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Messages - miroslav

Pages: [1] 2
1
Raw Tape / Re: RMGI SM911 vs Quantagy 456
« on: July 21, 2009, 01:21:18 PM »
Yes...I kinda' thought it was something along those lines, and in my own unscientific way, I've thought that 468 was better suited for archival stuff.

I was just wondering if there was something unusual about the 911 that I needed to be aware of.


2
Tape Tech / Re: LOW FREQUENCY COMPENSATION adjustments....?
« on: July 13, 2009, 01:38:24 PM »
...just adjust them up and down so that they average out to the same level as 1KHz. And ignore the 20 Hz level : it's normal to be rolled off.

If not the 20Hz...then which LF between 20Hz and 100Hz would you use as the "calibration frequency/center frequency"...
?or should it be an average of them all between 20Hz and 100Hz?


<<<<Then I probably will not touch the physical head alignment for a long time...except the azimuth>>>

Once your record or play heads start to wear (creating a groove) you can't do any further alignment. Even minor azimuth adjustments.  If you were to have have "relief-cut" heads installed in your deck, such as the Flux Magnetic, you in theory can do minor azimuth adjustments, but it's still not recommended because it will still create a new wear pattern which will compromise head-to-tape contact.

OK...I get what you are saying.
So then I would want to be 100% sure right now, while the heads are new, if all the head alignments are as good as they can be...and then after that, leave them alone for their lifetime.

It does say at the end of the "Alignment Procedure" manual to only perform the Height, Zenith and Wrap adjustments when heads are replaced...but they kinda stick the Azimuth alignment out in front of the initial electronic calibrations, right before the Reproduce electronics are adjusted...
so it wasn't very clear if it?s part of the ?daily? alignments.

While I've used R2Rs for many years?besides the basic "front-end" electronic adjustments, I always use to have the decks set up by a tech experienced with that stuff?it was just the easier/safer thing for me.
But since I do have a good electronics background and I'm comfortable with doing most things around my studio, I wanted to make the leap into full-tilt alignments/calibrations for a long time now...but I was just chicken!!! :-D
Whenever I considered the physical alignment...I was nervous for exactly the reason you mentioned.
I can see how it is VERY easy to totally mess it up, especially if you're not experienced at it, and you have to have a real good eye, steady hand and really know what to look for.
This Otari deck and the two manuals really made it a LOT easier for me to dive into the deep end of the pool.
The electronics open up for easy access, and if you follow the procedures with care and eyes wide open...it's not too complicated. I learned a LOT more about the whole process since I got this deck and manuals...and of course, thanks to the tips/suggestions from people like you!

Next I'm going to do a full setup on my 16-Track...and I'm glad you mentioned the concerns about head wear VS making physical alignment changes.
On my 16-Track...all the screws have paint on them, to prevent movement/adjustment without "breaking the seal"...so I will leave them be and just focus on the electronics. Luckily, even on my 16-Track, the heads are like-new...no visible head wear.

Thanks again!
Miroslav

3
Tape Tech / Re: LOW FREQUENCY COMPENSATION adjustments....?
« on: July 13, 2009, 11:14:22 AM »
Your low-end EQ control has no effect on them as you noted.  You were correct to set the low-end EQ so that the mid-points are flat relative to mid-band level (1 kHz).

Hi Tim

When the LFC circuit was turned on, it actually did allow me a good amount of correction of the low end with the trim pot. I could increase or decrease the lower frequency TAPE levels relative to the SOURCE levels. I just wasn't 100% sure where to set the trim pot following the manual?s described process.
What I did was to adjust the LFC trim so that the TAPE level was as close to the SOURCE level ?as possible? across the 20Hz to 200Hz range?with most of the differences being in the 20Hz-80Hz range?above that, the TAPE/SOURCE levels stayed matched regardless of the LFC trim.
Since I was using 0VU at +4dBm as my source signal level (SOURCE  & TAPE) for all the tones I was testing(20Hz-200Hz, 1kHz, 10kHz, etc)...my assumption was to then also set the low frequencies at that same level....which should result in a "flat" response across all?right?

I guess what I am asking is...should the LFC be adjusted so that the low end frequencies are maybe higher or lower than what I am seeing on the SOURCE?
The fact that they call it a LF "compensation"...seemed to imply that the LFC is there to add/increase the lows...but that's the part that I was not 100% clear on, so I just went with my own common sense, and did what I described above.


AFA the physical head alignment...I agree with you, and someone else once told me that too...that most likely, the heads are fine out of the factory, and mild bumps/movement shouldn't change their position.
What I did when checking the azimuth was to first mark the position if the alignment screws with a fine-point permanent marker...that way I would know where I started from.
After several passes, the Record and Playback heads ended up almost in the same spot.
There was a minute difference in screw head position that was less than 0.1mm...you could just b-a-r-l-e-y make out the position change when looking at the thin line I made down the side of the screw head and top of head block surface.
However, the additional 4-Track head was off just a pinch more...maybe 0.2mm.

These heads are brand new, so no worries about tape groove yet, and I was thinking of just checking out the rest of head position adjustments just to be sure.
While I agree with you that it?s not easy do the physical alignment correctly, and I'm sure they do a great setup at the factory, I also know that sometimes people make mistakes or rush things.
This deck had an unsoldered capacitor leg that was causing intermittent Record issues on the left channel...so I know stuff can slip past QC.
I figured that I should give it a onceover, just to check out the deck from A-Z, and just doo some of the tests they outline in the manual for head alignment just to see how they come out, though I wouldn?t mess with them unless I saw something really way off.
Ten I probably will not touch the physical head alignment for a long time...except the azimuth.
I?ve read and heard from some people that the azimuth can be off a bit with different tape brands/types...is that true? I mean, they seem to always suggest doing the azimuth as part of the daily/regular alignment per session.

Thanks
Miroslav

4
Tape Tech / LOW FREQUENCY COMPENSATION adjustments....?
« on: July 12, 2009, 02:32:54 PM »
?LOW FREQUENCY COMPENSATION? adjustment??

OK?so I recalibrated my Otari BIII yesterday using a fresh new MRL tape and the Visual Analyzer software (http://www.sillanumsoft.org/) in place of a hardware scope (the VA software works great).

Now?everything went well, and I did a full alignment/calibration, covering everything accept the actual head height, zenith and head wrap. The deck is almost new, with literally no use, and based on the fact that all my other adjustments were relatively minute, I felt no need to mess with the physical positions of the heads at this time. I also didn?t touch the Erase head.
I?ll check and save those alignment procedures for the next time.

Now, the only one thing I wasn?t 100% clear about was the Low Frequency Compensation adjustment.
I think I know it?s basic purpose, but the full ?Alignment Procedures? manual I have talks about setting it for the ?flattest frequency response??though it requires the use of 20Hz to 200Hz tones from the oscillator?and there is no way to get all of those tones ?flat?.
Meanwhile, the ?Operations and Maintenance? for this deck says to run the oscillator at 0VU Source, and then adjust the LFC pot to match 0VU when at TAPE while running in Record mode. It never mentions which frequency(s) to use.

What I did was something a bit different.
I ran my Left channel in TAPE mode and my Right Channel in SOURCE mode while in Record.
Then, using the VA software, I was able to monitor the frequency response of both channels. That way, I adjusted the LFC so that my Left (TAPE) curve was matching my Right (Source) curve?however, there were level differences between 20Hz ? 40Hz ? 100Hz ? 200Hz.

IOW?if I match at 20Hz?then the TAPE curve was several dB higher at 40Hz...if I match at 40Hz?it was lower at 20Hz by same amount.
When I looked at 100Hz and up to 200Hz?the LFC adjustment had les effect, and the TAPE/SOURCE curves were matched throughout, so I concluded that the LFC was mainly for the sub-80Hz range.
So what I did was to find the mid-point between the lowest and highest points curve positions at the frequencies from 20Hz to 80Hz.
What I ended up with was -3dB at 20Hz as my lowest differential between TAPE and SOURCE curves?and +3db differential at 40Hz. The differentials at 30/50/60/80Hz were less than that.

To me?that was the only way to obtain the ?flattest frequency response? as mentioned in the manual.

Turning off the LFC?at 20Hz ? 40Hz there was greater +dB hump on the TAPE curve when comparing to the SOURCE curves?which means the deck was boosting those frequencies above their source levels without the LFC.

So?is that what the Low Frequency Compensation is meant for?to trim/flatten the low frequencies as close as possible to their source levels?
I?m assuming it isn?t meant to be used to lower them severely below their source levels????

Anyone have a better/clearer explanation of the LFC adjustment from what the manuals describes?

I just want to make sure I didn?t mess it up?.

5
Tape Tech / Re: Oscilloscope for RTR Alignment.
« on: July 11, 2009, 08:29:05 PM »
I'm sure for fulltime bench work, a real good piece of hardware is the ticket, and you don't have to deal with the soundcards or PC...etc.
But since I have the DAW right next to the R2R decks and mixer in my studio...the software version is a good choice for me.

I installed it and tried it out tonight for my Otari R2R alignment?and it works great!
Ran smooth-n-steady, and never crashed, except one time when I clicked on a couple of options while also trying to open a couple of its windows in fast succession while I was running a calibration on the software?s input.
That was a bit much on my part! ;-D
Plus?I never restarted the PC after I installed, though it didn?t ask for it.
But once I restarted, then the software was better at quickly recognizing my soundcards since I have 24 channels of A/D/A split up as 12 input and 12 output pairs?plus the same number of digital I/O channels?so it?s no wonder the software was a bit confused at first.

Anyway?works like a charm for doing the azimuth, plus there are quite a few other analysis tools built in, so it has many more uses.

Not bad for FREE software?though I will donate some $$$ to the guy via PayPal.
He put some serious work into this and it has value for me.

6
Tape Tech / Re: Oscilloscope for RTR Alignment.
« on: July 11, 2009, 11:33:00 AM »
Just found this FREE audio analysis software tool that looks to be just the ticket of anyone not wishing to go the hardware oscilloscope route.

Visual Analyzer

http://www.sillanumsoft.org/

I will be installing the latest version (VA 2009HR) later today on my DAW, and will post back how well it works, but I already installed and earlier version (8.xx) on my XP laptop without issues, and it looks very good so far.

7
It's like the other half of the service manual.

Yup! :-D

I was sitting there looking at my deck and included manual...and I kept scratching my head, as it seemed like there were missing steps for the alignment procedure.
It was really bugging me that they never mentioned the initial calibration of your input channels and meters.

So I spent an hour running some Internet searches, and came across this official Otari "Alignment Procedure" manual, and I thought the exact same thing... "Hey look, the other half of the manual!"

Anyway...so far, I've compared all the steps in this BII/MKIII-2 "Alignment Procedures" manual...and all the pots/switches are named/number the same as in my BIII manual/deck...so I think this manual will apply to a few of the 5050 family decks without a problem, and even if there are some differences in the names/numbers of the switches...it's well detailed so that you can use it as general step-by-step process for most other decks too.

Not sure why Otari chose to "trim down" the manual and the step-by-step alignment details in the newer/later manual like I got with my BIII-2...?

8
Tape Tech / Re: "Software scopes" - BE CAREFUL!!!
« on: July 09, 2009, 10:36:18 AM »
I have nothing against software scopes but PLEASE keep in mind that you are using inputs and outputs to your soundcard that were "designed" to see signal levels from headphones/speakers and microphones.

You go using your PC as a piece of test equipment and you could inadvertently inject who-knows-what into it.  IF you do this please think about PROTECTING the I/O ports somehow.  I haven't done any research on this but someone probably has - like using back-to-back zeners from "hot to ground" to limit the voltages - and maybe even a micro fuse in series with the "hot" leads!  Hopefully there are I/O specs somewhere in your Soundcard literature - if not, ask.

Charles 

Appart from the issue I mentioned in my previous post where the software scope didn't like my 24 bit converters...I wouldn't think there's any real concern...if you have decent soundcards/converters.

The test signals coming from the the deck's outputs are typical Line level signals/voltages, +4dBm to +16dBm...which should work with OK with most soundcards made these days.

9
Found this on some website recently (not sure where)...so I thought I would pass it on.

This is a great step-by-step alignment procedure manual written by Otari back in 1988 for their ?desktop? R2R decks.
It tells you the proper sequence of the alignment steps and the exact details.

The only thing I noticed that is not specified is the Record Equalization for the Low speed (but thy give you the steps for the High speed). It's pretty much the same as for the High speed, you just put the machine into low speed mode and adjust the "L" pots (VR304 & VR404) on the front panel same as you did the "H" pots (VR303 & VR403) for the High speed.

Otherwise...everything else is clearly covered and takes some of the guesswork out of the many calibration points by providing the exact process as outlined by Otari for their decks.


http://www.miroslavmusic.com/audio/Otari/OtariAlignmentProcedures.pdf


Miroslav

10
Hi George

Yes...you are right.

I found an older Otari manual just on "Alignment Procedures" for the BII/MKIII-2 decks, and in it there is much greater detail than I have in my ?Operations and Maintenance manual? for my BIII...but that older manual still applies to the BIII, and even the pots/switches in it are numbered the same as on my BIII for all the calibrations points.

In the detailed ?Alignment Procedures? they specifically tell you when to and how to use the REF FLUX switch during alignment?something that was not mentioned anywhere in my BIII manual.
Actually, the BIII manual leaves out a few important steps and the correct full sequence for proper calibration from A-to-Z.

I?m not sure where I got it that ?Alignment Procedures? manual?it was on some website that I ran across while searching for info on my BIII?but it sure cleared up a few questions I had about my Otari.

11
Tape Tech / Re: Oscilloscope for RTR Alignment.
« on: July 08, 2009, 05:04:25 PM »

I have real good soundcards for my DAW that will do A/D/A at 24 bit up to 96 kHz...so no worries there.

I spoke too soon.

The software scope doens't work with 24 bit cards. :-(

I have an old 16bit card...not sure if I want to mess with my DAW just to install an old sound card because of the scope.

12
Tape Tech / Re: Oscilloscope for RTR Alignment.
« on: July 08, 2009, 01:32:24 PM »
Glad I stumbled on this thread.

I was just lining up to get a scope...but I think I will try out the software version first.
I have real good soundcards for my DAW that will do A/D/A at 24 bit up to 96 kHz...so no worries there.

With my couple of R2R decks...they've been babied and have seen only light to moderate use...so I was not too concerned that the heads had gone out of physical alignment...and they have no visible wear at this point.
That said...I figured it was time to put the decks up on a scope, especially my new Otari BIII which came by UPS, and they tend to bounce things!
I figure I can at least check the physical alignment...and if it comes up good...then I know my electronic calibration will be accurate.

I don't think I would have too much other use for a hardware scope...so maybe the software will be just the thing for me!


13
Yeah...I get like that too...but it's fun being in your own little world...isn't it?! :-D

14
Tape Tech / Re: Otari MX5050 Capstan oil...?
« on: July 07, 2009, 03:26:31 PM »
Thanks...I'll have to check out that site.
What did it cost for shipping on a small vile of oil?

So...how many drops roughly in a .5 oz vile...?

Will that last for several lubes?

15
SRL switch...?
Maybe your post was for another thread...?

I was talking about the REF FLUX switch on the back of the machine that selects between:
LOW/185nWb/m - MID/250nWb/m - HIGH/320nWb/m

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