 100HZ, Channels 11 and 12 stay about the same @ -15. These channels seem to bias funny as well meaning the level I see when biasing is way lower the the rest of the channels. for example when I bias channel 1 level seems to peak around +2 as do most of the channels. Thse do not. I tried swapping the audio cards thinking it was a problem there and the problem stayed with in those channels. I do not see any of the inputs set to other levels other then +4 suggestions Jedi?

I think there are also pre-amp cards under the head block, have you tried swapping those?
<Edit> Mind you, those are playback amps, so if the Hex numbers are similar for the other tracks with the test tape, then they are probably OK.

Another thought, I once had a machine doing similar things, turned out to be some tiny amounts of "something" stuck to the record head, effectivley either shorting out the gap or lifting the tape enough to reduce the level.

Well I am no stranger to analog so yeah gotta clean the heads before using it. Here is what I see. I/O without recording/playback is perfect. Playback alligns as normal. and If I play tapes it works fine @ any speed 15, 30, vari-speed. So it's something in the record side of things thats causing issues.
Hmmm I'll have to go at it again and really clean those heads with the IPA. dam another shorthand. Sorry Dave. IPA in this case is isopropyl alcohol. The nice thing is the machine is at a fellow engineers studio, he just got it used and hasn't had a need for analog yet but wants to get it all up and running. So there is time. Time to crack out the studio manual :thumb:

EDIT: I am over thinking the issue as usual. I will bet bottom dollar that it's athe channels individual Bias as on those perticular channels Biasing was all kinds of crazy meaning I would go up waiting for it to peak, and it would never peak It would stay @ +3VU for a long time before comming back down and the +^ and +9 light would like up. hmmmmm the machins is telling me something. Me things the previous owner was an artard and didn't know jack and totally fucked up the maching Bias. Now it needs to be brought back into shape. An adjustment here and Adjustment there. :thumb:

What speed are you working?

-30ips doesn't allow individual biasing, you have to go down to 15ips or slower, and build the 'map' for the head biasing. -Then switching up to 30ips will allow "M-Bias" (Master bias). (the bias 'map' is retained for all speeds, since the head doesn't change when you switch speeds, so the relative bias requirements channel-to-channel, should also remain unchanged. Studer don't let you build a head map at 30ips, because it's nt as accurate as the speed increases, so you have to go down to 15ips or slower. -Don't worry about the lack of a reproduce tape at whatever speed you set the bias map... it doesn't matter what the absolute reference is, so long as you find the bias peak, and set all the channels the same.)

Another tip for biasing the A827... SPECIALLY at high operating levels, which it sounds like you are: If you press the "cursor >" or "cursor <" buttons while in this mode, it adds +10dB to all channels playback and metering. This is so that you can drop the 10kHz level on the way in, and record a lower signal to tape, thereby avoiding tape/head HF saturation, which you are getting seriously close to, at elevated levels. Since you're really recording at -10dB, you move the signal away from it. Pressing the cursor button a second time makes it a 20dB gain instead of 10dB.

The top UK facilities used to bias tape this way in the days of white-coated engineers... think of the Beatles! -Several older Neve consoles had +10dB/+20dB switches on the meterbridge to facilitate this way of calibrating the machines. I reccommend trying it. -On the Sturer however, whenever you press "store" to store the calibration value before switching modes and channels, it also stores the +10/+20 gain... -so when you've done the last channel, make it a habit to 'cursor back' to +0dB gain, and press store one last time. -You may notice that when you get a machine new from Studer, they come with the default biasing level at +10dB, if tha ttells you anything...

Look at the hex numbers when you go down to 15ips. -If the master is set too low, the channel numbers will collectively be set too high, and will tend to start to run out of adjustment range. -The reverse is true, where if the channels are set too low, the master adjustment can run out of adjustment range.

-Oh, if you see Marty today, slap him round the chops and tell him it's from me! :wink:

It would stay @ +3VU for a long time before comming back down and the +^ and +9 light would like up

Click to expand...

That tells me that it's not at +3 at all. It's really at plus nine. the basic settings are WAY off. GO back to defaults and start again. I do find that MOST people don't know how to correctly set the master bias relationship, so it's no surprise that it's screwed up before you got it. -You have to 'undo' the damage before you can start to calibrate it.

From what you describe, you may think it's not rising after it stops at +3VU... It is. It's rising a LOT. The needle on the meter just can't tell you, because it's busy having an argument with the endstop.

