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Messages - reelnut

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Tape Tech / Re: VU meter calibration for Pro recorders
« on: November 26, 2008, 10:27:03 PM »

I'm workin' on it! Answers to all your questions soon with very precise answers, per Studer!

Tape Tech / Re: VU meter calibration for Pro recorders
« on: November 25, 2008, 06:52:29 PM »
Hi, it's me again-
Which A80 do you have exactly? I have the complete service manual for the A80 VU MKII/MKIII, A80 VU MKIV, and A80 MRMKII on DVD. If your machine is one of these it would help me to know which one. I have realized today that although basic alignment procedures would be the same for any machine the process gets complicated when you consider all the different standards that are used, and different machines can be referenced in differing ways!

For one thing, I can't find a reference to 1.228V. All of my Studer service manuals reference line level to the NAB standard, which is based on this relationship: 0dbm = 0.775V at 600 Ohms, or the CCIR/IEC1 standard, which is based on this relationship: 0dbu = 0.775V at 200 Ohms.

OK, I've just come across a table of some different levels. I can see that a line level of +4dbu = 1.23V, which would imply that your MRL tape is CCIR/IEC1, correct?

Tape Tech / Re: VU meter calibration for Pro recorders
« on: November 25, 2008, 03:57:04 PM »
Hi Ki-

First off let's double check a few things: Does your A80 manual specify that operating level at the tape outs is 1.228v?

Are your meters set to PPM or Peak? With my A810 there is a 6db difference between the two when calibrating. I would double check this in the A80 manual.

And what is the reference fluxivity of your MRL tape?

Tape Project Albums - general / Re: TP Tapes And Heat
« on: November 25, 2008, 04:10:18 AM »
OK guys-
It's really good to know that. The climate I was describing is NE Oregon, which is likely just about as perfect for tapes as you could ask for. Except for the fact that my apt does heat up to around 80degF for about a week in the summer,
due to overload of the building's swamp coolers and the fact we aren't allowed to have AC units hanging out of the windows. Thanks! One hurdle jumped and one more to go!

Tape Project Albums - general / TP Tapes And Heat
« on: November 24, 2008, 10:53:14 PM »
Hello readers-

One thing preventing me from becoming a TP subscriber is not knowing precisely what amount of heat it takes to degrade a tape, in this case the TP tapes I'd be buying!

I was writing another novel here, then went back and deleted it and decided to go right to the specifics:

I need to know what the effects of exposure to 80degF heat for one week every year would be, assuming the humidity is at the correct level of 55-60%. The tapes are to be stored on shelves behind closed doors, which should prevent any sudden extreme  changes in temp, but won't prevent the temp from getting up to 80deg.

And what are the ailments of a tape which has seen too much heat? Oxide shedding? Noisy tapes? Thanks!

Oh, I almost forgot: The rest of the year would see the media at about 55-60% humidity and 66-72degF!

Tape Tech / Re: VU meter calibration for Pro recorders
« on: November 24, 2008, 04:18:18 PM »

Why are you trying to set operating level at your outputs with an AF generator? (See the first sentence of Sound Signal's reply). In principle, the operating level at your tape outputs (in your case 1.228v) is set to a "reference" fluxivity recorded on the tape. If you don't do this the operating level of 1.228v has no meaning. To directly answer your question: NO, you should not expect to see 1.228v at the outputs when inputting 1.228v with AF generator. You need to completely forget about the voltage on the input side! A direct answer to your second question: NO, it is not correct to input 1.228v and adjust VU meter amp! Again, forget about the input voltage. The only time you will adjust VU meter amps to read "0" is after you have played the 1kHz tone on your test tape and used that tone to set the level of the playback amps so that 1.228v is produced at the outputs.

After you have made the above adjustments using your test tape you will be playing back at the reference level you have chosen (in this day and age with the high output tapes we have this will most likely be 320 or 355nWb/m), and producing operating level at the outputs. Here is a great link which covers this in a language I can understand:

Does your A80 have the "uncalibrate" pushbuttons next to your input and output knobs? I'm guessing from the pics I've been able to find of the A80 that it does! The ones next to input controls have no effect here, since we are concerned with playback only at this point. But the ones by the output knobs definitely need to be out to be released in order to avoid amplifying the output by an arbitrary amount. Machines that do not have "uncalibrate" switches, such as RS1500 and X-2000R will typically state in the manual that the output knob is to be placed in a certain position before performing the adjustments. I hope this helps!


Reel to Reel Tape Machines / Re: Studer A810 reel tables
« on: November 24, 2008, 03:02:26 PM »
Hi Ki Choi-

I'm not sure what you mean about getting the motor mounts back on right. There appeared to be only one way to put the motor back on. I don't think anything there would have caused the change in height of the reel tables, would it?

As for the small play in the 3 screws that hold down the brake chassis: Yeah!! Big 10/4 on that!! Apparently adjusting brakes on the A810 is one area where the skills of an experienced Studer tech really are needed! It took me about 2 weeks of tweaking to finally get the brake adjustment right after having removed the chassis! Fortunately, the brakes can be accessed by undoing only 3 screws at the top of the machine to let the top front panel come off- a real time-saver.

I have a thought regarding your attempts to calibrate VU meters to operating level on your A80 and will post it to you.

Tape Tech / Re: What are the effects of bias current?
« on: November 24, 2008, 02:36:05 AM »
Good point about freq response dropping off at 15kHz. My soundcard can record up to 192kHz/32bit and the Virtins software accepts sampling rates up to 192/24. I usually input the azimuth signal at 96/24 and it seems to work well. Actually I do have a generator which I purchased last spring that can generate sine,  square and saw waves. But I haven't even tried it out because I don't have the test leads with a banana jack on one end! Is that ridiculous, or what? So I use my test CD.

Although only an amateur, I do want to comment that the very FIRST thing anyone needs to make sure of in a calibration procedure, and this is almost NEVER explained clearly by anyone writing their papers on the internet, is that when the VU meters read zero the machine is producing operating level at the outputs. Your machine will have a specification in volts as to what (in the case of the A810 it's 0.775v) this is. You change this setting by playing back the 1kHz tone on your test tape and then adjust the playback output amps to show operating level in volts at the tape outputs. After this is done you will then adjust the VU meter amplifiers (NOT the screw on the meter front!) so the meters read zero. Your meters are now displaying the reference level of your test tape (in nWb/m) as 0db and you are producing operating level, in volts, at the tape outputs. The syncing of the VU meters to the deck's specified operating level is normally a one-time-only adjustment. Maybe that's why noone ever mentions it, but when buying a used machine it's certainly the first thing to check! There is a Swedish person who has a website- It's the only one I know of that explains how and why to do this. Highly recommended reading for the novice. Reading this page a few years ago was the first time I ever said "Hey! I can do this!" Lots of explanatory pics there, as well. Hint: Just start reading from the 1st page. There is a link at the bottom of every page that takes you to the next one.

Steve, as you noted, calibration of most systems using a test CD can be a pain, since there isn't a way to easily change the line level without changing rec level as well. The A810 has a way to do this. The entire control area under the headblock is actually a hinged panel that folds up and can lock in a 45 or 90 degree position. This is where the cards and periphery controller reside. So the procedure is simply to set input level from the 1kHz tone on the CD to read 0db on the meters when the machine is stopped (which produces an operating level of 0.775v at the outputs). Then I put the machine into rec mode and monitor repro output. The VU meters now indicate that the output level changed when the machine started recording, since the rec level hasn't been set yet. It's a simple matter to now adjust rec level for each channel using the periphery controller. After setting the VU meters to again read 0db by using the rec level control of the periphery controller and not moving the input level control I am now recording reference level on the tape (in my case 355nWb/m) and producing operating level (0.775v) at the outputs. I know that's a lot of words, but you can see this calibration can be done in less time than it took to read about it! Steve, I thought it might help some of the really new guys out there to hear about this. Operating level, reference level- it can all get very confusing! Also, for those who are now asking "What the heck is a periphery controller", it's a digital interface to calibration of the A810, which uses pushbuttons and precise values instead of tuning potentiometers, and each parameter is divisible into 256 steps, which are displayed on the tape counter when calibrating. Recording & playback of the machine itself is 100% analog. This system allows for 2 complete sets of values (including eq, where the time constant is programmable for recording and/or playback) to be stored for each speed! In addition, it's possible to change the settings in real-time during recording and/or playback if that is desired, and all settings, including the counter reading are stored in non-volatile memory when the machine is powered down.

I tried low-frequency biasing at 20Hz with a Q457 tape that I have. No results! At least I now know what to expect from a "newer" tape that this doesn't work on! Changing the bias current I could hear a difference in the sound of the noise, but it didn't vary enough in overall character so that I could say "Ah, I hear the point of lowest distortion". The sound didn't seem to change noticeably until I knew I was way away from the optimun bias point. Going to try it again as soon as I get some more of the 226 that I mentioned earlier. I have some on the way- should be here this week! I don't know alot about 226, having only one reel of it so far. I suspect it may also be of the "higher output" variety that Bill V. says this technique won't work on...

Larry I'm glad you commented on that. I know just what you're talking about, but I tend to overlook things sometimes. I'm thinking about buying some of those cables, but a person would definitely need to consult his/her own product manuals first to verify the configuration, and then contact to have them verify the configuration also. And I'm guessing that since that info isn't offered in the description there's a really good chance that monoprice wouldn't have a clue what it is!!!

Tape Tech / Re: Info on tape length in min...
« on: November 22, 2008, 12:44:34 PM »

The tape counter on the A810 which I use is extremely accurate and:

I noticed when I bought (1 only) RMGI LPR35 tape on metal reel in a setup box that the tape length appeared to be EXACTLY 96min @7.5ips.

However, when I bought (2 cases- equals 40 tapes) pancakes of this same tape, the length of every single tape was ALWAYS 96min, 30sec @7.5ips.

Has anyone else had an experience like this?

Tape Tech / Re: Info on tape length in min...
« on: November 22, 2008, 12:25:29 PM »
thanx rekloos- that's really nice to hear!

Tape Tech / Re: Info on tape length in min...
« on: November 22, 2008, 03:07:56 AM »
Yeah, I'm still surfin!
Here's one that's easy to read:

Tape Tech / Re: Info on tape length in min...
« on: November 21, 2008, 11:39:02 PM »
Hi rekloos-

Glad to help out here.

Firstoff let's consider speed:
You can record at whatever speed you like, but 7" reels usually have recordings at 3.75ips or 7.5ips. 10" reels are normally recorded at 7.5ips or 15ips, but again the speed is entirely up to you.

Now lets consider tape thickness and tape length:
Two variations are quite common: 1- The "standard" tape thickness is 1.5mil. This is your "toughest" tape in terms of resistance to breakage and print-through. 1.5mil tape is wound on 7" reels in lengths of 1200' or 1250', depending on the manufacturer, and wound on 10" reels in lengths of 2400' or 2500', depending on the manufacturer. 2- The "long-play" tape thickness is 1.0mil. A 7" reel will spool 1800' of 1mil tape and a 10" reel will spool 3600'. These two lengths are almost always what long-play tape is available in. There are also "double play" and "triple-play" tapes, which aren't common and aren't even being made anymore, to my knowledge. You really need a fine machine to safely handle these last two tape thicknesses because they are delicate and prone to stretching and breakage, so for our purpose we will only consider "standard" and "long-play" tapes.

Now consider recording time:
This is pretty easy to figure. For example, a 10" reel with 2500' of tape at 7.5ips: 2500' is 30,000in. And 30,000in/7.5ips = 4,000sec. And 4,000sec = 66.66 minutes. As you can see, what we did was convert feet to inches to get total number of inches. Then we divided speed (in this case 7.5) into total inches to get total seconds of recording time. Lastly we divided total seconds (4,000) by 60 to get recording time in minutes.

Here is a quick summary for you. I saw a really good table just the other day, but I'll need to look for it and get back to you on that:

7" reel
1200' @3.75ips = 64min.  @7.5ips = 32min.  @15ips = 16min.
1800' @3.75ips = 96min.  @7.5ips = 48min.  @15ips = 24min.

10" reel
2500' @3.75ips = 2hr, 13min, 20sec.  @7.5ips = 66min, 40sec.  @15ips = 33min, 20sec.
3600' @3.75ips = 3hr, 12min, 00sec.  @7.5ips = 96min, 00sec.  @15ips = 48min, 00sec.

I did have to work this out on the calculator, but after you live with these numbers for awhile and end up using one or two speeds and a couple of different tape lengths most of the time, you won't even have to think twice about this.

Cheers, and happy reeling!

No kiddin! After reading your post I went to and searched for XLR. Turned up a HUGE selection of cables and I couldn't believe the prices! I really like the fact that the RCA conncetion we need is actually one end of the cable.

Tape Tech / Re: What are the effects of bias current?
« on: November 21, 2008, 04:37:08 PM »
Hi George-
I did come across Bill Vermillion's paper yesterday and read it completely- another really good article for tweak freaks! I was really intrigued by his method of biasing for minimum mod noise. Am going to try that, but for me it involves patching in a synth to my record setup to get the 7Hz tone, since I don't have a dedicated oscillator to use and I haven't gotten around to that yet because it involves physically moving some gear. It's more likely I'll record the tone to a CD first... (more playing around!). Most of my tape stock is newer, so I don't know if that method will work for me or not. I have recently been buying some lightly used Scotch 226 which comes from a film vault that I'll bet that would work great on. FYI I can shoot you a message letting you know my results if you like.

A little off the topic, but I was also really intrigued by the statement in that paper that using your Sync switch is a preferred and much more accurate way to set azimuth for the record head. Although the A810 I use is just a 2-track, it does in fact have the Sync ability. Sync isn't enabled on my machine, so that means I have to look at the manual and figure out which switch I need to turn on to get that going. I can see where that method would also be a time-saver, as opposed to setting record azimuth from the playback head. I use a $25 software oscilloscope when doing azimuth checks, which, if anyone is interested in can be found free to try for 21 days here: It really is an incredible value for the money.

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