Drop the incoming level -Drop it a LOT. -VU needles should NEVER be allowed to get to +3VU, because you're WELL into the realms of tape saturation in that region, and you cannot calibrate it accurately when the tape is messing with your readings.

Here is a piece of great advice for calibration that nobody wants to take: Switch the console oscillator down, AWAY from the calibrated position whenever you do the bias. Instead of trying to push the needles up to +2VU to find the peak, drop the signal to -3 or so, and have the needles find the peak somewhere in the +1½ region. It's much better. the "cal" position on the console oscillator is only really there for level, HF and LF alignments... at 15ips, you CANNOT align a machine from 0VU if you need 4 to 4.5dB overdrop and you only have a meter that goes to +3VU...

-And yet I see people trying all the time!

Keith

I knew the it was still rising past when the VU meter physically stopped @ +3VU. Yes was working on the machine @ 15 ips, imho the only way to fly. I will slap Marty around should I see him. Shoul I use a 9 iron or a louieville. As for the +10,+20 with the curser I usually leave that off. After work got to go in and play with those m-bias settings and get all back it to normal. the machine, It's my buddies,will mainly be running 15 IPS @ +6/185 gp9 or 499 likely unles of couse ATR gets their tape out. Then will have to try that stuff out. Still working tape formula's I hear. Anyway thanks for the tips. :thumb:

Oh, more colected analog wisdom:

LF rolloff is a function of the playback head. -Even at 30ips, the low frequency on tape is not a problem. -It's READING it back that's the difficult bit.

The limiting feature is essentially the length of the pole-shoe in the reproduce head. Since you can take a tape from machine 'A' and have it flat down to -say 40Hz, then play it back and have it only play back flat down to 70Hz, there is some fluctuation in terms of where the rolloff starts to happen.

TO complensate for this, some people like to "bump" the LF a little, so that the overall impression of a low-frequency loss is 'hidden' behind a slight low frequency rise.

Sadly, with a 100Hz tone (which is usually all you get: 1kHz, 10kHz and 100Hz) there's little chance to identify how well you're doing, when you take your tape from an Otari and play it on a Studer... or an MCI, or a Stephens, or whatever.

Sometimes people will give you a 40Hz or 50Hz tone as well, but the "tradeoff" can be difficult, since the LF adjustment on your machine can affect one frequency more than the other, so you find yourself winding orwards and backwards a lot in order to strike a happy compromise.

Here's how I print tones for inter-studio playback cal:

1 minute of 1kHz, followed by:
1 minute of 10kHz, followed by:
1 minute of 100Hz.

Then I rewind back about 30seconds, so I'm midway into the 100Hz tone, and I select 40Hz (or 50Hz, depending on what the console oscillator allows) and hit play on teh multitrack, with all channels in record-armed condition.

I watch the counter, and count along with it... 33...34...35...36...37 etc. and get used to the 1-second rhythm.

On 41, I punch in.
On 42 I punch out.
On 43 I punch in.
On 44 I punch out.
45... in.
46... out.
...

and so on. stopping at 60.

Now, when you play back the LF tone, you get 40 seconds of 100Hz, followed by 20 seconds of alternating 100Hz...40Hz...100Hz...40Hz.

This is munumentally helpful when it comes to compromising LF performance, specially if a producer asks you to try either more or less of a bump. -You still have a minute of LF alignment tone, but it's MUCH more helpful. I've never found a single disadvantage to doing this, but it's taught me BUCKETS about how different machines' playback heads rolloff at the bottom end... and at different speeds also.

There ya go. -Trench wisdom.

Keith

if a doh moment. I remembered I can reset the audio card controller processor board and get back to factory default.

I did and fixed all channels but channel 24 which is still quirky. hmmmmmm..

DO you have ch. 24 set as a TC channel? -If so, it'll work differently.

It should say in the LCD window "TC Channel: 24" or "none".

If its 24, set TC channel with the "channel <", "channel >" buttons until it says "none", and press 'store'. it "back" a few times to get out.

TC channel is for unmuting the TC track before synchroniser lock... no real use of you're not slaving the machine with a lock synchroniser.

Keith

As marty would say I do know what i'm doing :razz: 24 is set to an audi channel as opposed to TC. I need to swap it and see if it moves with the audio card. That will narrow it down. :wink: